基于OpenSees平台的钢管混凝土结构力学性能数值模拟

基于非线性纤维梁-柱单元理论,以OpenSees为求解平台分别进行了钢管混凝土结构滞回曲线计算和弹塑性动力时程分析等数值模拟,计算结果与试验吻合良好。钢管内核心混凝土采用考虑钢管约束效应的应力—应变关系,钢材采用随动强化本构模型。在传统纤维模型法的基础上,通过直接在截面层次定义非线性剪切恢复力的方法建立了考虑非线性剪切效应的剪力墙结构数值模型,结果表明该模型能较好地模拟组合剪力墙的抗剪承载力、捏缩效应以及刚度退化等力学性能。对输入不同地震波下钢管混凝土框架体系的动力时程分析表明,基于OpenSees求解平台的非线性纤维模型法能够较好地模拟钢管混凝土框架结构的非线性动力特性。     

强震下混凝土剪力墙受弯模拟及测试实验研究

为提高混凝土剪力墙受弯性能计算的准确度,开展强震下混凝土剪力墙受弯性能试验研究。选取1个混凝土剪力墙对比试件和3个测试试件作为研究对象,对试件施加垂直荷载和水平荷载,模拟强烈地震作用力。试验前期准备工作完成后,建立分离式有限元模型,通过计算混凝土在受压和受拉状态下的损伤弹塑性刚度,完成对有限元模型中混凝土塑性损伤分析,在此基础上,计算混凝土剪力墙受弯承载力。利用有限元模型对3个测试试件进行模拟试验,结果表明,强烈地震后3个试件的荷载-位移曲线均与实际位移值接近,且混凝土剪力墙受弯承载力试验结果与实际值的误差在2%以内,表明试验研究方法具有一定的可行性,数值模拟结果较为准确。     

混凝土板墙加固后墙片与剪力墙性能的对比研究

首先通过3个墙片的水平低周反复伪动力试验,对比研究了混凝土板墙加固后墙片与剪力墙的承载力、耗能能力等各项抗震性能。由于试验条件的限制,试验仅对比研究了120mm混凝土剪力墙与双面60mm混凝土板墙加固后墙片的抗震性能。在试验基础上,利用有限元软件建立合理的计算模型,将计算结果与试验结果进行了对比分析;利用该计算模型模拟了用不同厚度的混凝土板墙加固墙片和混凝土剪力墙,系统分析了混凝土板墙加固后墙片与剪力墙的极限承载力,分析了将加固后墙片看作抗震墙的可行性。通过有限元的分析,弥补了试件不足的缺陷,完善了研究方法。     

边框SFRC剪力墙开裂弯矩影响因素和计算方法

针对剪力墙边缘构件受力复杂、施工困难的特点,提出了在剪力墙边缘构件中采用钢纤维局部增强的方法来改进其抗裂性能,并将其命名为边框钢纤维混凝土(SFRC)剪力墙。结合试验结果和有限元数值模拟,研究了钢纤维体积率和轴压比对边框SFRC剪力墙抗裂承载力的影响。结果表明,边缘构件钢纤维体积率为1.5%~2%之间时对剪力墙开裂弯矩增强效果最好,最大提高幅度达45.1%。相对于整体钢纤维混凝土剪力墙,仅边缘构件采用钢纤维增强的剪力墙在未降低过多承载力的情况下,具有较好的经济优势。基于上述计算结果,提出了边框SFRC剪力墙开裂弯矩计算公式中主要参数的取值建议和开裂弯矩的简化计算方法,可供该类剪力墙设计验算时参考。     

新型钢板剪力墙钢框架结构的地震响应分析

本文在单片带缝钢板剪力墙理论研究的基础上,提出带缝钢板剪力墙的等效计算模型,对钢板剪力墙钢框架结构工程实例结构进行自振特性分析、常遇地震作用下的动力响应分析以及结构在罕遇地震作用下的三维非线性时程响应分析,得到一些有意义的结果和结论。     

钢管混凝土边框高强混凝土组合剪力墙抗震性能试验研究

钢管混凝土边框组合剪力墙是一种新型组合剪力墙。本文进行了2个1/4缩尺的高强混凝土剪力墙模型的低周反复荷载试验,模型1为普通钢筋混凝土剪力墙,模型2为钢管混凝土边框组合剪力墙。在试验研究基础上,对比分析它们的承载力、延性、刚度及其衰减过程、滞回特性、耗能能力及破坏特征,建立了组合剪力墙的承载力计算模型,计算结果与实测结果符合较好。研究表明,钢管混凝土边框高强混凝土组合剪力墙与普通剪力墙相比抗震性能显著提高。     

考虑钢板与混凝土间粘结滑移的组合剪力墙模型化分析

应用ABAQUS对内置钢板的RC剪力墙在单调荷载作用下的荷载-位移特性进行了模拟分析;分析了轴压比、混凝土强度等级、高宽比和混凝土墙厚等参数对钢板与混凝土粘结性能的影响,发现了高宽比对粘结滑移影响最大,高宽比越大粘结滑移越明显,并降低了构件的抗剪承载力;混凝土强度等级对粘结滑移影响次之,混凝土强度的增加对钢板与混凝土间粘结性能略有提高。对比数值模拟结果与试验实测结果可知:ABAQUS仿真模拟与试验结果吻合较好。根据钢板与混凝土的粘结滑移模拟计算数据,修正了剪力墙抗剪承载力公式。     

