配置HRB500钢筋的框架结构非弹性地震反应分析

为实现建筑行业的可持续发展,中国土木建筑工程界正在推广应用HRB500级高强钢筋,但是,以HRB500钢筋作为主要受力钢筋的混凝土结构的抗震性能研究还相对缺乏.该文按<混凝土结构设计规范>最新修订稿设计了3个配置不同强度钢筋的8度0.3 g区一级抗震等级的混凝土框架结构,并完成了该3个结构在多波输入下的非弹性地震响应分...     

Effect of elaborate plastic hinge definition on the pushover analysis of reinforced concrete buildings

Due to its simplicity, lumped plasticity approach is usually used for nonlinear characterization of reinforced concrete (RC) members in pushover analysis. In this approach, the inelastic force deformation of hinges could be defined as either the nonlinear properties suggested in FEMA‐356 and ATC‐40 or defined hinges quantified on the basis of the properties of RC members. However, the nonlinear response of RC structures relies heavily on the inelastic properties of the structural members concentrated in the plastic hinges. To provide a comparative study, this paper attempts to show the results of pushover analyses of RC structures modeled on the basis of the FEMA nonlinear hinges and defined hinges. Following the validation of the adopted models, the force–deformation curves of the defined hinges are determined in a rigorous approach considering the material inelastic behavior, reinforcement details and dimensions of the members. For the case studies, two four‐story and one eight‐story frames are considered in order to represent low‐rise and mid‐rise buildings with different ductility. Nonlinear responses of both models are elaborated in terms of the inter‐story drift, hinging pattern, failure mechanism and the pushover curve. It is confirmed that FEMA hinges underestimate the strength and more importantly the displacement capacity, especially for the frame possessing low ductility. Copyright © 2012 John Wiley & Sons, Ltd.     

钢筋混凝土框架结构基于时变的抗震性能研究

钢筋混凝土结构在使用过程中由于钢筋锈蚀抗震性能退化。为了研究钢筋混凝土框架结构在正常使用环境下随使用时间的增加其抗震性能的退化规律,采用通用有限元分析软件ABAQUS对锈蚀钢筋混凝土框架进行多尺度建模以提高计算精度并保证计算效率。基于锈蚀钢筋混凝土构件及单榀框架的试验数据,验证了多尺度建模方法的正确性。采用多尺度模型对4层钢筋混凝土框架结构进行了静力推覆分析及弹塑性时程分析,对比不同使用时间的钢筋混凝土框架结构的地震反应和损伤情况。结果表明：当使用时间为25a时,结构的抗震性能与新建结构接近;当使用时间超过50a时,随着使用时间的增加,结构的承载能力及刚度退化明显,在地震作用下的位移响应逐渐增大,地震损伤范围不断扩大;相比新建结构,当使用时间为50、75a和100a时,结构的抗侧承载力分别降低了6.2%、14.1%及18.1%,罕遇地震作用下的最大层间位移角分别增大了9.2%、19.8%及25.1%。     

Parametric study of seismic performance of super-elastic shape memory alloy-reinforced bridge piers

One of the important measures of post-earthquake functionality of bridges after a major earthquake is residual displacement. In many recent major earthquakes, large residual displacements resulted in demolition of bridge piers due to the loss of functionality. Replacing the conventional longitudinal steel reinforcement in the plastic hinge regions of bridge piers with super-elastic shape memory alloy (SMA) could significantly reduce residual deformations. In this study, numerical investigations on the performance of SMA-reinforced concrete (RC) bridge bents to monotonic and seismic loadings are presented. Incremental dynamic analyses are conducted to compare the response of SMA RC bents with steel RC bents considering the peak and the residual deformations after seismic events. Numerical study on multiple prototype bridge bents with single and multiple piers reinforced with super-elastic SMA or conventional steel bars in plastic hinge regions is conducted. Effects of replacement of the steel rebar by SMA rebar on the performance of the bridge bents are studied. This paper presents results of the parametrical analyses on the effects of various design and geometric parameters, such as the number and geometry of piers and reinforcement ratio of the RC SMA bridge bents on its performance.     

