A regularized fiber element model for reinforced concrete shear walls

Reinforced concrete shear walls are used because they provide high lateral stiffness and resistance to extreme seismic loads. However, with the increase in building height, these walls have become slenderer and hence responsible of carrying larger axial and shear loads. Because 2D/3D finite element inelastic models for walls are still complex and computationally demanding, simplified but accurate and efficient fiber element models are necessary to quickly assess the expected seismic performance of these buildings. A classic fiber element model is modified herein to produce objective results under particular loading conditions of the walls, that is, high axial loads, low axial loads, and nearly constant bending moment. To make it more widely applicable, a shear model based on the modified compression field theory was added to this fiber element. Consequently, this paper shows the formulation of the proposed element and its validation with different experimental results of cyclic tests reported in the literature. It was found that in order to get objective responses in the element, the regularization techniques based on fracture energy had to be modified, and nonlinearities because of buckling and fracture of steel bars, concrete crushing, and strain penetration effects were needed to replicate the experimental cyclic behavior. Thus, even under the assumption of plane sections, which makes the element simple and computationally efficient, the proposed element was able to reproduce the experimental data, and therefore, it can be used to estimate the seismic performance of walls in reinforced concrete buildings. Copyright © 2016 John Wiley & Sons, Ltd.     

轴向压力对配筋砌体短肢剪力墙抗剪性能的影响

通过对6片足尺290mm厚全灌芯配筋砌块砌体短肢剪力墙拟静力试验结果的分析,利用非线性有限元方法,模拟了此种墙体在压弯剪共同作用下的抗剪特性,研究了轴向压力对配筋砌块砌体短肢剪力墙抗剪性能的影响。研究表明,在不同高宽比的墙体中,轴向压力均对墙体的抗剪能力有较大影响,随着轴向压力增大,墙体抗剪能力先增大后减小（轴压比n从0.1增长到0.4时,墙体抗剪能力逐渐增大,而n从0.4增长到0.6时,墙体抗剪能力却逐渐减小）;随着轴向压力的增大,墙体延性在逐渐减小。提出当轴压比等于0.3时,墙体抗剪能力和延性均较好,建议在建筑抗震设计规范中采用此值。     

混凝土核心筒的有限元模拟及若干参数的影响分析

运用ABAQUS分析软件,建立水平荷载作用下的钢筋混凝土核心筒有限元模型,进行非线性分析,并将分析结果与大比例试件的试验结果对比,对所采用的有限元模型加以验证。在此基础上,进行改变钢筋混凝土核心筒轴压比、高宽比和筒壁厚度的受力过程模拟分析,研究这些参数对筒体性能的影响。结果表明：随着轴压比的增大,筒体的破坏由受拉向受压破坏转变,筒体最大水平承载力经历先增加后减小的变化,延性变差;随着高宽比的增大,筒体破坏形态由剪切向弯曲破坏转变,延性增加,整体弯曲作用更加明显,最大底部剪力减小;随着壁厚的增大,试件破坏由截面压屈失稳向墙肢底部受弯破坏转变,墙肢破坏区域沿高度方向发展,耗能能力更强,承载力明显增大,变形能力显著增加。     

Discussion of paper ‘Seismic behavior and modeling of steel reinforced concrete (SRC) walls’ by Xiaodong Ji,Ya Sun,Jiaru Qian and Xinzheng Lu,Earthquake Engineering and Structural Dynamics 2015; 44(6):955–972

The paper under discussion presents a series of quasi‐static tests used to examine the behavior of steel reinforced concrete (SRC) walls subjected to high axial force and lateral cyclic loading. A total of six wall specimens were designed, including five SRC walls and one reinforced concrete (RC) wall. In the ‘Summary’ section of the discussed paper, the authors state that: ‘The use of SRC walls has gained popularity in the construction of high‐rise buildings because of their superior performance over conventional RC walls’. The authors also proposed that, the SRC wall specimens showed increased flexural strength and deformation capacity relative to their RC wall counterpart. The discussion is prompted to rectify some statements and conclusions of the paper under discussion. Copyright © 2015 John Wiley & Sons, Ltd.     

