Seismic shear force magnification in RC cantilever structural walls,designed according to Eurocode 8

The paper contains a discussion of the inelastic dynamic magnification of seismic shear forces in cantilever walls with rectangular cross-sections. An extensive parametric study was performed in order to determine the reliability of the procedure in Eurocode 8 (EC8). A large number of single cantilever walls which are characteristic for the design practice in Europe and designed to satisfy all the EC8 requirements were analysed. The results obtained with the (modified) code procedures were compared with the results of inelastic response history analyses. If properly applied, the EC8 procedure for DCH walls usually yields good results for the base shears. However, as presently formulated and understood in the EC8, it can yield significantly incorrect results (overestimations of up to 40%). For this reason three modifications were introduced: (1) Keintzel’s formula, which is adopted in EC8, should be used in combination with the seismic shears obtained by considering the first mode of the excitation only; (2) the upper limit of the shear magnification factor should be related to the total shear force; and (3) a variable shear magnification factor along the height of the wall should be applied. The present procedure in EC8 for DCM structures (using a constant shear magnification factor of 1.5 for all walls) is non-conservative. For DCM walls it is strongly recommended that the same procedure as required for DCH walls be used.     

带钢筋及钢骨暗支撑剪力墙抗震性能试验研究

选取剪力墙结构体系中较为薄弱的抗震构件“一”形剪力墙,进行了3个1／3缩尺的带钢筋、钢骨暗支撑剪力墙以及普通RC剪力墙构件的低周反复荷载试验,比较分析了它们的承载力、刚度、延性、滞回特性、耗能能力及破坏机制,并提出抗震设计建议。     

双向单排配筋混凝土低矮剪力墙抗震性能试验研究

双向单排配筋混凝土低矮剪力墙适用于多层住宅结构。对4个原型的剪跨比为1.0配筋混凝土低矮剪力墙进行了低周反复荷载试验研究,包括1个双向双排配筋混凝土低矮剪力墙和3个双向单排配筋混凝土低矮剪力墙。其中1个双向单排配筋混凝土低矮剪力墙加设暗支撑,用以研究暗支撑对这种新型墙体的作用。在试验研究的基础上,对比分析了各剪力墙的刚度及其衰减过程、承载力、延性、滞回特征、耗能能力及破坏特征。试验表明,经过合理设计,这种双向单排配筋混凝土低矮剪力墙可以满足多层住宅结构抗震要求。     

不同型式暗支撑短肢剪力墙抗震性能试验研究

本文选取短肢剪力墙结构体系中较为薄弱的抗震构件“一”形短肢剪力墙，采用不同的暗支撑型式进行了两个1／2缩尺的带暗支撑短肢剪力墙构件的低周反复荷载试验，比较分析了它们的承载力、刚度、延性、滞回特性、耗能能力及破坏机制，建立了其承载力计算模型与方法。计算结果与实测值符合较好。     

Experimental seismic behavior of squat shear walls with precast concrete hollow moulds

This study proposes an innovative precast shear wall system, called an EVE precast hollow shear wall structure (EVE-PHSW). Precast panels in EVE-PHSW are simultaneously precast with vertical and horizontal holes. Noncontact lap splices of rebars are used in vertical joints connecting adjacent precast panels for automated prefabrication and easy in situ erection. The seismic behavior of EVE walls was examined through a series of tests on six wall specimens with aspect ratios of 1.0∼1.3. Test results showed that EVE wall specimens with inside cast-in situ concrete achieved the desired “strong bending and weak shear” and failed in shear mode. Common main diagonal cracks and brittle shear failure in squat cast-in situ walls were prevented. Inside cast-in situ concrete could significantly improve the shear strength and stiffness of EVE walls. The details of boundary elements (cast-in situ or prefabricated) and vertical joints (contiguous or spaced) had little effect on the global behavior of EVE walls. Noncontact lap splices in vertical joints could enable EVE walls to exhibit stable load-carrying capacity through extensive deformations. Evaluation on design codes revealed that both JGJ 3-2010 and ACI 318-14 provide conservative estimation of shear strength of EVE walls, and EVE walls achieved shear strength reserves comparative to cast-in situ walls. The recommended effective stiffness for cast-in situ walls in ASCE 41–17 appeared to be appropriate for EVE walls.

     

Experimental observations on the seismic shear performance of RC beam-to-column connections subjected to varying axial column force

The paper presents results from the first series of an ongoing experimental study aimed at quantifying the effect of axial column load on the shear capacity of beam-to-column connections. This is deemed important due to the recent evidence showing that vertical earthquake ground motion, when combined with high overturning moments, may cause reduced column compression or even tension. In which case, the concrete contribution to shear resistance in the panel zone is diminished, which may lead to failure prior to the attainment of the full resisting capacity of the beam section. The results first show that the failure mode of the models was, as intended, shear failure of the panel zone. It is further observed that the axial column load has a marked effect on the shear deformation capacity, yield point, cracking pattern, ultimate capacity and ductility of the panel zone. Differences in the range of 30 per cent in capacity and 50 per cent in deformability were recorded. The preliminary results are useful in providing design guidance for structures located in areas of potential high vertical ground motion component. Also, for high-rise structures, where there are large overturning moments, the results may be of use in ensuring a uniform safety factor (or overstrength) in various non-dissipative parts of the structure.     

