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.     

基于SMA/ECC的新型自复位框架节#br# 点抗震性能试验研究

为了提高框架节点塑性铰区损伤自修复自复位能力,减小结构的残余变形,实现框架结构震后结构功能的快速恢复,文章采用超弹性SMA筋和超高韧性纤维增强水泥基复合材料(ECC)增强RC框架节点的抗震性能。设计制作了5个1/2缩尺比例框架节点,其中2个为考虑了梁端塑性铰区不同长度的SMA增强ECC节点模型,3个为对比节点模型,即普通混凝土节点、ECC增强混凝土节点和SMA增强混凝土节点。在新型SMA/ECC节点梁端塑性铰区,采用超弹性NiTi-SMA筋代替普通纵筋、ECC代替普通混凝土以增强其复位能力和耗能能力。通过低周往复加载试验,研究了新型节点的破坏过程、耗能能力、位移延性、残余变形和自复位性能。试验结果研究表明：往复荷载作用下,SMA节点均呈现“旗帜形”滞回性能,具有良好的自复位能力;ECC材料够优化框架节点梁端塑性铰的发展,提高结构的延性及耗能能力,延缓结构的屈服;SMA/ECC复合材料系统虽然会降低结构的初始刚度,但能够显著提高节点的延性及自复位能力,延缓刚度退化速度,提高结构抗侧移能力,可以实现结构损伤自修复和功能的快速恢复;覆盖梁端塑性铰区,SMA的长度的改变对自复位性能影响不大。     

基于SMA和ECC复合材料的功能自恢复剪力墙#br# 抗震性能试验研究

剪力墙作为高层建筑广泛采用的水平抗侧力构件,承担着结构绝大部分的水平地震作用。因此,剪力墙受力性能的优劣对整个建筑结构的抗震性能尤为重要。为提高剪力墙的变形能力,减小剪力墙的损伤和残余变形,实现震后的快速恢复,提出一种具有自复位功能的剪力墙。在该剪力墙塑性铰区采用形状记忆合金筋(Shape Memory Alloy,简称SMA)替代纵向钢筋,实现墙体的自复位功能;采用工程水泥基复合材料(Engineered Cementitious Composites,简称ECC)替代普通混凝土,解决混凝土的脆性剥落损伤。为检验新型剪力墙的抗震性能,设计制作4个剪力墙试件,分别为普通混凝土剪力墙、高延性ECC增强剪力墙、超弹性SMA增强剪力墙和SMA和ECC共同增强剪力墙,并进行低周往复荷载试验,对比分析剪力墙的破坏模式以及承载力、自复位能力、延性、耗能能力等抗震性能。研究结果表明：与普通钢筋混凝土剪力墙相比,SMA和ECC共同增强剪力墙不仅损伤小,实现功能的快速修复,而且自复位能力达到85%以上,构件复位效果显著;同时表现出较好的延性。     

Shape memory alloy bending bars as seismic restrainers for bridges in seismic areas

In general, shape memory alloy (SMA) cables do not resist in compression and, thus, their applications are limited. This study suggests a superelastic SMA bar in bending to be used to overcome the above problem. The objectives of this study are to analyze the characteristics of the bending behavior of an SMA bar and to prove its seismic applicability, especially to restrain openings in bridges. Single and double bending tests are conducted with varying loading speeds and maximum displacements. The loading and the unloading stiffness are estimated from the force-displacement curves, and the equivalent damping ratio of each test is assessed. The SMA bar shows the same stiffness hardening, during bending and under tension which appears to be due to stress-induced-martensite hardening. Increasing the loading speed does not influence the stiffness of the SMA bar with a single bend, but the stiffness of the double bending bar is about five times that of the single bending bar. This study also introduces the use of SMA bending bars as a seismic restrainer for bridges. The SMA bars are assessed as seismic restrainers for a three-span-simply-supported bridge in a zone of moderate seismic activity. The bars reduce the openings at the internal hinges and the pounding force on abutments. Thus, the SMA bending bars are assessed to prevent the unseating at internal hinges and cracks on abutments. This study shows the applicability of the SMA bending bars as a seismic restrainer.     

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...     

