In this study, a novel type of self-centering shear wall (SCSW), referred to as a topologically interlocking SCSW, is proposed. Topologically interlocking curved surfaces are utilized in this structure to connect self-centering wall elements and replace the conventional planar connection method. The hysteresis curves, stiffness degradation, self-centering capacity, energy dissipation characteristics, and damage forms of this new wall and the conventional SCSW were comparatively analyzed through horizontal cyclic loading tests. The test results demonstrate that the topological interlocking SCSW exhibits improved frictional rotation capacity and shear bearing capacity while reducing stress concentrations. Furthermore, the effects of topological interlocking surface parameters, prestressing tendon tension stress, and bending moment proportions on the hysteretic performance of this new wall were systematically investigated. The numerical results reveal the following: (1) the parameter h/l of the surface equation should neither be too large nor too small; it should be approximately 0.12, with a preference for positively symmetric surfaces; (2) the bending moment ratio phi provided by the prestressing tendons has a small influence on the bearing capacity and stiffness degradation, with a suggested range of 0.6-0.7; and (3) the optimal PT tendon stress (0.55 x fptk to 0.6 x fptk) balances the self-centering capacity and energy dissipation.

The Hybrid Precast Self-Centering (HPSC) walls exhibit exceptional seismic performance and possess inherent self-centering capability. In this study, an analytical model is developed to predict the flag-shaped hysteresis response of the HPSC walls, and four design constraint parameters are proposed. The specific values of wall moment and rotation at characteristic points under cyclic lateral loading are derived. The accuracy of the analytical model is verified by comparing it with experimental results obtained from cyclic loading test conducted on the wall specimen. The effectiveness of employing multi-layer shell and truss elements in ABAQUS to accurately simulate the hysteretic behavior of HPSC walls has been substantiated. This study employs the proposed analytical model to investigate the influence of key design parameters, namely the design moment ratio 7, initial post-tensioning (PT) prestress ratio alpha 0, and energy-dissipating bar moment contribution ratio kd, in relation to variations in the aspect ratio Hb of the walls. Research findings suggest that kd ranging from 0.5 to 0.8 typically satisfies design constraints, while Hb of the wall has a minimal impact on 7. It is advisable for 7 to remain below 0.6. Conversely, Hb significantly affects the permissible range of alpha 0. Specifically, when Hb is set at 2, 3, and 4, it is recommended to maintain alpha 0 below 0.5, 0.63, and 0.7, respectively. Furthermore, the seismic performance of a retrofitted six-story RC frame structure with external HPSC walls was significantly enhanced through nonlinear static pushover and dynamic time-history analyses, resulting in a notable reduction in residual drift. This study also provides valuable insights into the impact of design constraint parameters on structural seismic resilience, thereby offering substantial recommendations for engineering design practices.

Based on Gonçalves's geometrically exact beam theory considering cross-section deformation, the warping and distortional deformation of thin-walled members are described in this paper by means of a combination of section deformation modes. By integrating with the J2 elastic‒plasticity theory for the steel, a numerical model is established for the hysteretic behaviour of thin-walled steel members. Four classes of H-section members are selected on account of the design codes, and the influence of section warping and distortion deformation modes on the calculation of the hysteretic behaviour of components with different section types is analysed. The crucial aspect lies in the bending hysteresis behaviour around the strong and weak axes of the cross-section for H-beam steel members subjected to typical thin-walled members with relatively large widths and thicknesses. Test results on the hysteretic behaviour of H-section steel members are compared with those calculated from the proposed model in terms of the hysteric behaviour of components, strength degradation, energy-dissipating capacity, etc. These findings validate the correctness and feasibility of the established non-linear analysis model for thin-walled members.

Historical buildings are important assets that carry significant cultural and historical value. However, many of them become weathered over time and remain in poor condition with serious material degradation. This paper presents a nondestructive health assessment method by creating nonuniform finite element calculating units and then updating the Young's modulus by classifying the recombination with the modified Covariance Matrix Adaption Evolution Strategy algorithm. The method considers higher-dimensional parameters, which makes the results of finite element analysis more detailed. In addition, the method controls the updating step size, which avoids the need to sample at boundary positions and helps determine the location of damage and extent of degradation for large and complex historical brick masonry buildings. The method is validated through a case study of Minzhong Plaza. The results demonstrate that the modified Covariance Matrix Adaption Evolution Strategy method can accurately identify and quantify material deterioration in complex historical structures.