基于ABAQUS高层剪力墙结构的有限元建模及其振动台试验验证

采用ABAQUS建立12层剪力墙结构的有限元模型,利用该结构1/5缩尺模型振动台试验时预留试块的材性试验结果及相似关系,确定相应原型结构材料的性能参数,将试验参数和我国混凝土结构设计规范给出的混凝土单轴受拉/压应力-应变关系曲线相结合,确定ABAQUS模型中混凝土损伤塑性模型所需的应力-应变参数;将试验参数和张劲公式法相结合,确定ABAQUS模型中混凝土损伤塑性模型所需的损伤因子参数。对比有限元分析结果和振动台试验结果,验证参数设置的有效性。ABAQUS有限元分析和振动台试验所得原型结构前三阶振型和自振周期相差很小,说明ABAQUS模型和参数设置能够反映并用于计算实际结构的弹性响应。ABAQUS有限元分析得到的结构损伤情况与试验模型的损伤情况基本一致;结构的顶点加速度曲线和滞回曲线等响应的有限元分析结果与试验结果在多遇地震作用下基本吻合,但由于振动台试验累积损伤的影响,两者的差异随着地震波幅值的增大而逐渐增大;ABAQUS有限元分析得到的位移包络曲线与剪力墙结构弯曲变形的特点相符。以上弹塑性分析结果进一步表明了ABAQUS模型和参数设置能够很好地模拟结构在地震作用下的响应。     

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。     

移动荷载对桥梁动力响应的影响研究——以开裂预应力混凝土简支梁为例

混凝土桥梁在工作过程中会产生裂缝,为分析移动荷载对开裂混凝土桥梁结构刚度的影响,对开裂梁动力响应进行分析。建立简支T梁桥有限元模型,并将移动荷载施加至有限元模型中。根据简支T梁桥破坏横向分布位置和强度的不同,研究不同工况下各梁荷载横向分布及不同移动速度对裂缝扩展宽度的影响。结果表明,数值模拟结果能较好地验证计算模型的准确性;在较大的移动荷载作用下,混凝土开裂,导致结构刚度减小、位移增大;随着移动荷载和速度的增加,开裂时间增加,结构刚度降低,持续时间增加,位移增大,使结构响应呈现明显非线性。     

钢筋混凝土剪力墙结构基于自平衡力的非线性地震反应分析

本文简要评述了现有钢筋混凝土剪力墙的非线性分析模型，着重介绍了多竖线单元模型，并对其竖向单元的轴向刚度和水平弹簧的剪切刚度分别建议了改进的滞变模型，最后将基于自平衡力的非线性动力反应分析方法应用于求解剪力墙结构的非线性地震反应，并用传统分析方法对其结果进行了检验，表明该分析方法计算简便，而且是有效和可靠的。     

Shaking table tests and numerical analyses of an RC coupled wall structure with replaceable coupling beams

The replaceable coupling beam (RCB) is an innovative structural component developed to increase the seismic resilience of reinforced concrete (RC) shear wall structures. In this study, two 1/5‐scale 5‐story 3‐dimensional RC shear wall structures—one with conventional RC coupling beams and the other with RCBs—were designed, constructed, and tested on a shaking table. The failure pattern, dynamic properties, and structural responses, including the acceleration, displacement, story force, and strain responses, of the 2 structures are compared under earthquake excitations. The test results demonstrate that the seismic performance of the structure with RCBs was improved when RCBs were working compared with the structure with conventional RC coupling beams. In addition, the replaceable devices suffering the severe damage during an earthquake can be conveniently replaced after the earthquake. However, after the sudden failure of RCBs during the severe earthquakes, the inter‐story drift and floor acceleration of the structure with RCBs became larger. The design and manufacture quality of RCBs should be improved to avoid the sudden failure. Then, numerical models for the test structures were established using the commercial software PERFORM‐3D. Numerical simulations of the tests were conducted. The simulation results correspond well with the experimental results, thus verifying the accuracy of the numerical models. The RC shear wall structure installed with RCBs can be applied as a new type of earthquake‐resilient structure in engineering practice.     

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     

An efficient fiber beam-column element considering flexure–shear interaction and anchorage bond-slip effect for cyclic analysis of RC structures

In this paper, a fiber beam-column element considering flexure–shear interaction and bond-slip effect is developed for cyclic analysis of reinforced concrete (RC) structures. The element is based on conventional displacement-based Timoshenko beam theory, where the transverse shear deformation is included, and adopts the fiber model to describe the section force–deformation behavior. In the fiber model, shear deformation is assumed to be uniformly distributed along the section and is only resisted by concrete, thus the multi-dimensional concrete damage model is used for concrete fibers and therefore flexure–shear interaction is reflected naturally at the material level. Meanwhile, to account for the significant bond-slip effect at critical regions, the anchorage slip of bars at these regions is analytically derived. Then it is used to modify the uniaxial stress–strain model for steel fibers by assuming that the total strain can be treated as the sum of the bar deformation and anchorage slip, therefore the bond-slip effect is implicitly but simply represented. To validate the proposed element, a series of RC member and structure tests under cyclic loading are simulated. The results indicate that the proposed element can predict cyclic responses of RC structures, and can be used as a reliable tool for analysis of RC structures.     