钢筋混凝土核心筒体抗震性能试验研究

本文对两组五个钢筋混凝土核心筒试件进行了低周反复荷载试验，研究了不同轴压比和剪跨比的核心筒破坏机理、承载能力、延性和耗能能力等方面的抗震性能。结果表明，轴压比对核心筒的抗震性能有较大影响。     

高强钢筋混凝土短肢剪力墙抗震性能试验研究

通过对采用高强钢筋的6片T形混凝土短肢剪力墙和采用高强钢筋高强混凝土的6片L形短肢剪力墙进行低周往复加载试验,研究了T形和L形的破坏形态与性能差异,分析了高厚比、轴压比、配箍间距等参数对构件破坏形态、滞回耗能、骨架曲线、延性及耗能等抗震性能的影响,对比分析了构件与普通短肢剪力墙的抗震性能差异。试验结果表明:采用腹板端部箍筋加密的方式可减轻构件端部的损伤和降低正负向加载时承载力和延性的不对称性;T形构件中高厚比为5的试件表现为弯曲破坏,其他构件表现为弯剪破坏;试验中高厚比小的构件相对于高厚比大的试件延性耗能更好,轴压比增大,构件承载力提高但延性降低;与普通短肢剪力墙相比,T形短肢剪力墙承载力和变形能力提高,耗能增加,L形短肢剪力墙承载力提高较大,极限位移增大,构件后期变形能力略有降低,但可以满足抗震性能要求。     

轴压比对中等高度LC结构剪力墙抗震性能的影响

轻骨料混凝土(L ight-we ight concrete,简称LC)剪力墙的轴压比是剪力墙抗震设计时一个重要的控制因素,直接关系到其延性性能。为使设计规程具有足够的理论依据,本文通过对六榀轻骨料混凝土剪力墙试件的试验,研究了在低周反复荷载作用下,着重考虑不同轴压比对中等高度有边框剪力墙的破坏形态和变形性能的影响效应,对其滞回特性进行分析,计算了各剪力墙的刚度退化率与延性系数,并将无竖缝剪力墙与带竖缝剪力墙的抗震性能进行了对比。     

Seismic behavior and modeling of steel reinforced concrete (SRC) walls

The steel reinforced concrete (SRC) wall consists of structural steel embedded at the boundary elements of a reinforced concrete (RC) wall. The use of SRC walls has gained popularity in the construction of high‐rise buildings because of their superior performance over conventional RC walls. This paper presents a series of quasi‐static tests used to examine the behavior of SRC walls subjected to high axial force and lateral cyclic loading. The SRC wall specimens showed increased flexural strength and deformation capacity relative to their RC wall counterpart. The flexural strength of SRC walls was found to increase with increasing area ratio of embedded structural steel, while the section type of embedded steel did not affect the wall's strength. The SRC walls under high axial force ratio had an ultimate lateral drift ratio of approximately 1.4%. In addition, a multi‐layer shell element model was developed for the SRC walls and was implemented in the OpenSees program. The numerical model was validated through comparison with the test data. The model was able to predict the lateral stiffness, strength and deformation capacities of SRC walls with a reasonable level of accuracy. Finally, a number of issues for the design of SRC walls are discussed, along with a collection and analysis of the test data, including (1) evaluation of flexural strength, (2) calculation of effective flexural stiffness, and (3) inelastic deformation capacity of SRC walls. Copyright © 2014 John Wiley & Sons, Ltd.     