钢筋砼框架结构抗震控制研究

在分析钢筋砼框架结构实际受力特征的基础上，从结构控制的角度出发，本文提出了允许框架柱下端出现塑性铰的新型延性框架结构方案。通过对延性框架与普通框架结构的非线性全过程分析、弹塑性动力分析和振动合模型对比试验，研究了其受力过程、动力特性、地震反应和破坏形态。结果表明，延性框架结构具有良好的延性和抗震性能。     

高层屈曲约束钢板墙-混凝土框架结构抗震性能研究

为研究高层屈曲约束钢板墙-混凝土框架结构的抗震性能,分别设计了一个10层钢筋混凝土框架结构和屈曲约束钢板墙-混凝土框架结构模型,进行了地震作用下动力非线性分析。结果表明：屈曲约束钢板墙可显著减小高层钢筋混凝土框架结构在地震作用下的层间位移,同时在罕遇地震作用下框架中塑性铰的数量也有大幅减少,表现出良好的抗震性能。在此基础上,综合规范对框架结构和框架-抗震墙结构抗震等级和柱轴压比限值的规定,并结合屈曲约束钢板墙-混凝土框架结构的受力特点,提出了高层屈曲约束钢板墙-混凝土框架结构的抗震设计建议。建议屈曲约束钢板墙的边缘构件按框架结构确定抗震等级和柱的轴压比限值,其他框架部分根据其承担的地震倾覆力矩比例大小,按框架结构或框架-抗震墙结构确定抗震等级和柱的轴压比限值。     

地震作用下框架结构“强梁弱柱”分析

在四川汶川地震中一些混凝土框架结构出现"强梁弱柱"的破坏机制,柱发生剪切破坏,最终导致结构形成侧移机构。通过对"强梁弱柱"框架破坏过程分析,以及考虑随机多维地震作用下框架的受力特性,并与中国规范进行对比,为完善框架结构抗震设计提供参考。     

单向预应力混凝土空间框架弹塑性时程分析

参照中国现行结构设计规范,按不同抗震等级设计4个处于结构临界高度(24m)和临界跨度(18m)的7度二、三级和8度一、二级单向预应力空间框架(一级框架中柱"强柱弱梁"级差调整按建议公式弱化设计),然后基于OpenSEES有限元分析平台,进行双向地震动下的弹塑性时程分析,研究其在罕遇地震下的抗震性能和能力。结果表明:各框架沿两个方向屈服程度均不高、具有较好的整体抗震能力。其中,取较低抗震等级的7度三级和8度二级框架,其整体地震反应较取较高抗震等级的7度二级和8度一级框架略大,但差异并不明显。RC框架方向形成理想的"梁铰机制",PC框架方向形成"柱铰机制",PC框架抗侧刚度更大、抗震能力更强。抗震等级为一级的PC框架经弱化中柱设计后,可以有效引导框架在中柱出铰,但仍不能避免边柱少量出铰,可考虑适当加强边柱予以控制。     

扇形铅黏弹性阻尼器加固RC框架的抗震性能试验研究

针对钢筋混凝土框架结构梁柱节点震害严重的抗震问题,提出采用扇形铅黏弹性阻尼器加固框架结构的 方法,结合扇形阻尼器型式提出外包箱形钢板和外包U形钢板两种不同的加固连接方式。为研究扇形铅黏弹性阻 尼器加固框架的抗震性能,设计并制作了3榀框架试件,分别为空框架和两榀不同连接的扇形铅黏弹性阻尼器加 固框架,通过低周反复加载试验分析了其滞回性能、承载能力、刚度退化、耗能能力等参数。试验结果表明：采 用扇形铅黏弹性阻尼器加固的框架滞回曲线饱满、耗能能力强、加固效果良好;扇形铅黏弹性阻尼器为框架提供 了一定的抗侧刚度,提高了框架的水平承载能力,延缓了框架塑性铰的产生,使框架具有良好的耗能能力;外包 U形钢板和外包箱形钢板用于扇形铅黏弹性阻尼器与主体结构的连接都是有效的,这两种不同的连接方式对加固 框架的整体抗震性能影响不大。     

Theory of seismic response analysis of steel-concrete composite structures using fiber beam elements

通过大型通用有限元程序MSC.MARC(2005r2)二次开发将纤维截面模型和基于位移的无滑移分布塑性铰梁单元相结合,得到了一种用于钢-混凝土组合结构地震反应分析的纤维梁单元。该单元在兼顾模型的准确性、通用性以及高效性的同时,具有较优的求解效率、数值稳定性以及前后处理速度。根据工程中常用组合截面的特点提出了组合截面的定义方式及其纤维离散过程,并给出了截面本构关系的求解流程。分析了混凝土、钢材以及钢筋三种材料的单轴本构关系,混凝土材料模型能反映普通、高强以及约束混凝土的不同力学特性,并在已有的考虑单次加卸载强度退化模型的基础上发展了能够考虑多次加卸载强度退化行为的混凝土滞回准则,从而使模型更符合地震作用下组合构件中混凝土材料的实际复杂非线性行为,钢材和钢筋模型能较合理地考虑往复荷载作用下的包兴格效应。     