内藏钢桁架混凝土组合高剪力墙抗震性能试验研究

进行了3个1/3缩尺的高剪力墙的抗震性能试验研究,包括1个普通混凝土高剪力墙、1个内藏钢框架混凝土组合高剪力墙和1个内藏钢桁架混凝土组合高剪力墙。在试验研究基础上,对比分析了各剪力墙的刚度及其衰减过程、承载力、延性、滞回特性及破坏特征。试验表明:内藏钢框架混凝土组合高剪力墙的抗震性能比普通混凝土高剪力墙明显提高;内藏钢桁架混凝土组合高剪力墙的抗震性能比普通混凝土高剪力墙显著提高。     

Static inelastic analysis of RC shear walls

A macro-model of a reinforced concrete (RC) shear wall is developed for static inelastic analysis. The model is composed of RC column elements and RC membrane elements. The column elements are used to model the boundary zone and the membrane elements are used to model the wall panel. Various types of constitutive relationships of concrete could be adopted for the two kinds of elements. To perform analysis, the wall is divided into layers along its height. Two adjacent layers are connected with a rigid beam. There are only three unknown displacement components for each layer. A method called single degree of freedom compensation is adopted to solve the peak value of the capacity curve. The post-peak stage analysis is performed using a forced iteration approach. The macro-model developed in the study and the complete process analysis methodology are verified by the experimental and static inelastic analytical results of four RC shear wall specimens. Supported by: National Natural Science Foundation of China, Grant number 59895410     

内藏钢桁架混凝土组合低剪力墙抗震性能试验研究

进行了3个1/3缩尺的低剪力墙的抗震性能试验研究,包括1个普通混凝土低剪力墙、1个内藏钢框架混凝土组合低剪力墙和1个内藏钢桁架混凝土组合低剪力墙。在试验研究基础上,对比分析了各剪力墙的刚度及其衰减过程、承载力、延性、滞回特性、钢筋应变、耗能能力及破坏特征。试验表明:内藏钢框架和内藏钢桁架混凝土组合低剪力墙的抗震性能比普通混凝土低剪力墙明显提高。     

小剪跨比格构式混凝土墙体抗震性能试验

文章旨在研究不同剪跨比的格构式混凝土墙体抗震性能.将生产车间预制成EPS保温模块拼接成墙体模板,在横向和纵向孔洞中分别布置钢筋,然后在孔内浇筑自密实混凝土,形成“EPS新型节能”格构式混凝土墙体,然后对6个参数不同的试件进行低周反复水平荷载作用的试验.结果,墙体破坏形态为:首先墙体相邻格构柱间的连梁出现环状裂缝和“X”...     

型钢混凝土短肢剪力墙抗震性能的试验研究

型钢混凝土短肢剪力墙是一种新型的剪力墙结构形式,它可以充分发挥钢和混凝土两种材料的优势,改善普通钢筋混凝土短肢剪力墙延性和耗能能力较差的缺点,其抗弯、抗剪承载力和抗震性能均好于后者.文中对3个1/2缩尺的型钢混凝土组合"一"字形短肢剪力墙进行了低周反复荷载下的抗震性能试验研究,墙肢截面宽厚比分别为5、5.5、6.在试验研究基础上,分析了各剪力墙承载力、延性、滞回特性及破坏特征,并提出了抗震设计建议.试验结果表明型钢暗柱的存在提高了混凝土短肢剪力墙的后期强度储备,改善混凝土短肢剪力墙的抗震性能.     

钢筋混凝土带暗支撑一字形截面短肢剪力墙抗震性能试验研究

对6个1／2缩尺的一字形截面短肢剪力墙构件进行了低周反复荷载下的抗震性能试验研究，墙肢截面高厚比分别为5．O、6．5、8．O，按普通与墙板中加设暗支撑两种情况进行设计。研究了带暗支撑一字形截面短肢剪力墙的承载力、刚度、延性、耗能、滞回特性等，并提出了抗震设计建议。     

钢筋混凝土带暗支撑Z形截面短肢剪力墙抗震性能试验研究

对6个1／2缩尺的Z形截面短肢剪力墙构件进行了低周反复荷载下的抗震性能试验研究，墙肢截面高厚比分别为5、6．5、8，按普通与墙板中加设暗支撑两种情况进行设计。研究了带暗支撑Z形截面短肢剪力墙的承载力、刚度、延性、耗能、滞回特性等，并提出了抗震设计建议。     