双向单排配筋中高剪力墙抗震性能试验研究

双向单排配筋剪力墙结构适用于多层住宅结构。本文进行了1个普通双向双排配筋混凝土中高剪力墙、2个双向单排配筋混凝土中高剪力墙和1个带暗支撑双向单排配筋混凝土中高剪力墙的低周反复荷载试验,以研究双向单排配筋混凝土中高剪力墙的抗震性能及暗支撑对这种新型墙体结构的作用。较系统地分析了其承载力、刚度及其退化过程、延性、耗能、破坏机制和破坏特征等。试验表明,经过合理设计,这种双向单排配筋混凝土中高剪力墙可以满足多层住宅结构抗震要求。     

Three‐dimensional beam‐truss model for reinforced concrete walls and slabs – part 1: modeling approach,validation, and parametric study for individual reinforced concrete walls

A three‐dimensional beam‐truss model for reinforced concrete (RC) walls developed by the first two authors in a previous study is modified to better represent the flexure–shear interaction and more accurately capture diagonal shear failures under static cyclic or dynamic loading. The modifications pertain to the element formulations and the determination of the inclination angle of the diagonal elements. The modified beam‐truss model is validated using the experimental test data of eight RC walls subjected to static cyclic loading, including two non‐planar RC walls under multiaxial cyclic loading. Five of the walls considered experienced diagonal shear failure after reaching their flexural strength, while the other three walls had a flexure‐dominated response. The numerically computed lateral force–lateral displacement and strain contours are compared with the experimentally recorded response and damage patterns for the walls. The effects of different model parameters on the computed results are examined by means of parametric analyses. Extension of the model to simulate RC slabs and coupled RC walls is presented in a companion paper. Copyright © 2016 John Wiley & Sons, Ltd.     

Effects of column axial force – bending moment interaction on inelastic seismic response of steel frames

It is well known that axial force – bending moment interaction (N–M interaction) affects to a large extent the cyclic inelastic behaviour of structural elements, especially columns in framed structures, with reduction in bending capacity and loss of available ductility. A few studies have also shown that significant inelastic axial shortening affects the response of column elements subjected to medium–high levels of axial loads and cyclic bending. This paper is primarily aimed at evaluating the effects of column N–M interaction on the inelastic seismic response of steel frames. By considering the contemporaneous action of vertical loads, due to gravity, and of horizontal seismic excitation, it is shown that the progressive axial shortening of adjacent columns may differ substantially, thus inducing significant relative settlements at the ends of the connecting beams and, then, remarkable amplifications in beam plastic rotations. An evaluation of additional beam plastic rotations induced by column N–M interaction is carried out for real structures by investigating the inelastic response of steel frames designed according to European standards under horizontal and vertical earthquake excitations. Copyright © 2003 John Wiley & Sons, Ltd.     

基于等效框架模型的砌体结构抗震模拟及验证

等效框架模型采用宏观模型来模拟砌体墙在平面内的抗震性能。砌体墙的墙柱和墙梁采用同时考虑轴向弯曲和剪切变形的基于力法的纤维截面进行模拟,且两者的连接视为刚性区域。轴向压缩及弯曲效应在截面纤维模型中考虑,而剪切效应由V-γ剪切恢复力模型表达,弯曲和剪切在单元层面进行耦合。通过统计和分析,确定骨架曲线的计算方法,并基于Ibarra-Krawinkler模型提出剪切恢复力模型。通过算例得出:该模型在单调加载和循环加载下的数值计算结果与试验结果均吻合较好。     

Seismic behavior and strength capacity of steel tube‐reinforced concrete composite columns

