Experimental testing of joints for seismic design of lightweight structures. Part 1. Screwed joints in straps

Connections in x-braced shear walls play a crucial role in the seismic performance of lightweight structures: they should be strong enough to allow energy dissipation via plastification of the diagonal straps. An extensive experimental research on tensile screwed joints between straps is reported here. Two dominant failure modes are identified: (1) tilting and net section failure (T+NSF) and (2) tilting, bearing and pull out (T+B+PO). The analysis in terms of strength and ductility shows that T+NSF joints are suitable for seismic design, because the straps yield before the connections fail. T+B+PO joints, on the contrary, are not suited because the connection fails before the straps can yield. The influence of various design parameters (strap thickness, number and diameter of screws, steel grade) in the failure mode is studied, and design criteria to induce a T+NSF response are given.     

四层两跨高性能混凝土框架的抗震性能

通过低周反复荷载试验对四层两跨高性能混凝土框架的破坏形态、破坏机制、恢复力模型、变形恢复能力、位移延性、刚度退化以及耗能能力等进行了研究,并对多层多跨框架结构的最优破坏机制进行了分析。研究表明,实现逐层梁铰机制的框架具有良好的整体延性和耗能能力,框架顶点和层间位移延性系数达到4.5~8.0。编制了基于恢复力模型的滞回全过程分析程序,应用该程序对四层两跨高性能混凝土框架进行了模拟计算,计算结果与试验值吻合良好。在此基础上,对高性能混凝土框架结构基于"中震可修"的性能指标及其限值进行了初步探讨。     

Cyclic behaviour of hinged steel frames enhanced by masonry columns and/or infill walls with/without CFRP

Abstract

This paper investigates the in-plane seismic behaviour of hinged steel frames that are enhanced with masonry columns and/or infilled walls. First, eight half-scaled hinged steel frame specimens were constructed according to the realistic structural system of Bund 18, which is a historical building in Shanghai, China. Then, cyclic loads were exerted on these frames. The test results indicated that the seismic behaviours of the hinged steel frames can be significantly improved with the use of masonry columns and/or infilled masonry walls as well as with proper strengthening due to carbon fibre-reinforced polymer (CFRP) sheets. A simplified model was developed to simulate the seismic behaviours of these frames. In this model, infilled walls and CFRP sheets were replaced by diagonal struts, and the steel members and their surrounding elements were treated as composite members. Finally, this model was verified by experimental results.     

考虑损伤效应的型钢高强高性能混凝土框架柱恢复力模型研究

为研究型钢高强高性能混凝土框架柱的抗震特性,基于已进行的9榀型钢高强高性能混凝土框架柱低周反复加载试验结果,进一步分析了其滞回特性,并将其骨架曲线简化为带下降段的理想三折线型骨架曲线模型,给出了骨架曲线的确定方法,同时简化了滞回环。通过引入基于损伤的循环退化指数对构件在反复荷载作用下的屈服荷载、硬化刚度、卸载刚度、再加载刚度以及承载力等各项力学性能指标的退化规律进行了描述,建立了基于损伤的型钢高强高性能混凝土框架柱的恢复力模型,给出了具体的滞回规则。结合试验结果,对恢复力模型的有效性进行了验证。研究结果表明：该模型能够较好地描述型钢高强高性能混凝土框架柱在反复荷载作用下的滞回特性,研究结果可为该类结构的弹塑性时程分析提供理论参考。     

带砌体填充墙框架弹性抗侧刚度计算方法对比分析

对于带砌体填充墙框架,当填充墙与框架紧密接触时,填充墙将会提高纯框架的侧向刚度,可能改变结构的平面及竖向侧向刚度分布,影响其在地震作用下的承载力及耗能能力等抗震性能。 为研究带填充墙框架在弹性阶段抗侧刚度的合理计算方法, 整理了以等效斜压杆模型为主的国内外相关计算公式, 并结合近年来带填充墙的框架在低周往复荷载作用下的试验, 将理论计算结果与试验实测值进行对比分析。结果表明： 在带填充墙的RC框架中,直接考虑填充墙弯曲变形和剪切变形得到的弹性阶段抗侧刚度计算值为实测值的1.94~8.05倍;在等效斜压杆模型中,斜压杆的宽度对抗侧刚度的计算结果影响很大;斜压杆宽度的取值应考虑填充墙与框架之间相对刚度的影响,其中MSJC提出的斜压杆宽度计算公式较为合理。     