This paper proposes a novel structural damage identification approach coupling the Mayfly algorithm (MA) with static displacement-based response surface (RS). Firstly, a hybrid optimal objective function is established that simultaneously considers the sensitivity-based residual errors of static damage identification equation and the static displacement residual. In the objective function, the static damage identification equation is addressed by the Tikhonov regularization technique. The MA is subsequently employed to conduct an optimal search and pinpoint the location and intensity of damages at the structural element level. To handle the inconformity of the static loading points and the measurement points of displacements, the model reduction and displacement extension techniques are implemented to reconstruct the static damage identification equation. Meanwhile, the static displacement-based RS is constructed to calculate the displacement residual in the hybrid objective function, thereby circumventing the time-consuming finite element calculations and improving computational efficiency. The identification results of the numerical box girder bridge demonstrate that the proposed method outperforms the particle swarm optimization, differential evolution, Jaya and whale optimization algorithms about both convergence rate in optimal searching and identification accuracy. The proposed method enables more accurate damage identification compared to methods solely based on the indicator of the residual of static damage identification equations or displacement residual. The results of identifying damage in the 21 element-truss structure and the static experiments on identifying damage in an aluminum alloy cantilever beam confirm the high efficiency of the proposed approach.

Local bond behavior of glass fiber reinforced polymer (GFRP) bars under cyclic loading is systematically analyzed by beam-end tests. Meanwhile, the corresponding bond tests under monotonic loading were carried out for comparative analysis. In addition, the influence of concrete strength and lateral confinement from the concrete cover and stirrups on the bond behavior was considered in the tests. The results revealed that the specimen under cyclic loading exhibits narrower cracks but more seriously damaged bond interface than that under monotonic loading. It indicates that interface crushing exerts a decisive role in inducing the bond deterioration under cyclic loading, and the bond deterioration of specimens under cyclic loading was more severe. The increase of concrete strength and lateral confinement magnified the effects of cyclic loading on bond deterioration. Furthermore, a bond stress-slip model for GFRP bars under cyclic loading was put forward to better predict the bond behavior of GFRP bars with different confinements.

This paper focuses on studying the impaction of the correlation between the measurement data on structural model updating. A new homotopy based stochastic finite element model updating frame is constructed to cope with the correlated static measurement data. To judge whether considering the correlation of the measurement data, the sensitivity analysis of structural responses about structural parameters is implemented firstly. Then the discrete Karhunen–Loeve expansion is utilized to transform the correlated measurement data into a linear combination of multiple independent random variables. Furthermore, a novel stochastic model updating equation about the correlated static measurement data is set up, and is solved by the homotopy stochastic finite element method. It is significant to check the consistence of the correlation coefficients of the responses of the updated model with those of the measured data when the correlation actually exists. In this case, the proposed approach can effectively update the structural model.

Based on the up-floating incident of the basement in a high-rise residential building, the finite element (FE) model of the up-floating destruction region is established to investigate the damage mechanism. The stress states and the deformations of the basement structure are obtained under complex loads including water buoyancy forces, vehicle loads and construction loads. To assess the extent of damage, a novel damage indicator is defined based on two levels: the cracking bending moments and the yield bending moment. The first-level cracking bending moment, second-level cracking bending moment and the yield bending moment can be determined using the section stratification method. By comparing the maximum bending moment of the component with its corresponding cracking moment, one can determine whether the cracks have occurred and assess their severity. Meanwhile, the antifloating failure model is constructed to analyze the mechanism of the up-floating destruction. Finally, a detailed reinforcement treatment plan of 'decompression first and then reinforcement' is presented to reinforce and repair the damaged basement structure. The mechanism analysis of the up-floating destruction and the comprehensive reinforcement treatments ensure the simulation of the life cycle of emergence, development and treatment to ensure structural safety.

