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Articles online first have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
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2020 No. 9, Publish Date: 2020-09-07
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2020, 37(9).
[Abstract](13) [PDF 1553KB](7)
Abstract:
2020, 37(9): 1-7, 29.   doi: 10.6052/j.issn.1000-4750.2020.07.0446
[Abstract](53) [FullText HTML](19) [PDF 812KB](31)
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Using super-convergent solutions calculated by the Element Energy Projection (EEP) method, equivalent nodal load vectors from the residual load term were derived in this paper without changing the finite element (FE) meshes and the global stiffness matrices. The subsequent back-substitutions can generate highly accurate estimates for the errors of nodal displacements and hence greatly improve the nodal accuracy. Taking a general second-order ordinary differential equation as the model problem, the algorithm of the proposed method and associated numerical examples were given to show that the proposed method is simple and effective, and that using elements of degree m≥1, the improved nodal displacements can gain the super-super-convergence orders h2m+2 and h3m+mod(m, 2) for simplified and condensed EEP forms, respectively. A variety of significant further extensions and applications were also discussed.
2020, 37(9): 8-17.   doi: 10.6052/j.issn.1000-4750.2019.10.0634
[Abstract](63) [FullText HTML](37) [PDF 1865KB](14)
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The scaled boundary finite element method (SBFEM) is a high-precision semi-analytical numerical solution method, which is especially suitable for solving problems such as unbounded media and stress singularity, and the advantage of the polygon boundary element is more obvious to simulate the crack growth process and local mesh re-segmentation problems than the finite element method. At present, the scaled boundary finite element method is more concerned with the solution of the linear elasticity problem, while the research of the nonlinear scaled boundary element is in its infancy. An efficient inelasticity-separated scaled boundary finite element method (IS-SBFEM) is proposed based on the basic theory of the SBFEM and the inelasticity-separated theory. The proposed method considers that the sector sub-element of each boundary line covered domain is independent, and its shape function and strain-displacement matrix can be obtained by the semi-analytical elastic solution. Moreover, the nonlinearity strain field of each sector sub-element is establish by introducing nonlinear strain interpolation points, and the nonlinear constitutive relations can be introduced to achieve efficient nonlinear analysis of polygon scaled boundary element. The stiffness matrix of the polygon scaled boundary element can be obtained by assembling the stiffness of each sector sub-element, the numerical integration of each sector domain can be obtained by using Gaussian integration scheme, and its accuracy remains unchanged. Because more nonlinear strain interpolation points are introduced, the dimension of the Schur complement matrix is larger. The Woodbury approximation approach is used to solve the governing equations of the inelasticity-separated scaled boundary element. This method has efficiency advantages for the calculation of large-scale nonlinear problems. Numerical examples are adopted to verify the correctness and efficiency of the algorithm. Popularize this method that is important to practical engineering analysis.
2020, 37(9): 18-29.   doi: 10.6052/j.issn.1000-4750.2019.10.0611
[Abstract](71) [FullText HTML](49) [PDF 1253KB](12)
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A four-node co-rotational quadrilateral shell element for smooth and non-smooth shell structures is presented. Each node of the element has three translational degrees of freedom and two or three vectorial rotational degrees of freedom. For the nodes of smooth shells or nodes away from the intersection of non-smooth shells, the two smallest components of the mid-surface normal vector are defined as the nodal rotational variables. For the nodes at intersections of non-smooth shells, two smallest components of one orientation vector, together with one smaller or the smallest component of another nodal orientation vector, are employed as rotational variables. In a nonlinear incremental solution procedure, the vectorial rotational variables are additive and the symmetric tangent stiffness matrices are obtained in both global and local coordinate systems, thus, one-dimensional linear storage scheme can be adopted, saving computer storage and computing time effectively. To alleviate membrane and shear locking phenomena, one-point quadrature is adopted in calculating the element tangent stiffness matrices and the internal force vector, and the physically stabilized method is employed to avoid the occurrence of spurious zero energy modes. The reliability and computational accuracy are verified through two smooth shell problems and two non-smooth shell problems undergoing large displacements and large rotations.