钢筋混凝土框架结构震损定量评定方法研究

针对目前震后钢筋混凝土框架结构的损伤程度多以定性评定为主的现状,本文提出借助Pushover分析方法,并结合现有的国内外规范,通过考虑结构的层间位移、塑性铰发展、频率降低等指标的变化,对结构在地震作用下可能出现的五种破坏状态"基本完好、轻微损坏、中等破坏、严重破坏、倒塌"进行定量划分。以某8层振动台模型试验的框架结构作为工程实例进行Pushover分析,计算结构在8度基本地震作用下的反应,将分析结果与本文提出的震损定量评估综合指标相对比,得出该建筑物在不同地震作用下的破坏等级。结果表明,本文的分析结果与试验震害现象基本一致。     

复合配筋管桩抗震性能试验研究

传统PHC管桩在地震作用下表现出脆性破坏特征,限制了其使用范围。已有室内试验研究结果表明,通过在PHC管桩中加入非预应力钢筋形成复合配筋管桩可提高其抗震性能。目前针对管桩破坏机理以及抗震性能的研究,主要采用室内模型试验或振动台试验,未能充分考虑实际工程中桩的受力条件和土体的作用。为研究复合配筋管桩的抗震性能,在软土地区对PHC管桩和复合配筋管桩进行了现场足尺抗震性能试验研究。试验比较了常规管桩以及掺入不同含量非预应力钢筋的复合配筋管桩的滞回曲线、骨架曲线、延性系数、曲率分布等数据,分析复合配筋管桩的抗震性能。研究结果表明：与PHC管桩相比,复合配筋管桩的抗震性能得到明显改善,且对于提高管桩延性来说,存在最优的非预应力筋配筋率。     

复合配筋增强工程水泥基复合材料梁受弯性能试验研究

为了研究不同筋材增强工程水泥基复合材料（ECC）受弯构件的力学性能,设计并制作6个几何尺寸相同的试验梁,包括形状记忆合金（SMA）增强ECC（SMA-ECC）梁、GFRP增强ECC（GFRP-ECC）梁、钢绞线增强ECC（SS-ECC）梁、SMA/GFRP增强ECC（SMA/GFRP-ECC）梁、钢筋增强ECC（R-ECC）梁和普通钢筋混凝土（RC）对比梁。通过低周单向循环加载试验,研究相同加载条件下相同配筋率的各试验梁的破坏过程、承载能力、耗能能力、位移延性、残余变形和自复位性能,考察SMA/GFRP-ECC梁的力学性能。结果表明：与普通钢筋混凝土梁相比,复合配筋增强ECC梁在加载过程中呈现出明显的多缝开裂特征,具有更好的延性;与采用其他筋材的复合配筋增强ECC梁相比,SMA/GFRP可以使梁兼具大承载力、高耗能以及自复位能力;SMA/GFRP-ECC梁具有较高承载力、延性以及损伤自修复、位移自复位能力。     

配置核心钢管的钢筋混凝土柱-钢骨混凝土梁组合框架抗震性能试验研究

进行两榀配置核心钢管的钢筋混凝土柱-钢骨混凝土梁组合框架试件在水平低周往复荷载作用下的试验研究,观察试验过程及破坏形态,研究试件的滞回特性、骨架曲线、刚度退化、耗能能力、残余变形等抗震性能,同时对梁柱端纵筋、钢骨翼缘及钢管在不同加载位移下的应变变化规律进行分析,得到框架结构的出铰顺序。研究结果表明：两榀框架滞回曲线饱满,施加预应力后仍具有较好的耗能能力和延性,表现出良好的抗震性能;框架柱底塑性铰区的钢管环向应变在整个加载过程中呈不均匀变化趋势,截面受压区钢管环向受拉,能够对受压区混凝土提供有效约束;钢骨混凝土梁由于施加预应力的作用,可延缓其裂缝的出现;此外,两榀框架试件均呈现“先梁端后柱底”的出铰顺序,能实现梁铰耗能机制,延迟柱底出铰时刻。     

