Experimental study on the seismic response of braced reinforced concrete frame with irregular columns

A 15-storey K-braced reinforced concrete model frame with irregular columns, i.e., T-shaped, L-shaped, as well as ＋-shaped columns, was constructed and tested on the six-degree-of-freedom shaking table at the State Key Laboratory for Disaster Reduction in Civil Engineering in Tongji, China. Two types of earthquake records, El-Centro wave （south-north direction） and Shanghai artificial wave （SHAW） with various peak accelerations and principal-secondary sequences, were input and experimentally studied. Based on the shaking table tests and theoretical analysis, several observations can be made. The failure sequence of the model structure is brace→beam→column→joints, so that the design philosophy for several lines of defense has been achieved. Earthquake waves with different spectrums not only influence the magnitude and distribution of the earthquake force and the storey shear force, but also obviously affect the magnitude of the displacement response. The aftershock seismic response of previously damaged reinforced concrete braced frames with irregular columns possesses the equivalent elastic performance characteristic. Generally speaking, from the aspects of failure features and drift ratio, this type of reinforced concrete structure provides adequate earthquake resistance and can be promoted for use in China.

Nonlinear fi nite element analysis of high-strength concrete columns and experimental verification

This paper describes a nonlinear finite element （FE） analysis of high strength concrete （HSC） columns, and verifies the results through laboratory experiments. First, a cyclically lateral loading test on nine cantilever column specimens of HSC is described and a numerical simulation is presented to verify the adopted FE models. Next, based on the FE model for specimen No.6, numerical simulations for 70 cases, in which different concrete strengths, stirrup ratios and axial load ratios are considered, are presented to explore the effect of these parameters on the behavior of the HSC columns, and to check the rationality of requirements for these columns specified in the China Code for Seismic Design of Buildings （GB 50011- 2001）. In addition, three cases with different stirrup strengths are analyzed to investigate their effect on the behavior of HSC columns. Finally, based on the numerical results some conclusions are presented.

Pseudo-dynamic test and numerical simulation of high-strength concrete frame structure reinforced with high-strength rebars

This paper describes an investigation of a high-strength concrete frame reinforced with high-strength rebars that was tested in the structure engineering laboratory at Shenyang Jianzhu University. The frame specimen was pseudo- dynamically loaded to indicate three earthquake ground motions of different hazard levels, after which the test specimen was subjected to a pseudo-static loading. This paper focuses on the design, construction and experiment of the test frame and validation of the simulation models. Research shows that a high-strength concrete frame reinforced with high-strength rebars is more efficient and economical than a traditional reinforced concrete frame structure. In addition to the economies achieved by effective use of materials, research shows that the frame can provide enough strength to exceed conventional reinforced concrete frames and provide acceptable ductility. The test study provides evidence to validate the performance of a high- strength concrete frame designed according to current seismic code provisions. Based on previous test research, a nonlinear FEM analysis is completcd by using OpenSees software, The dynamic responses of the frame structure are numerically analyzed, The results of the numerical simulation show that the model can calculate the seismic responses of the frame by OpenSees. At the same time, the test provides additional opportunities to validate the performance of the simulation models.

Seismic behavior of multiple reinforcement,high-strength concrete columns:experimental and theoretical analysis

This study investigates the seismic performance of multiple reinforcement,high-strength concrete(MRHSC)columns that are characterized by multiple transverse and longitudinal reinforcements in core areas.Eight MRHSC columns were designed and subjected to a low cycle,reversed loading test.The response,including the failure modes,hysteretic behavior,lateral bearing capacity,and displacement ductility,was analyzed.The effects of the axial compression ratio,stirrup form,and stirrup spacing of the central reinforcement configuration on the seismic performance of the columns were studied.Furthermore,an analytical model was developed to predict the backbone force-displacement curves of the MRHSC columns.The test results showed that these columns experienced two failure modes:shear failure and flexure-shear failure.As the axial compression ratio increased,the bearing capacity increased significantly,whereas the deformation capacity and ductility decreased.A decrease in the spacing of central transverse reinforcements improved the ductility and delayed the degradation of load-bearing capacity.The proposed analytical model can accurately predict the lateral force and deformations of MRHSC columns.

Model Experiment on Integral Seismic Behavior of Reinforced Concrete Frame with Split Columns

Based on a series of previous studies, an experiment on the integral seismic behavior of a 1/3 scaled model of two-bay and three-story reinforced concrete frame with split columns at lower two stories is performed under cyclic loading. The original columns at lower two stories of the model frame are short columns and they are replaced by the split columns. The hysteresis curves between the horizontal cyclic load and the lateral displacement at the top of the model frame, indicate that under the cyclic loading, the model frame undergoes the process of cracking, yielding, and maximum loading before being destroyed at the ultimate load. They also indicate that the model frame has better ductility, and the ratio of the ultimate displacement to the yielding displacement, reaches 6.0. The yielding process of the model frame shows that for the frame with split columns, plastic hinges are generated at the ends of beams and then the columns begin yielding while the frame still possesses the bearing and deformation capacity. The design idea of directly changing the short column to long one in the reinforced concrete frame may be realized by replacing the short column with the split one.

