2016 Vol. 33 No. 增刊
Abstract：
Finite element method of lines (FEMOL) is an excellent semi-discrete method. To improve the accuracy along the discrete direction, the Element Energy Projection (EEP) method, which is a powerful super-convergent recovery method in 1D FEM, was successfully extended to FEMOL. Accordingly, a set of formulas named simplified formulation was proposed in previous papers. The displacement and its derivatives calculated by the simplified formulas have been proved to have one order higher convergence than that of FEMOL itself. However, deepened studies showed that the formula for derivatives in this simplified formulation could be further simplified and a more simplified formula for derivatives is proposed in this paper. Numerical experiments are conducted to demonstrate the effectiveness of the proposed approach.
Finite element method of lines (FEMOL) is an excellent semi-discrete method. To improve the accuracy along the discrete direction, the Element Energy Projection (EEP) method, which is a powerful super-convergent recovery method in 1D FEM, was successfully extended to FEMOL. Accordingly, a set of formulas named simplified formulation was proposed in previous papers. The displacement and its derivatives calculated by the simplified formulas have been proved to have one order higher convergence than that of FEMOL itself. However, deepened studies showed that the formula for derivatives in this simplified formulation could be further simplified and a more simplified formula for derivatives is proposed in this paper. Numerical experiments are conducted to demonstrate the effectiveness of the proposed approach.
2016, 33(增刊): 6-10,17.
DOI: 10.6052/j.issn.1000-4750.2015.05.S020
Abstract：
This paper focuses on the textile reinforced concrete(TRC) thin-plates with the addition of short steel fibers. The influence of the length-diamond ratio and the volume content of short steel fiber on the bearing capacity of TRC thin-plates are investigated by means of four-point bending tests. ISO-834 International Standard Fire Curve is controlled by programmed temperature furnace, and the heating time is 0.5h or 1.0h respectively. The experimental results show that the addition of short steel fibers can improve the bending capacity and stiffness after the cracking of the TRC thin-plates. Length-diamond ratio of short steel fibers has little influence on the bearing capacity and deformability of the TRC thin-plates. The bending capacity of specimens with 1.0% steel fiber addition has increased by 61%. With longer heating temperature time, the bearing capacity of the TRC thin-plates decreases gradually, and the number of continuous crack reduces greatly. All the specimens almost lost the damage characteristics of multiple cracking after heated by 1.0h. Whether exposed to room temperature or high temperature, the TRC thin-plates with 1.0% steel fibers addition shows a certain residual mechanical property.
This paper focuses on the textile reinforced concrete(TRC) thin-plates with the addition of short steel fibers. The influence of the length-diamond ratio and the volume content of short steel fiber on the bearing capacity of TRC thin-plates are investigated by means of four-point bending tests. ISO-834 International Standard Fire Curve is controlled by programmed temperature furnace, and the heating time is 0.5h or 1.0h respectively. The experimental results show that the addition of short steel fibers can improve the bending capacity and stiffness after the cracking of the TRC thin-plates. Length-diamond ratio of short steel fibers has little influence on the bearing capacity and deformability of the TRC thin-plates. The bending capacity of specimens with 1.0% steel fiber addition has increased by 61%. With longer heating temperature time, the bearing capacity of the TRC thin-plates decreases gradually, and the number of continuous crack reduces greatly. All the specimens almost lost the damage characteristics of multiple cracking after heated by 1.0h. Whether exposed to room temperature or high temperature, the TRC thin-plates with 1.0% steel fibers addition shows a certain residual mechanical property.
Abstract：
Based on the solution of consolidation equations in which the soil layer thickness changes with time, this paper introduces continuous drainage boundaries, deduces and preliminarily proves the formula of pore pressure distribution and the formula of the average degree of consolidation, discusses the difference and connection between continuous drainage boundaries whose permeability changes with time and the undrained boundary in dredger fill engineering, the constraints of the Gibson formula for the average degree of consolidation. In view of the possible situation that negative pressure drainage system were located in the bottom boundary, a continuous drainage boundary was introduced to analyze the average degree of consolidation in different cases. Overall, the average degree of consolidation about soil layer thickness changing with time was studied in a certain depth. The conclusion has a certain theoretical significance and engineering reference value.
Based on the solution of consolidation equations in which the soil layer thickness changes with time, this paper introduces continuous drainage boundaries, deduces and preliminarily proves the formula of pore pressure distribution and the formula of the average degree of consolidation, discusses the difference and connection between continuous drainage boundaries whose permeability changes with time and the undrained boundary in dredger fill engineering, the constraints of the Gibson formula for the average degree of consolidation. In view of the possible situation that negative pressure drainage system were located in the bottom boundary, a continuous drainage boundary was introduced to analyze the average degree of consolidation in different cases. Overall, the average degree of consolidation about soil layer thickness changing with time was studied in a certain depth. The conclusion has a certain theoretical significance and engineering reference value.
2016, 33(增刊): 18-22,28.
DOI: 10.6052/j.issn.1000-4750.2015.05.S002
Abstract：
There are many engineering structures with circular sections. At regular wind speed, the Reynolds number of these structures can reach 107 or more which falls into high supercritical Reynolds number region. However, researches on circular cylinder in this region are few. Based on this situation, the wind load of a single circular cylinder of 5 meters in diameter is studied by numerical calculation. The computational domain, number of circumjacent grid, height of the first normal layer grid and computational time step are examined. The drag coefficient and the flow field distribution around the circular cylinder are obtained.
There are many engineering structures with circular sections. At regular wind speed, the Reynolds number of these structures can reach 107 or more which falls into high supercritical Reynolds number region. However, researches on circular cylinder in this region are few. Based on this situation, the wind load of a single circular cylinder of 5 meters in diameter is studied by numerical calculation. The computational domain, number of circumjacent grid, height of the first normal layer grid and computational time step are examined. The drag coefficient and the flow field distribution around the circular cylinder are obtained.
2016, 33(增刊): 23-28.
DOI: 10.6052/j.issn.1000-4750.2015.05.S038
Abstract：
Superconvergent solution can be obtained from finite element (FE) solution by using a p-type superconvergent recovery scheme. The recovered superconvergent solution is used to estimate the error of FE solution in place of the exact solution. The Zienkiewicz mesh refinement strategy is improved by making small adjustments. Based on reliable error estimation and efficient mesh refinement, adaptive process can be conducted successfully. Numerical experiments show that the adaptive scheme can produce excellent mesh and solution.
Superconvergent solution can be obtained from finite element (FE) solution by using a p-type superconvergent recovery scheme. The recovered superconvergent solution is used to estimate the error of FE solution in place of the exact solution. The Zienkiewicz mesh refinement strategy is improved by making small adjustments. Based on reliable error estimation and efficient mesh refinement, adaptive process can be conducted successfully. Numerical experiments show that the adaptive scheme can produce excellent mesh and solution.
2016, 33(增刊): 29-32.
DOI: 10.6052/j.issn.1000-4750.2015.05.S004
Abstract：
Because of many factors such as the discreteness of concrete materials and measured noise, the effects of uncertain parameters should be taken into consideration during the damage identification. This paper proposes a probability approach for the damage identification of structures considering uncertainties in structural parameters. The random parameter is assumed to follow Gaussian and non-Gaussian distribution. Based on the theoretical model and the statistical moment-sensitivity, the probabilistic structural models in undamaged and damaged states are obtained by two-stage model updating, and then the Probabilities of Damage Existence (PDE) of each element are calculated as the damage criterion and two-stage model updating. On the other hand, some improvement has been made to lessen the measured responses with segmentation time. The new stochastic damage detection method can not only locate structural damage but also identify damage severity. A ten-story shear building model subjected to ground motions and a simply supported beam with white noise are considered to demonstrate the proposed method.
Because of many factors such as the discreteness of concrete materials and measured noise, the effects of uncertain parameters should be taken into consideration during the damage identification. This paper proposes a probability approach for the damage identification of structures considering uncertainties in structural parameters. The random parameter is assumed to follow Gaussian and non-Gaussian distribution. Based on the theoretical model and the statistical moment-sensitivity, the probabilistic structural models in undamaged and damaged states are obtained by two-stage model updating, and then the Probabilities of Damage Existence (PDE) of each element are calculated as the damage criterion and two-stage model updating. On the other hand, some improvement has been made to lessen the measured responses with segmentation time. The new stochastic damage detection method can not only locate structural damage but also identify damage severity. A ten-story shear building model subjected to ground motions and a simply supported beam with white noise are considered to demonstrate the proposed method.
2016, 33(增刊): 33-38,55.
DOI: 10.6052/j.issn.1000-4750.2015.03.S001
Abstract：
For statically indeterminate beams of variable stiffness under complicated load, a continuous subsection independently systematic integral method (CSISIM) is presented for fast determination of the analytical solutions of deformation. In CSISIM, the beam is first separated into segments series. The general mechanical model is established for variable stiffness beams under complicated load. The forth-order differential deflection equation of any cross section is derived from the model. Then the general solutions of beam deflection are obtained independently by forth-fold integration. Integral constants are determined by boundary conditions and continuity conditions. The solution procedure is developed for the corresponding mathematical model. It does not need to simplify loads and beam structure during establishing the model of the continuous curve shaped variable stiffness beam and its process of derivation. This method is used to give the analytic solutions of three engineering examples of statically indeterminate beams including beams of stepped cross sections, beams of inertia moment varied quadratically and beams of inertia moment varied by the fourth power. The results show that the CSISIM is suitable for computer programming. Compared with the finite element method, the advantage of the method is that it can quickly get the analytical solution of bending deformation.
For statically indeterminate beams of variable stiffness under complicated load, a continuous subsection independently systematic integral method (CSISIM) is presented for fast determination of the analytical solutions of deformation. In CSISIM, the beam is first separated into segments series. The general mechanical model is established for variable stiffness beams under complicated load. The forth-order differential deflection equation of any cross section is derived from the model. Then the general solutions of beam deflection are obtained independently by forth-fold integration. Integral constants are determined by boundary conditions and continuity conditions. The solution procedure is developed for the corresponding mathematical model. It does not need to simplify loads and beam structure during establishing the model of the continuous curve shaped variable stiffness beam and its process of derivation. This method is used to give the analytic solutions of three engineering examples of statically indeterminate beams including beams of stepped cross sections, beams of inertia moment varied quadratically and beams of inertia moment varied by the fourth power. The results show that the CSISIM is suitable for computer programming. Compared with the finite element method, the advantage of the method is that it can quickly get the analytical solution of bending deformation.
2016, 33(增刊): 39-44.
