考虑非线性侧移的钢板剪力墙设计

近几年来,加劲钢板剪力墙结构作为一种很有潜力的抗侧力结构不断涌现,但关于此类结构的抗震规范却仍基于弹性设计方法。为满足设计过程高效性和可靠性的要求,提出了一种基于性能的抗震设计方法。对钢板剪力墙的抗震设计方法基于非线性目标侧移和预选屈服机制。该方法很简捷,能得出更先进的设计指标。以不同钢板长宽比和不同允许侧移条件下某4层结构为例,通过强震下的非线性时程分析,对该方法进行检验。结果表明:实际的非线性侧移与目标侧移非常接近。将峰值处的位移图与所选屈服机制进行了对比。基于上述试验,今后还需对该方法进行进一步修正。     

近断层地震作用下钢板剪力墙结构基于MECE谱的性态设计方法

结构在近断层地震作用下的损伤通常与强速度脉冲所携带的瞬时输入能量相关,为反映这种近场地面运动特征,以10条坚硬场地的近场地震记录为输入,建立了适用于设计的最大有效滞回耗能（MECE）谱,提出了基于MECE谱确定钢板剪力墙结构屈服基底剪力的性态设计方法。该方法不仅反映近场地震速度脉冲的影响,而且还可区别不同结构体系滞回特性的影响。同时,结合已有研究成果完善了钢板剪力墙结构周边构件能力设计的简化公式。通过对1榀10层3跨钢板剪力墙结构的弹塑性时程分析,对建议方法进行了验证。结果表明：在多遇及罕遇地震作用下结构层间位移角满足我国现行建筑抗震设计规范的要求,结构出现理想的渐进式梁铰屈服机构,证明了基于MECE谱钢板剪力墙结构性态设计方法的合理性和可靠性。     

Computer‐based evaluation of design methods used for a steel plate shear wall system

Vertical boundary elements (VBEs) play a key role in seismic performance of steel plate shear wall (SPSW) system and consume major part of the steel material in a structure. The different methods allowed by design standards for computing the force demands exerted on the VBEs yield in widely varied results and are evaluated in this study through a computer‐based approach. After elaborating these methods, development of a versatile and user‐friendly program is presented that implements various SPSW design algorithms. The program relies on component object model technology and interactively communicates with a component object model supporting program, etabs , as the analysis core. It also benefits from an object‐oriented structure. At the next phase, the developed program is utilized to design SPSWs with different heights and extract VBE demands using different methods. Nonlinear time history analyses of the structures, performed in opensees software using a bin of seven ground motion records, have been ultimately used for assessing the precision of different demand estimation methods. The AISC 341‐10 capacity‐based design method was shown to provide overestimations that reached 90% and 1888%, respectively, for axial and flexural VBE demands of 17‐story building. Lower overestimation ratios were found for shorter structures. Copyright © 2016 John Wiley & Sons, Ltd.     

Performance-based plastic design of steel plate shear walls

The existing codes and design guidelines for steel plate shear walls (SPSWs) fail to utilise the excellent ductility capacity of SPSW systems to its fullest extent, because these methods do not consider the inelastic displacement demand or ductility demand as their design objective. A performance-based plastic design method for SPSW systems with rigid beam-to-column connections is proposed in this work, which sets a specific ductility demand and a preferred yield mechanism as its performance targets. The effectiveness of the proposed method in achieving these targets is illustrated through sample case studies of four- and eight-storey SPSW systems for varied design scenarios. A comparison with the existing AISC method for the same design scenario shows that the proposed method consistently performs better, in achieving these performance-based targets. The proposed method is modified to account for P-Delta effects, wherever necessary. This modified method is found to be more effective than the original proposal, whenever P-Delta effects are significant.     