Inelastic response analysis of reinforced concrete structures using modified force analogy method

A modified force analogy method (MFAM) is developed to simulate the nonlinear inelastic response of reinforced concrete (RC) structures. Beam–column elements with three different plastic mechanisms are utilized to simulate inelastic response caused by moment and shear force. A multi‐linear hysteretic model is implemented to simulate the nonlinear inelastic response of RC member. The P‐Δ effect of the structure is also addressed in MFAM. Static and dynamic inelastic response of structure, damage condition and failure type for structural element, structural limit state and collapse time can also be simulated using MFAM. Compared with the general algorithm, the MFAM provides less computational time especially in the case of large structural system. It is also easier to be written as computer program. Three test data groups, which include cyclic loading test data of a non‐ductile RC bridge column, a two‐storey RC frame, and dynamic collapse test data of a non‐ductile RC portal frame, are selected to confirm the effectiveness of applying MFAM to simulate the inelastic behaviour of structures. Copyright © 2007 John Wiley & Sons, Ltd.     

遮帘式板桩码头地基地震液化破坏机理

遮帘式板桩码头作为一种新型的板桩结构型式,其抗震性能研究是设计建造过程中的重要环节。在FEM-FDM水土耦合计算的平台上引入循环弹塑性本构模型,借助FORTRAN编程软件形成饱和砂土动力液化分析的数值方法,可有效模拟饱和砂土在地震动力作用下的非线性及大变形特性,同时也可模拟砂土液化流动对遮帘桩和前墙的动土压力。研究表明:地震作用下可液化土层超孔隙水压力比增长并发生较大的水平流动变形,对前墙的水平破坏大于竖向破坏;前墙剪力最大值位于海床与前墙交界处;遮帘桩剪力最大值位移与前墙底平行的位置;后拉杆拉力逐渐变大,前拉杆拉力逐渐变小。通过对板桩码头地震液化灾害的分析,可为抗震和抗液化设计提供参考依据。     

A study on the seismic performance of steel‐reinforced concrete frame‐concrete core wall high‐rise mixed structure by large‐scale shaking table tests and numerical simulations

This paper reports a study for the seismic performance of one large‐scaled (1/15) model of 30‐story steel‐reinforced concrete frame‐concrete core wall mixed structure. The study was implemented by both shaking table tests, in which the similarity ratio for lateral and gravitational accelerations was kept to 1:1, and numerical nonlinear dynamic analysis. The test observations presented herein include story displacement, interstory drift, natural vibration periods, and final failure mode. The numerical analysis was performed to simulate the shaking table test procedure, and the numerically obtained responses were verified by the test results. On the basis of the numerical results, the progressions of structural stiffness, base shear, and overturning moment were investigated, and the distributions of base shear and overturning moment between frame and core wall were also discussed. The test demonstrates the seismic performance of the steel‐reinforced concrete frame‐core wall mixed structure and reveals the potential overturning failure mode for high rise structures. The nonlinear analysis results indicate that the peripheral frames could take more shear forces after core wall damaged under severe earthquakes. Copyright © 2013 John Wiley & Sons, Ltd.     

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.     

Seismic performance assessment of a hybrid coupled wall system with replaceable steel coupling beams versus traditional RC coupling beams

This study assesses the seismic performance of a hybrid coupled wall (HCW) system with replaceable steel coupling beams (RSCBs) at four intensities of ground motion shaking. The performance of the HCW system is benchmarked against the traditional reinforced concrete coupled wall (RCW). Nonlinear numerical models are developed in OpenSees for a representative wall elevation in a prototype 11‐story building designed per modern Chinese codes. Performance is assessed via nonlinear dynamic analysis. The results indicate that both systems can adequately meet code defined objectives in terms of global and component behavior. Behavior of the two systems is consistent under service level earthquakes, whereas under more extreme events, the HCW system illustrates enhanced performance over the RCW system resulting in peak interstory drifts up to 31% lower in the HCW than the RCW. Larger drifts in the RCW are because of reduced coupling action induced by stiffness degradation of RC coupling beams, whereas the stable hysteretic responses and overstrength of RSCBs benefit post‐yield behavior of the HCW. Under extreme events, the maximum beam rotations of the RSCBs are up to 42% smaller than those of the RC coupling beams. Moderate to severe damage is expected in the RC coupling beams, whereas the RSCBs sustain damage to the slab above the beam and possible web buckling of shear links. The assessment illustrates the benefits of the HCW with RSCBs over the RCW system, because of easy replacement of the shear links as opposed to costly and time‐consuming repairs of RC coupling beams. Copyright © 2016 John Wiley & Sons, Ltd.