Elasto-plastic Analysis of High-strength Concrete Shear Wall with Boundary Columns Using Fiber Model

In this study,an experimental study and numerical calculations using fiber model were conducted for four high-strength concrete shear walls with boundary columns under low cyclic load.The boundary column and shear wall were divided into fiber elements,and PERFORM-3D finite element analysis software was used to carry out push-over analysis on the test specimens.The results show that the finite element analysis results were in good agreement with the experimental results.The proposed analysis method could perform elasto-plastic analysis on the high-strength concrete shear wall with boundary columns without distinguishing the categories of frame column and shear wall.The seismic performance of high-strength concrete shear wall with boundary columns was analyzed using the following parameters:axis compression ratio,height to width ratio,ratio of vertical reinforcement,and ratio of longitudinal reinforcement in the boundary column.The results show that the increase in the axial compression ratio causes the bearing capacity of the shear wall to increase at first and then to decrease and causes the ductility to decrease.The increase in the height to width ratio causes the bearing capacity of the shear wall to decrease and its ductility to increase.The ratio of vertical reinforcement was found to have little effect on the bearing capacity and ductility.The increase in the ratio of longitudinal reinforcement in boundary column resulted in a significant increase in the bearing capacity and caused the ductility to decrease at first and then to slowly increase.

Evaluation of the fishbone model in simulating the seismic response of multistory reinforced concrete moment-resisting frames

The fishbone model is a simplified numerical model for moment-resisting frames that is capable of modelling the effects of column-beam strength and stiffness ratios. The applicability of the fishbone model in simulating the seismic responses of reinforced concrete moment-resisting frames of different sets of column-beam strength and stiffness ratios are evaluated through nonlinear static, dynamic and incremental dynamic analysis on six prototype buildings of 4-, 8-and 12-stories. The results show that the fishbone model is practically accurate enough for reinforced concrete frames, although the assumption of equal joint rotation does not hold in all cases. In addition to the ground motion characteristics and the number of stories in the structures, the accuracy of the model also varies with the column-beam stiffness and strength ratios. The model performs better for strong column-weak beam frames, in which the lateral drift patterns are better controlled by the continuous stiffness provided by the strong columns. When the inelastic deformation is large, the accuracy of the model may be subjected to large record-to-record variability. This is especially the case for frames of weak columns.

Effects of edge beams on mechanic behavior under lateral load in reinforced concrete hollow slab-column structure

In order to get the formulae for calculating the equivalent frame width coefficient of reinforced concrete hollow slab-column structures with edge beam,the finite element structural program was used in the elastic analysis of reinforced concrete hollow slab-column structure with different dimensions to study internal relationship between effective beam width and the frame dimensions.In addition,the formulas for calculating the increasing coefficient of edge beam were also obtained.

基于转动摩擦铰阻尼器的干式装配梁-柱节点抗震性能试验

基于转动摩擦铰阻尼器(RFHD),提出了转动摩擦耗能干式装配梁-柱节点(DRFDBJ)。为了验证DRFDBJ结构对于实现预期力学性能的可行性和合理性,以施加在摩擦片表面的螺栓预紧力(P_(c))为变量,开展了2个工况下的DRFDBJ试件低周往复拟静力试验研究。结果表明:DRFDBJ结构的力学性能主要由RFHD提供并控制,试验中节点呈现了稳定的承载力和理想的变形、耗能能力,并实现了预期的损伤集中;2个不同P_(c)水准下节点承载力的试验值与理论值误差不超过5%,通过调整P_(c)可实现节点承载力的调控,为DRFDBJ结构承载力的可调控提供了支撑。

设有叠合柱的局部错层RC框架结构地震易损性分析

为研究某一设有叠合柱的局部错层钢筋混凝土(reinforced concrete,RC)框架结构在近断层和远场地震作用下的破坏概率,自定义钢管混凝土叠合柱塑性铰参数,并与试验对比验证塑性铰参数的有效性。采用SAP2000建立非线性分析模型,选取近断层和远场地震波共22条,分别以地震峰值加速度(peak ground acceleration,PGA)和最大层间位移角作为地震动强度指标和结构性能指标,基于增量动力分析(incremental dynamic analysis,IDA)结果和点估计函数对错层框架结构进行易损性分析。结果表明:对于远场地震动,结构满足“三水准”抗震设防要求,在罕遇地震下超越防止倒塌极限状态的概率仅为0.24%;结构在近断层多遇地震下仍能满足“小震不坏”的设计要求,设防地震下结构超越修复后使用极限状态的概率为53.63%,发生中等破坏的概率较大,罕遇地震下结构达到倒塌极限状态的概率为5.37%,较远场地震作用破坏更为严重。研究结果可为错层框架结构的设计和地震风险评估提供参考。