2020, 37(9): 30-37, 111.   doi: 10.6052/j.issn.1000-4750.2019.10.0588
[Abstract](72) [FullText HTML](33) [PDF 985KB](22)
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Structural damage detection techniques using time domain vibration responses are of interests in structural health monitoring. Two structural characteristic vectors (SCVs) defined by cross correlation functions of time domain vibration responses, i.e. inner product vector (IPV) and cross correlation function amplitude vector (CorV), as well as the corresponding damage detection technique are reviewed. In order to utilize more information in the correlation functions, the two SCVs are then generalized to several derived SCVs, and the damage detection procedure using data fusion technique with these SCVs is also proposed to enhance the accuracy of the damage detection results. The damage detection results of an experimental 8-storey shear frame structure show that the small damage in the frame structure can be located by the proposed method.
2020, 37(9): 38-49.   doi: 10.6052/j.issn.1000-4750.2019.11.0639
[Abstract](66) [FullText HTML](47) [PDF 975KB](9)
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The warping torsion of thin-walled members with open and closed cross sections was well addressed by the classical theories presented by Timoshenko and Benscoter, respectively. However, the restrained torsional behavior of thin-walled members with open-closed profile cannot be correctly accounted for without considering the distinctive warping properties between open and closed parts of the cross section. The development of warping shear flows within the mid-plane of the cross section needs further elaborations. This work assumes that the torsional warping of open and closed segments correspondingly adheres to the classical assumptions of Vlasov and Umanskii. The warping displacements are required to coincide at the common points of the open and closed segments, leading to a compatible warping field which contains undetermined warping parameter. The warping parameter is explicitly obtained based on the equilibrium requirements. A one-dimensional finite element model is naturally developed for warping torsion analysis of a thin-walled member with open-closed cross section. It is shown by numerical investigations and parametric studies that the type I method based on the Second Umanskii theory can artificially introduce the additional shear flows that reduce the accuracy of shear stresses. As an alternative, the type II method based on the Second Umanskii theory can only obtain the average shear stress of each segment of thin-walled section which fails to provide the correct distribution of shear flows. The Beam-189 element model based on the Vlasov assumption unfortunately neglects the induced warping displacements and shear flows by the constrained effects of the closed contour. Hence, the use of Beam-189 element will reduce the accuracies of both normal and shear stresses. Close agreement can be observed between the Shell-63 element model and the present method for calculating the torsional deformation and stresses, which demonstrates the capability of the one-dimensional finite element model to describe the torsional and warping stiffness of the thin-walled members with open-closed cross section.
2020, 37(9): 50-62.   doi: 10.6052/j.issn.1000-4750.2019.10.0591
[Abstract](60) [FullText HTML](5) [PDF 1916KB](13)
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For the construction of steel structures of Beijing Daxing International Airport Terminal, and based on the completed full-scale multi-planar DKT-joint tests, 192 groups of finite element models with different parameters are simulated and analyzed to further study the mechanical mechanism of the DKT-joint. The influences of opening size, thickness and quantity of stiffeners on mechanical properties of the multi-planar DKT-joint are investigated. Multiple nonlinear regression towards the design and ultimate bearing capacity of the multi-planar DKT-joint containing various stiffener arrangements under axial compression is conducted, and the magnification coefficient η for design value and ultimate capacity of the DKT-joint is obtained. The formulas of design value and ultimate capacity of the multi-planar DKT-joint containing internal stiffeners are derived based on current Standard for design of steel structures. Experiments and finite element analysis (FEA) results indicate that the formulas of design value and ultimate capacity of the multi-planar DKT joint containing internal stiffeners meet the precision requirements well, and can provide reliable reference for the design of similar joints in practical engineering.