DOI: 10.6052/j.issn.1000-4750.2015.05.S006
Abstract：
Interfacial fracture energy at the steel bar-concrete interface is a very important parameter which affects the value of interfacial shear-slip and the interfacial crack propagation after debonding. In previous tests of interfacial shear stress-slip relationship between the steel bar and concrete, the measured value of shear-slip is overestimated, resulting in the overestimation of the interfacial fracture energy. However, the actual local shear stress-slip relationship can be hardly obtained based on the present test approaches. The intention of this paper is to determine the local interfacial fracture energy between steel bar and concrete by combing the analytical model with test results. For the round plain steel bars with diameters of 18 mm anchored in concrete anchorage specimens, PVC tube was used to determine different unbonded lengths denoted as the initial crack lengths. Then the maximum pull-out load of steel bar from concrete can be experimentally measured. The distributions of tensile stress in the bar and interfacial shear stress along the bonding length were expressed in closed form at different loading stages based on the deformation compatibility conditions at the interface and equilibrium conditions of forces. Thus, the maximum pull-out load can be given analytically. The results show that the analytically determined maximum pull-out load is related to the bonding strength, residual frictional stress and local fracture energy at the crack-tip region. The correlation between the crack-tip local fracture energy and initial crack length is established upon the comparison between the analytically determined maximum pull-out loads and the experimentally measured ones. The interfacial local fracture energy distribution along the bonding length is then given, and the size-independent interfacial fracture energy is 25 N/m.
Interfacial fracture energy at the steel bar-concrete interface is a very important parameter which affects the value of interfacial shear-slip and the interfacial crack propagation after debonding. In previous tests of interfacial shear stress-slip relationship between the steel bar and concrete, the measured value of shear-slip is overestimated, resulting in the overestimation of the interfacial fracture energy. However, the actual local shear stress-slip relationship can be hardly obtained based on the present test approaches. The intention of this paper is to determine the local interfacial fracture energy between steel bar and concrete by combing the analytical model with test results. For the round plain steel bars with diameters of 18 mm anchored in concrete anchorage specimens, PVC tube was used to determine different unbonded lengths denoted as the initial crack lengths. Then the maximum pull-out load of steel bar from concrete can be experimentally measured. The distributions of tensile stress in the bar and interfacial shear stress along the bonding length were expressed in closed form at different loading stages based on the deformation compatibility conditions at the interface and equilibrium conditions of forces. Thus, the maximum pull-out load can be given analytically. The results show that the analytically determined maximum pull-out load is related to the bonding strength, residual frictional stress and local fracture energy at the crack-tip region. The correlation between the crack-tip local fracture energy and initial crack length is established upon the comparison between the analytically determined maximum pull-out loads and the experimentally measured ones. The interfacial local fracture energy distribution along the bonding length is then given, and the size-independent interfacial fracture energy is 25 N/m.
2016, 33(增刊): 45-48.
DOI: 10.6052/j.issn.1000-4750.2015.06.S024
Abstract：
IsoTruss structure is a one-dimensional (1D) lattice truss composite structure, and it attracts attentions in lightweight engineering structures. The compression behaviors of IsoTruss columns in uniaxial compression were studied through finite element modelling (FEM). Besides the material failure, there are two potential buckling failure modes: local buckling and global column buckling. It is revealed that the buckling mode and the critical buckling load change with the column length and the spiral angle of helical members. The research paper gives the critical buckling load theory of three failure modes in uniaxial compression, and compares their results of numerical simulation.
IsoTruss structure is a one-dimensional (1D) lattice truss composite structure, and it attracts attentions in lightweight engineering structures. The compression behaviors of IsoTruss columns in uniaxial compression were studied through finite element modelling (FEM). Besides the material failure, there are two potential buckling failure modes: local buckling and global column buckling. It is revealed that the buckling mode and the critical buckling load change with the column length and the spiral angle of helical members. The research paper gives the critical buckling load theory of three failure modes in uniaxial compression, and compares their results of numerical simulation.
2016, 33(增刊): 49-55.
DOI: 10.6052/j.issn.1000-4750.2015.05.S029
Abstract：
Creep-stess relaxation coupling experiments were carried out and the induced catastrophic failure in concrete materials was investigated in the paper. An initial displacement was imposed to the cross-head of testing machine and then it was kept constant, a stress relaxation was observed associated with the increase of deformation. The growth of concrete's deformation leads to a continuous increase of the stored energy in the concrete samples. But, the total energy of the system decreases monotonically. This indicates that the tested concrete undergoes a damage propagation process even though the stress is relaxing. The energy-time curves can be typically divided into three temporal stages: the primary stage with rapid evolution, followed by a steady stage with a constant slope, and finally the accelerating tertiary stage which eventually leads to a macroscopic failure. Ahead of macroscopic failure, the energy release rates of all samples present a power law behavior with the same critical exponent -2/3, although these experiments exhibit a large variability in time-to-failure and failure strain or stress. This observation suggests a way to predict the timing of failure by monitoring the critical accelerating behaviors of the quantities such as energy, strain or stress.
Creep-stess relaxation coupling experiments were carried out and the induced catastrophic failure in concrete materials was investigated in the paper. An initial displacement was imposed to the cross-head of testing machine and then it was kept constant, a stress relaxation was observed associated with the increase of deformation. The growth of concrete's deformation leads to a continuous increase of the stored energy in the concrete samples. But, the total energy of the system decreases monotonically. This indicates that the tested concrete undergoes a damage propagation process even though the stress is relaxing. The energy-time curves can be typically divided into three temporal stages: the primary stage with rapid evolution, followed by a steady stage with a constant slope, and finally the accelerating tertiary stage which eventually leads to a macroscopic failure. Ahead of macroscopic failure, the energy release rates of all samples present a power law behavior with the same critical exponent -2/3, although these experiments exhibit a large variability in time-to-failure and failure strain or stress. This observation suggests a way to predict the timing of failure by monitoring the critical accelerating behaviors of the quantities such as energy, strain or stress.
Abstract：
The effect of temperature on the fracture toughness of weld thermal simulated X80 pipeline steel in ductile-to-brittle transition (DBT) regime is studied. A large number of fracture toughness (as denoted by crack tip opening displacement, CTOD) tests together with finite element analyses are carried out using single edge notched tension specimens at various temperatures (-90℃, -60℃, -30℃ and 0℃). 3D finite element models of the tested specimens are used for the numerical simulation. It is concluded that fracture toughness CTOD values decrease with decreasing temperature. The tendency of brittle fracture with decreasing temperature is significant. The transferability of the true stress-strain curves obtained from weld thermal simulated round tensile bar to the fracture mechanics specimen works very well. The temperature shows only a slight effect on the material hardening behavior. As compared with the experimental results, the 3D model can precisely predict CTOD values at different temperatures considered in this study.
The effect of temperature on the fracture toughness of weld thermal simulated X80 pipeline steel in ductile-to-brittle transition (DBT) regime is studied. A large number of fracture toughness (as denoted by crack tip opening displacement, CTOD) tests together with finite element analyses are carried out using single edge notched tension specimens at various temperatures (-90℃, -60℃, -30℃ and 0℃). 3D finite element models of the tested specimens are used for the numerical simulation. It is concluded that fracture toughness CTOD values decrease with decreasing temperature. The tendency of brittle fracture with decreasing temperature is significant. The transferability of the true stress-strain curves obtained from weld thermal simulated round tensile bar to the fracture mechanics specimen works very well. The temperature shows only a slight effect on the material hardening behavior. As compared with the experimental results, the 3D model can precisely predict CTOD values at different temperatures considered in this study.
2016, 33(增刊): 62-66,71.
DOI: 10.6052/j.issn.1000-4750.2015.05.S010
Abstract：
A finite element model (FEM) is established with proper constitutive laws of materials, element types, meshing technology, and boundary conditions. After being verified with experimental results, the FEM is used to study the shear strength of circular concrete-filled steel tubular (CFST) members with a circumferential gap between the tube and concrete. The numerical investigation indicates that the existence of the gap decreases the ultimate shear strength of CFST members, and the influence is closely related to the gap ratio and the span-to-depth ratio. However, the influence of the concrete strength, steel strength and steel ratio on the shear strength reduction is less significant. When the span-to-depth ratio equals to 0.5, the gap has the most significant influence on the mechanical performance of CFST members with initial concrete imperfection. Based on the parametric study, a simplified formula is proposed to calculate the shear strength of circular CFST members with a circumferential gap.
A finite element model (FEM) is established with proper constitutive laws of materials, element types, meshing technology, and boundary conditions. After being verified with experimental results, the FEM is used to study the shear strength of circular concrete-filled steel tubular (CFST) members with a circumferential gap between the tube and concrete. The numerical investigation indicates that the existence of the gap decreases the ultimate shear strength of CFST members, and the influence is closely related to the gap ratio and the span-to-depth ratio. However, the influence of the concrete strength, steel strength and steel ratio on the shear strength reduction is less significant. When the span-to-depth ratio equals to 0.5, the gap has the most significant influence on the mechanical performance of CFST members with initial concrete imperfection. Based on the parametric study, a simplified formula is proposed to calculate the shear strength of circular CFST members with a circumferential gap.
2016, 33(增刊): 67-71.
DOI: 10.6052/j.issn.1000-4750.2015.05.S005
Abstract：
For the problems of connecting joint between BRB and concrete beam-column,such as stress state, strength and stiffness factors, a new type of angle steel connection node is designed in this paper. Through the finite element simulation of the node under monotonic and cyclic displacement loading, the load-displacement curve, the skeleton curve and the impact on each component of the node are analyzed, the mechanical properties and the force transmission mechanism are also studied. The results show that the structure of the node form, power transmission mechanism is clear. Good work performance are showed under monotonic and cyclic loading.
For the problems of connecting joint between BRB and concrete beam-column,such as stress state, strength and stiffness factors, a new type of angle steel connection node is designed in this paper. Through the finite element simulation of the node under monotonic and cyclic displacement loading, the load-displacement curve, the skeleton curve and the impact on each component of the node are analyzed, the mechanical properties and the force transmission mechanism are also studied. The results show that the structure of the node form, power transmission mechanism is clear. Good work performance are showed under monotonic and cyclic loading.
2016, 33(增刊): 72-78.
DOI: 10.6052/j.issn.1000-4750.2015.05.S026
Abstract：
Floor slabs are important components of frame structures which largely affect the structural progressive collapse performance. This paper presents a simplified numerical simulation method for reinforced concrete (RC) slabs. A RC slab is discretized along two directions transferring into a beam network. The meshes at each direction are simulated by fiber beam elements to consider the composite mechanical behavior of steel reinforcement and concrete. In this method, beam-slab joints at the edge area of slabs are simulated by fiber beam elements with T/L sections, by which the effects of slabs on the bending behavior and the damage mode of the beams under small deformation in progressive collapse are considered. On the other hand, fiber beam elements with rectangle sections are used to simulate the interior area of slabs, by which the tensile membrane action of slabs under large deformation can be considered. This method can not only avoid the high stiffness problem when using shell elements, but also greatly improve the efficiency of the calculation of the whole structure. Finally, existing tests on special-shaped columns (T/L cross sections), one-way slabs and two-way slabs are simulated, respectively. The results show that the simplified method can efficiently and accurately simulate the reinforced concrete slabs under large deformation, providing a powerful tool for the simulation of progressive collapse analysis of whole structures.