Ductile metal materials during a ductile failure will suffer from micro-void damage, simulation of which can contribute to the prediction of the macro fracture of steel structure. In this paper, the Gurson-Tvergaard-Needleman (GTN) constitutive model which describes the aggregate failure of metal voids is selected as the constitutive relation to investigating the damage evolution and fracture of semi-rigid joints in steel structures during a progressive collapse. During the process, specific parameters of the GTN model of steel are confirmed based on the combined results of the test and numerical simulation. The progressive collapse of two kinds of semi-rigid joints of steel pipe-to-H shaped steel were simulated by a nonlinear finite element method. A comparison between the simulation and test results verified that the GTN constitutive model can accurately simulate the fracture failure of the steel semi-rigid joints. Besides, a simplified joint failure model based on concentrated plastic hinge theory is proposed. Considering the damage and fracture of semi-rigid joints and the collision contact among different components, the progressive collapse of the semi-rigid steel frame structure is simulated by explicit dynamic analysis based on a finite particle method. Afterwards, the dynamic response of the structural progressive collapse can be predicted more accurately.

基础隔震技术是一种利用减、隔震装置将结构与基准面解耦来降低主体结构地震作用的控制技术,近几十年来在诸多重要工程中取得了成功应用.结合我国相关规范新引入极罕遇地震作用的研究背景,介绍了近年来国内外橡胶隔震支座和摩擦摆支座的理论与试验研究成果,重点探讨了复杂环境条件下隔震支座的性能演变规律与相应的性能提升方法,进而分析了被动自适应隔震系统与组合隔震系统的研究动态,并总结了研究存在的不足,为基础隔震体系性能评估与提升的进一步研究提供参考.

Transmission tower-line systems are vulnerable to failure when subjected to downbursts. For the long-span structure in which towers and wires extend for many kilometers, the collapse of one tower probably triggers the progressive collapses of towers along the line. Therefore, this study tries to probe the progressive collapse mechanisms of a tower-line system by fully coupled dynamic simulations. The downburst wind field is generated based on the empirical model by Chen & Letchford. A refined brace element is developed to have capacities of considering several failure modes in a member, such as the inelastic compression buckling, tension yielding and fractures, which is helpful to accurately capture the nonlinear behavior of towers subjected to downburst loading. The motion equations of the system are solved through the explicit central difference method that is programmed using MATLAB. The reliabilities of the developed element and program are validated against experiments and commercial software ANSYS, respectively. To identify the effects of the movement paths of downbursts on progressive collapse patterns of tower-line systems, three load cases (LCs) with different downburst paths are defined. For each LC, the time histories of displacements at tower tops and the middle of each span are presented. Additionally, the collapse scenarios at representative moments are plotted. The results indicate that the progressive collapse patterns of tower-line systems are greatly affected by downburst center movement paths. Downbursts with the same intensity but different paths probably lead to the collapse of one or three towers in the system. The dynamic behavior of wires is also important, which could cause local failures of tower heads.

Hysteresis models of structural members form a basis for the seismic analysis of structures. In this study, a new hysteresis model for circular steel tube (CST) members, which includes a skeleton curve part, a Bauschinger part, a strength and stiffness degradation part, and an unloading part, is proposed. The stiffness and strength degradation of the members are considered from the perspective of energy dissipation. The skeleton curve also includes the softening range due to local buckling. The key parameters of the hysteresis model, such as yield rotation and elastic stiffness, are strongly nonlinearly related to the geometric and material parameters of the members. Therefore, an artificial neural network method is employed to establish the nonlinear mapping relation between the parameters of the hysteresis model and the geometric and material parameters by training a large number of samples. To verify the validity of the model, the restoring force curves of the CST members predicted by the proposed hysteresis model are compared with those calculated using the finite element method. The results show that the artificial neural network-based model has relatively high accuracy and generalization ability and can effectively and accurately simulate the restoring force curve of the CSTs.