2020, 37(9): 63-73.   doi: 10.6052/j.issn.1000-4750.2019.10.0617
[Abstract](52) [FullText HTML](28) [PDF 2175KB](16)
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The discrete linear spatial truss structure composed of many bar members is taken as a continuous beam by using an equivalent method. The transient vibration suppression of the truss structure is studied by adding nonlinear energy sinks (NES) to the equivalent beam. The lattice structure of the beam is modeled as an equivalent linear continuous system (finite length beam) by an equivalent method, which is verified by a finite element model. The vibration control equations of an equivalent cantilever beam with a NES attachment are established. The Galerkin method is adopted for discretization. The displacement responses of beams with and without a NES attachment under external excitation are analyzed. The vibration suppression effect of NES on the structure is studied by calculating the external excitation response of NES attachments at different positions in the structure. In addition, the external excitation response of NES attachments with different masses at different positions are also investigated. The effect of NES additional mass on the vibration reduction is obtained. The results show that the NES attachments can reduce the response efficiency of the x-truss under transient excitation When the mass of the NES attachments increases, the vibration amplitude of the system declines more rapidly and the energy consumption efficiency of the NES attachments becomes higher. The NES passive vibration reduction effect is compared with the linear stiffness damping damper (TMD). The results show that, in the structure with additional NES, the attenuation of the structure amplitude is appreciable at about 5 seconds after the excitation occurred, and the decline in the amplitude is steeper. This means that the NES passive reduction effect is much better than that of the linear stiffness damping damper (TMD). Additionally, the attenuation effect of the NES attachments with different qualities is verified through experiments, in which the same displacement excitation amplitude (15 mm) is applied to the free end of a beam. The results show that the greater the mass of the NES attachment is, the higher is the attenuation efficiency of the transient response of the cantilever structure. The experimental results are in good agreement with the theoretical calculation results.
2020, 37(9): 74-83.   doi: 10.6052/j.issn.1000-4750.2019.01.0045
[Abstract](99) [FullText HTML](42) [PDF 968KB](21)
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In order to study the axial compressive behavior of reinforced concrete (RC) columns strengthened with high ductile concrete (HDC) and reactive powder concrete (RPC) jackets. Eight RC square columns were prepared; four of them were jacketed with HDC, three with RPC and one control specimen. Axial compression tests were carried out to investigate the influence of the material types, the loaded ways and the reinforcement arrangements of the jackets on test results. The failure modes, bearing capacity, load-displacement curves and strain development of specimens are analyzed. Test results show that the failure modes of strengthened columns have been improved. The jackets reinforced with steel mesh exhibit good integrity. The interface between jacket and concrete has reliable bond strength. Thusly, the bearing capacity and deformation capacity of all strengthened specimens have been improved. The bearing capacity of strengthened specimens is increased greatly, whose jackets are directly loaded. Based on the analysis of the strengthening mechanism of jackets, the formulas for calculating the bearing capacity of the strengthened specimens is developed, in which the stress lag of jackets is considered. And the calculating results are in a good agreement with the experimental results.
2020, 37(9): 84-93.   doi: 10.6052/j.issn.1000-4750.2019.10.0593
[Abstract](47) [FullText HTML](14) [PDF 1087KB](11)
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To provide a quick and easy calculation for the seismic design loads of tunnel lining, the simplified analytical solutions are widely employed in preliminary tunnel design. So it is very important to assess the accuracy and applicability of these analytical solutions. In this study, the time-domain finite element method is adopted to verify the accuracy of four simplified analytical solutions for different types of surrounding soil or rock and different tunnel depths. Through the numerical validation, it can be concluded that: the analytical solutions by Wang, Bobet and Park generate the same thrusts; with the increasing of flexibility ratio, the error deceases for shadow tunnels, and decreases first and then increases for deep tunnels; the Bobet’s and Park’s solutions generate the same bending moments, more accurate than Wang’s solution; the error of Bobet’s and Park’s solutions decreases with the increasing of flexibility ratio; the errors of Bobet’s and Park’s solutions are lower than 15% for tunnel’s internal forces when the tunnel depth is over 10 m, 5 m, 5 m, 1 m and 1 m, respectively for soft soil, medium soft soil, medium hard soil, hard soil or soft rock and hard rock.