功能可恢复RCS混合框架结构研究进展

钢筋混凝土柱-钢梁(RCS)混合框架结构以其结合了混凝土优异的抗压性能及钢材优异的抗弯性能而受到广泛关注,而可恢复功能结构以其震后快速恢复使用功能的能力,也成为地震工程界研究的新热点。功能可恢复RCS混合框架结构可以在弯矩较大的梁端和柱脚部位设置可更换构件,实现结构的功能可恢复能力。文中简述了近年来功能可恢复RCS混合框架结构研究进展,重点关注各类型功能可恢复钢梁、功能可恢复摇摆柱脚的构造研究,介绍了功能可恢复RCS混合框架结构性能分析研究进展。最后,对功能可恢复RCS混合框架结构仍需深入研究的问题进行了展望。

提升RC框架结构抗震韧性的冗余柱性能分析

本文提出了一种通过设置可更换冗余柱以增强钢筋混凝土框架结构抗震韧性的方法。通过冗余柱纵筋在钢筋机械套筒里的锚固长度以控制冗余柱与框架连接节点处的钢筋失效,节点的刚性连接转变为铰链连接。以钢筋直径和锚固长度为变量,对钢筋机械连接套筒试件进行了13组拉伸试验和6组高应力拉压试验,每组包含3个试件,一个试件包含两段钢筋和一个机械套筒。试验结果表明,适当设计机械连接套筒锚固长度,可实现可控成铰性能。将实测数据应用于冗余柱的截面和构件仿真分析中,证明可通过改变钢筋于套筒锚固长度控制当冗余柱极限变形达到设计值时柱端自动成铰,使冗余柱损坏后仍为关键结构柱提供竖向承载能力,同时保护关键柱在遭遇强震时不易发生严重破坏。

双阶受力干式装配梁-柱节点抗震性能试验研究

研究提出了一种双阶受力干式装配梁-柱节点(DADBJ)。该节点的关键组件是摩擦铰(RFH)和预设缝防屈曲钢板(SBRSP),具备2个受力工作阶段和损伤集中易修复的特性。为了验证DADBJ构造的合理性,揭示其双阶段受力工作机理,设计加工了DADBJ试件,以SBRSP的预设缝隙宽度作为试验变量,进行了2个工况的低周往复拟静力试验。结果表明:提出的DADBJ构造实现了预期的双阶段受力特性,第一阶段由RFH提供节点的力学性能,第二阶段由RFH和SBRSP共同提供节点的力学性能;DADBJ的损伤集中于芯板,通过更换SBRSP芯板对节点快速修复,节点的性能可恢复到初始状态;SBRSP的预设缝隙宽度可直接决定DADBJ第二阶段的启动位移;提出的DADBJ双阶屈服荷载理论公式和二阶启动位移理论公式精确度好。该研究可为装配式框架结构和多阶受力型结构的设计和研究提供参考。

基于静力试验的柱端铰型受控摇摆钢筋混凝土框架地震响应数值分析

柱端铰型受控摇摆钢筋混凝土框架(CR-RCFC)是一种新型的可恢复功能结构,通过摇摆节点的构造来“弱化”结构整体抗侧刚度,从而达到减小地震响应的目的。CR-RCFC结构在振动台试验中呈现了在中震和大震作用下“主体构件免损伤,耗能构件易更换”的韧性抗震效果。振动台试验后进行低周反复静载试验得到拆除阻尼器后的CR-RCFC结构柱铰节点弯矩-转角滞回曲线和转动刚度等抗震性能参数。利用静力试验得到的结构抗震性能参数进行结构地震响应数值模拟,将数值模拟结果与振动台试验结果进行对比分析。对比分析结果表明:通过静力试验数据可以精确得到CR-RCFC结构节点抗震性能参数,根据该抗震性能参数进行的数值模拟结果与振动台试验结果吻合较好。