上部再生混凝土双肢剪力墙抗震性能试验研究

进行了3个1∶4缩尺的四层双肢剪力墙模型抗震性能的对比试验,连梁跨高比为1.5。模型1为普通混凝土双肢剪力墙,模型2为全再生混凝土双肢剪力墙,模型3为底部两层普通混凝土、上部两层再生混凝土双肢剪力墙。分析了各双肢剪力墙的承载力、延性、刚度、滞回特性、耗能及破坏特征。结果表明:与普通混凝土双肢剪力墙相比,全再生混凝土双肢剪力墙的抗震性能略差,底部两层普通混凝土、上部两层再生混凝土的双肢剪力墙与普通混凝土双肢剪力墙抗震性能接近。建立了再生混凝土双肢剪力墙的承载力计算模型,计算结果与试验结果吻合较好。     

带缝空心保温RC剪力墙耗能性能试验研究

为研究带缝空心保温钢筋混凝土剪力墙的耗能性能,设计并制作了3组钢筋混凝土空心保温剪力墙。通过水平低周反复荷载试验,研究了该剪力墙的破坏机理、滞回特性、延性与耗能性能等力学性能,分析了竖缝形式、连接键等对空心保温剪力墙耗能性能的影响。研究表明:设置竖缝和连接键可以改变剪力墙的受力模式,使剪力墙在刚度和承载力下降较小的情况下,延性和抗震性能得到较大提高。由于耗能机理的转变,连接键、竖缝内的钢筋和橡胶带参与耗能,较大程度地提高剪力墙的耗能性能。     

Modelling of elastic damping in nonlinear time-history analyses of cantilever RC walls

Damping constitutes a major source of uncertainty in dynamic analysis and an open issue to experimental and analytical research. After a thorough review of the current views and approaches existing in literature on damping and its appropriate modelling, this paper focuses on the implications of the available modelling options on analysis. As result of a series of considerations, a damping modelling solution for nonlinear dynamic analyses of cantilever RC walls is suggested within the frame of Direct Displacement-Based Design, supported by comparative analyses on wall structures.     

Seismic shear distribution among interconnected cantilever walls of different lengths

Mid‐rise to high‐rise buildings in seismic areas are often braced by slender reinforced concrete (RC) walls, which are interconnected by RC floor diaphragms. In design, it is typically assumed that the lateral forces are distributed in proportion to the wall's elastic stiffness. Pushover analyses of systems comprising walls of different lengths have, however, shown that large compatibility forces can develop between them, which should be considered in design, but the analyses have also shown that the magnitude of the computed forces is very sensitive to the modelling assumptions. Using the results of a complex shell element model as benchmark, different simple hand‐calculation methods and inelastic beam element models are assessed and improved to yield reliable estimates of the base shear distribution among the individual walls comprising the interconnected wall system. Copyright © 2014 John Wiley & Sons, Ltd.     

基于性能的抗震设计方法在剪力墙结构中的应用

本文对基于性能的抗震设计方法中最具有代表性的直接基于位移的设计方法在剪力墙结构中的应用进行了研究。采用结构非线性分析程序探讨了墙厚、混凝土强度等级、纵筋配筋率、钢筋级别、轴压比、墙长等因素对单肢剪力墙屈服位移的影响,从而对现有的屈服曲率计算公式进行了改进。另外将按顶点荷载作用下的屈服位移计算公式求出的屈服位移与实际倒三角形荷载作用下的剪力墙屈服位移进行了比较,,从而推导出倒三角形荷载作用下的屈服位移计算公式。     

不同轴压比下内藏钢桁架混凝土组合剪力墙抗震研究

轴压比是影响剪力墙抗震性能的一个主要因素,直接决定其延性性能。本文对两组共六个高剪力墙1/3缩尺的试件模型进行了不同轴压比下的低周反复荷载试验,研究了轴压比对内藏钢桁架混凝土组合剪力墙抗震性能的影响,对比了各试件的承载力、刚度及其退化过程、延性、滞回特性及破坏特征。试验表明:随着轴压比的提高其试件的承载力提高但延性下降;不同轴压比下内藏钢桁架混凝土组合剪力墙均能明显提高钢筋混凝土剪力墙的抗震性能。     

Experimental and analytical study on seismic behavior of steel-concrete multienergy dissipation composite shear walls

In this paper, a steel-concrete multi-energy dissipation composite shear wall, comprised of steel-reinforced concrete(SRC) columns, steel plate(SP) deep beams, a concrete wall and energy dissipation strips, is proposed. In order to study the multi-energy dissipation behavior and restorability after an earthquake, two stages of low cyclic loading tests were carried out on ten test specimens. In the first stage, test on five specimens with different number of SP deep beams was carried out, and the test lasted until the displacement drift reached 2%. In the second stage, thin SPs were welded to both sides of the five specimens tested in the first stage, and the same test was carried out on the repaired specimens(designated as new specimens). The load-bearing capacity, stiffness, ductility, hysteretic behavior and failure characteristics were analyzed for both stages and the results are discussed herein. Extrapolating from these results, strength calculation models and formulas are proposed herein and simulations using ABAQUS carried out; they show good agreement with the test results. The study demonstrates that SRC columns, SP deep beams, concrete wall and energy dissipation strips cooperate well and play an important role in energy dissipation. In addition, this study shows that the shear wall has good recoverability after an earthquake, and that the welding of thin SP’s to repair a deformed wall is a practicable technique.