2020, 37(9): 94-102.   doi: 10.6052/j.issn.1000-4750.2019.10.0596
[Abstract](77) [FullText HTML](39) [PDF 1568KB](4)
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A central difference virtual initial condition method is proposed to address the instability of the solution of hysteretic damping system. The proposed method develops virtual initial conditions associated with the real initial conditions, which generates the direct integration solution eliminating the divergence term of complementary solution and converges to the exact solution. Then, the procedure of central difference virtual initial condition method is established based on central difference method which is of conditional stability. Numerical examples of three different natural frequency systems under three different seismic excitations are analyzed by the central difference virtual initial condition method, the analytical solution and the frequency domain method, respectively. The results show that the frequency domain analysis results only contain the steady state solutions, which will lead to significant errors in the initial stage of vibration of low natural frequency system; the central differential virtual initial condition method is stable for different conditions, and it will converge to theoretical solution including transient response.
2020, 37(9): 103-111.   doi: 10.6052/j.issn.1000-4750.2019.10.0598
[Abstract](25) [FullText HTML](29) [PDF 1549KB](13)
Abstract:
Surface damage and deformation are important indicators for testing, appraisal and monitoring of structural safety. The adoption of digital image method can effectively overcome the shortcomings of current manual inspection methods. However in engineering practice, challenges are encountered such as the difficulty in correcting the geometric deformation of the image during quantitative detection, the difficulty of damage localization of images in the overall structure, and the inability to measure the spatial deformation of the steel structure. By combining the research and application of multi-view geometric 3D reconstruction method, the above problems can be effectively solved. This paper discusses the principle and algorithm for the implementation of multi-view geometric 3D reconstruction, and introduces the classic and efficient algorithms for practice. Aiming at the problem of the digital image detection method in engineering practice, a surface projection method for the correction of imaging geometric deformation and damage localization, and a reverse engineering modeling and feature extraction method for the geometric deformation damage detection are proposed. Through three application studies including structural surface crack identification, large structure surface damage localization and steel structure component deformation identification, the specific operation methods and comparative advantages of multi-view geometric 3D reconstruction method for structural surface damage and deformation identification are discussed. The multi-view geometry three-dimensional reconstruction method has the benefits of low equipment requirements, convenient operation, rich model color and relatively high point cloud precision, After combined with the digital image method, it shows great research and application potential in the field of engineering structure inspection and monitoring.
2020, 37(9): 112-122.   doi: 10.6052/j.issn.1000-4750.2019.10.0601
[Abstract](141) [FullText HTML](35) [PDF 1561KB](18)
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Accurately simulating inflow turbulence for large eddy simulation (LES) is a hot topic in the field of computational wind engineering. Defining appropriate inflow boundary conditions in accordance with the turbulence characteristics of various atmospheric boundary layers (ABLs) is a prerequisite and indeed a great challenge in numerical research of wind effects on building structures at current stage. Based on the newly proposed LES inflow turbulence generation technology-NSRFG method, which belongs to the category of the turbulence synthesis method, the appropriate values of several parameters in the mathematical model were systematically studied. Detailed parameter sensitivity analyses were conducted to investigate several key parameters, including the sampling frequency intervals Δƒ, the introduced time scale factor \begin{document}${\tau }_{0}$\end{document}, the introduced spatial scale factor θ, the decay coefficient \begin{document}${c}_{j}$\end{document} and the tuning factor \begin{document}${\gamma }_{j}$\end{document}, on the simulated turbulent fluctuating wind velocity spectra, the RMS values as well as the spatial correlations. Based on it, a serials of model parameters corresponding to four typical standard wind terrains defined in Chinese building code were then proposed in order to build a ‘standard numerical wind terrain model’. Numerical simulations and equilibrium state verifications for those standard wind fields were subsequently performed. The results showed that key parameters had significant impacts on the numerical reconstructions of the turbulent wind fields by employing NSRFG method, and the proposed standard numerical wind terrain models would be referential for similar LES research of building structures.
2020, 37(9): 123-132.   doi: 10.6052/j.issn.1000-4750.2019.10.0603
[Abstract](97) [FullText HTML](10) [PDF 1440KB](23)
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In order to improve the seismic performance of high-strength concrete shear walls, the high-strength rectangular spiral reinforcements (HRSRs) are applied to the constrained edge members and wall body of high-strength concrete shear wall. Through the seismic performance investigations of 10 high-strength concrete shear walls confined with HRSR, and considering the strong constraint of HRSR, the bending moment curvature calculation method of high-strength concrete shear walls confined with HRSR is proposed corresponding to the cracking, yielding, peak and ultimate states. The study shows that the bending moment curvature formula of the bending member can describe the load-deformation relation of the shear wall more accurately, and the calculated values are in good agreement with the experimental values. Compared with the form of common stirrup, the continuous closed HRSR can significantly improve the sectional bearing capacity and deformation capacity of high-strength concrete shear walls.