Floor slabs are important components of frame structures which largely affect the structural progressive collapse performance. This paper presents a simplified numerical simulation method for reinforced concrete (RC) slabs. A RC slab is discretized along two directions transferring into a beam network. The meshes at each direction are simulated by fiber beam elements to consider the composite mechanical behavior of steel reinforcement and concrete. In this method, beam-slab joints at the edge area of slabs are simulated by fiber beam elements with T/L sections, by which the effects of slabs on the bending behavior and the damage mode of the beams under small deformation in progressive collapse are considered. On the other hand, fiber beam elements with rectangle sections are used to simulate the interior area of slabs, by which the tensile membrane action of slabs under large deformation can be considered. This method can not only avoid the high stiffness problem when using shell elements, but also greatly improve the efficiency of the calculation of the whole structure. Finally, existing tests on special-shaped columns (T/L cross sections), one-way slabs and two-way slabs are simulated, respectively. The results show that the simplified method can efficiently and accurately simulate the reinforced concrete slabs under large deformation, providing a powerful tool for the simulation of progressive collapse analysis of whole structures.
Abstract：
The scaled test of single span double-layer braced frame structure presented in this paper focuses on the influence of initial geometric imperfections on the deformation property. The test results and the finite element analysis results are in good agreement, which proves the correctness of the finite element model by taking random initial imperfection into consideration. A great deal of full-path analysis of 32-story three-span steel braced-frame structures with random imperfections is carried out by using the finite element program ANSYS. The distribution of random initial imperfections is achieved by employing Monte Carlo method and Latin hypercube sampling technique. In addition, the deformation properties of the structure and components were analyzed emphatically, comparing with some methods of the standards at home and abroad. The results show that the defect simulation calculation values of lateral drifts are close to those for ideal frames without any initial imperfections. It could be neglected in advanced design for slender flexible structure. The specification of the frame designed by the Chinese standard is far beyond the framework of random defects because the additional horizontal force exaggerates the detrimental effect of defects.
The scaled test of single span double-layer braced frame structure presented in this paper focuses on the influence of initial geometric imperfections on the deformation property. The test results and the finite element analysis results are in good agreement, which proves the correctness of the finite element model by taking random initial imperfection into consideration. A great deal of full-path analysis of 32-story three-span steel braced-frame structures with random imperfections is carried out by using the finite element program ANSYS. The distribution of random initial imperfections is achieved by employing Monte Carlo method and Latin hypercube sampling technique. In addition, the deformation properties of the structure and components were analyzed emphatically, comparing with some methods of the standards at home and abroad. The results show that the defect simulation calculation values of lateral drifts are close to those for ideal frames without any initial imperfections. It could be neglected in advanced design for slender flexible structure. The specification of the frame designed by the Chinese standard is far beyond the framework of random defects because the additional horizontal force exaggerates the detrimental effect of defects.
2016, 33(增刊): 85-89,149.
DOI: 10.6052/j.issn.1000-4750.2015.05.S044
Abstract：
The dynamic response of an underground-commercial-street structure subjected to different types of seismic waves and corresponding influence factors are studied. Based on a monolayer underground-commercial-street structure, the three-dimensional finite element model with three-dimensional equivalent viscoelastic boundary element of a soil-underground structure-interaction system is established, then the structural dynamic response is calculated with different types of seismic excitations, and the effect of buried depth, soil stiffness, and seismic input types are discussed. The results indicate that: for the seismic response of such underground structure, there is most unfavorable buried depth; soil stiffness has a significant impact; seismic response value under long-period seismic waves is significantly larger than that under ordinary seismic waves.
The dynamic response of an underground-commercial-street structure subjected to different types of seismic waves and corresponding influence factors are studied. Based on a monolayer underground-commercial-street structure, the three-dimensional finite element model with three-dimensional equivalent viscoelastic boundary element of a soil-underground structure-interaction system is established, then the structural dynamic response is calculated with different types of seismic excitations, and the effect of buried depth, soil stiffness, and seismic input types are discussed. The results indicate that: for the seismic response of such underground structure, there is most unfavorable buried depth; soil stiffness has a significant impact; seismic response value under long-period seismic waves is significantly larger than that under ordinary seismic waves.
2016, 33(增刊): 90-94.
DOI: 10.6052/j.issn.1000-4750.2015.04.S051
Abstract：
The stiffness and strength demands of high-rise rocking wall are large, and the pre-casting and erection constructions are difficult. To mitigate the structural displacement response and the damage concentration effect, a novel structural system of continuously rocking wall-buckling restrained braced frames (CRW-BRBF) is proposed. In this system, continuously rocking wall (CRW) controls its interlayer displacement distribution pattern. The seismic action is undertaken by buckling-restrained braces (BRB), which can be regarded as the device of energy dissipation to shock absorption. As a second aseismic line, a frame is employed to bear the vertical load. Nonlinear dynamic time-history analyses under 22 ground motions are conducted in OpenSees to investigate comparatively the seismic performance of buckling-restrained braced frames (BRBF), rocking wall-buckling restrained braced frames (RW-BRBF) and CRW-BRBF. The results show that the CRW can decrease the drift concentration factor (DCF) of the BRBF. Compared with the RW-BRBF, the moment and shear force demands of the rocking wall in the CRW-BRBF are smaller.
The stiffness and strength demands of high-rise rocking wall are large, and the pre-casting and erection constructions are difficult. To mitigate the structural displacement response and the damage concentration effect, a novel structural system of continuously rocking wall-buckling restrained braced frames (CRW-BRBF) is proposed. In this system, continuously rocking wall (CRW) controls its interlayer displacement distribution pattern. The seismic action is undertaken by buckling-restrained braces (BRB), which can be regarded as the device of energy dissipation to shock absorption. As a second aseismic line, a frame is employed to bear the vertical load. Nonlinear dynamic time-history analyses under 22 ground motions are conducted in OpenSees to investigate comparatively the seismic performance of buckling-restrained braced frames (BRBF), rocking wall-buckling restrained braced frames (RW-BRBF) and CRW-BRBF. The results show that the CRW can decrease the drift concentration factor (DCF) of the BRBF. Compared with the RW-BRBF, the moment and shear force demands of the rocking wall in the CRW-BRBF are smaller.
2016, 33(增刊): 95-100.
DOI: 10.6052/j.issn.1000-4750.2015.06.S016
Abstract：
This paper presents a nonlinear 3-D finite element (FE) study on the seismic behaviour of concrete-encased concrete-filled steel tubular column to steel beam joints with RC slabs. The FE model considers material and geometric nonlinearity, the cumulative damage of concrete and the interaction between concrete and steel. The proposed finite element model is verified by previous experimental results. The failure mechanism of such composite joints is analyzed using this model. It is found that a compression strut is formed in the concrete panel zone to resist the shear force together with the steel tube and reinforcement cage in the panel zone.
This paper presents a nonlinear 3-D finite element (FE) study on the seismic behaviour of concrete-encased concrete-filled steel tubular column to steel beam joints with RC slabs. The FE model considers material and geometric nonlinearity, the cumulative damage of concrete and the interaction between concrete and steel. The proposed finite element model is verified by previous experimental results. The failure mechanism of such composite joints is analyzed using this model. It is found that a compression strut is formed in the concrete panel zone to resist the shear force together with the steel tube and reinforcement cage in the panel zone.
2016, 33(增刊): 101-106.
DOI: 10.6052/j.issn.1000-4750.2015.05.S015
Abstract：
U-shaped steel plates (USPs) can be used for displacement restraining devices or dampers. Single push and push-pull static tests of four kinds of USP made by mild steel or hardened steel were completed. The tests show that thick USPs made by hardened steel fracture easily. Hardened steel USPs provide greater yield load and yield displacement and are more suitable for displacement restraining devices than mild steel ones. Hysteresis curves of hardened steel USPs showed typical spindle shape, and the load increased significantly after yielding. Hysteresis curves of mild steel USPs are parallelograms, and the load increased a little after yielding. Formulae of yield load, yield displacement and elastic stiffness for laminated U-shaped steel plates (LUSP) are derived. Four USPs and four LUSPs were designed and analyzed by Abaqus. The calculation of finite element fits the theory well. The ratios of LUSP to USP in terms of elastic stiffness, yield load and yield displacement are 1/n2, 1/n and n, respectively.
U-shaped steel plates (USPs) can be used for displacement restraining devices or dampers. Single push and push-pull static tests of four kinds of USP made by mild steel or hardened steel were completed. The tests show that thick USPs made by hardened steel fracture easily. Hardened steel USPs provide greater yield load and yield displacement and are more suitable for displacement restraining devices than mild steel ones. Hysteresis curves of hardened steel USPs showed typical spindle shape, and the load increased significantly after yielding. Hysteresis curves of mild steel USPs are parallelograms, and the load increased a little after yielding. Formulae of yield load, yield displacement and elastic stiffness for laminated U-shaped steel plates (LUSP) are derived. Four USPs and four LUSPs were designed and analyzed by Abaqus. The calculation of finite element fits the theory well. The ratios of LUSP to USP in terms of elastic stiffness, yield load and yield displacement are 1/n2, 1/n and n, respectively.
2016, 33(增刊): 107-112.
DOI: 10.6052/j.issn.1000-4750.2015.05.S047
Abstract：
To study the curvature ductility of a Prestressed High Strength Concrete Pile (PHC pile), the hysteretic performance of a PHC pile was analyzed with OpenSees under cyclic loading. The comparison between analytical and experimental results shows that the model is capable of accurately describing the cyclic behavior of a PHC pile. Finite element analysis was conducted to study the displacement ductility and curvature ductility of a PHC pile. The results indicated that the hysteretic loops pinched, and that the displacement ductility was bigger than 2.0. The maximum curvature of PHC piles should be controlled below 0.01 m-1, used in engineering for a magnitude 7 earthquake, and the ultimate curvature of a PHC pile should be bigger than 0.03 m-1, utilized in engineering for a magnitude 8 earthquake. The ultimate curvature of an existing PHC pile is bigger than 0.01 m-1, and the curvature ductility is above 2.8. It does not satisfy the curvature ductility demand of a major earthquake, and it needs to be improved.
To study the curvature ductility of a Prestressed High Strength Concrete Pile (PHC pile), the hysteretic performance of a PHC pile was analyzed with OpenSees under cyclic loading. The comparison between analytical and experimental results shows that the model is capable of accurately describing the cyclic behavior of a PHC pile. Finite element analysis was conducted to study the displacement ductility and curvature ductility of a PHC pile. The results indicated that the hysteretic loops pinched, and that the displacement ductility was bigger than 2.0. The maximum curvature of PHC piles should be controlled below 0.01 m-1, used in engineering for a magnitude 7 earthquake, and the ultimate curvature of a PHC pile should be bigger than 0.03 m-1, utilized in engineering for a magnitude 8 earthquake. The ultimate curvature of an existing PHC pile is bigger than 0.01 m-1, and the curvature ductility is above 2.8. It does not satisfy the curvature ductility demand of a major earthquake, and it needs to be improved.
2016, 33(增刊): 113-118.
