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工程力学

Engineering Mechanics

Since 1984  Monthly

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Chief Editor: Xinzheng LU

Editor & Publisher: 《工程力学》杂志社

ISSN 1000-4750CN 11-2595/O3

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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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2022 No. 9, Publish Date: 2022-09-01
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2022, 39(9).  
[Abstract](113) [FullText HTML](46) [PDF 1543KB](77)
Abstract:
METHODOLOGIES
IMPROVED RELIABILITY METHOD BASED ON HLRF AND MODIFIED SYMMETRIC RANK 1 METHOD
FAN Wen-liang, LIU Cheng, LI Zheng-liang
2022, 39(9): 1-9.   doi: 10.6052/j.issn.1000-4750.2021.05.0379
[Abstract](212) [FullText HTML](50) [PDF 4409KB](103)
Abstract:
The first-order reliability method (FORM) is simple and efficient, but the error is significant when dealing with strong nonlinear functions. With existing second-order reliability methods (SORM), the calculation accuracy is improve, but the efficiency is reduced. In this research, an improved SORM, which can achieve better balance between accuracy and efficiency, is presented. The modified symmetric rank 1 method is combined with the determination of step length of the HLRF method, and an improved FORM with better convergence is proposed, in which the approximate Hessian matrix of performance function is obtained without increasing the amount of function evaluations. Combining the coordinate rotation with the univariate dimensional reduction approximation of the performance function according to its known gradient vector and Hessian matrix, and introducing the non-central chi-square distribution, the paper proposes an improved SORM with the same efficiency but higher accuracy. The wide applicability and advantages in both accuracy and efficiency of the proposed methods are verified by several numerical examples and engineering examples.
STUDY ON APPROXIMATE METHOD OF STRESS INTENSITY FACTOR VALUE AT BENDING CRACK TIP
WANG Zi-yang, YANG Li-yun, WU Yun-xiao, LIN Chang-yu
2022, 39(9): 10-19.   doi: 10.6052/j.issn.1000-4750.2021.05.0340
[Abstract](172) [FullText HTML](45) [PDF 5337KB](61)
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A large number of unevenly distributed bending cracks exist in engineering structures, which have great influence on the stability of structures. To obtain the stress intensity factor (K) values of the bending crack tips easily and quickly, the bending cracks are approximated as equivalent straight. By calculating the equivalent straight crack tip K value, the bending crack tip K value is obtained. Based on the existing approximate methods (horizontal projection method), three new approximate methods are proposed, which are vertical projection method, center rotation method and line method. The comparison of the three new approximation methods with the existing ones shows that the approximation process of obtaining equivalent straight cracks is optimized. The application range of approximate calculation method is modified and expanded. When calculating the main crack tip K of the bending crack, when the main crack is perpendicular to the load direction and the angle between the branch crack and the load direction is less than 45°, the vertical projection method is the best approximation method; but when the angle between the branch crack and the load direction is greater than 45°, the central rotation method is the best one. When calculating the branch crack tip K of the bending crack, the horizontal projection method is the best approximate method. When the branch crack tip K is calculated, the vertical projection method and the center rotation method are superior to the horizontal projection method in the range of the length ratio (b/a) of the main and branch cracks of the bending crack less than 0.3. Compared with the horizontal projection method, the line method is more suitable for the calculation of K value when the angle between the main crack and the direction of load is small.
CIVIL ENGINEERING
UNCOUPLED ANALYSIS METHOD FOR SEISMIC RESPONSE OF WIND TURBINES IN THE OPERATIONAL CONDITION
XI Ren-qiang, XU Cheng-shun, DU Xiu-li, XU Kun
2022, 39(9): 20-30.   doi: 10.6052/j.issn.1000-4750.2021.04.0309
[Abstract](153) [FullText HTML](33) [PDF 5444KB](71)
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For the wind tubrines in their running conditions, their seismic responses involve the combined excitation of wind and earthquake loadings. In order to establish an uncoupled analysis method for the dynamic response of wind turbines excited by wind and earthquake, a bilinear simplified model for the aerodynamic damping ratios of horizontal-axis wind turbines was established by the least square method first. An uncoupled seismic response analysis method was built up where the aerodynamic damping forces on the rotor were replaced by equivalent modal aerodynamic damping ratios added to the support structure. The simulation results of this uncoupled method were compared with those of the coupled one to evaluate the reliability of this decoupled model. The analysis result indicates that the bilinear model can describe the regularity of modal aerodynamic damping ratios with respect to mean wind speed at the hub-height. Both errors of tower-top acceleration amplitudes and tower-base bending moment amplitudes obtained by the uncoupled and coupled method are less than 15 %. In addition, the computational efficiency of this uncoupled method is higher than that of the coupled one.