高层支撑钢框架弹塑性地震反应简化分析模型

本文首先将高层支撑钢框架结构分解成纯框架和纯支撑体系两部分,并与一列受载铰接刚性杆并联,以考虑几何非线性的影响;然后将框架部分简化为半刚架,将支撑体系部分简化为铰接桁架,以此进行结构弹塑性地震反应分析.在前人试验和理论研究成果的基础上,本文还提出了能准确反映钢支撑主要滞回特征的支撑恢复力模型,便于工程实用.通过算例对比分析,表明采用本文提出的高层支撑钢框架简化模型进行弹塑性地震反应分析,具有计算精度高、计算自由度少、计算时间省的优点,是一种有效的近似方法.     

角部连接钢框架-玻璃纤维增强无机板组合墙体抗震性能试验研究

为研究角部连接钢框架 玻璃纤维增强无机板组合墙体的抗震性能,考察人字形斜撑和玻璃纤维增强无机板对钢框架 组合墙体的影响,设计2榀足尺的双层双跨钢框架和2榀足尺的双层双跨组合墙体进行拟静力试验。观察不同形式钢框架和组合墙体在低周往复荷载下的破坏过程及破坏形态,得到了各试件的滞回曲线、骨架曲线、刚度退化曲线、累积耗能、关键部位应变、延性系数等性能指标,对比分析人字形斜撑和玻璃纤维增强无机板对钢框架 组合墙体耗能性能、延性、承载力的影响。试验结果表明：组合墙体抗侧承载力高,刚度大,而变形能力与耗能能力较差;人字形斜撑能有效提高钢框架承载力、延性及耗能能力,但在组合墙体中人字形斜撑作用不明显,且圆钢管人字形斜撑易发生平面外失稳,建议设计时采用平面外刚度大于平面内刚度的H型钢;玻璃纤维增强无机板可以较大程度提高钢框架的抗侧承载力,由于玻璃纤维增强无机板过早开裂破坏,导致其延性降低,刚度退化速度加快,耗能能力变弱。基于已有的侧移刚度公式,对其进行参数修正并给出组合墙体侧移刚度简化计算式,理论值与试验初始抗侧刚度吻合较好,可为后续研究提供理论基础。     

外挂复合墙板半刚性钢管混凝土框架抗震试验研究

为了研究在地震作用下外挂复合墙板装配式钢结构的抗震性能,本文进行了4榀外挂复 合墙板半刚性钢管混凝土框架试件和1榀半刚性钢管混凝土框架试件的水平低周反复荷载试验。 研究参数为墙板的混凝土类型、墙连方式、斜撑设置和是否设置墙板。研究了地震作用下墙板 与框架的共同工作性能和破坏模式,分析了结构的滞回曲线、骨架曲线、强度和刚度退化规律 、耗能能力等。结合现有规范评价了结构的延性。试验结果表明,采用螺栓连接方式外挂复合 墙板的半刚性钢管混凝土框架试件具有良好的滞回性能、耗能能力和延性,可以安全可靠地确 保复合墙板与组合框架在地震作用下共同工作;位移延性系数μ=2.53~3.81,弹性极位移角 θy=(3.33~5.03)［θe］,弹塑性极限位移角θf=(2.35~2.55)［θp］;等效黏滞阻尼系数 ξe=0.147~0.182,能量耗散系数E=0.973~1.145;复合墙板破坏主要发生在墙板预埋件附近, 整体性能优于传统墙体。研究成果将为我国装配式钢结构设计理论与应用提供科学依据。     

多层钢框架偏心支撑的抗震性能试验研究

偏心支撑钢框架结构是一种比较理想的多层钢结构抗侧力体系,刚度大,受力性能合理。为了研究偏心支撑钢框架在地震作用下的滞回性能,为多层钢框架偏心支撑结构体系设计提供试验依据,选用耗能梁长度为可变参数,完成了2个不同构造形式的弯曲型耗能梁-偏心支撑框架在水平低周循环荷载下的破坏试验,分析了框架的承载能力及变形特征,研究了框架的破坏模式。研究表明,偏心支撑框架在弹性阶段内具有良好的变形能力,屈服荷载和框架刚度随弯曲型耗能梁长度增加呈下降趋势;偏心支撑框架能够控制框架破坏模式,地震作用下框架在耗能梁段屈服后屈曲破坏,破坏发生在耗能梁端部翼缘和支撑与柱脚连接的节点板位置,降低了梁柱节点受力。     