基于有限单元柔度法的钢筋混凝土空间框架非弹性地震反应分析

本文基于有限单元柔度法纤维模型梁柱单元理论,编制了钢筋混凝土空间杆系结构非弹性动力分析程序。通过对一个退台六层钢筋混凝土空间框架振动台试验结果与数值模拟分析结果的对比,对基于非线性有限单元理论和纤维模型的空间杆系分析模型进行钢筋混凝土空间框架非弹性地震反应分析的有效性进行了验证和评价。对地震振动台试验的模拟分析表明,纤维模型梁柱单元对中等以下损伤的结构地震反应具有很好的模拟能力,对于结构处于严重损伤的阶段,模拟所得的结构位移和损伤程度将会小于结构的实际位移和损伤程度,这可能是由于目前纤维模型梁柱单元尚不能考虑钢筋的粘结滑移以及将现浇楼板简单处理为刚性并未考虑楼板刚度实际会出现明显降低的现象所致。     

塑性铰区埋入高阻尼隔震橡胶层厚度的数值模拟分析

钢筋混凝土(RC)桥墩一旦出现塑性铰后,混凝土的破坏主要集中在塑性铰区域,而且塑性铰区混凝土的损伤及破坏程度在较大程度上影响RC桥墩的抗震性能。本文希望通过在RC桥墩塑性铰区域埋入橡胶层来提高其变形能力、增强延性和耗能能力,改善传统RC桥墩的抗震性能。基于橡胶、混凝土和钢筋的本构模型及承载力—变形理论,采用条带法,本文提出了不同轴压比、不同层间位移角所需要橡胶层厚度的计算方法,并编制了计算程序;分析得到了不同轴压比、不同层间位移角的RC柱中所需埋入的橡胶层的最小厚度,为确定RC柱塑性铰区所埋入橡胶层厚度提供参考。     

纤维增强水泥基复合材料加固震损RC框架抗震性能试验研究

针对震损钢筋混凝土框架,提出了基于纤维增强水泥基复合材料（ECC）的加固修复方法,并开展了振动测试和低周反复荷载试验。研究结果表明：震损加固框架在加载试验后的基本频率仅下降了6.8%,损伤程度较轻,屈服和峰值荷载时的顶点位移角分别为1/48和1/25,破坏时位移角超过1/19。震损加固框架的峰值荷载较未损伤原框架提高了9.6%,表明ECC加固修复震损框架的方法能够使其抗震承载能力完全恢复并略高于原框架;ECC加固震损框架的耗能能力也可恢复至原框架的水平。此外,ECC加固对震损框架的刚度提高有限,震损加固框架的初始刚度仅为原框架的36.0%,但刚度退化较为缓慢。应变分析结果表明,ECC置换梁端混凝土能够显著改善塑性铰区的受力性能和破坏模式。     

Seismic performance of repaired hollow-bridge piers

To develop an effective repair technique for rapid bridge restoration after an earthquake, four hollow bridge columns were cyclically loaded to failure, repaired and retested. The repair process includes using dog-bone shape bars to replace the fractured longitudinal bars in plastic hinges and using FRP (Fiber Reinforced Plastic) wraps to enhance the deformation capacity of columns. The repair aims to restore seismic capacity in terms of strength and ductility. Test results indicate that the fractured longitudinal bars can be completely repaired and the deformation capacities of the columns were enhanced by FRP wraps. However, due to concrete deterioration and the buckling of the longitudinal bars in the inner layer of the hollow sections, the test results also indicate the repaired column strengths are less than anticipated.     

Failure mechanism of single-layer steel reticular domes with reinforced concrete substructure subjected to severe earthquakes

This paper performs the research on failure mechanism of single-layer steel reticulated domes with the reinforced concrete substructure subjected to sever earthquakes. Based on ABAQUS, this paper built user-defined material subroutines of the steel and the reinforced concrete, which took material non-linearity and the material damage accumulation into consideration. The failure mechanism of reticulated domes with reinforced concrete substructures under severe earthquakes is studied by the nonlinear dynamic response analysis. Three different failure modes of single-layer reticular domes with different sizes of reinforced concrete substructure are illustrated. Failure criterion is put forward to discriminate the failure modes and to estimate the critical load strength for single-layer reticular domes based on the structural damage theory. It has been found that reinforced concrete substructure has significant impact on the failure behaviors and the critical load of reticulated domes under seismic loads. It is essential to consider the influence of the reinforced concrete substructure upon the failure behaviors in the structural analysis and design process of reticular domes.     