PROBABILISTIC SEISMIC DEMAND MODELS AND RISK ASSESSMENT FOR HIGH-RISE BUILDINGS
ZHENG Xiao-wei, LI Hong-nan, ZHANG Ying-ying, YIN Shi-ping
2022, 39(9): 31-39.   doi: 10.6052/j.issn.1000-4750.2021.05.0329
[Abstract](222) [FullText HTML](70) [PDF 5173KB](96)
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It presents a Bayesian-based seismic risk assessment methodology for high-rise buildings, in which, uncertainties associated with the seismic hazard model, input seismic loads, structural properties, and the demand model are taken into consideration. Using the earthquake data from 1970-2017 in Dali, the presented method is discussed in detail. Based on the traditional probabilistic seismic hazard analysis (PSHA), a Bayesian-based PSHA (B-PSHA) method is proposed herein. The Bayesian updating rule is used to develop the posterior probability distributions of the unknown parameters in the hazard model. The probabilistic demand model is constructed by the Bayes theory, which will be applied to account for the epistemic uncertainty associated with the demand model for seismic fragility analysis. The Bayesian-based risk assessment is implemented on a 42-story steel frame-reinforced concrete (RC) core tube building. The results indicate that: A more rational seismic hazard model can be obtained by the B-PSHA method; Erroneous estimates of fragility may be made when ignoring the uncertainty in the unknown parameters of the demand model; Seismic loading directions will have significant impacts on the seismic risk. The presented risk assessment method provides an effective approach to investigate the effects of both aleatory and epistemic uncertainties and is beneficial for the progress of seismic resilience assessment and structural design theory.
EXPERIMENTAL STUDY ON NONLINEAR AUTOREGRESSIVE WITH EXOGENOUS INPUT FOR REAL-TIME HYBRID SIMULATION
CHEN Meng-hui, XU Wei-jie, GAO Xiao-shu, GUO Tong, CHEN Cheng
2022, 39(9): 40-47, 71.   doi: 10.6052/j.issn.1000-4750.2021.05.0365
[Abstract](294) [FullText HTML](146) [PDF 5320KB](55)
Abstract:
In traditional real-time hybrid simulation (RTHS), numerical substructures are usually calculated by finite element method; as a result, it is difficult to complete the calculation for complex structures within specified integral step time. In order to improve computational efficiency, a RTHS method based on nonlinear autoregressive with exogenous input (NARX) is proposed. The NARX model is trained through numerical simulation to replace numerical substructure. RTHS of a nonlinear single-degree-of-freedom structure with a self-centering damper is conducted for proof-of-concept. RTHS tests show that results of NARX based RTHS are almost the same as those of traditional RTHS. Thus it is indicated that NARX based RTHS is a potential alternative for traditional RTHS.
STUDY ON TWO-PARAMETER CRITERION OF RETICULATED SHELL STRUCTURES UNDER EARTHQUAKE ACTION BASED ON PARK-ANG DAMAGE MODEL
HUA Wen, YE Ji-hong
2022, 39(9): 48-57.   doi: 10.6052/j.issn.1000-4750.2021.05.0375
[Abstract](140) [FullText HTML](63) [PDF 5281KB](52)
Abstract:
The performance-based seismic design method requires explicit categorization of performance levels of structures, as well as reasonable definition of corresponding performance indicators. Based on the Park-Ang damage model and the response characteristics of displacement and energy dissipation of reticulated shells under earthquake action, a two-parameter model is proposed which is a non-linear combination of two dimensional parameters: maximum deformation and plastic energy dissipation. According to China's seismic code, characteristics of reticulated shells and existing research results, four performance points (LS-1, LS-2, LS-3, and LS-4) are used to classify the performance of reticulated shells into five levels: intact, slightly damaged, moderately damaged, severely damaged, and collapsed. Through 216 groups of comprehensive calculation examples considering different spans, rise-span ratios, roof loads, member sizes and seismic effects, the pending parameter values of the model are fitted. And then a two-parameter criterion suitable for reticulated shell structures is proposed. The corresponding index values (D) atthe four performance points (LS-1, LS-2, LS-3, and LS-4) are 0.3, 0.6, 1.0, and ∞, respectively. The effectiveness and universality of the criterion are verified by shaking table tests of two large-scale reticulated shell. The results show that the two-parameter criterion and the values of performance points proposed in this paper can reflect the performance levels of reticulated shell structures, and have good effectiveness and universality. This criterion can be used for the performance-based seismic design and seismic risk assessment of reticulated shell structures.