2020, 37(9): 133-143.   doi: 10.6052/j.issn.1000-4750.2019.10.0604
[Abstract](78) [FullText HTML](70) [PDF 1224KB](17)
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To evaluate the damage degree of Composite Frame with Reinforced Concrete Column and Steel Beam after the earthquake, the seismic damage model of RCS composite frame structure was established by modifying the relevant parameters of the Park-Ang double parameter seismic damage model. By analyzing the influence of the slab on the key parameters of the model, the formula to calculate the ultimate deformation capacity of the composite beam members under the influence of the slab space combination effect was given. The formula was verified. Based on the test results, the parameter β under the influence of cyclic loading of the composite beam member was obtained by inverting the component at a damage index equal to 1 at the point of failure. The range of damage index corresponding to the degree of damage of the structure was given, and a seismic damage assessment method for this structure was proposed. The seismic damage assessment of a 4-layer RCS composite frame structure under the action of El-Centro wave shows that the seismic damage model proposed in this paper can better reflect the damage evolution process and degree of RCS composite frame structure. The research results provide a theoretical basis for seismic damage assessment and performance-based seismic design of RCS composite frame structures.
2020, 37(9): 144-152.   doi: 10.6052/j.issn.1000-4750.2019.10.0623
[Abstract](113) [FullText HTML](37) [PDF 1155KB](13)
Abstract:
To investigate the damage distribution and evolution of the tunnel lining by train loads, the incremental damage constitutive relation under complex stress state was derived based on the uniaxial tension and compression constitutive relation in the Code for design of concrete structures and embedded into the standard calculation program of ANSYS. Its reliability was verified through a comparison with the uniaxial tension and compression experiment results. The coupled circular tunnel-soil dynamic FE model was then established. Based on the improved Miner’s cumulative damage theory, the damage distribution, dynamic response and the evolution of damage increment and cumulative damage of tunnel lining due to long-term train loads were studied. It is found that the long-term train-induced damage is symmetrical about the tunnel centerline, and mainly distributes in the inverted arch with an angle of 120 degree. There are two damage concentration areas right beneath the train load applying points, where the damage amplitude is larger than any other areas. With the increase in train operation time, the amplitude of single train-induced dynamic stress in concentration area decreases by about 83% whereas that of dynamic strain increases by about 150%. The damage increment and cumulative damage both increase nonlinearly with the increase in train operation time. Accordingly, the improved Miner’s cumulative damage theory could improve the accuracy for fatigue life prediction of tunnel lining.
2020, 37(9): 153-160, 207.   doi: 10.6052/j.issn.1000-4750.2019.10.0624
[Abstract](84) [FullText HTML](41) [PDF 866KB](36)
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Creep test is performed on Chengdu clay to study the nonlinear property of clay creep. It is found that instantaneous elastic deformation, attenuated creep deformation, steady creep deformation, and accelerated creep deformation are included in clay deformation. The long-term elastic modulus of clay is nonlinear softening with the increase of time and stress. The viscosity coefficient is nonlinear softening with the increase of stress and nonlinear hardening with the increase of time. Based on the rheology theory, fractional calculus theory and Harris attenuation function, fractional derivative components, nonlinear elastic components and nonlinear viscous components are established, respectively. A nonlinear fractional derivative creep model with simple form, few parameters and clear concept is established. Then, the nonlinear fractional derivative creep model and Burgers creep model are compared. It is found that the fitting effect of nonlinear fractional derivative creep model is better in each stage, and can give more reasonable description of the nonlinear creep of clay, and can accurately reflect the whole process of clay creep. The scientific rationality of the nonlinear fractional derivative creep model is proved.