DOI: 10.6052/j.issn.1000-4750.2015.03.S050
Abstract：
Earthquake-induced building collapses and casualties have been effectively controlled in the last two decades. However, earthquake-induced economic losses have continued to rise. Following the objective and procedure of next-generation performance-based seismic design, the economic loss prediction method proposed by FEMA-P58 (referred to as 'the FEMA-P58 method' hereinafter) is introduced in this study. The building seismic responses needed by the FEMA-P58 method for loss prediction are obtained by using multi-story concentrated-mass shear (MCS) models and non-linear time-history analysis (THA). A case study of three example buildings is performed to demonstrate the implementation of the proposed earthquake loss prediction method. The results show that when subjected to earthquakes of which the peak ground acceleration (PGA) are 0.2 g and 0.4 g, the earthquake loss mainly comes from repair costs of structural and drift-sensitive nonstructural components such as walls.
Earthquake-induced building collapses and casualties have been effectively controlled in the last two decades. However, earthquake-induced economic losses have continued to rise. Following the objective and procedure of next-generation performance-based seismic design, the economic loss prediction method proposed by FEMA-P58 (referred to as 'the FEMA-P58 method' hereinafter) is introduced in this study. The building seismic responses needed by the FEMA-P58 method for loss prediction are obtained by using multi-story concentrated-mass shear (MCS) models and non-linear time-history analysis (THA). A case study of three example buildings is performed to demonstrate the implementation of the proposed earthquake loss prediction method. The results show that when subjected to earthquakes of which the peak ground acceleration (PGA) are 0.2 g and 0.4 g, the earthquake loss mainly comes from repair costs of structural and drift-sensitive nonstructural components such as walls.
2016, 33(增刊): 119-124.
DOI: 10.6052/j.issn.1000-4750.2015.05.S053
Abstract：
The performance based design for structures should be based on the theory of probability; thus establishing a reasonable probabilistic seismic demand model of structures is very important. This paper aims at the regular girder bridges of highway. 8 representative samples are built by OpenSees software and the time history analyses are carried out with the selected 2390 earthquake records at three different site conditions by cloud approach. The spectral acceleration at the fundamental period with 5% damping (Sa) is selected as the ground motion intensity measure and the displacement drift ratio at the top of pier (D) is selected as the engineering demand parameter. The probability distribution between Sa and D for different bridge samples is obtained at three different site conditions. The result shows that the EDP follows an approximate lognormal distribution with different level of IM at three different site conditions; the relevant simplified probabilistic seismic demand model is built by the analysis results. Example of verification shows that the simplified probabilistic seismic demand model has a high calculation accuracy to simplify the calculation of probabilistic seismic demand for regular bridges.
The performance based design for structures should be based on the theory of probability; thus establishing a reasonable probabilistic seismic demand model of structures is very important. This paper aims at the regular girder bridges of highway. 8 representative samples are built by OpenSees software and the time history analyses are carried out with the selected 2390 earthquake records at three different site conditions by cloud approach. The spectral acceleration at the fundamental period with 5% damping (Sa) is selected as the ground motion intensity measure and the displacement drift ratio at the top of pier (D) is selected as the engineering demand parameter. The probability distribution between Sa and D for different bridge samples is obtained at three different site conditions. The result shows that the EDP follows an approximate lognormal distribution with different level of IM at three different site conditions; the relevant simplified probabilistic seismic demand model is built by the analysis results. Example of verification shows that the simplified probabilistic seismic demand model has a high calculation accuracy to simplify the calculation of probabilistic seismic demand for regular bridges.
2016, 33(增刊): 125-132.
DOI: 10.6052/j.issn.1000-4750.2015.04.S007
Abstract：
To replace the traditional clay-brick structure and adapt to the requirements for the development of energy-saving buildings, the reinforcement concrete (RC) shear wall structure with a single layer of web reinforcement and inclined steel bars was proposed. Compared with conventional RC shear wall structures with double layers of web reinforcement, it has the advantages of smaller wall thickness, simpler construction details and lower cost. The inclined steel bars can prevent base sliding so that the shear wall has higher anti-shearing and energy dissipation capacity. Cyclic loading tests on four low-rise RC shear walls with rectangle cross section were carried out. The inclined steel bars arrangement and axial force ratio were taken as the major test variables. Based on the experimental research, the failure characteristics, hysteresis properties, load-carrying capacity, ductility, stiffness and energy dissipation of each specimen were analyzed. The seismic performance of RC shear walls with inclined steel bars was compared with that of RC shear walls without the inclined steel bars. Calculative formulas for the load-carrying capacity of low-rise RC shear walls with single web reinforcement and inclined steel bars were also established. The research results indicate that the seismic performance of low-rise RC shear walls with inclined steel bars is better than that of shear walls without the inclined steel bars. So it is able to better satisfy the requirements of seismic design for multistory residential buildings.
To replace the traditional clay-brick structure and adapt to the requirements for the development of energy-saving buildings, the reinforcement concrete (RC) shear wall structure with a single layer of web reinforcement and inclined steel bars was proposed. Compared with conventional RC shear wall structures with double layers of web reinforcement, it has the advantages of smaller wall thickness, simpler construction details and lower cost. The inclined steel bars can prevent base sliding so that the shear wall has higher anti-shearing and energy dissipation capacity. Cyclic loading tests on four low-rise RC shear walls with rectangle cross section were carried out. The inclined steel bars arrangement and axial force ratio were taken as the major test variables. Based on the experimental research, the failure characteristics, hysteresis properties, load-carrying capacity, ductility, stiffness and energy dissipation of each specimen were analyzed. The seismic performance of RC shear walls with inclined steel bars was compared with that of RC shear walls without the inclined steel bars. Calculative formulas for the load-carrying capacity of low-rise RC shear walls with single web reinforcement and inclined steel bars were also established. The research results indicate that the seismic performance of low-rise RC shear walls with inclined steel bars is better than that of shear walls without the inclined steel bars. So it is able to better satisfy the requirements of seismic design for multistory residential buildings.
2016, 33(增刊): 133-137.
DOI: 10.6052/j.issn.1000-4750.2015.04.S056
Abstract：
In order to future understand the mechanical properties and calculation method of large shipyard industrial floor, the application analysis is conducted according to the road engineering multilayer elastic system and elastic foundation. According to the analysis result and mechanical property of floor, the improved multilayer elastic foundation model is put forward, which focuses on the floor block stiffness calculation method and interfacial sliding between floor layers. The numerical simulation results show that different regional block stiffness can adjust the deformation curve; the mechanical performance of floor is close to the plate member by considering interfacial sliding coefficient. The study described in this paper can provide a basis for simple, practical calculation method in future research.
In order to future understand the mechanical properties and calculation method of large shipyard industrial floor, the application analysis is conducted according to the road engineering multilayer elastic system and elastic foundation. According to the analysis result and mechanical property of floor, the improved multilayer elastic foundation model is put forward, which focuses on the floor block stiffness calculation method and interfacial sliding between floor layers. The numerical simulation results show that different regional block stiffness can adjust the deformation curve; the mechanical performance of floor is close to the plate member by considering interfacial sliding coefficient. The study described in this paper can provide a basis for simple, practical calculation method in future research.
2016, 33(增刊): 138-142.
DOI: 10.6052/j.issn.1000-4750.2015.04.S014
Abstract：
According to the structural characteristics and the specific used situation of both concrete bridge decks and steel bridge decks, a new type of steel and concrete composite bridge deck was presented. A reasonable section form of the composite bridge deck has been attained through the optimization of the main parameters of the composite section. The comparison between the bearing loads of the composite bridge deck, the concrete deck and the steel deck is conducted by theoretical analysis. It is demonstrated that it is feasible to use the orthotropic corrugated steel plate and concrete composite bridge deck on some projects. The full-scale loading test proves that the bending capacity of the composite bridge deck is 5.67 times that of the vehicle load action capacity in the current specification, which shows that considerable safety reservation was retained in the deck system by adopting the composite bridge deck. Based on the experimental results, the load behavior of the composite bridge deck in the serviceability limit state can be calculated according to the plane section assumption.
According to the structural characteristics and the specific used situation of both concrete bridge decks and steel bridge decks, a new type of steel and concrete composite bridge deck was presented. A reasonable section form of the composite bridge deck has been attained through the optimization of the main parameters of the composite section. The comparison between the bearing loads of the composite bridge deck, the concrete deck and the steel deck is conducted by theoretical analysis. It is demonstrated that it is feasible to use the orthotropic corrugated steel plate and concrete composite bridge deck on some projects. The full-scale loading test proves that the bending capacity of the composite bridge deck is 5.67 times that of the vehicle load action capacity in the current specification, which shows that considerable safety reservation was retained in the deck system by adopting the composite bridge deck. Based on the experimental results, the load behavior of the composite bridge deck in the serviceability limit state can be calculated according to the plane section assumption.
Abstract：
A finite element (FE) model of concrete filled square steel tubular column with internal profiled steel under standard fire conditions was developed using ABAQUS software. The FE model was verified with experimental results. The loading versus axial displacement curves were calculated in overall stage fire conditions, and loading versus lateral displacement curves were also studied. The stress distribution was analyzed in loading at the ambient stage, heating stage, cooling stage, and post fire stage. The results under loading at major axis and secondary axis were compared. The main parameters that affected the residual bearing capacity coefficients after exposure to full stage fire conditions were analyzed. The results show that the fire loading ratio, fire duration time ratio, and the slenderness ratio of column have significant effect on the residual bearing capacity.
A finite element (FE) model of concrete filled square steel tubular column with internal profiled steel under standard fire conditions was developed using ABAQUS software. The FE model was verified with experimental results. The loading versus axial displacement curves were calculated in overall stage fire conditions, and loading versus lateral displacement curves were also studied. The stress distribution was analyzed in loading at the ambient stage, heating stage, cooling stage, and post fire stage. The results under loading at major axis and secondary axis were compared. The main parameters that affected the residual bearing capacity coefficients after exposure to full stage fire conditions were analyzed. The results show that the fire loading ratio, fire duration time ratio, and the slenderness ratio of column have significant effect on the residual bearing capacity.
2016, 33(增刊): 150-155.
DOI: 10.6052/j.issn.1000-4750.2015.05.S013
Abstract：
There are three kinds of methods for modeling and analyzing the existing curved girder bridges. They are single-beam method, grillage method and entity method. According to the previous literature, the single-beam method is not so accurate, but it is generally popular because of its higher speed in analyzing and higher efficiency in calculating. So the research of the single-beam method has practical significance. Central angle is the key factor to determine whether the curved girder bridge can be analyzed with the single-beam method. According to A ramp bridge of Jingkai overpass, several models of curved girder bridges with different spans, deck widths and central angles are built and compared using the grillage method and the single-beam method in this paper. Then by taking 10% as the control index, the applicable condition of the single-beam method is obtained.