LIGHTWEIGHT STRUCTURAL CONTROL BASED ON TUNED MASS INERTER SYSTEM (TMIS) UNDER TYPICAL EXCITATION
ZHANG Rui-fu, CAO Yan-ru, PAN Chao, HU Xiu-yan
2022, 39(9): 58-71.   doi: 10.6052/j.issn.1000-4750.2021.05.0328
[Abstract](328) [FullText HTML](157) [PDF 6099KB](85)
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Classical tuned mass vibration control systems often require large additional mass and installation space, which is inconvenient in common use. Inerter system is a high-efficiency vibration control system with the characteristic of two-terminal inertia, apparent mass enhancement and damping enhancement, among which the apparent mass enhancement characteristic can realize lightweight structural vibration control. This research focuses on a generalized tuned mass inerter system (TMIS) with lightweight characteristic, and explains its basic theory and typical topology. A demand-based optimal design method is proposed to determine the parameters of the vibration control systems, aiming at reducing the required additional mass as well as meeting the structural performance demand. Three typical external excitations are considered in this research, including seismic effect, wind load and human-induced excitation. The lightweight advantage of the proposed TMIS is illustrated through a comparison with the classical tuned mass damper, and structural case study with dynamic response analysis is conducted to verify the control effect. The results show that TMIS is an efficient structural vibration control system, which can effectively mitigate the structural dynamic response under different types of typical external excitations, and lightweight the required additional tuned mass. TMIS provides an alternative vibration suppression device and is convenient for structural design and installation.
RESEARCH ON COHESIVE ZONE MODEL OF THE INTERFACE BETWEEN CRTS Ⅱ TRACK SLAB AND CA MORTAR
WANG Jun, LU Zhao-hui, ZHANG Xuan-yi, ZHAO Yan-gang
2022, 39(9): 72-80, 109.   doi: 10.6052/j.issn.1000-4750.2021.05.0336
[Abstract](159) [FullText HTML](81) [PDF 4839KB](58)
Abstract:
Debonding between track slab and CA mortar layer is one of the main defects of CRTS Ⅱ slab-type ballastless track system. In order to describe the constitutive behavior of the interface and reveal the mechanism of debonding, an improved exponential cohesive zone model was proposed with parameters determined based on theoretical analysis and experimental data. The proposed model is a segmentation function and adopts exponential coefficients to reflect the nonlinearity of the tension-displacement relationship of the interlayer interface. It is found that: The proposed model can efficiently calculate the interface cohesive strength, the interface relative displacement at damage initiation, and the interface critical fracture energy between track slab and CA mortar, and the results are basically consistent with the experimental results. The proposed model can simulate the normal and tangential cracking behavior of the interface between track slab and CA mortar layer with relatively high accuracy.
RESEARCH ON THE SHEAR PERFORMANCE OF SELF-DRILLING SCREW DOUBLE-SIDED SHEAR CONNECTIONS
DENG Lu, LIU Wen-hao, LIU Ding-rong, HE Yu-long, LIU Yan-zhi
2022, 39(9): 81-94.   doi: 10.6052/j.issn.1000-4750.2021.05.0344
[Abstract](217) [FullText HTML](121) [PDF 5075KB](83)
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The shear performance of self-drilling screw double-sided shear connections is studied by numerical simulation using the ABAQUS finite element software. The accuracy of the finite element (FE) model is verified through a comparison with the existing test results. Based on this model, the steel strength, the steel plate thickness, the screw diameter and the middle steel plate thickness are discussed on their influences on the failure modes and shear capacity of the screw double-sided shear connections. The results show that the failure modes can be divided into three categories: namely bearing failure, shear-compression failure and shear failure. With the increase of the steel strength grade and the steel plate thickness, the shear capacity of the screw double-sided shear connections continues to increase and gradually stabilizes. With the increase of the screw diameter, the shear capacity of the screw double-sided shear connections increases linearly. Moreover, the shear capacity of the screw double-sided shear connections can also be significantly increased by increasing the middle steel plate thickness in a certain range. The numerical simulation results are compared with the calculated values of the Chinese, American and European standards. The results show that when the bearing failure of the steel plates occurs, the calculated values of the Chinese, European and AISC standards formulas are conservative, and the calculated values of the AISI standard are closer to the FE values. When the shear failure of the screws occurs, the AISI, Chinese and European standards are too conservative. The calculated values of the AISC standard formula are in good agreement with the FE values. Therefore, the calculation of the AISC standard formula is of reference value when the shear failure of the screws occurs.