2020, 37(9): 161-172.   doi: 10.6052/j.issn.1000-4750.2019.10.0627
[Abstract](58) [FullText HTML](36) [PDF 1534KB](13)
Abstract:
To investigate the characteristics of transverse force in the top slabs of a single-box triple-cell composite box girder with corrugated steel webs (CBGCSW) and the effective distribution width under wheel loads, a finite element model of a single-box CBGCSW with single-cell, double-cell and triple-cell was established. The regulation of transverse stress and effective distribution width of three different box girders were compared. The results of finite element analysis, which had been verified by scaled-models tests, show that the transverse force in a single-box multi-cell CBGCSW can be approximately simplified as that of a single-box single-cell box girder. However, there is a big error in calculating the effective distribution width of CBGCSW according to the current code. Using finite element models, the influences of the transverse location of wheel load, the distance between webs, the length of flange slabs, the thickness of top slabs, the size and type of corrugated steel webs on the effective distribution width of a single-box single-cell CBGCSW were analyzed. It is shown that the transverse location of wheel load and the distance between webs of loading chambers are the most important factors. The practical calculation formulas of the effective distribution width of a single-box single-cell CBGCSW were obtained by the surface fitting according to results of parametric analysis. The formulas of the effective distribution width of a single-box multi-cell CBGCSW were proposed to be 0.9 times of that of a single-cell CBGCSW. Finally, the transverse stress in the top slab of a single-box triple-cell CBGCSW were analyzed as an illustration under transverse single and multiple wheel loads, separately. The transverse stress was calculated by the elastic frame method, using the effective distribution width calculated by formulas proposed and the current code method. The results, compared with the finite element analysis, show that when transverse multiple wheel loads were imposed the calculated transverse stress may be unsafe, on the condition that the effective distribution width of different chambers were adopted as the same value. Consequently, the stress reduction factor of transverse stress in adjacent chamber which is presented in this paper are proposed to improve accuracy. The formulas presented are more accurate than those of current code, and the errors can be reduced by 20%-40%, comparing with current code method.
2020, 37(9): 173-183.   doi: 10.6052/j.issn.1000-4750.2019.10.0628
[Abstract](29) [FullText HTML](11) [PDF 1114KB](9)
Abstract:
Longitudinally profiled (LP) steel plates will be widely used in engineering structures due to their adaptation to the needs of modern buildings such as super high-rise and large span buildings. Because of the geometric characteristics, the local buckling deformation of LP steel plates is more likely to occur at positions near the thin end, and the performance of local stability is significantly different from that of the steel plates with a constant thickness under the same load case. As a consequence, the local stability problem of LP steel plates needs to be studied in depth. Based on the energy principle, the Galerkin and Rayleigh-Ritz method (GRM) is used in the theoretical formulae derivation of the elastic buckling coefficient, where the target rectangular LP steel plates are under uniaxial uniform compression and four different boundary conditions. The resultant formulas are verified by using finite element software ANSYS. The relationship curves between the elastic buckling coefficient of rectangular LP plates with different thickness parameters and length-to-width ratios are obtained, which provide a theoretical guidance and design basis for engineering applications of LP steel plates.
2020, 37(9): 184-198.   doi: 10.6052/j.issn.1000-4750.2019.10.0640
[Abstract](63) [FullText HTML](43) [PDF 3725KB](12)
Abstract:
In order to satisfy the requirements on seismic behavior and spatial flexibility of high-rise buildings, based on the combination of high-performance materials and high-performance structures, the low yield point (LYP) steel plate shear wall structure with coupling beams was proposed. The finite element models of steel plate shear wall structures were established by ABAQUS, which were proved accurate through a comparison with the published tests. Using the verified numerical method, five coupled and uncoupled LYP steel plate shear wall structure models with different degrees of coupling were established. These models were subjected to static pushover loads and cyclic loads to compare their failure modes, lateral load carrying-capacities, hysteretic behaviors and energy dissipation performances. The influence of the interaction between infill plates and boundary frame on the mechanical properties of the structures and their members was discussed, and some suggestions were proposed for the design of coupled steel plate shear wall structures. The analysis results show that the interaction between infill plates and boundary frame can effectively improve the bearing capacity, bearing efficiency and energy dissipation capacity of the whole structure. Considering the material efficiency, bearing capacity and energy dissipation capacity, it is suggested that the coupling degree of the connecting beam should be controlled within 0.45. With the increase of coupling degree, the shear force shared by the boundary frame increases to 60%, the axial forces of the internal frame columns significantly decreases, and the rotation of coupling beams keeps decreasing. Therefore, the interaction between infill plates and boundary frame should be fully considered in the design of coupled shear wall structures, which is able to effectively reduce the design thickness of infill plates and the section size of boundary frame, and improves the material efficiency and design economy. At the same time, compared with the pure frame, the interaction between infill plates and boundary frame effectively improves the initial lateral stiffness and bearing capacity of the boundary frame.