There are three kinds of methods for modeling and analyzing the existing curved girder bridges. They are single-beam method, grillage method and entity method. According to the previous literature, the single-beam method is not so accurate, but it is generally popular because of its higher speed in analyzing and higher efficiency in calculating. So the research of the single-beam method has practical significance. Central angle is the key factor to determine whether the curved girder bridge can be analyzed with the single-beam method. According to A ramp bridge of Jingkai overpass, several models of curved girder bridges with different spans, deck widths and central angles are built and compared using the grillage method and the single-beam method in this paper. Then by taking 10% as the control index, the applicable condition of the single-beam method is obtained.
2016, 33(增刊): 156-160.
DOI: 10.6052/j.issn.1000-4750.2015.05.S017
Abstract：
A steel coupling beam equipped with a friction damper in the mid span is proposed for the use in high-rise buildings. Damage is only likely to take place on the brake pad-to-steel friction interface while the other parts of the steel coupling beam are expected to remain elastic under major earthquakes. High-strength bolts and disc springs are placed in series to pressure multiple brake pad-to-steel interfaces to reduce the impact of temperature stress on the friction force. One can easily release the residual deformation after earthquake by loosening the bolts, either for damage inspection or for replacement if necessary. Cyclic loading tests on steel coupling beams with the proposed friction damper were conducted to show the reliable frictional behavior of the chosen material and superior energy dissipating capacity of the friction damper. The well-defined frictional force without much overstrength makes it easier to design the strength demand for adjacent elements and joints.
A steel coupling beam equipped with a friction damper in the mid span is proposed for the use in high-rise buildings. Damage is only likely to take place on the brake pad-to-steel friction interface while the other parts of the steel coupling beam are expected to remain elastic under major earthquakes. High-strength bolts and disc springs are placed in series to pressure multiple brake pad-to-steel interfaces to reduce the impact of temperature stress on the friction force. One can easily release the residual deformation after earthquake by loosening the bolts, either for damage inspection or for replacement if necessary. Cyclic loading tests on steel coupling beams with the proposed friction damper were conducted to show the reliable frictional behavior of the chosen material and superior energy dissipating capacity of the friction damper. The well-defined frictional force without much overstrength makes it easier to design the strength demand for adjacent elements and joints.
2016, 33(增刊): 161-167.
DOI: 10.6052/j.issn.1000-4750.2015.04.S018
Abstract：
A technique of a steel reinforced concrete consolidated hinged joint in prefabricated slab bridges was proposed. To research the consolidation effect of this new method, specimens of different reinforcement methods were tested with static and fatigue loading. Based on the experimental results, it is found that the hinged joint specimens with SRC exhibited better bearing capacity, global deformation capacity and fatigue capacity than other reinforced joints. Meanwhile, based on the damage phenomena, force-deformation relationships observed during static tests on different ways of reinforced joints, two typical failure patterns were identified, that is, interfacial flexural failure and interfacial flexural-shear failure. Two analytical strength models were established corresponding to the aforementioned two failure patterns. Error analysis shows that these two models give accurate and reliable predictions, which can provide practical references for the seismic design of joints.
A technique of a steel reinforced concrete consolidated hinged joint in prefabricated slab bridges was proposed. To research the consolidation effect of this new method, specimens of different reinforcement methods were tested with static and fatigue loading. Based on the experimental results, it is found that the hinged joint specimens with SRC exhibited better bearing capacity, global deformation capacity and fatigue capacity than other reinforced joints. Meanwhile, based on the damage phenomena, force-deformation relationships observed during static tests on different ways of reinforced joints, two typical failure patterns were identified, that is, interfacial flexural failure and interfacial flexural-shear failure. Two analytical strength models were established corresponding to the aforementioned two failure patterns. Error analysis shows that these two models give accurate and reliable predictions, which can provide practical references for the seismic design of joints.
Abstract：
Durability deterioration caused by chloride penetration is one of the most serious problems of marine concrete structures in chloride environment. This paper explores the application of empirical durability deterioration model to marine concrete structures, utilizing the in-situ test data from durability inspection and assessment reports in South China. This paper discusses the environmental load (Cs) model of concrete structures subjected to chloride penetration, and determines the probability distribution, mean and standard deviation of Cs by regression analysis based on the Fick's Second Law. Finally, this paper adopts a Monte Carlo Simulation program to compare the obtained environmental load model with existing ones, and discusses the influence of environmental load model on durability analysis.
Durability deterioration caused by chloride penetration is one of the most serious problems of marine concrete structures in chloride environment. This paper explores the application of empirical durability deterioration model to marine concrete structures, utilizing the in-situ test data from durability inspection and assessment reports in South China. This paper discusses the environmental load (Cs) model of concrete structures subjected to chloride penetration, and determines the probability distribution, mean and standard deviation of Cs by regression analysis based on the Fick's Second Law. Finally, this paper adopts a Monte Carlo Simulation program to compare the obtained environmental load model with existing ones, and discusses the influence of environmental load model on durability analysis.
2016, 33(增刊): 173-178.
DOI: 10.6052/j.issn.1000-4750.2015.05.S021
Abstract：
A novel self-equilibrium cable-strut tensile strucuture called torus-dome was proposed. The system consists of a surrounding tensegrity torus and a central Levy type cable dome. Because of the low redundancy, the anti-collapse performance of torus-dome structures under local cable rupture is studied. Considering the rupture of cables in the tensegrity torus, the constraint reduction of tensegrity around the cable dome is systematically discussed. The impacts on the overall structural stiffness and the internal force redistribution of cables and struts are also discussed. Based on the explicit dynamic integration method, the behavior of the remaining structure was investigated by ANSYS/LS-DYNA software package. Alternative load path method was applied to simulate the structural responses, including the nodal displacements and the internal forces of cables and struts. The invalid cables are divided into four groups and the anti-collapse capacity of the remaining structure is evaluated. The results indicate that the structure has good performance to resist progressive collapse. The conclusions will provide a reference of engineering application and safety assessment for such structures.
A novel self-equilibrium cable-strut tensile strucuture called torus-dome was proposed. The system consists of a surrounding tensegrity torus and a central Levy type cable dome. Because of the low redundancy, the anti-collapse performance of torus-dome structures under local cable rupture is studied. Considering the rupture of cables in the tensegrity torus, the constraint reduction of tensegrity around the cable dome is systematically discussed. The impacts on the overall structural stiffness and the internal force redistribution of cables and struts are also discussed. Based on the explicit dynamic integration method, the behavior of the remaining structure was investigated by ANSYS/LS-DYNA software package. Alternative load path method was applied to simulate the structural responses, including the nodal displacements and the internal forces of cables and struts. The invalid cables are divided into four groups and the anti-collapse capacity of the remaining structure is evaluated. The results indicate that the structure has good performance to resist progressive collapse. The conclusions will provide a reference of engineering application and safety assessment for such structures.
2016, 33(增刊): 179-183.
DOI: 10.6052/j.issn.1000-4750.2015.05.S023
Abstract：
Based on the nonlienar dynamics model of a single pile subjected to transverse excitation, the frequency-response equation of the primary resonance of the pile foundation is obtained by employing the motion equation of the pile and the method of multiple scales. Using the Vlasov foundation model and the empirical method to determine the pile group interaction coefficients, the modified elastic foundation parameters can be obtained. The influence of pile group effect on the nonlinear response of pile groups is examined by means of the frequency-response curves, the evolution of transverse displacement and the change of shear force of piles. Meanwhile, the effect of the boundary conditions on the pile group effect is also investigated. The results show that the pile group effect leads to complex behavior that exists in the primary resonance response of piles. Moreover, the influence of pile group effect on the dynamic response of piles is closely related to the main factors such as the boundary condition and the positional relationship of piles.
Based on the nonlienar dynamics model of a single pile subjected to transverse excitation, the frequency-response equation of the primary resonance of the pile foundation is obtained by employing the motion equation of the pile and the method of multiple scales. Using the Vlasov foundation model and the empirical method to determine the pile group interaction coefficients, the modified elastic foundation parameters can be obtained. The influence of pile group effect on the nonlinear response of pile groups is examined by means of the frequency-response curves, the evolution of transverse displacement and the change of shear force of piles. Meanwhile, the effect of the boundary conditions on the pile group effect is also investigated. The results show that the pile group effect leads to complex behavior that exists in the primary resonance response of piles. Moreover, the influence of pile group effect on the dynamic response of piles is closely related to the main factors such as the boundary condition and the positional relationship of piles.
2016, 33(增刊): 184-189.
DOI: 10.6052/j.issn.1000-4750.2015.04.S027
Abstract：
The model of multiple cracking of high toughness concrete is established by analyzing the interface stress of fiber in the cement matrix. Based on this model, the effects of friction bond strength, chemical bond strength, matrix cracking strength and elastic modulus of fiber on the strain and crack width at the end of multiple-cracking zone are analyzed. The analysis results show that the strain and the crack width decrease with the increase of the friction bond strength; the strain increases and the crack width decreases with the increase of the chemical bond strength; the strain and the crack width increase with the increase of the matrix cracking strength; the strain and the crack width decrease with the increase of the elastic modulus of fiber. The crack control ability of high toughness concrete with initial crack defects is researched through direct tensile test. The notched specimens are used in the research. The test results show that, when the initial crack-depth ratio is 0.2, the ultimate stress is 5.3MPa at the notch and is 4.3MPa at the non-cutting position, and the phenomenon of multiple cracking appears in the whole specimen, and the crack width is controlled in less than 0.1mm. When the initial crack-depth ratio is 0.4, the ultimate stress is 5.8MPa at the notch and is 3.5MPa at the non-cutting position, and the development of cracks is not controlled effectively by the fibers at the fracture plane. Therefore, only some similar arc cracks appear near the notch of the specimen.
The model of multiple cracking of high toughness concrete is established by analyzing the interface stress of fiber in the cement matrix. Based on this model, the effects of friction bond strength, chemical bond strength, matrix cracking strength and elastic modulus of fiber on the strain and crack width at the end of multiple-cracking zone are analyzed. The analysis results show that the strain and the crack width decrease with the increase of the friction bond strength; the strain increases and the crack width decreases with the increase of the chemical bond strength; the strain and the crack width increase with the increase of the matrix cracking strength; the strain and the crack width decrease with the increase of the elastic modulus of fiber. The crack control ability of high toughness concrete with initial crack defects is researched through direct tensile test. The notched specimens are used in the research. The test results show that, when the initial crack-depth ratio is 0.2, the ultimate stress is 5.3MPa at the notch and is 4.3MPa at the non-cutting position, and the phenomenon of multiple cracking appears in the whole specimen, and the crack width is controlled in less than 0.1mm. When the initial crack-depth ratio is 0.4, the ultimate stress is 5.8MPa at the notch and is 3.5MPa at the non-cutting position, and the development of cracks is not controlled effectively by the fibers at the fracture plane. Therefore, only some similar arc cracks appear near the notch of the specimen.
2016, 33(增刊): 190-195.