MECHANICAL PROPERTIES OF ANTI-COLLISION X-TYPE DAMPER AND A NEW STATION COLUMN WITH ENERGY DISSIPATION AND COLLISION REDUCTION FUNCTIONS
YIN Yao, ZHU Xiang, WANG Rui
2022, 39(9): 95-109.   doi: 10.6052/j.issn.1000-4750.2021.05.0358
[Abstract](160) [FullText HTML](67) [PDF 6687KB](58)
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An effective anti-collision device is important for the station structure column which is frequently subjected to collision. A new type of station column with collision reduction and energy dissipation functions is proposed to ensure the normal use of the structure while achieving the optimal energy dissipation capacity. LS-DYNA is used to analyze the anti-collision performance of the new energy dissipation anti-collision design of the structural column of high-speed railway station, and the main energy dissipation elements, anti-collision X-type damper and aluminum foam, are studied. The numerical simulation was carried out based on the existing classical tests, including unidirectional quasi-static loading test of steel plate, impact test of steel reinforced concrete and impact test of aluminum foam-filled thin-walled structure. The analysis results show that the numerical model established in this paper can simulate the impact force and deformation development during the test well. The numerical models of the anti-collision X-type damper and the new type of station column with energy dissipation and collision reduction functions were established to optimize the cross section of the single anti-collision X-type damper to achieve the best energy consumption. The energy absorption characteristics of the new type station column under different factors and the influence of the additional aluminum foam on the energy absorption of the new type of station column were investigated. The results show that when the anti-impact X-type damper reaches the optimal energy consumption, the damper absorbs 97% of the impact energy in the new type station column under the impact load, while only partial concrete cracks appear in the internal structure column. The energy absorption distribution of the new type station column with aluminum foam is more reasonable and the energy absorption is greatly improved, but the plastic strain of the structural column also increases accordingly. On the whole, the new type of station column with energy dissipation and collision reduction functions has good energy absorption capacity, which ensures the safety of the structural column.
EXPERIMENTAL STUDY ON SEISMIC BEHAVIOR OF SELF-CENTERING CONCRETE-FILLED SQUARE STEEL TUBULAR COLUMN-STEEL BEAM JOINTS WITH SLOTTED ENERGY DISSIPATION PLATES
WANG Xian-tie, JIA Zi-han, XIE Chuan-dong, GUO Yi-wei
2022, 39(9): 110-122.   doi: 10.6052/j.issn.1000-4750.2021.05.0360
[Abstract](163) [FullText HTML](55) [PDF 5958KB](57)
Abstract:
In order to reduce the unloading resistance, a self-centering (SC) concrete-filled square steel tubular column and steel beam joint with slotted energy dissipation plates was designed. Low cyclic reversed loading tests of five full-scale joints were conducted to study the aseismic behavior. The mechanical properties were analyzed and the restoring force model was established. The results show that the self-centering joint with slotted energy dissipation plates has good bearing capacity, self-centering capacity and energy dissipation with the "double flag" shape hysteresis curve. The residual deformation is small under 4.00% drift, and the components remain elastic except energy dissipation plates which can be quickly repaired by replacing the plates. The wider the individual slat, the weaker the self-centering ability and the stronger the energy dissipation capability. The larger the width and thickness of the plates, the stronger the bearing and energy dissipation capacity, but the self-centering ability becomes weaker. The prestress of strands has significant influence on the initial stiffness, bearing capacity and self-centering ability, but has little influence on energy dissipation. The restoring force model agrees well with the experimental results.
DAMAGE RATIO STRENGTH CRITERION FOR STEEL FIBER REINFORCED CONCRETE UNDER MULTIAXIAL STRESSES
DING Fa-xing, WU Xia, XIANG Ping, YU Zhi-wu, NIE Lei-xin
2022, 39(9): 123-132.   doi: 10.6052/j.issn.1000-4750.2021.05.0372
[Abstract](149) [FullText HTML](64) [PDF 5589KB](75)
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Based on the damage ratio strength theory, the true triaxial damage ratio strength criterion for steel fiber reinforced concrete (SFRC) was established. The six empirical parameters in the expression of the damage ratio variable of the criterion were recommended according to the test data of SFRC. The values of the damage ratio variable were verified by the experimental results of SFRC under uniaxial, biaxial and triaxial loading conditions, and the values of damage ratio of SFRC under uniaxial tension, uniaxial compression and biaxial equal compression stress conditions were compared with those of plain concrete. By comparing the predicted results with the experimental data of 104 SFRC specimens containing 0.5%~2.5% of fibers, against some strength criteria, the proposed criterion is verified that it can represent the triaxial failure surfaces of SFRC and give relatively good approximation of the experimental results. A simplified conventional triaxial damage ratio strength criterion for SFRC was proposed for confining triaxial stress state, and was compared with the existing conventional triaxial strength criteria. In addition, the empirical parameters of the simplified biaxial damage ratio strength criterion were recommended for biaxial stress states.