钢筋混凝土框架结构基于性能的抗震设计方法

以变形需求作为设计参数,阐明了RC框架结构基于性能的抗震设计方法的基本原理及步骤：利用弹塑性位移谱法求解结构的位移与变形需求,在层间位移角满足特定要求后,将梁柱塑性铰区的转动量值作为性能设计的参数,结合预期的性能目标由梁柱性能设计方程进行构件变形能力设计。以-10层框架结构为例,给出了RC框架结构基于性能的抗震设计的完整过程,并通过弹塑性时程分析作了比较验证。结果表明：弹塑性位移谱法求解结构位移需求是一种可为工程接受的、简便有效的方法,通过梁柱性能设计方程对变形能力进行定量设计,可将结构的破损程度控制在预先设定的性能目标范围内。     

Reduction of inelastic seismic demands in a mid‐rise rocking wall structure designed using the displacement‐based design procedure

Precast post‐tensioned rocking wall structural system has been developed in the recent past as a damage‐avoidance structural system for seismic regions. For a widespread use of this structural system, suitable design procedures are required to ensure a reliable and well‐predicted performance under different levels of seismic hazard. In the current study, a mid‐rise 20‐story rocking wall structure is selected and designed using the displacement‐based design procedure. Furthermore, two different capacity design procedures are used to predict the increased force demands due to higher mode effects. The time history results against moderate and severe level of seismic hazards show the effectiveness of displacement‐based design procedure in predicting and controlling the displacement and drift demands, while the simplified procedure and the modified modal superposition procedure for the capacity design are found to be unconservative and conservative, respectively. To further investigate the seismic demands, modal decomposition of inelastic seismic responses is carried out, and the contribution of different modes in the total responses is calculated. Based on this improved understanding, a mitigation technique of dual gap opening is employed. A detailed discussion about the location and design strength of the extra gap‐opening is carried out by considering different performance parameters. Copyright © 2016 John Wiley & Sons, Ltd.     

钢板剪力墙抗震行为与设计

本研究主要目的在于针对未束制型钢板剪力墙的使用性与消能特性加以改良,并研发束制型钢板剪力墙试体,共规划四座试体,3cm厚之低降伏LYS钢板为墙体:一座完全不加束制构件,另两座试体分别在LYS钢板墙体之两面以矩型钢管束制之,第四座则以钢筋混凝土板(简称为CP板)束制LYS钢板墙,于地震工程研究中心进行试验,同时并研究钢板剪力墙的分析模型,包括精准的Strip Model供研究者应用,与较简易的等效斜撑模型供工程实务应用。试验结果显示,束制型钢板剪力墙,LYS钢板挫屈所产生之声响减小,且平面外侧向挫屈变形也随之减少,而消能效果也明显增加。束制与未束制钢板剪力墙之分析模型采用Strip Model,皆可以准确仿真出试验所得之迟滞循环。在单向侧推分析中,采用等效层斜撑模型仿真束制型钢板剪力墙的初始劲度以及强度与试验结果接近。     

多楼层钢板剪力墙之耐震设计研究

现有钢板剪力墙耐震设计规范对于多楼层钢板剪力墙边界梁柱的容量设计并无清楚交代,本研究的目的在于研发方便且有效的多楼层钢板剪力墙的耐震分析与容量设计方法。探讨不同原理的钢板剪力墙底层边界柱容量设计法,研究如何避免底层柱顶塑性铰的产生,并以ABAQUS有限元模型证实所提设计方法可以有效地避免柱顶塑性铰的发生,而避免侧向变形集中在底层时的软弱层现象。本研究采用美国洛杉矶市反应谱分别设计了6层以及20层的钢板剪力墙建筑结构,并用结构非线性分析软件PISA3D建立双向板条模型进行非线性时程分析,依SAC计划中20组475年回归期的地震分析统计结果讨论钢板剪力墙结构在强烈地震下的反应。由构架动力分析反应和所估计的最大静态需求比较,可观察到钢板对边界柱的最大累积拉力的静态估计值会随着楼层位置越低时有越高估的趋向。此外,边界梁端的最大剪力在上下层钢板厚度相同处,静态估计值有严重低估的情形发生,因此会造成边界梁端的最大累积剪力静态估计值随着楼层位置越低时有越低估不保守的趋向。最后依时程分析结果给出不同楼层数的钢板剪力墙边界柱轴力需求的估算方式建议,依此建议可设计出安全且经济的边界柱。     