DOI: 10.6052/j.issn.1000-4750.2015.05.S028
Abstract：
To study the shear performance of high-strength reinforced reactive powder concrete simply supported beams without stirrups, based on the test results of four RPC beams' shear failure experiment under concentrated load, the influence of steel fiber volume ratio on diagonal crack development pattern, load-deflection curves, shear toughness of beams and diagonal crack width is analyzed. Results show that steel fiber can reduce the diagonal crack spacing, increase the shear-compression zone height, and improve the shear ductility of the beam. Steel fiber has less effect on shear toughness of beams at the initial stage of loading, but it has great effect on shear toughness of beams after the initial yield point. The greater the steel fiber volume ratio is, the smaller the diagonal crack width and the greater the peak load are. Its influence on peak load is more obvious than the effect on mid-span deflection.
To study the shear performance of high-strength reinforced reactive powder concrete simply supported beams without stirrups, based on the test results of four RPC beams' shear failure experiment under concentrated load, the influence of steel fiber volume ratio on diagonal crack development pattern, load-deflection curves, shear toughness of beams and diagonal crack width is analyzed. Results show that steel fiber can reduce the diagonal crack spacing, increase the shear-compression zone height, and improve the shear ductility of the beam. Steel fiber has less effect on shear toughness of beams at the initial stage of loading, but it has great effect on shear toughness of beams after the initial yield point. The greater the steel fiber volume ratio is, the smaller the diagonal crack width and the greater the peak load are. Its influence on peak load is more obvious than the effect on mid-span deflection.
2016, 33(增刊): 196-200.
DOI: 10.6052/j.issn.1000-4750.2015.05.S030
Abstract：
Due to the advantage of overall mechanical performance of concrete box girder, it could be a good choice to solve the problem of limited urban land resources and traffic jam by taking its roof and floor as deck system to achieve double deck traffic. A double traffic concrete box girder model with a scale of 1:6 was designed. Tests under the double uniformly distributed load in elastic state, and bending failure tests under the concentrated load were carried out. The development of stress and strain, load deflection curve of key section, the flexural bearing capacity and failure mode was studied. The results show that there is different shear lag phenomenon under different load conditions in the elastic working state. In double deck concentrated load experiment, the test confirmed the bending process of double traffic concrete box girder with large wide-span ratio and depth-span ratio can be divided into the three phases, i.e., elastic, elastic-plastic and destruction phases. This research is expected to provide experimental data and reference for design and application of double transportation concrete box girder bridge.
Due to the advantage of overall mechanical performance of concrete box girder, it could be a good choice to solve the problem of limited urban land resources and traffic jam by taking its roof and floor as deck system to achieve double deck traffic. A double traffic concrete box girder model with a scale of 1:6 was designed. Tests under the double uniformly distributed load in elastic state, and bending failure tests under the concentrated load were carried out. The development of stress and strain, load deflection curve of key section, the flexural bearing capacity and failure mode was studied. The results show that there is different shear lag phenomenon under different load conditions in the elastic working state. In double deck concentrated load experiment, the test confirmed the bending process of double traffic concrete box girder with large wide-span ratio and depth-span ratio can be divided into the three phases, i.e., elastic, elastic-plastic and destruction phases. This research is expected to provide experimental data and reference for design and application of double transportation concrete box girder bridge.
2016, 33(增刊): 201-206.
DOI: 10.6052/j.issn.1000-4750.2015.05.S031
Abstract：
Based on static loading test analysis, the tensile-compressive fatigue tests of wood in ancient buildings were carried out using the MTS858 machine with a frequency of 2 Hz. The result shows that most specimens failure along the veins of wood. The stress-strain and deformation characteristics of the specimens were analyzed. The stress-strain curves become sparse gradually and the tensile-strain become significant due to the increase of upper stress radio. The deformation growth of the specimen can be divided into three phases similar to the development of fatigue deformation and damage of material, namely, the occurrence of damage, the stable propagation of damage and the failure. S-N relationship of wood sample is plotted with an index function fitted. The upper limit of the stress ratio of ancient wood is suggested to be 0.30.
Based on static loading test analysis, the tensile-compressive fatigue tests of wood in ancient buildings were carried out using the MTS858 machine with a frequency of 2 Hz. The result shows that most specimens failure along the veins of wood. The stress-strain and deformation characteristics of the specimens were analyzed. The stress-strain curves become sparse gradually and the tensile-strain become significant due to the increase of upper stress radio. The deformation growth of the specimen can be divided into three phases similar to the development of fatigue deformation and damage of material, namely, the occurrence of damage, the stable propagation of damage and the failure. S-N relationship of wood sample is plotted with an index function fitted. The upper limit of the stress ratio of ancient wood is suggested to be 0.30.
2016, 33(增刊): 207-213.
DOI: 10.6052/j.issn.1000-4750.2015.05.S041
Abstract：
The repair of Eccentrically Braced Steel Frames with replaceable link is convenient and economical compared with traditional Eccentrically Braced Steel Frames, and the research on replaceable link is limited worldwidely. In the paper, finite element analysis was performed for the one-way loading and cycle loading of eight replaceable link beams with different parameters using ABAQUS. Analysis results indicate that the space between ribbed stiffeners has small influence on the bearing capacity of replaceable link beams and the increase of replaceable link beam length causes the decrease of bearing capacity; Under monotonic loading, large displacement ductility coefficients and large angle ductility coefficients of replaceable link beams were obseved, showing good ductility; Under cyclic loading, the hysteresis curves of replaceable links are plumper with no pinch, showing good energy dissipation property.
The repair of Eccentrically Braced Steel Frames with replaceable link is convenient and economical compared with traditional Eccentrically Braced Steel Frames, and the research on replaceable link is limited worldwidely. In the paper, finite element analysis was performed for the one-way loading and cycle loading of eight replaceable link beams with different parameters using ABAQUS. Analysis results indicate that the space between ribbed stiffeners has small influence on the bearing capacity of replaceable link beams and the increase of replaceable link beam length causes the decrease of bearing capacity; Under monotonic loading, large displacement ductility coefficients and large angle ductility coefficients of replaceable link beams were obseved, showing good ductility; Under cyclic loading, the hysteresis curves of replaceable links are plumper with no pinch, showing good energy dissipation property.
2016, 33(增刊): 214-218,226.
DOI: 10.6052/j.issn.1000-4750.2015.05.S043
Abstract：
Six singly symmetric H-section beams welded by Q460GJ flame-cut steel plates were tested under a concentrated force at middle-span. The tested beams were laterally restrained at middle-span. Compared with the design strength from Code for Design of Steel Structures (GB50017-2003) and the latest version of the steel structure design code (GB50017-201X), it is found that the test results are very close to the strength calculated by GB50017-2003 and the resistance calculated by GB50017-201X is more conservative.
Six singly symmetric H-section beams welded by Q460GJ flame-cut steel plates were tested under a concentrated force at middle-span. The tested beams were laterally restrained at middle-span. Compared with the design strength from Code for Design of Steel Structures (GB50017-2003) and the latest version of the steel structure design code (GB50017-201X), it is found that the test results are very close to the strength calculated by GB50017-2003 and the resistance calculated by GB50017-201X is more conservative.
Abstract：
According to one of the Beijing subway section which crossed the high-speed railway, the impact of choosing different shield parameters and tunneling support conditions on the force and deformation of pile group is analyzed. In the pre-engineering test section of the tunnel excavation, the relationship between the shield parameters and equivalent layer in finite element calculation is established. Six different construction conditions of different equivalent layers and the existence of isolated piles are analyzed. The effect of optimizing the shield parameters and using isolated pile on the pile group in shield tunnel excavation is described. The analysis result indicates that: 1) Optimizing the shield parameters and using isolated pile has a significant effect on controlling the bending moment, horizontal displacement, axial force and settlement. However, the isolated pile has better effect than shield parameter optimization; 2) The isolated pile basically eliminates the dynamic changes in the moment of the pile during tunneling. It also makes uniform the effect on the displacement of the pile group during tunneling; 3) The monitoring results show that the numerical results reflect the actual excavation process well. The final calculated settlement value is very close to the measured cumulative value.
According to one of the Beijing subway section which crossed the high-speed railway, the impact of choosing different shield parameters and tunneling support conditions on the force and deformation of pile group is analyzed. In the pre-engineering test section of the tunnel excavation, the relationship between the shield parameters and equivalent layer in finite element calculation is established. Six different construction conditions of different equivalent layers and the existence of isolated piles are analyzed. The effect of optimizing the shield parameters and using isolated pile on the pile group in shield tunnel excavation is described. The analysis result indicates that: 1) Optimizing the shield parameters and using isolated pile has a significant effect on controlling the bending moment, horizontal displacement, axial force and settlement. However, the isolated pile has better effect than shield parameter optimization; 2) The isolated pile basically eliminates the dynamic changes in the moment of the pile during tunneling. It also makes uniform the effect on the displacement of the pile group during tunneling; 3) The monitoring results show that the numerical results reflect the actual excavation process well. The final calculated settlement value is very close to the measured cumulative value.
2016, 33(增刊): 227-233.
DOI: 10.6052/j.issn.1000-4750.2015.05.S046
Abstract：
In order to obtain the seismic wave of the bedrock in a thick soft soil site, the inversion program based on wave propagation theory and equivalent linearization technique is developed. Six bedrock acceleration time histories under typical Shanghai soft soil are inverted by a self-compiled inversion program, and they are validated by the comparison with forwarded simulation. Then, the finite element model of the subway station considering soil-structure dynamic interaction is established, and the bedrock time history inverted El-Centro wave is selected as input motion to conduct the dynamic response analysis of an underground structure in a soft soil site. The analysis results show that: the seismic wave inversion program can attain the precise inverted bedrock motions; for different types of seismic waves, the ratios of peak surface acceleration to bedrock acceleration are significantly different; compared to superstructures, an underground structure has a larger horizontal displacement, but the relative horizontal displacement between top and bottom plates is small.
In order to obtain the seismic wave of the bedrock in a thick soft soil site, the inversion program based on wave propagation theory and equivalent linearization technique is developed. Six bedrock acceleration time histories under typical Shanghai soft soil are inverted by a self-compiled inversion program, and they are validated by the comparison with forwarded simulation. Then, the finite element model of the subway station considering soil-structure dynamic interaction is established, and the bedrock time history inverted El-Centro wave is selected as input motion to conduct the dynamic response analysis of an underground structure in a soft soil site. The analysis results show that: the seismic wave inversion program can attain the precise inverted bedrock motions; for different types of seismic waves, the ratios of peak surface acceleration to bedrock acceleration are significantly different; compared to superstructures, an underground structure has a larger horizontal displacement, but the relative horizontal displacement between top and bottom plates is small.
2016, 33(增刊): 234-238.
DOI: 10.6052/j.issn.1000-4750.2015.04.S048
Abstract：
According to the actual operating environment and structural stress condition, the online structural monitoring system is established on a half-through steel arch bridge with single arch face. On the basis of monitoring records, the data of the strain, acceleration, temperature and humidity are preliminarily analyzed. The system establishing practice and test data analysis could provide effective references to structural analysis of similar bridge and practical application of the structural online monitoring system.