EFFECT OF FREEZE-THAW ACTION ON ACOUSTIC EMISSION CHARACTERISTICS OF SELF-COMPACTING LIGHTWEIGHT AGGREGATE CONCRETE
LI Jing-jun, YAN Jun, NIU Jian-gang
2022, 39(9): 133-140, 169.   doi: 10.6052/j.issn.1000-4750.2021.05.0373
[Abstract](115) [FullText HTML](43) [PDF 6778KB](60)
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To study the acoustic emission (AE) characteristics of self-compacting lightweight aggregate concrete (SCLC) under uniaxial compression after freeze-thaw action, 0, 50 and 100 rapid freeze-thaw tests are carried out on self-compacting lightweight aggregate concrete specimens without air entraining agent. The results show that: with the increase of freeze-thaw cycles, the uniaxial compressive stress-strain curves of the specimen tend to be complete, and the peak stress decreases significantly. The peak frequency of AE is mainly located in the four 'dominant frequency bands' of 15 kHz-45 kHz, of 85 kHz-105 kHz, of 235 kHz-255 kHz and of 285 kHz-320 kHz, corresponding to the compression of pre-existing cracks or pore in concrete, the cracking of aggregate/paste interface reinforcement layer, the penetration fracture of coarse aggregate and the cracking of mortar, respectively. Under the action of uniaxial compression, the freeze-thawed specimens undergo the alternating transformation between tensile cracks and shear cracks, and finally form the main crack which leads to failure. Freeze-thaw action and the variation of stress level have a great influence on the distribution of AE signal source. With the increase of stress level, AE signal tends to be active and gathers on the fracture surface of the sample.
SHAKING TABLE TESTS ON RIGID-DRAINAGE PIPE PILE GROUPS AT LIQUEFIED LATERALLY SPREADING SITE
CHEN Zhi-xiong, LI Kang-yin, WANG Cheng-long, DING Xuan-ming, JIANG Xue-feng, CHEN Yu-min
2022, 39(9): 141-152.   doi: 10.6052/j.issn.1000-4750.2021.05.0374
[Abstract](185) [FullText HTML](66) [PDF 6570KB](64)
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The lateral expansion of soil liquefaction under the action of an earthquake may well be fatally destructive to foundations, especially for the piles of building structures and bridges, thus, it is of urge demand to reduce and to eliminate the threaten of soil liquefaction and expansion to the structure safety. The rigid drainage pipe pile is composed of a circular hollow rigid pile and a drainage body, which enables the large bearing capacity and the favorable drainage characteristics. However, the research on the anti-liquefaction performance of rigid drainage pipe pile groups is still limited. In this study, a series of shaking table tests on rigid drainage pipe piles and on ordinary piles under vertical loads were carried out, and the dynamic responses of excess pore pressure ratios, of accelerations, of average settlements, of cap displacements, of quay wall displacements and of pile bending moments were comparatively analyzed. The results show that compared with the ordinary pile model, the rigid drainage pipe pile foundation the excess pore pressure, pile body bending moment, foundation settlement, cap displacement, and quay wall displacement of rigid drainage pipe pile foundation are obviously reduced, while the acceleration is increased, which fully shows that the anti-liquefaction effect of rigid drainage pipe pile is remarkable.
EXPERIMENTAL STUDY ON POST-FIRE MECHANICAL PROPERTIES OF HIGH STRENGTH FIRE-RESISTANT STEEL
LOU Guo-biao, FEI Chu-ni, WANG Yan-bo, CHEN Lin-heng
2022, 39(9): 153-159.   doi: 10.6052/j.issn.1000-4750.2021.05.0380
[Abstract](131) [FullText HTML](56) [PDF 5996KB](62)
Abstract:
A series of static tensile tests on high-strength fire-resistant steel such as grades Q460FR, Q420FR, Q345FR after fire were carried out in this study. The stress-strain curves and mechanical parameters of high-strength fire-resistant steel with post-fire temperatures from 200℃ to 800℃ were obtained. After comparing their mechanical properties with those of ordinary structural steels after high-temperature cooling, the coefficient of variation fitting equationthe of yield strength and tensile strength were proposed. It is shown that: the yield strength and tensile strength of high-strength fire-resistant steel with natural cooling after fire have been improved, while the modulus of elasticity is not influenced by exposing to fire. The results of this study can be applied to the assessment of load-bearing performance of fire-resistant steel structures after fire.