Evaluation of low-cycle fatigue damage in RC exterior beam-column subassemblages by acoustic emission

Since Acoustic Emission (AE) is effective in monitoring the initiation of cracks in materials and structures, it has been widely used as a real-time evaluation technique for damage in reinforced concrete (RC) elements such as beams or columns in moment-resisting frames. This paper investigates its applicability for assessing the low-cycle fatigue damage in RC exterior beam-column subassemblages, which are especially vulnerable parts of the RC frames when subjected to earthquakes. Two 3/5 scale specimens representing connections from the lower and upper part of a prototype building located in a moderate-seismicity area are tested under cyclic loading until collapse. Important differences between the two specimens are observed owing to the different size and amount of reinforcing steel. First, a significant increase in AE activity is observed when the steel reinforcement begins to undergo plastic deformations. Second, by means of the AE improved b-value method, it is clearly shown that the macroscopic fracture processes occur mainly during the loadings paths. Thus, on the basis of AE source location with four sensors situated around the beam-column joint, the AE is successfully correlated with the observed cracks. A strong correlation is also found between the accumulated plastic strain energy dissipated by the concrete and the accumulated AE energy. Based on this fact, a formula is proposed to predict the level of damage and the closeness to failure of an exterior beam-column subassemblage from the AE as recorded by sensors located near the joint.     

多层多跨钢筋混凝土平面框架拟静力倒塌试验研究#br#

建筑结构的破坏具有离散性和系统性的特点,该特性决定结构抗地震倒塌的研究需多参数、多层次考虑问题。文章结合结构地震倒塌破坏模式的研究,完成了三榀钢筋混凝土平面框架的低周反复荷载试验,通过对模型框架破坏过程、破坏形态、滞回耗能及刚度退化的分析,探讨轴压比和梁柱线刚度比对RC框架结构抗震性能的影响,以期为后续结构地震倒塌破坏机理的研究提供参考。分析结果表明：降低结构的竖向荷载和梁柱线刚度比,有利于梁端塑性铰的充分发育,从而更易实现理想的“梁铰”破坏机制;试验框架的最终破坏是由底层柱下端塑性铰充分发育后、混凝土突然压溃所致,底层构件的耗能能力得到充分发挥,而中间层构件和顶层构件所耗散的能量较少;KJ-2的峰值荷载及极限荷载比KJ-1的峰值荷载及极限荷载分别大约9.9%和8.7%、等效黏滞阻尼系数比KJ-1大约16.5%,但位移延性系数比KJ-1小约57.1%,说明增大结构的竖向荷载可以提高其承载能力及耗能能力,但会降低延性及变形能力,同时,一定程度地增大竖向荷载,有利于强化结构的初始抗侧刚度,延缓刚度退化趋势,但在层间位移角较大情况下P-Δ效应的影响凸显;结构梁柱线刚度比的增大可以提高其耗能能力,但会降低结构的承载能力、延性及初始抗侧刚度;对于轴压比及梁柱线刚度比较小的“梁铰”结构,临近倒塌时的层间位移角可达1/25,此时结构仍具有一定的竖向承载能力。     

RC异形柱框架反复加载试验及数值模拟

通过对2榀由两个"L"形与一个"T"形截面柱组成的非对称混凝土框架结构进行低周反复加载试验,对试验现象、破坏特征、滞回曲线和变形性能等进行描述和分析。分析结果表明:2层混凝土异形框架结构具有良好的抗震性能。此外,还使用大型有限元分析软件MARC进行了数值模拟分析,对结构进行了骨架曲线、塑性铰出现顺序的计算分析,结果与试验吻合较好。     

A Fiber Model Based on Secondary Development of ABAQUS for Elastic–Plastic Analysis

With the aim to provide an efficient platform for the elastic–plastic analysis of steel structures, reinforced concrete (RC) structures and steel–concrete composite structures, a program iFiberLUT based on the fiber model was developed within the framework of ABAQUS. This program contains an ABAQUS Fiber Generator which can automatically divide the beam and column cross sections into fiber sections, and a material library which includes several concrete and steel uniaxial material models. The range of applications of iFiberLUT is introduced and its feasibility is verified through previously reported test data of individual structural members as well as planar steel frames, RC frames and composite frames subjected to various loadings. The simulation results indicate that the developed program is able to achieve high calculation accuracy and favorable convergence within a wide range of applications.     