According to the actual operating environment and structural stress condition, the online structural monitoring system is established on a half-through steel arch bridge with single arch face. On the basis of monitoring records, the data of the strain, acceleration, temperature and humidity are preliminarily analyzed. The system establishing practice and test data analysis could provide effective references to structural analysis of similar bridge and practical application of the structural online monitoring system.
2016, 33(增刊): 239-243,250.
DOI: 10.6052/j.issn.1000-4750.2015.05.S049
Abstract：
A sectional model wind tunnel test of a flat box girder in smooth flow was performed and the spanwise correlation of vortex-induced forces was investigated. The study results show that spanwise correlation of lift force becomes weakened with the decrease of vibration amplitudes at vibration amplitude-decreasing stage in lock-in range. At vibration amplitude-increasing stage in lock-in range, with the increase of vibration amplitudes, spanwise correlation of lift force becomes strengthened first and then weakened. The maximum value of spanwise correlation coefficient appears in a wind speed in vibration amplitude-increasing stage, rather than the wind speed corresponding to maximum vibration amplitude; In lock-in range, spanwise correlation of vortex-induced forces of flat box girder is dependent on both vibration amplitude and wind speed in smooth flow.
A sectional model wind tunnel test of a flat box girder in smooth flow was performed and the spanwise correlation of vortex-induced forces was investigated. The study results show that spanwise correlation of lift force becomes weakened with the decrease of vibration amplitudes at vibration amplitude-decreasing stage in lock-in range. At vibration amplitude-increasing stage in lock-in range, with the increase of vibration amplitudes, spanwise correlation of lift force becomes strengthened first and then weakened. The maximum value of spanwise correlation coefficient appears in a wind speed in vibration amplitude-increasing stage, rather than the wind speed corresponding to maximum vibration amplitude; In lock-in range, spanwise correlation of vortex-induced forces of flat box girder is dependent on both vibration amplitude and wind speed in smooth flow.
2016, 33(增刊): 244-250.
DOI: 10.6052/j.issn.1000-4750.2015.05.S054
Abstract：
The seismic response of Five-span isolated continuous bridges under far field and near field long-period ground motions are discussed. Lead rubber bearings (LRB) or friction pendulum bearings (FPB) are used in the bridges and the ground motions have significant pulse impacts. Comparing with an aseismic structure, the isolation effects of two isolated bridges are declined, and the seismic performance of an FPB structure is better than that of an LRB structure. Furthermore, the far field long-period ground motion has an adverse effect on an isolated continuous bridge with LRB in view of the larger displacement and internal force comparing with FPB bridges.
The seismic response of Five-span isolated continuous bridges under far field and near field long-period ground motions are discussed. Lead rubber bearings (LRB) or friction pendulum bearings (FPB) are used in the bridges and the ground motions have significant pulse impacts. Comparing with an aseismic structure, the isolation effects of two isolated bridges are declined, and the seismic performance of an FPB structure is better than that of an LRB structure. Furthermore, the far field long-period ground motion has an adverse effect on an isolated continuous bridge with LRB in view of the larger displacement and internal force comparing with FPB bridges.
2016, 33(增刊): 251-256.
DOI: 10.6052/j.issn.1000-4750.2015.05.S055
Abstract：
During post-earthquake reconstruction, bridges and other key infrastructures should be quickly repaired or reconstructed for travel demand. During construction, integrated structural system of a bridge has not formed yet and aftershocks occurred at a high frequency in a short time, which would threaten the security of the structures. By the statistical results of aftershock occurrence in the early stage after the main shock, the current study regressed the probabilistic model of aftershock occurrence, which is based on the Probabilistic Seismic Hazard Analysis (PSHA), and proposed a fragility index in the process of the bridge construction and considered the calculation model of fragility in construction process. Take Wenchuan earthquake as an example. By analyzing the fragility of high piers in a mountainous area during the whole construction, it is shown that cracking damage easily occurs during the bridge construction in aftershock area and can affect the durability of the structure. Therefore, it is necessary to make a special assessment on the risk of earthquake damage to bridges under construction after strong shocks.
During post-earthquake reconstruction, bridges and other key infrastructures should be quickly repaired or reconstructed for travel demand. During construction, integrated structural system of a bridge has not formed yet and aftershocks occurred at a high frequency in a short time, which would threaten the security of the structures. By the statistical results of aftershock occurrence in the early stage after the main shock, the current study regressed the probabilistic model of aftershock occurrence, which is based on the Probabilistic Seismic Hazard Analysis (PSHA), and proposed a fragility index in the process of the bridge construction and considered the calculation model of fragility in construction process. Take Wenchuan earthquake as an example. By analyzing the fragility of high piers in a mountainous area during the whole construction, it is shown that cracking damage easily occurs during the bridge construction in aftershock area and can affect the durability of the structure. Therefore, it is necessary to make a special assessment on the risk of earthquake damage to bridges under construction after strong shocks.
2016, 33(增刊): 257-261.
DOI: 10.6052/j.issn.1000-4750.2015.04.S057
Abstract：
A novel Information-gap-based (Info-gap) damage detection method for uncertainty quantification is proposed in this study. The modal shapes of structures are selected as damage indices, and the uncertainty level of these indices caused by measurement errors and modal identification are described by Info-gap model. The decision function is defined as the distance of modal shape between health and unknown condition of structures, and then the solution of this function is translated into an optimization problem. The results from a numerical simulation and lab-scale structure show that the location and severity of damage can be successfully identified.
A novel Information-gap-based (Info-gap) damage detection method for uncertainty quantification is proposed in this study. The modal shapes of structures are selected as damage indices, and the uncertainty level of these indices caused by measurement errors and modal identification are described by Info-gap model. The decision function is defined as the distance of modal shape between health and unknown condition of structures, and then the solution of this function is translated into an optimization problem. The results from a numerical simulation and lab-scale structure show that the location and severity of damage can be successfully identified.
2016, 33(增刊): 262-265.
DOI: 10.6052/j.issn.1000-4750.2015.04.S008
Abstract：
Different battery arrangement for large aspect ratio solar-powered aircraft propulsion system can affect the natural frequency and vibration response of wing structure. Large vibration response will affect the safety of aircraft. Firstly, three-dimensional model of the wing is established and the theory is analyzed. Then finite element analysis is performed. The study shows that the results of theoretical analysis are consistent with the results of finite element analysis. Battery position has significant influence on the first order torsional frequency of wing structure, and a more forward battery leads to smaller vibration response. The study results can be used as a basic reference of battery arrangement.
Different battery arrangement for large aspect ratio solar-powered aircraft propulsion system can affect the natural frequency and vibration response of wing structure. Large vibration response will affect the safety of aircraft. Firstly, three-dimensional model of the wing is established and the theory is analyzed. Then finite element analysis is performed. The study shows that the results of theoretical analysis are consistent with the results of finite element analysis. Battery position has significant influence on the first order torsional frequency of wing structure, and a more forward battery leads to smaller vibration response. The study results can be used as a basic reference of battery arrangement.
2016, 33(增刊): 266-269,295.
DOI: 10.6052/j.issn.1000-4750.2015.03.S034
Abstract：
The deformation mechanism of a ship bottom floor when the ship runs aground over sharp rocks is analyzed, based on plastic mechanics theory and numerical simulation technique. Numerical simulation using the code LS_DYNA is first conducted for understanding the behavior of bottom floors and establishing the analytical models. Then the analytical expressions of the resistance of a bottom floor are derived and the accuracy is verified by numerical simulations. The proposed analytical method can be used to predict the ship bottom structure crashworthiness during the structural design phase.
The deformation mechanism of a ship bottom floor when the ship runs aground over sharp rocks is analyzed, based on plastic mechanics theory and numerical simulation technique. Numerical simulation using the code LS_DYNA is first conducted for understanding the behavior of bottom floors and establishing the analytical models. Then the analytical expressions of the resistance of a bottom floor are derived and the accuracy is verified by numerical simulations. The proposed analytical method can be used to predict the ship bottom structure crashworthiness during the structural design phase.
2016, 33(增刊): 270-274.
DOI: 10.6052/j.issn.1000-4750.2015.05.S035
Abstract：
The purpose of the paper is to design a single-shaft folding high wing for "Dream IV" Light Sport Aircraft. A simplified wing model was established, and analytic geometry principles were used to analysis it. And then the structural separation surface position was adjusted according to the results to eliminate the constructive interference of the airframe structure. With the results from the simplified model, a more realistic model of the wing was founded by Catia. Through the DMU in Catia, the interference of inner and outer sections of the wing was eliminated, the detailed structural design of ear piece was made, and the fixed issue of the wing before and after folding was solved. The design was finally applied to "Dream IV" LSA, in which only one rotation was needed to package the wing, demonstrating the advantages of fast and convenient package, simplified structure and less weight.
The purpose of the paper is to design a single-shaft folding high wing for "Dream IV" Light Sport Aircraft. A simplified wing model was established, and analytic geometry principles were used to analysis it. And then the structural separation surface position was adjusted according to the results to eliminate the constructive interference of the airframe structure. With the results from the simplified model, a more realistic model of the wing was founded by Catia. Through the DMU in Catia, the interference of inner and outer sections of the wing was eliminated, the detailed structural design of ear piece was made, and the fixed issue of the wing before and after folding was solved. The design was finally applied to "Dream IV" LSA, in which only one rotation was needed to package the wing, demonstrating the advantages of fast and convenient package, simplified structure and less weight.
2016, 33(增刊): 275-282.
DOI: 10.6052/j.issn.1000-4750.2015.06.S036
Abstract：
The finite element contact analysis on two-dimensional cylinder-flat models was conducted. The results indicate that the critical amplitude of strain load transforming partial slip condition into gross slip condition is approximately proportional to the normal force. The fretting wear of zircaloy was simulated by secondary development of finite element based on Archard model and multilayer nodes update method. It is discovered that the wear rate of zircaloy increases rapidly under gross slip condition and increases slowly under partial slip condition with the increase of amplitude of strain load. The wear rate firstly increases and then decreases as the normal force under gross slip condition increases. Under partial slip condition, the wear rate decreases slowly with the increase of normal force.
The finite element contact analysis on two-dimensional cylinder-flat models was conducted. The results indicate that the critical amplitude of strain load transforming partial slip condition into gross slip condition is approximately proportional to the normal force. The fretting wear of zircaloy was simulated by secondary development of finite element based on Archard model and multilayer nodes update method. It is discovered that the wear rate of zircaloy increases rapidly under gross slip condition and increases slowly under partial slip condition with the increase of amplitude of strain load. The wear rate firstly increases and then decreases as the normal force under gross slip condition increases. Under partial slip condition, the wear rate decreases slowly with the increase of normal force.
2016, 33(增刊): 283-289.