2020, 37(9): 199-207.   doi: 10.6052/j.issn.1000-4750.2019.10.0644
[Abstract](47) [FullText HTML](15) [PDF 807KB](10)
Abstract:
To solve the problem of detecting and repairing defects of constructed grouted sleeve, a defect detectable and repairable half grouted sleeve (referred to as DDRHGS hereafter) is proposed. To investigate the tensile performance of the connection using DDRHGS and validate the reliability of its repair function, 26 groups with 78 specimens were tested under uniaxial tensile load. Numerous factors were comprehensively considered, including with or without grouting defects, grouting defect ratio, with or without repair, material used to repair, and diameter of the rebar. Test results indicate that the specimens without defects exhibit a good tensile performance and meet the requirements specified in relevant codes. Grouting defect ratio has significant influence on the corresponding tensile performance. A higher defect ratio will lead to the bond-slip failure mode, and the tensile capacity as well as deformation capacity of such specimens can not meet the requirements in codes. The defect repairing function of DDRHGS is overall proved to be reliable. The 48 repaired specimens all exhibited the desirable failure mode, and correspondingly, the tensile capacity and deformation capacity were basically identical with those of specimens without defects. Grout and epoxy mortar can both be used as the repairing material to ensure the repair quality.
2020, 37(9): 208-216.   doi: 10.6052/j.issn.1000-4750.2019.11.0657
[Abstract](35) [FullText HTML](21) [PDF 1146KB](23)
Abstract:
The reinforcement slip in the beam-column joints or column footings can make a significant contribution to the total lateral displacement of reinforced concrete members. In order to accurately evaluate the seismic performance of reinforced concrete (RC) with freeze-thaw damage, the reinforcement slip effect is taken into consideration in this study based on the framework of the fiber model accounting for the uneven distribution of freeze-thaw damage. Firstly, the bond strength degradation model with the consideration of the distribution of freeze-thaw damage is built according to the bar pull-out test data. An analytical procedure is proposed for the prediction of reinforcement slip in the frozen-thawed anchorage area based on the assumption of simplified bond stress distribution along the bar and on the governing equations. The model is validated by comparing the data come from frozen-thawed bar pullout experiments. Then the proposed model is implemented to the zero-length section using the finite element software OpenSEES for formulating the modelling method for RC columns considering the uneven distribution of freeze-thaw damage and reinforcement slip effects. Pseudo-static test data from column specimens subjected to freeze-thaw cycles are used to validate the proposed column model and previous fiber model. The research results show that comparing with the fiber modelling results, the calculated hysteretic curves through using the proposed column model are closer to that of the test results, and that the strength errors, the ultimate displacement errors, and accumulated energy errors indicated that the proposed column model can accurately simulate the seismic response of RC column with freeze-thaw damage.