Experimental evaluation of the seismic performance of modular steel-braced frames

Several studies have shown that the lateral response of concentrically-braced frames is dominated by the inelastic behavior of the bracing members. However, the overall performance of the entire frame depends on the frame configuration including its connections. In this study, the hysteretic characteristics of modular steel-braced frames under reversed cyclic loading are evaluated. The design and construction of the test specimen accounted for the unique detailing requirements of these frames. A regular concentrically-braced frame with similar physical characteristics was also tested for comparison. Both test specimens consisted of a one-storey X-braced system with tubular brace cross-section. This paper describes the behavior characteristics and provides a detailed comparison of the two systems to assess the strength, stiffness, inelastic force and deformation, and energy dissipation characteristics of the modular system. An analytical model capable of capturing the effect of the system’s unique detailing requirements is proposed and validated using the test results.     

考虑楼板组合作用的方钢管混凝土组合框架受力性能试验研究

为研究钢梁与混凝土楼板的组合作用对钢-混凝土组合框架体系的刚度、承载力及耗能能力的影响,并考察组合框架结构在大震作用下进入弹塑性阶段的受力性能,进行了2榀足尺方钢管混凝土组合框架的低周反复荷载试验。2榀组合框架分别为组合梁-钢管混凝土框架及纯钢梁-钢管混凝土框架。试验中结构的最大层间位移角达到1/21。试验结果表明：组合框架结构具有稳定的滞回性能及良好的延性;钢梁与混凝土楼板的组合作用能显著提高结构的刚度、强度及耗能能力,并且能有效保证钢梁上翼缘的局部稳定性及钢梁的整体稳定性;楼板组合作用将使钢梁下翼缘应变显著增大,导致楼盖梁转动能力的减小;两个试件的破坏均是由梁端失效引起,说明试验中采用的梁翼缘贯通式节点能够满足强柱弱梁、强节点弱构件的抗震设计要求。     

钢框架内填混凝土墙结构体系有限元分析

对钢框架—内填混凝土墙结构体系进行了非线性有限元分析,得到了该体系在单向荷载作用下的变形及应力分布状况。为了简化计算,采用对角单压杆模型模拟内填墙的受力特性,并将计算结果同有限元实体模型以及纯钢框架模型结果进行比较,得出了一些结论。     

The design and seismic performance of low-rise long-span frames with semi-rigid connections

Moment-resisting steel frames are used frequently in low-rise and mid-rise buildings located in high seismic areas due to their high ductility and economic solutions. In these type of structures, strong-column weak-beam design requirements result in larger column sections and overdesign in low-rise long-span buildings. To mitigate this problem, moment-resisting steel frames with energy-dissipative semi-rigid/partial strength connections can be used as an alternative to perimeter frames. By using energy-dissipative semi-rigid connections, the strong-column weak-beam requirement is eliminated and more economical column sections are used. In this study, a three-span three-bay frame with 7 and 9 m span lengths is designed with semi-rigid connections having four different capacities in high seismic zones. Their seismic performance is evaluated analytically under three different earthquake levels by modeling connections with two different moment-hardening ratios and two different hysteretic behavior models. The design with reduced connection capacity resulted in an increase in the beam weights, a decrease in the column weights and an overall decrease in the structural weight. The seismic performances of 26 sample frames are evaluated with pushover and dynamic analyses under 25 real strong ground motion records. All of the sample frames satisfied the acceptance criteria and showed reliable performance under earthquake loading. The overdesign problem in low-rise long span-buildings is eliminated to some extent without using the perimeter frame approach. Furthermore, under some specific ground motion records, the top displacements in semi-rigid frames become lower than those of their rigid counterparts.     