A PREDICTION METHOD FOR THE CHLORIDE DIFFUSIVITY IN PRESTRESSED CONCRETE CONTAINMENT VESSELS IN NUCLEAR POWER PLANTS
ZENG Bin, RONG Hua, CAI Da-hua, ZHANG Jiang-tao, GENG Yan, ZHENG Jian-jun
2022, 39(9): 160-169.   doi: 10.6052/j.issn.1000-4750.2021.05.0381
[Abstract](151) [FullText HTML](38) [PDF 4743KB](49)
Abstract:
Chloride diffusivity is an important parameter for assessing the durability of prestressed concrete containment vessels in nuclear power plants located in a marine environment. Based on a two-scale method, a quantitative relationship between the capillary porosities of cement paste matrix and interfacial transition zone (ITZ), and the prestress is established by analyzing the mesostructures of cement paste matrix, ITZ and concrete under an equi-biaxial compression. To quantify the effect of prestress on the closure, initiation and extension of microcracks, an empirical formula between the critical capillary porosity and the prestress is proposed. Concrete is then modeled as a three-phase composite material, composed of aggregate, ITZ and cement paste matrix, and the chloride diffusivity ratio of concrete is obtained. Through comparison with experimental results, two parameters in the empirical formula are calibrated. The validity of the prediction method is preliminarily verified with three sets of experimental data.
A COMPARATIVE STUDY ON TRANSLATION FUNCTION WITH THE UNRESTRICTED APPLICATION REGION FOR EXTREME VALUE ESTIMATION OF NON-GAUSSIAN WIND PRESSURES
WU Feng-bo, GUO Zeng-wei, LIU Min, WU Bo, HUANG Guo-qing
2022, 39(9): 170-178, 203.   doi: 10.6052/j.issn.1000-4750.2021.05.0386
[Abstract](114) [FullText HTML](42) [PDF 5339KB](47)
Abstract:
The extreme value estimation for the non-Gaussian wind pressures is extremely important for the wind-resistant design of building envelope. With its simplicity and unrestricted application region, the moment-based piecewise HPM (PHPM), Johnson transformation model (JTM) and piecewise JTM (PJTM) are usually used to estimate the non-Gaussian wind pressure extremes. Currently, the systematic research on the performance of the PJTM in the non-Gaussian wind pressure extreme estimation is less addressed, and the differences in extreme values estimated by the three unrestricted application region models are unclear. To compare the differences of the three models and provide certain selection principles, this paper systematically compares the accuracy of the three models to estimate the non-Gaussian wind pressure extremes. Firstly, this paper compares the parent probability distribution functions (PDFs) and translation functions by the three models theoretically. Secondly, the very long wind pressure data from a wind tunnel test are used to evaluate the accuracy of the three models to estimate the extreme values of the non-Gaussian wind pressures. The results show that, for the minimum value estimation of the non-Gaussian wind pressure with negative skewness, the accuracy of PHPM is generally higher than that of JTM and PJTM, while for the maximum value estimation of the non-Gaussian wind pressure with negative skewness, the accuracy of PJTM and PHPM is generally higher than that of JTM.
RESEARCH ON STIFFNESS OF HUB-SHAPE INLAY JOINT AND BEARING CAPACITY OF SINGLE-LAYER SPHERICAL RETICULATED SHELL
ZHANG Xiao-lei, LI Hui-jun, CHEN Xu, ZHU Zhi-qiang, YU Xiao-chen
2022, 39(9): 179-190.   doi: 10.6052/j.issn.1000-4750.2021.05.0388
[Abstract](117) [FullText HTML](60) [PDF 6450KB](46)
Abstract:
The hub-shape inlay joint is a new type of assembled joint designed and developed in China, and has the advantages of convenient construction, smooth shape and high positioning accuracy, and it belongs to a typical semi-rigid joint. However, the research on this kind of joints is limited, and existing codes do not contain the relevant theoretical calculation formulas and design requirements for the semi-rigid single-layer spherical reticulated shell. Recognizing the aforementioned issues, a refined model of the hub-shape inlay joint is established by ANSYS package, and the moment-rotation curve of the joint is fitted based on the power function model. Meanwhile, the influence of joint stiffness on ultimate bearing capacity of the semi-rigid shell with different spans and rise-to-span ratios is discussed in detail. The results show that the moment-rotation curves of the hub-shape inlay joints in out-of-plane bending and torsional bending are in good agreement with the power function model. The sensitivity of the ultimate bearing capacity of shell to the bending stiffness of the joints is greater than the axial stiffness of the joints, and the sensitivity of the ultimate bearing capacity to the stiffness of the joints will get weaker with the increase of the span or rise-to-span ratio of the shell.