通过ABAQUS分析软件对一系列不同长细比、径厚比圆管截面钢支撑的压屈承载力、非线性屈曲平衡路径、卸载-再加载路径及损伤进行计算和统计,并选取典型构件计算结果与现有试验结果进行了对比,证明了有限元模型的准确性.通过统计的数值数据及现有的试验数据,拟合了简单、有效的圆管截面钢支撑现象滞回模型.该模型采用Coffin-Manson公式和Miner线性累积法则进行支撑低周疲劳损伤预测,建立了材料强度折减与疲劳损伤的相关公式,可以考虑支撑在滞回过程中的一些复杂非线性行为,如受拉屈服、受压非线性屈曲、包辛格效应及低周疲劳效应引起的材料强度折减和断裂等.该模型预测的支撑滞回曲线和累积能量耗散曲线与现有试验和校正的有限元模型的计算结果吻合较好,且计算耗时大幅缩减,适用于圆管截面钢支撑结构的非线性分析.

强震作用下桁架结构中的杆件破坏形式一般为受压屈曲和受拉屈服,但是常用的双线性理想模型不能考虑杆件受压屈曲的情况.根据杆件受压屈曲时的物理行为推导了相应的显式表达式,并嵌入到显式动力分析方法中实现了空间桁架结构的地震倒塌分析.采用三种不同的杆单元模型,对一个三层空间桁架进行了动力弹塑性分析,并与ANSYS的计算结果进行了对比,发现杆单元模型对结构的响应影响较大,压杆屈曲软化模型既能模拟杆件受拉屈服,又可以考虑杆件受压非线性屈曲,能较合理地模拟结构的动力响应.最后分别对三种单元模型定义了相应的破坏准则,比较了高耸输电塔桁架结构在不同破坏准则下地震倒塌特征,该结构在压杆屈曲破坏准则下发生倒塌时的最小加速度峰值PGA为11.7m/s2,具有较高的安全系数.

Lunar exploration has become increasingly popular, and lunar habitation research must be a core focus during the exploration of the Moon. The lunar habitation research must mainly include architectural and structural designs built using suitable material-forming technology and construction equipment. To address these issues, Chinese Super Mason (CSM) was proposed. This technology is an autonomous robotic construction system that is capable of automated assembling on-site prefabricated multistructural bricks and arched segments. The compound fabrication system was composed of a six-axis robotic manipulator and a dry mixed autoclaving fabricator carried on an autonomous-limbed vehicle platform. The Xuanwu Station for the lunar habitation conceptual design was developed and intended for erection by the CSM. A case study was conducted in a 2.8 m-long, 0.8 m-wide, and 1.1 m-high open arched-formwork structure fabricated within 8.5 h on the Earth. In addition, the Xuanwu Station was evaluated using finite element analysis software considering the temperature, air pressure, and other special environments on the Moon. The reliabilities and limitations of the CSM method were analyzed. Finally, the applications of the CSM in the extreme environment of the Earth and several improvements of the experimental equipment were discussed along with the proposed future applications for autonomous construction.

This study presents a simple yet efficient phenomenological hysteretic model for hollow circular steel (HCS) braces without a middle connection in concentrically braced frames (CBFs). The model is calibrated on the basis of the available experimental results and on a series of numerical simulations by finite-element (FE) models, which are validated by existing experiments. The Miner linear cumulative damage theory based on the Coffin-Manson expression is used to represent the low-cycle fatigue deterioration of a brace subjected to cyclic loading. Furthermore, the cumulative yielding strength degradation is considered by a simplified formulation, which is defined as the cumulative fatigue damage. Comparisons of the hysteretic responses obtained by the proposed model with the results of the FE models show that this model can capture several failure modes of a brace during inelastic cyclic behaviors, such as yielding, inelastic postbuckling, strength degradation, and fracture due to low-cycle fatigue, as well as the fracture point. The cumulative dissipated energy of a brace is well-predicted by the model. In addition, this model takes much less computing time than the FE model and is therefore suitable for structural analyses. The model should be further examined to more precisely consider the effect of the local buckling of a brace with different cross-sectional geometries. (c) 2019 American Society of Civil Engineers.