混凝土框架结构抗震分析的塑性损伤模型

地震作用下,结构会遭受损伤.为了对结构进行损伤评估,本文基于经典塑性模型与连续损伤模型,根据广义应力空间塑性力学确定塑性变形的演化法则,建立了一种塑性损伤模型,用来进行混凝土框架结构的抗震分析,将塑性损伤的本构关系运用于在两端具有塑性铰的梁模型,模拟框架结构的梁柱.同时该模型的损伤指数可以确定结构各单元和整体的地震时性...     

混杂FRP复合材料性能及其加固腐蚀RC梁弯曲性能研究

在混杂FRP(Fiber Reinforced Polymer)复合材料单轴拉伸性能研究的基础上,通过对四根腐蚀混凝土梁的弯曲试验,研究了碳/芳纶/玻璃三种纤维层间混杂布对腐蚀混凝土梁弯曲性能的影响。结果表明:(1)混杂FRP复合材料均表现出良好的混杂效应,但碳/芳纶/玻璃三种纤维的混杂效应最优,其混杂效应系数达到0.453。(2)碳/芳纶/玻璃层间混杂纤维布加固腐蚀梁的开裂、屈服、峰值、极限荷载相比未加固腐蚀梁分别提高了14%、60%、98%和91%,而位移延性系数仅降低11%,表明混杂纤维布可显著改善腐蚀混凝土梁的弯曲性能,这将为混杂FRP复合材料加固腐蚀混凝土结构性能评估与加固设计提供参考。     

楼板对钢筋砼异形柱框架破坏机制的影响分析

采用基于柔度法的纤维模型梁柱单元,对按现行混凝土异形柱结构技术规程设计的异形柱框架结构,分别按考虑和忽略现浇楼板及其钢筋对梁抗弯能力的增强作用2种情况,分别进行了单向水平罕遇地震输入下的空间结构弹塑性动力分析.对比分析结果表明,现浇楼板及其钢筋将提高框架梁的抗弯能力,从而改变罕遇地震作用下混凝土异形柱结构的破坏模式,对...     

钢筋混凝土框架结构地震易损性分析

本文以一榀7层的钢筋混凝土框架结构为分析对象,采用SAP2000建立有限元模型,选取非线性Nlink单元来模拟梁和柱两端的塑性角,其中柱铰单元采用纤维PMM铰,梁铰单元设置弯矩铰。分别指定最大层间位移角和最大顶点位移角作为结构地震需求参数,并定义了相应的破坏状态。输入8条地震动记录进行结构地震易损性分析,得到了相应的易损性曲线。该方法可为结构的抗震性能评价提供参考。     

Strain monitoring of RC members strengthened with smart NSM FRP bars

Fiber-reinforced polymer (FRP) bars can be used as internal reinforcement for new reinforced concrete (RC) structures and as near-surface mounted (NSM) reinforcement for the strengthening of RC structures. The NSM method is an emerging strengthening technique for RC structures, where FRP bars are embedded into grooves cut in the cover of RC members. In both cases, strain monitoring of the FRP bars is desirable either for the investigation of the structural behavior or for the long-term health monitoring of the structure. This paper presents a study in which fiber-optic sensors were embedded into glass FRP (GFRP) bars to produce smart GFRP bars for NSM applications. The manufacturing process of the smart FRP bars is illustrated and their performance in tensile, bond and beam flexural tests is examined to assess the effectiveness of these smart FRP bars for achieving the dual purpose of structural strengthening and strain monitoring. On the basis of the test results, the advantages and limitations of fiber-optic sensors compared to electrical strain gages in the strain monitoring of NSM FRP bars are discussed. The bond and beam test results also confirm the effectiveness of the NSM method for the strengthening of RC structures.     

L形钢管混凝土框架结构抗震性能试验研究

为了探讨L形钢管混凝土柱 钢梁框架的抗震性能,进行了4个1/2.5缩尺比例两层单跨L形钢管混凝土柱 钢梁空间框架的拟静力试验研究,主要考察了柱轴压比（n=0.4,0.6）、加载方向（β=0°,45°）对试件抗震性能的影响,对结构的破坏形态、破坏机制、滞回曲线、结构塑性铰出现的位置及次序、位移延性和耗能能力等性能进行了研究。试验结果表明：结构的破坏形态基本相同,梁端先屈曲,形成塑性铰,然后柱脚核心混凝土开裂压碎,钢管屈曲,形成塑性铰,节点核心区没有出现破坏现象,满足“强柱弱梁、强节点”的抗震设计要求;结构的滞回曲线呈饱满的梭形,强度和刚度退化不明显,变形能力和耗能能力较强;结构的延性较好,正向和反向的位移延性系数均大于4.0;轴压比对结构的抗震性能影响较大,随着轴压比的增大,框架的位移延性和耗能能力降低。