The steel tube‐reinforced concrete (ST‐RC) composite column is a novel type of composite column, which consists of a steel tube embedded in RC. In this paper, the seismic behavior of ST‐RC columns is examined through a series of experiments in which 10 one‐third scale column specimens were subjected to axial forces and lateral cyclic loading. The test variables include the axial force ratio applied to the columns and the amount of transverse reinforcement. All specimens failed in a flexural mode, showing stable hysteresis loops. Thanks to the steel tube and the high‐strength concrete it is filled with, the ST‐RC column specimens had approximately 30% lower axial force ratios and 22% higher maximum bending moments relative to the comparable RC columns when subjected to identical axial compressive loads. The amount of transverse reinforcement made only a small difference to the lateral load‐carrying capacity but significantly affected the deformation and energy dissipation capacity of the ST‐RC columns. The specimens that satisfied the requirements for transverse reinforcement adopted for medium ductile RC columns as specified by the Chinese Code for Seismic Design of Buildings (GB 50011‐2010) and EuroCode 8 achieved an ultimate drift ratio of around 0.03 and a displacement ductility ratio of approximately 5. The design formulas used to evaluate the strength capacity of the ST‐RC columns were developed on the basis of the superposition method. The predictions from the formulas showed good agreement with the test results, with errors no greater than 10%. Copyright © 2013 John Wiley & Sons, Ltd.     

Research on seismic performance of shear walls with concrete filled steel tube columns and concealed steel trusses

In order to further improve the seismic performance of RC shear walls, a new composite shear wall with concrete filled steel tube (CFT) columns and concealed steel trusses is proposed. This new shear wall is a double composite shear wall; the first composite being the use of three different force systems, CFT, steel truss and shear wall, and the second the use of two different materials, steel and concrete. Three 1/5 scaled experimental specimens: a traditional RC shear wall, a shear wall with CFT columns, and a shear wall with CFT columns and concealed steel trusses, were tested under cyclic loading and the seismic performance indices of the shear walls were comparatively analyzed. Based on the data from these experiments, a thorough elastic-plastic finite element analysis and parametric analysis of the new shear walls were carried out using ABAQUS software. The finite element results of deformation, stress distribution, and the evolution of cracks in each phase were compared with the experimental results and showed good agreement. A mechanical model was also established for calculating the load-carrying capacity of the new composite shear walls. The results show that this new type of shear wall has improved seismic performance over the other two types of shear walls tested.     

Substructure hybrid testing of reinforced concrete shear wall structure using a domain overlapping technique

An online hybrid test was carried out on a 40-story 120-m high concrete shear wall structure. The structure was divided into two substructures whereby a physical model of the bottom three stories was tested in the laboratory and the upper 37 stories were simulated numerically using ABAQUS. An overlapping domain method was employed for the bottom three stories to ensure the validity of the boundary conditions of the superstructure. Mixed control was adopted in the test. Displacement control was used to apply the horizontal displacement, while two controlled force actuators were applied to simulate the overturning moment, which is very large and cannot be ignored in the substructure hybrid test of high-rise buildings. A series of tests with earthquake sources of sequentially increasing intensities were carried out. The test results indicate that the proposed hybrid test method is a solution to reproduce the seismic response of high-rise concrete shear wall buildings. The seismic performance of the tested precast high-rise building satisfies the requirements of the Chinese seismic design code.     

Seismic behavior of a partially grouted reinforced masonry structure: Shake-table testing and numerical analyses

In regions of low to moderate seismicity in North America, reinforced masonry structures are mostly partially grouted. The behavior of such structures under lateral seismic loads is complicated because of the interaction of the grouted and ungrouted masonry. As revealed in past experimental studies, the performance of partially grouted masonry (PGM) walls under in-plane cyclic lateral loading is inferior to that of fully grouted walls. However, the dynamic behavior of a PGM wall system under severe seismic loads is not well understood. In this study, a full-scale, one-story, PGM building designed for a moderate seismic zone according to current code provisions was tested on a shake table. It was shown that the structure was able to develop an adequate base shear capacity and withstand two earthquake motions that had an effective intensity of two times the maximum considered earthquake with only moderate cracking in mortar joints. However, the structure eventually failed in a brittle manner in a subsequent motion that had a slightly lower effective intensity. A detailed finite element model of the test structure has been developed and validated. The model has been used to understand the distribution of the lateral force resistance among the wall components and to evaluate the shear-strength equation given in the design code. The code equation has been found to be adequate for this structure. Furthermore, a parametric study conducted with the finite element model has shown that the introduction of a continuous bond beam right below a window opening is highly beneficial.     