钢管混凝土框架基于性能的抗震设计探讨

基于性能的抗震设计(PBSD)是现代工程抗震理论研究的重要问题。与传统抗震设计方法相比,基于性能的抗震设计可反映具体结构的抗震性能目标。本文在综述基于性能的抗震设计理论的背景、概念、主要内容的基础上,根据钢管混凝土结构的特点,较系统地分析了钢管混凝土框架基于性能的抗震理念和设计方法,讨论了基于位移的抗震设计(DBSD)应用于钢管混凝土结构时的方法和步骤,并对确定该类结构的目标位移和相应的侧移模式进行了初步探讨。采用SAP2000软件建立了某12层钢管混凝土框架模型并进行了静力推覆(pushover)分析,初步评价了地震作用下钢管混凝土框架结构的性能指标。     

Effects of soil‐structure interaction and lateral design load pattern on performance‐based plastic design of steel moment resisting frames

The effects soil‐structure interaction (SSI) and lateral design load‐pattern are investigated on the seismic response of steel moment‐resisting frames (SMRFs) designed with a performance‐based plastic design (PBPD) method through a comprehensive analytical study on a series of 4‐, 8‐, 12‐, 14‐, and 16‐story models. The cone model is adopted to simulate SSI effects. A set of 20 strong earthquake records are used to examine the effects of different design parameters including fundamental period, design load‐pattern, target ductility, and base flexibility. It is shown that the lateral design load pattern can considerably affect the inelastic strength demands of SSI systems. The best design load patterns are then identified for the selected frames. Although SSI effects are usually ignored in the design of conventional structures, the results indicate that SSI can considerably influence the seismic performance of SMRFs. By increasing the base flexibility, the ductility demand in lower story levels decreases and the maximum demand shifts to the higher stories. The strength reduction factor of SMRFs also reduces by increasing the SSI effects, which implies the fixed‐base assumption may lead to underestimated designs for SSI systems. To address this issue, new ductility‐dependent strength reduction factors are proposed for multistory SMRFs with flexible base conditions.     

Bracing systems for seismic retrofitting of steel frames

The present study assesses the seismic performance of steel moment resisting frames (MRFs) retrofitted with different bracing systems. Three structural configurations were utilized: special concentrically braces (SCBFs), buckling-restrained braces (BRBFs) and mega-braces (MBFs). A 9-storey steel perimeter MRF was designed with lateral stiffness insufficient to satisfy code drift limitations in zones with high seismic hazard. The frame was then retrofitted with SCBFs, BRBFs and MBFs. Inelastic time-history analyses were carried out to assess the structural performance under earthquake ground motions. Local (member rotations) and global (interstorey and roof drifts) deformations were employed to compare the inelastic response of the retrofitted frames. It is shown that MBFs are the most cost-effective bracing systems. Maximum storey drifts of MBFs are 70% lower than MRFs and about 50% lower than SCBFs. The lateral drift reductions are, however, function of the characteristics of earthquake ground motions, especially frequency content. Configurations with buckling-restrained mega-braces possess seismic performance marginally superior to MBFs despite their greater weight. The amount of steel for structural elements and their connections in configurations with mega-braces is 20% lower than in SCBFs. This reduces the cost of construction and renders MBFs attractive for seismic retrofitting applications.     