In this paper, a wind turbine tower with a hub height of 60m is taken as the research object, and its wind-induced fatigue analysis is carried out. First, the general method of wind-induced fatigue analysis of the wind turbine tower is given. The maximum stress time history curve of the tower is calculated by the time history analysis method. The stress amplitude, the mean value and the cycle times of the stress time history are counted by the rain-flow counting method. Finally, the fatigue life of tower is calculated by linear damage theory. According to the study, the fatigue life of the wind turbine is greater than that of the design service life, and it can meet the requirements of the design. The influence of wind load on the fatigue damage of the tower is different from the wind load of different wind speed and wind direction.

This study develops a force–displacement hysteresis model (computer program) for a bar element based on a physical theory model. The model is capable of capturing complex physical phenomena of member, such as yielding under tension, non-elastic buckling under compression, growth effect and degradation of buckling capacity due to the Bauschinger effect. The proposed element model is validated by comparing the simulation results with previous experimental results and is applied to the dynamic analysis of space truss structures. The explicit dynamic analysis method is adopted for solving the nonlinear equations of motion. Furthermore, a case study of a three-layer space truss structure is conducted. The reliability of the proposed algorithm and the need to develop the bar element are verified by comparing the results obtained using the proposed method and the ANSYS finite element analysis software package. Moreover, several fracture criteria for bar elements are defined and are used to analyse the progressive collapse of a space truss structure under seismic loading. The analytical results demonstrate that the selection of the fracture criterion for the bar members significantly affects the calculation of the collapse of the space truss structure under seismic loading. The strut buckling/softening-based fracture criterion can be used to relatively accurately evaluate the collapse resistance of a space truss structure under seismic loading. Finally, the collapse mode of a power transmission tower model under seismic loading is simulated. The simulation results are then compared with the collapse mode of a power transmission tower with a similar structure that collapsed during the Wenchuan earthquake. The simulation results agree closely with the observations, thereby verifying the reliability of the proposed algorithm.

In the seismic design of continuous girder bridges, rubber shock absorbers set between the girders and between the girders and the abutments could reduce the magnitude of impact behaviors and mitigate the damage incurred by structural collisions effectively. However, in practice, rubber shock absorbers are only considered as a construction measure, and the current research on the impact mechanical properties of rubber shock absorbers is very limited. In this paper, two types of rubber shock absorbers: natural rubber shock absorbers (N-RSA) and high-damping rubber shock absorbers (HD-RSA) were selected for study. Shape factor, volume, and shape (square vs round shapes) were proposed as controlling variables for the design of multiple sets of rubber shock absorbers. We also studied the impact of various factors on the force-displacement of rubber shock absorbers under the application of static loading. Using self-designed pendulum impact equipment, this research investigated the impact of pendulum impact velocity, the shape factor, volume, and shape of the rubber shock absorber on the force-displacement of the shock absorber. The results of this work may provide reference for the establishment of a nonlinear impacting mechanical model of a rubber shock absorber and the seismic design and analysis of bridge structure.

In this paper, the pattern of wind turbine tower collapse as a result of the coupled effects of wind and an intense, near-field earthquake is investigated. The constitutive relation of the tower cylinder steel is simulated via a nonlinear kinematic hardening model, and the specific value of each parameter in the constitutive model is provided. A precise model of the tower structure coupled with the blade is created using a nonlinear, finite element method. This method is compared with the results from a static pushover test of a small cylindrical tower to validate the finite element modeling method in this research. Two earthquake wave sets are selected as inputs. One contains 20 near-field velocity pulse-like ground motion waves with various pulse periods; the other contains 20 ordinary far-field ground motion waves. A wind turbine tower with a hub height of 60 m is selected as an example for analysis. The dynamic response of this tower as a result of the coupled effects of the two ground motion wave sets and a transient wind load is calculated using nonlinear time-history analysis. The calculation results shows that the average horizontal displacement of the tower top as a result of the near-field velocity pulse-like ground motion is 33% larger than the case with far-field ground motion. Finally, the seismic collapse vulnerability curve of this wind turbine tower is calculated. The seismic collapse capacity of the tower is evaluated, and the seismic collapse pattern of the tower is analyzed.