Effect of earthquake‐induced axial load fluctuations on asymmetric frame–wall–rocking foundation systems

Fluctuations in axial load imposed on a rocking footing will affect its moment capacity, the shape of its moment–rotation hysteresis, and potentially the system's seismic performance. Structural asymmetry increases the likelihood of axial load variation during earthquake excitations. To investigate this issue, a unique centrifuge testing program was carried out on low‐rise frame–wall–rocking foundation systems. In this paper, the seismic behaviors of asymmetric and symmetric models from this test program are systematically compared. Experimental results reveal that placing the lateral force resisting shear wall outboard produces significant axial load fluctuation, which in turn greatly deteriorate the lateral load‐carrying capacity of a foundation rocking dominated frame–wall system, particularly in its weak direction. However, it strengthens the system when loading is towards the shear wall, leading to a highly asymmetric hysteretic response. During earthquake loading, all asymmetric rocking foundation systems observe smaller peak roof accelerations, but larger peak and permanent roof drifts compared with the symmetric systems. Despite these differences in response, the axial load fluctuation and structural asymmetry do not significantly change the relative energy dissipated by the rocking foundations and inelastic structural components within each frame–wall–rocking foundation model. Copyright © 2015 John Wiley & Sons, Ltd.     

型钢混凝土低矮剪力墙抗震性能试验研究

剪力墙构件是现代高层建筑结构中的主要抗侧向力构件.为了对比型钢桁架混凝土组合低矮剪力墙与型钢框架混凝土组合低矮剪力墙以及普通钢筋混凝土低矮剪力墙在地震作用下的抗震性能,本文进行了四榀1/4缩尺模型的低矮混凝土剪力墙在单调和低周反复荷载作用下的对比试验,其中单调加载试验包括一榀内置型钢桁架的型钢混凝土组合低矮剪力墙,反复加载试验包括一榀普通钢筋混凝土低矮剪力墙、一榀内置型钢框架的型钢混凝土低矮剪力墙和一榀内置型钢桁架的型钢混凝土低矮剪力墙,给出了各试件的刚度、承载力、变形、延性和破坏形态等试验结果,并对其进行分析.试验结果表明,在这三种墙体中,型钢桁架混凝土组合低矮剪力墙的承载力、变形能力、耗能能力较其他类型剪力墙好,并为型钢桁架混凝土组合低矮剪力墙在实际中的应用提供了试验依据.     

Test and analysis of reinforced concrete (RC) precast shear wall assembled using steel shear key (SSK)

Reinforced concrete (RC) precast shear walls are extensively applied in practical engineering, owing to their fast construction speed. However, because of the transport conditions, RC precast shear walls have to be separated into small wall segments during the factory prefabrication procedure before being assembled on site. Typically, wet-type jointing methods are adopted to link the segments, which is time-consuming and results in unreliable post-pouring area strength. To overcome this problem, the novel scheme of the steel shear key (SSK) featuring steel shear panels and combined fillet and plug welding is proposed. Three RC precast shear wall specimens with different linking strength, termed as weakened SSK wall, standard SSK wall, and strengthened SSK wall, respectively, and an integrated shear wall specimen were designed. Quasi-static cyclic loading was applied to investigate the specimens' dynamic properties. The test results suggest the prefabricated wall segments equipped with SSKs showed reliable stiffness and bearing capacity and were improved in energy dissipation ability, compared with conventional shear walls. As the shear stiffness and number of equipped SSKs increased, the specimens exhibited higher strength, but their ductility and energy dissipation were slightly decreased. Most importantly, the standard SSK wall specimen could achieve satisfactory bearing capacity and deformability and is thus recommended for precast building structures. Finite element method (FEM) models were established to validate the test results, and parametric study analysis was conducted based on the coupling ratio of the SSK walls. Finally, an appropriate coupling ratio range is recommended for practical engineering applications.