STUDY ON ULTIMATE BEARING CAPACITY OF BIAXIAL COMPRESSION-BENDING STEEL MEMBERS WITH THIN AND SLENDER H-SHAPED SECTION
DU Hui-bo, CHENG Xin, ZHANG Chao, CHEN Yi-yi
2022, 39(9): 191-203.   doi: 10.6052/j.issn.1000-4750.2021.05.0390
[Abstract](103) [FullText HTML](106) [PDF 15944KB](32)
Abstract:
To investigate the ultimate behavior of H-section members with large width-thickness ratios under a combined biaxial compression-bending, the parametric analysis models of H-section members with different axial force ratios, web and flange width-thickness ratios and different loading angles were developed by ABAQUS. Material and geometric nonlinearity were considered throughout the whole analysis, and the finite element models were validated by previous laboratory test results. Based on the elastic-plastic stability theory, a criterion for determining the ultimate state of biaxial compression-bending members was proposed. For plastic-hinge sections, the ultimate state is defined as the occurrence of plastic hinge. For slender sections controlled by local buckling, the ultimate state is the initial buckling moment, with the occurrence of plate local buckling been accurately identified through the criterion. The ultimate interactive curves of biaxial bending moments were obtained by least-square method, within which complicated interactive effects of width-thickness ratios of web and flange and the axial force were noted. The ultimate interactive formula for biaxial moments considering the strain hardening effect of material and the correlation effect of plate was proposed. Not limited by section classification, the proposed method is proved to have good applicability and accuracy.
STUDY ON INTERFACIAL BOND-SLIP RELATIONSHIP BETWEEN HSSWM-ECC AND CONCRETE
ZHU Jun-tao, ZHANG Kai, WANG Xin-ling, LI Ke
2022, 39(9): 204-214.   doi: 10.6052/j.issn.1000-4750.2021.05.0399
[Abstract](161) [FullText HTML](57) [PDF 5990KB](73)
Abstract:
Eminent interfacial bond behavior is a prerequisite to ensure the cooperative work between high-strength steel wire mesh reinforced engineered cementitious composite (HSSWM-ECC) and concrete, and the effectiveness of the interfacial bonding determines the utilization of the performance of HSWM-ECC. In order to study the interfacial bond performance between HSSWM-ECC and concrete, nine groups of modified beam specimens (totally 27 specimens) were designed and tested by considering the influences of the factors such as concrete compressive strength, interfacial bond length, interfacial bond width and, interfacial treatment methods. According to the test results, the bond failure characteristics and stress mechanism of the interface between HSSWM-ECC and ECC were explored, and the interfacial bond-slip relationship model was developed by considering the influences of design parameters. A micro-segment analysis method was used to analyze the characteristic parameters of the model. The study results showed that the proposed model and model parameter calculation formulas agree well with test results and can well characterize the mechanical behavior of the interfacial bond-slip relationship between HSSWM-ECC and concrete.
STUDY ON SHEAR BEHAVIOR AND BEARING CAPACITY OF STEEL REINFORCED CONCRTE DEEP BEAMS
CHEN Bu-qing, ZENG Lei, LIU Chang-jun, MO Jin-xu
2022, 39(9): 215-224.   doi: 10.6052/j.issn.1000-4750.2021.05.0402
[Abstract](144) [FullText HTML](46) [PDF 5287KB](64)
Abstract:
In order to study the shear behavior of steel reinforced concrete (SRC) deep beams, seven SRC deep beams subjected to mid-span loading were tested. The failure pattern, load-displacement curves and deformation characteristics were recorded to investigate the failure mode and strength of the specimens of different shear span ratio, height ratio (steel web height to beam height) and, flange width ratio (steel flange width to beam width). Based on the modified compression field theory, a formula for calculating shear bearing capacity of SRC deep beams are developed, considering the influence of steel flange. The calculation results indicate that: the model not only consider the effects of shear span ratio and flange width ratio on shear strength synthetically, but also the calculated values obtained by the model are in a good agreement with the experiment values.