预制装配式分体柱框架抗震性能研究

已有研究表明分体柱具有较好的延性,能运用于地震多发的房屋结构中。为方便施工,提出预制装配式分体柱框架结构的设想,通过有限元数值模拟,对整体柱框架结构和分体柱框架结构的抗震性能进行对比分析。结果表明:地震作用下装配式分体柱框架结构加速度响应较现浇整体柱框架更易趋于稳定;与整体柱框架相比,装配式分体柱框架位移响应较大;装配式分体柱框架结构的基底剪力均小于整体柱框架结构的;现浇整体柱框架结构的混凝土节点损伤区域与分体柱框架结构相比较大,证明钢套筒对框架结构节点起到保护作用;装配式分体柱框架结构更适用于硬质场地。整体表明装配式分体柱框架结构的延性更强、耗能性能更好,且更加稳定。

考虑节点域影响的钢管约束钢筋混凝土柱框架结构抗震性能研究

近年来,钢管约束钢筋混凝土(STRC)柱结构已成为组合结构研究热点之一。约束钢管在柱端断开能够充分发挥其对混凝土的约束效果,增强柱体承载力及抗震性能。然而,节点区域将变得相对薄弱,传统结构体系性能分析中多以节点为刚性域,不考虑节点本身的变形及受损对结构的影响,这将导致STRC柱结构分析及设计存在一定的安全隐患。本文在STRC框架结构中引入节点单元Joint2D来模拟节点的受荷变形全过程,对比分析了节点单元对抗震性能模拟结果的影响,评价了不同强节点系数结构的地震易损性和抗倒塌性能。结果表明,不考虑节点性能的分析结果过高地估计了结构性能,造成不满足规范限值要求的性能指标被分析为满足要求。《钢管约束混凝土结构技术标准》中一级抗震的强节点系数1.5在罕遇地震时将偏于不安全,为满足结构使用安全及抗倒塌能力,建议取强节点系数为1.7。

现浇混凝土箱式梁桥“梁柱式”支架系统设计及受力分析

新建津潍高铁某跨河简支梁桥,其独立柱墩支撑高度16.5 m,为确保梁桥结构施工安全,综合考虑施工环境、梁桥截面型式及尺寸等因素,本文提出采用“梁柱式”支撑架体系,构建了贝雷架与盘扣式钢管脚手架组合的支撑方案,在正常使用、承载能力等不同极限状态下,通过理论计算和有限元分析对组合支撑体系的主次梁受力及变形、支撑立柱稳定性和架体抗倾覆等进行分析,验证了设计方案的安全性和可行性,形成了成套组合的支撑技术体系,并将该支撑体系应用于现浇混凝土箱梁施工中。实践结果表明,该研究成果可为项目的顺利实施提供技术支撑,提升了“梁柱式”组合支撑体系的应用水平,为同类工程的建造提供参考。

含斜柱RC框架结构抗震能力计算分析

为研究含斜柱RC框架结构的抗震能力,采用ABAQUS有限元软件,建立一榀含斜柱RC框架的数值模型,在框架顶部施加单调递增的水平荷载进行Pushover分析,得到该框架的荷载-位移曲线、刚度退化曲线、结构主拉应力以及等效塑性应变的计算结果,分析了加载过程中框架的破坏模式、屈服机制、承载力及抗侧刚度变化。结果表明:单调水平荷载作用下框架中两个柱脚区首先发生破坏,推覆相对侧脚部区为剪切破坏,推覆方向一侧脚部区为受压破坏。加载初期弹性阶段框架刚度退化较快,到达屈服阶段之后刚度退化缓慢,易损区位于左立柱脚部区,破坏时刚度退化为初始刚度的1/14.3,框架的抗推覆能力较强,具有较好的延性。研究结果能够为含斜柱框架的抗震设计提供依据。

某250m超高层建筑的塔楼结构设计分析

某超高层建筑高度为249.9m高度,位于6度设防地震烈度区,是采用叠合柱、型钢剪力墙并带有斜柱转换的框架-核心筒(双筒)结构体系。分析了整体结构在地震作用下的变化,并采用有限元软件着重分析了斜柱、型钢剪力墙和楼层楼板等构件的受力特点。结果表明,结构可满足“小震不坏、中震可修、大震不倒”的预期抗震性能目标要求,承载能力、变形能力、层间弹塑性位移、层间位移角可满足抗震性能目标C的各项抗震性能水准要求。

装配式混凝土框架节点抗震性能研究进展

装配式混凝土框架结构,凭借其施工速度快、质量可控及造价低廉等显著优点,已在建筑领域得到广泛应用。然而,在地震易发区,该结构的抗震性能仍待提升。梁柱节点作为该结构体系中的关键部分,其抗震性能研究尤为重要。文中总结了5种常见的装配式混凝土框架梁柱节点连接方式,并深入分析了它们在抗震性能方面的研究进展及各自的优缺点,展望了装配式混凝土框架节点抗震性能研究的未来趋势,为后续相关领域研究者提供参考。