基于结构性能的抗震设计理论与方法

基于性能的抗震设计(PBSD)是20世纪90年代国际抗震工程界提出的新概念,也是工程抗震发展史上的一个重要里程碑。详细阐述了基于性能的抗震设计理论产生的背景、基本概念、主要内容和特点,较系统地分析了基于性能的抗震分析和设计方法,并指出了基本性能抗震设计理论与传统设计理论的主要区别。     

钢框架-防屈曲开斜槽耗能钢板剪力墙装配式结构体系抗震性能分析

防屈曲开斜槽耗能钢板剪力墙(简称开斜槽钢板墙)是一种新提出的抗侧力构件,相比于普通钢板剪力墙,具有多个可调参数、耗能稳定且延性好的优点,并可作为装配式单元,通过组装单元的方式形成装配式剪力墙结构,进一步形成不同的装配式抗侧力体系。本文介绍了钢框架-开斜槽钢板墙装配式结构体系,包括开斜槽钢板墙设计方法,装配式剪力墙结构以及结构体系设计方法,并以20层办公大楼为例进行设计,对结构在小震和大震下的抗震性能进行分析。计算结果表明,开斜槽钢板墙可提供较大的抗侧刚度,能充分发挥耗能作用,保护主体结构安全,符合双重抗侧力体系的原则,该结构体系具有优越的抗震性能。     

Prediction of nonlinear seismic demands of high‐rise rocking wall structures using a simplified modal pushover analysis procedure

This study presents a simplified analysis procedure for the convenient estimation of nonlinear seismic demands of high‐rise rocking wall structures. For this purpose, the displacement modification approach used in the nonlinear static procedure of ASCE/SEI 41‐13 is adopted. However, in the current study, this approach is extended to every significant vibration mode of the structure whereas the displacement modifying coefficients for different modes are calculated using the typical flag‐shaped hysteresis behavior of rocking walls. The parameters of this hysteresis behavior are selected to represent rocking walls with a practical range of energy dissipation capacity and postgap‐opening stiffness. The computed peak inelastic‐to‐elastic displacement ratios are presented as mean spectra, which can be used for the convenient estimation of pushover target displacement for every significant vibration mode. The accuracy of proposed procedure is examined using the seismic demands obtained from the nonlinear response history analysis of a 20‐story case study rocking wall structure. Furthermore, a modal decomposition technique is used to determine the individual modal seismic demands. The proposed procedure is found to predict both the combined and the individual modal demands with a reasonable accuracy and can serve as a convenient analysis option for the design and performance evaluation of high‐rise rocking wall systems.     

Estimating inelastic drift demands for wood portal frame systems considering accumulated damages

As one key to the implementation of the performance‐based design methodologies for wood structures, the performance objectives and their corresponding limit state criteria are usually correlated with the peak (maximum) interstory drift demands. This paper evaluates the inelastic drift demands including the peak drift and the residual drift for the prototype timber portal frame structural elements. Analytical 2D‐framed model representative of the study‐case were subjected to a suite of 50 pulse‐type earthquake ground motions. In addition, an accumulated damage index is added to the inputs of the nonlinear analyses to account for the damage caused by the previous ground excitations. Larger accumulated damages lead to larger inelastic drifts. Strong correlation is revealed among the drift demands, the peak ground accelerations, and the variables characterizing the nonlinear system behavior. Finally, estimation formulas for the peak and residual drift demands are proposed and validated with the simulated results from nonlinear time‐history analyses. Based on the presented formulas, the resilience ratio and the effective elastic drift are further derived to comprehend the nonlinear behavior of such timber made structures.     

Assessment of current nonlinear static procedures for seismic evaluation of BRBF buildings

Nonlinear static procedures (NSPs) are now standard in engineering practice to estimate seismic demands in the design and evaluation of buildings. This paper aims to investigate comparatively the bias and accuracy of modal, improved modal pushover analysis (MPA, IMPA) and mass proportional pushover (MPP) procedures when they are applied to buckling-restrained braced frame (BRBF) buildings which have become a favorable lateral-force resisting system for earthquake resistant buildings. Three-, 6-, 10-, and 14-storey concentrically BRBF buildings were analyzed due to two sets of strong ground motions having 2% and 10% probability of being exceeded in 50 years. The assessment is based on comparing seismic displacement demands such as target roof displacements, peak floor/roof displacements and inter-storey drifts. The NSP estimates are compared to results from nonlinear response history analysis (NL-RHA). The response statistics presented show that the MPP procedure tends to inaccurately estimate seismic demands of lower stories of tall buildings considered in this study while MPA and IMPA procedures provide reasonably accurate results in estimating maximum inter-storey drift over all stories of studied BRBF systems.     