A DAMAGE IDENTIFICATION METHOD BASED ON STRAIN MODAL RESPONSE RECONSTRUCTION
ZOU Yun-feng, LU Xuan-dong, YANG Jin-song, HE Xu-hui
2022, 39(9): 225-233.   doi: 10.6052/j.issn.1000-4750.2021.06.0419
[Abstract](189) [FullText HTML](70) [PDF 8336KB](86)
Abstract:
Damage identification technology of civil structures is of great significance to improve the reliability and safety of structures, and it is a hot topic in the research of civil structural health monitoring. Current damage identification methods often need to identify the modal parameters or accurately obtain the external load information of a structure, which greatly limits their application in practical engineering. To overcome the limitations of the existing methods, the structural dynamic response reconstruction method is introduced into the damage identification and a damage identification method based on strain modal response reconstruction is proposed. The finite element model of the healthy structure is constructed, and the measurement signal is input from the damaged structure. The global modal response of the structure using the undamaged model could be obtained through the strain reconstruction method based on empirical mode decomposition. The discrepancy between the modal response collected by sensors and the reconstructed modal response was taken as the basis of finite element model modification, and the damage location and damage degree were obtained through iterative calculation of the sensitivity matrix of the transmissibility constructed by the strain mode ratio. This method does not need to obtain the external excitation information of the structure, and can realize the accurate identification of structural damage with a few measurement signals through the efficient time-domain strain reconstruction. To verify the accuracy and efficiency of this method, single damage and multiple damage identifications of a continuous beam were carried out. The influence of measurement noise and modal order selection on the identification results was discussed. The results show that this method can accurately and efficiently identify the damage of different degrees, and has strong robustness against measurement noise.
A MODEL OF CALCULATING THE BOND STRENGTH BETWEEN REBARS AND CONCRETE CONSIDERING THE SOFTENING EFFECT OF CONCRETE
LAN Guan-qi, WANG Yi-hong, LIU Le, LIU Xi, SONG Mei-mei
2022, 39(9): 234-241, 256.   doi: 10.6052/j.issn.1000-4750.2021.06.0433
[Abstract](204) [FullText HTML](105) [PDF 4846KB](62)
Abstract:
The bond strength between high-strength rebars and concrete with different strengths was tested by pull-out tests. The bonding mechanism between rebars and concrete was analyzed. The bilinear softening constitutive model was used to describe the softening behavior of concrete in the cracked zone, and the theoretical calculation model of the bond strength considering the influence of concrete in cracked and non-cracking zones were established. The effects of different radial displacement distributions in the cracked zone on the calculation results are studied. The validity of the calculation model was verified by comparing the calculated results with the experimental results. The results show that the computational model has the best accuracy when the radial displacement distribution in the fracture zone is assumed to be equivalently elastic. However, the bond strength of low-strength concrete specimens was overestimated under this assumption. It is suggested that the elastic assumption be used as the radial displacement distribution of concrete in the cracked zone to ensure adequate safety reserves.
OTHER ENGINEERING DISCIPLINES
BUCKLING FAILURE ANALYSIS OF SUBSEA BURIED PIPELINE CROSSING STRIKE-SLIP FAULT
YU Yang, LI Zhen-mian, YU Jian-xing, SUN Wen-zheng, LIU Xiao-wei, MA Jian-dong, LIU Cheng
2022, 39(9): 242-256.   doi: 10.6052/j.issn.1000-4750.2021.05.0391
[Abstract](171) [FullText HTML](51) [PDF 6188KB](64)
Abstract:
Long-distance subsea pipelines often inevitably pass through seismic faults which may impose great threats to pipeline safety, such as twist deformation, wrinkling and tensile rupture. The innovative vector finite element method (VFIFE) was used to analyze the buckling failure behavior of subsea buried pipeline crossing seismic faults. First, the calculation formula of the VFIFE 3D thin shell element were derived considering the material nonlinearity and a custom-made nonlinear pipe-soil interaction model was proposed for the shell element. Then we focused on solving the self-collision contact problem of the inner wall of the pipeline during its collapse and buckle propagation. A Fortran program as well as a corresponding post-processing program was developed. The computation models were verified through a comparison with the published results. A simulation of the buckling failure process of empty subsea pipeline under the strike-slip faults was carried out, and the influences of crossing angle, soil property and water pressure on the buckling failure behavior were analyzed. The results show that the subsea pipeline can hold a higher capacity against fault displacements due to its small diameter-thickness ratio, high steel grade and softer surrounding soil. Under the combined action of lower external pressure and strike-slip faults, the deformation of the subsea pipeline is S-shaped and the buckling failure is dominated by excessive bending caused by fault displacements. The buckling mode is that the compression side of the second bend or both the two bends undergo obvious invagination and the cross-section deformation is elliptical. Under such loads, the smaller the crossing angle, the smaller the critical fault displacement for buckling failure of the pipeline; the higher the strength of the surrounding soil (sand>clay>slit and sand), the more serious the bending deformation and the smaller the critical fault displacement for buckling failure. Under the combined action of high external pressure and strike-slip faults, the buckling failure is dominated by external pressure. The main mode is that the first or second bend collapses firstly and then buckle propagation occurs. Under different combinations of water pressure and fault displacement, the degrees of destruction of the pipeline are different. Moreover, the collapse position, the direction and range of buckle propagation, and deformed cross-sectional shape exhibit different patterns. The results can be used to guide the seismic design and buckling prevention research of subsea pipeline crossing seismic faults.

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