实腹式型钢混凝土异形柱边框架抗震性能试验研究

为研究实腹式型钢混凝土(SRC)异形柱边框架的抗震性能,对1榀两跨三层的框架模型进行低周反复荷加载试验。观察结构的受力过程及破坏形态,并分析结构的荷载-位移滞回曲线和骨架曲线、承载能力、层间位移角、延性、耗能及刚度退化等力学特性。结果表明:实腹式SRC异形柱边框架破坏时形成梁铰机制,符合"强柱弱梁"的要求;滞回曲线饱满,刚度退化小;破坏时,等效黏滞阻尼系数和位移延性系数分别大于0.24和5.3;弹塑性极限层间位移角大于抗震规范规定的限值,抗倒塌能力强。实腹式SRC异形柱边框架显示出良好的抗震性能,可以应用于高抗震设防烈度区的建筑以及高层建筑中。     

The establishing of performance level thresholds for steel moment‐resisting frame using an energy approach

In this study, an energy design approach is proposed within the framework of the performance‐based seismic design of steel frames. Accumulated plastic rotation is selected as a parameter to establish the performance level thresholds. The test results of steel connections are investigated to quantify the performance level thresholds. The hysteretic energy input is acquired from a previous statistical study of twelve six‐storey steel moment‐resisting frames. The seismic performance of three‐storey steel moment resisting frames using the energy approach is examined. The research concluded that the structure designed by the energy method performed better than the steel frame designed by the equivalent lateral force (ELF) of UBC‐97 in view of accumulated plastic rotation. Performance levels such as functional, life safety and collapse are discussed based on the ductility level and the performance characteristics. Copyright © 2001 John Wiley & Sons, Ltd.     

现浇柱预制梁混凝土框架结构抗震性能试验研究

为研究装配整体式混凝土框架结构的滞回性能、延性和耗能能力等抗震性能,并考察其在罕遇地震作用下进入弹塑性阶段的受力性能,进行了2个1/2比例的2层2跨现浇柱预制梁框架试件的低周反复荷载试验。2个试件分别为对比装配式框架试件和预制梁端底部钢筋带套管的框架试件,试验中结构的最大层间位移角达到1/25。试验结果表明：现浇柱预制梁框架结构具有稳定的滞回性能及良好的延性;整个试验过程中结构刚度退化明显,且刚度退化主要发生在屈服之前;梁端钢筋的套管很好地发挥了作用,套管将接缝处钢筋变形平均到套管中,增大了梁端塑性铰长度,进而提高了结构的变形能力。研究成果可为装配整体式混凝土框架在抗震设防区的推广和应用提供参考。     

混凝土空心砌块填充墙RC框架抗震性能试验研究

通过对4榀单层单跨填充墙RC框架试件在水平低周往复荷载作用下的抗震性能试验,研究了填充墙砌块类型及高宽比对框架结构抗震性能的影响,对试件的破坏特征、滞回曲线、骨架曲线、位移延性、刚度退化、强度退化和耗能性能等进行了分析。试验结果表明：框架柱和填充墙的受剪承载力之比是影响结构破坏形态的重要因素,满足“强框架,弱填充墙”要求的4个试件均发生梁柱端塑性铰破坏,具有良好的抗倒塌性能;填充墙的存在影响了结构的滞回性能,提高了框架结构的抗侧刚度、水平承载力和滞回耗能能力;在相同位移幅值下,混凝土空心砌块填充墙的破坏程度比实心黏土砖填充墙的严重,存在一定的安全隐患。     

A Simplified Plastic Zone Method for Frame Analysis

Abstract: A methodology for the geometric and material nonlinear analysis of plane steel frames suitable for implementation in a microcomputer or personal computer platform is presented. The proposed procedure takes into consideration both geometric and material nonlinearities in its formulation. Geometric nonlinearity in the form of member and frame instabilities is accounted for by the use of pseudo-joint loads derived from the geometric stiffness matrix of the structure. Material nonlinearity in the form of cross-sectional plastification and progressive member yielding is accounted for by the use of a cross-sectional plastification model and the concept of effective member stiffness. Since both cross-sectional plastification and spread of yield along member length are considered in the analysis, the proposed approach is regarded as a plastic zone model. Unlike conventional plastic zone models in which intensive computations are required to obtain solutions, the proposed model employs simplified procedures by which spread of plasticity in the structural frame is accounted for in an approximate manner. Despite its simplicity, the proposed model gives reasonably accurate results when compared with other more rigorous approaches. To verify the applicability of the approach in predicting inelastic frame behavior, the proposed method was used to analyze a variety of frame structures. The results, expressed in terms of load-deflection responses, member forces, and moments, compared well with those obtained using other more elaborate inelastic analysis methods.