基于能量原理的钢筋混凝土框架结构层间弹塑性位移求解

本文按照我国现行《建筑抗震设计规范》设计了三个层数分别为4、7和10层的钢筋混凝土框架结构。利用能量法对各框架结构按等效单自由度体系计算了其滞回输入能;利用pushover方法分析了钢筋混凝土框架结构的层间能量分布规律,通过与非线性动力时程分析结果进行比较,证明该法是可行的;利用文献[1]中楼层弹塑性变形耗能与弹塑性层间位移的关系求出各框架结构的层间弹塑性位移,并与现行《建筑抗震设计规范》中简化计算方法的计算结果进行了对比。     

Seismic response of plane steel MRF with setbacks: Estimation of inelastic deformation demands

An extensive parametric study on the inelastic seismic response of plane steel moment resisting frames (MRF) with setbacks is presented. A family of 120 such frames, designed according to the European seismic and structural codes, are subjected to an ensemble of 30 ordinary (i.e. without near-fault effects) earthquake ground motions scaled to different intensities in order to drive the structures to different limit states. The statistical analysis of the created response databank indicates that the number of stories, beam-to-column strength ratio, geometrical irregularity and limit state under consideration strongly influence the heightwise distribution and amplitude of inelastic deformation demands. Nonlinear regression analysis is employed in order to derive simple formulae which reflect the aforementioned influences and offer, for a given strength reduction (or behaviour) factor, three important response quantities, i.e. the maximum roof displacement, the maximum interstorey drift ratio and the maximum rotation ductility along the height of the structure. A comparison of the proposed method with the procedures adopted in current seismic design codes reveals the accuracy and efficiency of the former.     

Effect of column stiffness on drift concentration in steel plate shear walls

Steel plate shear walls (SPSWs) are a lateral force resisting system consisting of thin infill steel plates surrounded by boundary frame members. Hysteretic energy dissipation and lateral force resistance of the system are primarily achieved through the yielding of the infill steel plates. However, during an earthquake event, the infill plates at different building stories may not yield simultaneously due to many factors such as overstrength of some infill plates and the actual lateral force distribution which is different from the one assumed in design, possibly resulting in inter-story drift concentrations in the system. This paper investigates the effect of column stiffness on mitigating drift concentration in SPSWs. Based on an example two-story SPSW, mathematical models are derived to characterize the system behavior and quantify the effect of column stiffness on the mitigation of drift concentration. Nonlinear static pushover analyses using finite element models are performed to further validate the developed models. Finally, based on the developed models, parametric analyses are conducted to investigate the effect of column stiffness over a practical range of the considered parameters, followed by a discussion of the minimum SPSW column stiffness specified in North American codes. The results from this investigation show that column stiffness should be a design parameter to ensure a reasonably uniform drift distribution and hence a more uniform infill plate yielding along the height of SPSW buildings.     

抗震结构弹塑性反应谱的研究与应用

随着基于性能抗震设计理论的提出,以及对结构弹塑性地震反应研究的深入,弹塑性反应谱的研究得到更多的重视与发展。文中首先阐明了弹性和弹塑性反应谱的基本概念;其次,归纳和讨论了国内外弹塑性反应谱的研究现状,阐述了现有一些弹塑性反应谱研究的不足,并指出研究的基于Park和Ang双参数损伤模型的弹塑性反应谱,能够综合考虑了结构最大位移反应和结构累积滞回耗能的耦合作用,使弹塑性反应谱的研究进一步深化;最后,指出了弹塑性反应谱在基于性能抗震评估中的应用,但要将弹塑性反应谱应用于抗震设计规范中还存在诸多困难。