DOI: 10.6052/j.issn.1000-4750.2015.05.S003
Abstract：
Wind load is one of the main loads on ground radomes, which affects the strength and stability of the radome and also affects the accuracy of the radar antenna, resulting in partial focal point deviation and defocusing. Thus, the research on radomes under wind load is an important aspect in the design of radomes. In this paper, SolidWorks is used to establish the radome gemotory model. After meshing the model in ANSYS ICEM CFD, the radome is imported into FLUENT to calculate the flow field under wind load. Three turbulence models, including the standard model, RNG model and Reliable model, are adopted to calculate the coefficient of aerodynamic characteristics and pressure distribution in FLUENT. As a result, it can be found that the RNG model is more suitable for the simulation. Moreover, a wind tunnel test is performed to verify the simulation results under wind speed of 20 m/s, 28 m/s and 36 m/s, respectively. Then, the wind pressure on the radome surface in the simulation and experiments is compared. It is found that the pressure curves on the windward side of the radome in the simulation match the experiment very well, while the results obtained on the cover body side and leeward side show a deviation. Furthermore, wind pressure on the radome appears to increase with the increase of wind speed. According to the comparison results obtained in the numerical simulation and wind tunnel trials, it can be concluded that the application of the numerical simulation in radome design fields plays an important role, and the data obtained in the simulation is also meaningful to direct wind tunnel test in real engineering fields.
Wind load is one of the main loads on ground radomes, which affects the strength and stability of the radome and also affects the accuracy of the radar antenna, resulting in partial focal point deviation and defocusing. Thus, the research on radomes under wind load is an important aspect in the design of radomes. In this paper, SolidWorks is used to establish the radome gemotory model. After meshing the model in ANSYS ICEM CFD, the radome is imported into FLUENT to calculate the flow field under wind load. Three turbulence models, including the standard model, RNG model and Reliable model, are adopted to calculate the coefficient of aerodynamic characteristics and pressure distribution in FLUENT. As a result, it can be found that the RNG model is more suitable for the simulation. Moreover, a wind tunnel test is performed to verify the simulation results under wind speed of 20 m/s, 28 m/s and 36 m/s, respectively. Then, the wind pressure on the radome surface in the simulation and experiments is compared. It is found that the pressure curves on the windward side of the radome in the simulation match the experiment very well, while the results obtained on the cover body side and leeward side show a deviation. Furthermore, wind pressure on the radome appears to increase with the increase of wind speed. According to the comparison results obtained in the numerical simulation and wind tunnel trials, it can be concluded that the application of the numerical simulation in radome design fields plays an important role, and the data obtained in the simulation is also meaningful to direct wind tunnel test in real engineering fields.
2016, 33(增刊): 290-295.
DOI: 10.6052/j.issn.1000-4750.2015.04.S032
Abstract：
Topology optimizations for an electrorheological sandwich plate under semiactive variable modality stiffness vibration control are investigated. First of all, on the basis of topological particle swarm optimization (PSO) and taking the needed amount of electrorheological (ER) material and the maximization of semiactive control ability as the objective function, the topological optimization design method of damping structure was presented, and the topological configurations of maximizing a single or multiple modal frequency mobility of the ER sandwich plate structure under certain needed amount of ER material were obtained. Subsequently, the comparisons of equivalent modal damping ratio and time responses with the optimal configurations and fully covered layout validate the effectiveness of the proposed semiactive controller and topology optimized approach.
Topology optimizations for an electrorheological sandwich plate under semiactive variable modality stiffness vibration control are investigated. First of all, on the basis of topological particle swarm optimization (PSO) and taking the needed amount of electrorheological (ER) material and the maximization of semiactive control ability as the objective function, the topological optimization design method of damping structure was presented, and the topological configurations of maximizing a single or multiple modal frequency mobility of the ER sandwich plate structure under certain needed amount of ER material were obtained. Subsequently, the comparisons of equivalent modal damping ratio and time responses with the optimal configurations and fully covered layout validate the effectiveness of the proposed semiactive controller and topology optimized approach.
Abstract：
The application of composite materials in commercial aircraft is increasing, and the wide body aircrafts with all-composite fuselage have appeared, in which the reinforcement of cabin door area structure of the composite fuselage is an important issue. With this regard, the paper performed finite element analysis and structure optimization of a certain typer of large aircraft with all-composite fuselage, and the results meet the requirement.
The application of composite materials in commercial aircraft is increasing, and the wide body aircrafts with all-composite fuselage have appeared, in which the reinforcement of cabin door area structure of the composite fuselage is an important issue. With this regard, the paper performed finite element analysis and structure optimization of a certain typer of large aircraft with all-composite fuselage, and the results meet the requirement.
2016, 33(增刊): 301-305.
DOI: 10.6052/j.issn.1000-4750.2015.04.S037
Abstract：
A sidedraw silo with chutes is studied. This silo can effectively reduce the dynamic overpressure and can be able to make stored materials flow in separated layers from top to bottom, thus significant energy can be saved. PFC3D is used to build a model, which is the same as the test model. The static and dynamic lateral pressures are simulated using this model. The range of the maximum overpressure coefficient is calculated and verified by the test. The results show that the dynamic lateral pressure is lager on the wall which is farthest away from the discharging port and the peak value is 1.4. It also happens in this wall at a 90-degree angle to discharging port. However, there are two peak values on the wall which is farthest away from the discharging port, one is on the upper part and another is on the lower part of the silo wall at a depth of 0.8m. Furthermore, the flow pattern of particles in the numerical simulation is basically identical to that observed in the test.
A sidedraw silo with chutes is studied. This silo can effectively reduce the dynamic overpressure and can be able to make stored materials flow in separated layers from top to bottom, thus significant energy can be saved. PFC3D is used to build a model, which is the same as the test model. The static and dynamic lateral pressures are simulated using this model. The range of the maximum overpressure coefficient is calculated and verified by the test. The results show that the dynamic lateral pressure is lager on the wall which is farthest away from the discharging port and the peak value is 1.4. It also happens in this wall at a 90-degree angle to discharging port. However, there are two peak values on the wall which is farthest away from the discharging port, one is on the upper part and another is on the lower part of the silo wall at a depth of 0.8m. Furthermore, the flow pattern of particles in the numerical simulation is basically identical to that observed in the test.
2016, 33(增刊): 306-311.
DOI: 10.6052/j.issn.1000-4750.2015.05.S039
Abstract：
According to the structure geology, geological condition and the inspection information of bore hole, the paper analyzes the original stress existing in the km depth of Cixi colliery production area using EFM model based on gravity principal and considering the dip and fault strata structure. With FEM results, the three dimensional stress state and the relationship between the vertical and horizontal inspection lines are graphically displayed. Although the three coordinate direction stress are proportional to the depth according to the analytic solution, the curve of stress vs. depth is not continues, which is interrupted at the fault and juncture of two kind of strata. The max ratio of the two cross horizontal stress is 1.22, which occurs at the depth of 613m. Based on orthogonal analysis, the ratio of the two cross directional stresses, called non-uniform coefficient, is affected mainly by the ratio of mutual shear modules, as well as the incline angle of strata. On the same level and same strata, the stress behavior is related to the incline state, and the stress in the uphill side is higher than that in the downhill by 10-3 to 10-4. The stress gradient is mainly related to the incline angle of strata and it does not influence the assessment of horizontal stress.
According to the structure geology, geological condition and the inspection information of bore hole, the paper analyzes the original stress existing in the km depth of Cixi colliery production area using EFM model based on gravity principal and considering the dip and fault strata structure. With FEM results, the three dimensional stress state and the relationship between the vertical and horizontal inspection lines are graphically displayed. Although the three coordinate direction stress are proportional to the depth according to the analytic solution, the curve of stress vs. depth is not continues, which is interrupted at the fault and juncture of two kind of strata. The max ratio of the two cross horizontal stress is 1.22, which occurs at the depth of 613m. Based on orthogonal analysis, the ratio of the two cross directional stresses, called non-uniform coefficient, is affected mainly by the ratio of mutual shear modules, as well as the incline angle of strata. On the same level and same strata, the stress behavior is related to the incline state, and the stress in the uphill side is higher than that in the downhill by 10-3 to 10-4. The stress gradient is mainly related to the incline angle of strata and it does not influence the assessment of horizontal stress.
2016, 33(增刊): 312-319.
DOI: 10.6052/j.issn.1000-4750.2015.04.S052
Abstract：
Since the response of storage tanks includes rigid body motion, impulse motion with middle and high natural frequency, convection motion with low natural frequency of storage liquid part, and structural motion of tower part, the storage tank system response is sensitive under the earthquake ground motion with broad frequency and high random parameters. In this paper, the seismic response of non-isolated model, story isolated model and base isolated model and its influential factors are studied by an optimal method. The governing motion equation of non-isolated model, story-isolated model and base-isolated model are built on Haroun-Housner theory. The optimal model, which is computed in MATLAB, is established using the mean and standard deviation of base shear as the objective function, and using the isolated period as the optimized parameter. Then the relationship between optimization model parameters and seismic response is illustrated. The influence rules are presented that the storage tank response is affected by the weight ratio of tank and tower, tower stiffness, tank aspect ratio and site classification. The research method and conclusion may be beneficial to isolated storage tank and improve the seismic performance of the tank.
Since the response of storage tanks includes rigid body motion, impulse motion with middle and high natural frequency, convection motion with low natural frequency of storage liquid part, and structural motion of tower part, the storage tank system response is sensitive under the earthquake ground motion with broad frequency and high random parameters. In this paper, the seismic response of non-isolated model, story isolated model and base isolated model and its influential factors are studied by an optimal method. The governing motion equation of non-isolated model, story-isolated model and base-isolated model are built on Haroun-Housner theory. The optimal model, which is computed in MATLAB, is established using the mean and standard deviation of base shear as the objective function, and using the isolated period as the optimized parameter. Then the relationship between optimization model parameters and seismic response is illustrated. The influence rules are presented that the storage tank response is affected by the weight ratio of tank and tower, tower stiffness, tank aspect ratio and site classification. The research method and conclusion may be beneficial to isolated storage tank and improve the seismic performance of the tank.
2016, 33(增刊): 320-324.
DOI: 10.6052/j.issn.1000-4750.2015.05.S059
Abstract：
Under the condition of reality demand of traffic emergency rescue and traffic engineering security against future disasters, a pavement channel equipment composed of airbag and deck bearing plate capsule combination structure is developed. On the basis of analyzing the superiority of airbag bearing structure, a theoretical calculation model is established and the compressive deformation of the proposed structure using the finite element is analyzed. Through pressure tests, the deformation of the composite structure under actual load condition is verified. The experiment proved that this kind of structure conforms to the requirements of the design load and deformation. The structure can meet the needs of the traffic emergency rescue and disaster relief.
Under the condition of reality demand of traffic emergency rescue and traffic engineering security against future disasters, a pavement channel equipment composed of airbag and deck bearing plate capsule combination structure is developed. On the basis of analyzing the superiority of airbag bearing structure, a theoretical calculation model is established and the compressive deformation of the proposed structure using the finite element is analyzed. Through pressure tests, the deformation of the composite structure under actual load condition is verified. The experiment proved that this kind of structure conforms to the requirements of the design load and deformation. The structure can meet the needs of the traffic emergency rescue and disaster relief.