2020, 37(9): 217-229.   doi: 10.6052/j.issn.1000-4750.2019.10.0584
[Abstract](52) [FullText HTML](29) [PDF 2054KB](5)
Abstract:
A three-dimensional fluid-structure interaction (FSI) model with arbitrary Lagrangian-Eulerian(ALE) liquid-structure coupling and sliding-mesh fluid-fluid coupling of a displacement-sensitive (DS) liquid damper with cylinder-wall grooves was constructed. The synchronous-iterative FSI method combined with the moving mesh control method was utilized to calculate the dynamic responses of the damper system under dynamic excitations. The results were partially verified by experiments. Several important problems were analyzed, including the damping characteristics under a high-speed and shock input, effects of the piston’s initial position offset and the grooves’ structural variation on the damping characteristics. The results show that the offset of the piston’s initial position along the direction of the compression stroke was favorable, but the initial piston offset along the direction of the extension stroke was unfavorable. The damper with cylinder-wall grooves could reduce the instantaneous peak of damping force under a shock condition. The damping characteristics of the damper with multi-grooves showed to be an approximate superposition of the effect of each groove. The damping ratio was increased when the piston velocity amplitude decreased. The damping force fluctuation occurred when the groove paths were opened and closed under higher speed conditions, but it could be improved by extending the end section. These results are helpful for the design of the passive controlled damping characteristics of this kind of liquid dampers.
2020, 37(9): 230-239.   doi: 10.6052/j.issn.1000-4750.2019.10.0590
[Abstract](81) [FullText HTML](23) [PDF 1201KB](8)
Abstract:
In order to explore the reasons of fatigue failure of vena cava filters, it is necessary to study the fatigue strength of the filter under cyclic variable loads. SolidWorks software was used to build models of 8 filters, ABAQUS software was used to analyze the fatigue strength of 8 filters under circumferential pulsating cyclic load and radial compression cyclic load, and the safety of one filter was verified by experiments. In the circumferential fatigue analysis, all the alternating strain points of 8 filters are below the fatigue limit curve, and the safety factors are greater than 1, which meet the fatigue life requirements. In the radial fatigue analysis, some alternating strain points of the new filter and the TrapEase filter are above the fatigue limit curve, and the safety factors are less than 1. The other 6 filters meet the fatigue life requirements. The recyclable filter may not meet the requirement of fatigue life of 10 years and can be used as a temporary filter. Through 14 days, 21 days and 28 days of animal experiments, three small sweetgum pigs were implanted with Aegisy filter. The safety of Aegisy filter is comprehensively evaluated. The results show a good reference for the design, development and clinical application of vena cava filters.
2020, 37(9): 240-247.   doi: 10.6052/j.issn.1000-4750.2019.10.0613
[Abstract](152) [FullText HTML](38) [PDF 1506KB](13)
Abstract:
To suppress the vortex-induced vibration (VIV) of a cylindrical structure, an optimal design simulation model of a nonlinear energy sink (NES) vibration-absorber is established based on Van der Pol wake oscillator model, structural dynamics and optimization algorithm. The Van der Pol wake oscillator model and the structural dynamic equation of a two-dimensional elastically supported cylinder are used to establish the model, which predicts one-degree-of-freedom VIV of a two-dimensional elastically supported cylinder. And the accuracy of the model is verified by comparing it with the reference’s experimental data. The nonlinear governing equations of motion with NES are embedded in the above model to modify the VIV model under the action of NES. Combining with an optimization algorithm which changes the parameters of the initial NES, nonlinear energy sink meeting design requirements are achieved. The effect and mechanism of the optimized NES parameters on suppression of the VIV are analyzed by a mount of simulations. The results of optimization case show that the amplitude of the cylinder under NES decreases by 66.39%, when \begin{document}$U_{\rm{r}} = 5.5$\end{document}. The effect of vibration reduction is obvious. At the same time, the structure parameters of NES obtained by this optimization method meet requirements of actual production and ensure the possibility of physical production design.
2020, 37(9): 248-256.   doi: 10.6052/j.issn.1000-4750.2019.10.0615
[Abstract](58) [FullText HTML](31) [PDF 1098KB](9)
Abstract:
The numerical analysis of static and dynamic problems of functionally graded material beams is usually conducted with the finite element method and suffers from the inherent deficiencies of the method. The governing equations for static analysis of functionally graded material beams are transformed to the forms for static analysis of isotropic material beams, and the Green’s functions corresponding to isotropic material beams are used for static analysis of functionally graded material beams. On this basis, the compliance matrix of a functionally graded material beam is further derived, and the equation of motion is established and solved for the dynamic problem of the functionally graded material beam. Numerical examples show that the proposed method can analyze the static and dynamic problems of functionally graded material beams with high efficiency and accuracy, indicating the feasibility of the present approach.