Application of shape memory alloy bars in self-centring precast segmental columns as seismic resistance

The objective of this study is to investigate analytically the performance of self-centring precast segmental bridge columns with shape memory alloy (SMA) starter bars under nonlinear static and lateral seismic loading. For this purpose, a 3D finite element model for hybrid post-tensioned bridge column has been developed. The precast post-tensioned segmental bridge columns possessing a central tendon and adequate transverse confinement provided by the steel tube jacketing as self-centring bridge columns have an undesirable high lateral seismic demand due to their low energy dissipation. In order to eliminate this deficiency while keeping the residual displacement small, SMA starter bars are applied in this system. The effect of post-tensioning (PT) forces of the central strands and SMA bar size are investigated. The results indicate that in high seismicity zones, bridge columns with SMA bars at a higher level of PT forces have a superior performance against earthquake loading.     

建筑结构地震火灾效应分析方法

为在建筑结构设计时考虑地震引发火灾对建筑结构的作用和影响,提出建筑结构地震火灾效应分析计算方法,此方法结合结构地震反应分析与火灾热力反应分析,通过简化的建筑结构地震损伤模型,考虑地震损伤的同时,连接结构的热传导分析与热力分析,从而实现地震火灾效应计算.运用此方法对一单层和一多层混凝土框架分别进行了分析,并与没有考虑地震...     

复合筋增强ECC混凝土组合柱抗震性能研究

ECC是一种具有假应变硬化特性和多裂缝开展机制的高性能纤维增强水泥基复合材料,将ECC替代混凝土用于建筑结构能有效避免因混凝土脆性导致的开裂和耐久性问题。提出了新型FRP筋-钢筋复合增强ECC-混凝土组合柱构件,将FRP筋配制在柱构件边角处,而ECC仅用于柱构件薄弱的柱底。为进一步研究ECC与混凝土对柱构件抗震性能的影响,通过对比5根柱构件的滞回曲线、骨架曲线进行分析。结果表明,将ECC替代混凝土用于FRP筋-钢筋复合增强柱构件能够避免因混凝土脆性性质导致的诸多缺陷,有效的给FRP筋提供一个有效的保护,构件的延性和变形能力得到提高。在0.1~0.42轴压比情况下,随着轴压比的增大,承载力增大,而变形能力变差。     

钢筋混凝土框架"强柱弱梁"抗震措施的试验研究

针对历次震害中钢筋混凝土框架结构的梁柱节点容易破坏的问题,本文进行了4个足尺框架梁柱组合节点试件的低周反复荷载试验。重点研究了不同柱梁强度比值对钢筋混凝土框架抗震性能的影响。结果表明,提高柱梁抗弯强度比值可以更好地保证梁端率先出现塑性铰,有效减小节点核心区和柱端的破坏程度,进而提高水平地震作用中框架节点的延性。     

Deterministic seismic design procedures for reinforced concrete buildings

A brief review is given of a deterministic design philosophy with respect to earthquake resisting ductile structures for reinforced concrete buildings. This was developed recently mainly in New Zealand. In this approach a preferred hierarchy in the development of energy dissipating mechanisms is postulated. Some applications of ‘capacity design procedures’ relevant to beams, columns and shear walls, are outlined. The paramount importance of quantifiable good detailing is emphasized and the relevance of this with respect to shear effects in plastic hinges, the confinement of compressed concrete, and bond between reinforcement and concrete are examined. These aspects of the specific seismic environment are also utilized to show fundamental differences in structural behaviour when effects of gravity loads or seismic displacements are compared.     

延性钢筋混凝土建筑的确定性抗震设计步骤

本文扼要地回顾了钢筋混凝土抗震延性结构确定性设计的基本原理。这是最近主要在新西兰发展起来的。这个设计方法要求能量耗散机构可以按照某一个预先选定的次序来完成。本文也概要地叙述了“承载能力设计法步骤”(capacity design procedures)在梁、柱、剪力墙中的应用。文中同时也强调了定量的构造要求的极端重要性,如:它与塑性铰中的剪力影响的关系,受压混凝上的约束关系和钢筋与混凝土之间握裹力的关系,文中都作了探讨,并用这些具体的抗震措施来表明承受重力荷载和承受地震位移时,其结构表现是有原则性区别的。