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.     

Evaluation of deformation capacity including yield deformation in displacement‐based design of special RC shear wall

A displacement‐based design scheme can be applied to the seismic designs of special reinforce concrete (RC) shear walls. However, the displacement‐based design in the current seismic design codes does not consider the contribution of yield deformation of RC shear walls. In this study, the evaluation method of the deformation capacity for seismic designs of RC shear walls was analyzed and applied to a parametric study for the lateral deformations of RC shear walls. From the results of analyses with various design conditions, the contribution of yield deformation to the deformation capacity of an RC shear wall was analyzed. It was demonstrated that, for RC shear walls in tall buildings, the yield deformation increased as the ratio of wall height to length increased and reached more than 50% of total deformation. Therefore, for the reasonable design of special RC shear walls in tall buildings, the design equation including the yield deformation in the displacement‐based design process is proposed. Copyright © 2012 John Wiley & Sons, Ltd.     

Optimal reduction of inelastic seismic demands in high‐rise reinforced concrete core wall buildings using energy‐dissipating devices

Recently, the issue of large inelastic seismic force demands at severe ground shakings such as maximum considered earthquake level has been highlighted in the conventionally designed high‐rise reinforced concrete core wall buildings. Uncoupled modal response history analysis was used in this study to identify the modes responsible for the large inelastic seismic force demands. The identification of dominant modes and mean elastic design spectra of seven representative ground motions for different damping ratios has led to the identification of three control measures: plastic hinges (PHs), buckling‐restrained braces (BRBs) and fluid viscous dampers (FVDs). The identified control measures were designed to suppress the dominant modes responsible for the large inelastic seismic force demands. A case‐study building was examined in detail. Comparison of the modal as well as the total responses of the case‐study building with and without the control measures shows that all the control measures were effective and able to reduce the inelastic seismic demands. A reduction of 33%, 22% and 27% in the inelastic shear demand at the base and a reduction of 60%, 22% and 26% in the inelastic moment demand at mid‐height were achieved using the PHs, BRBs and FVDs, respectively. Furthermore, a reduction of about 30–40% in the inelastic seismic deformation demands was achieved for the case of the BRBs and FVDs. The study enables us to gain insight to the complex inelastic behavior of high‐rise wall buildings with and without the control measures. Copyright © 2011 John Wiley & Sons, Ltd.     

Direct displacement‐based design of steel‐braced reinforced concrete frames

This study investigates a direct displacement‐based design procedure for dual system structures composed of reinforced concrete frames and steel bracings. In this procedure, in order to establish the design displacement profile before any analysis, strength proportions between bracings and frames are assigned. By using the displacement profile and damping characteristics of the structural components, the structure can be represented as an equivalent single‐degree‐of‐freedom system. The effective period and secant stiffness of the structure are then calculated, and finally, after the base shear was computed, the design process can be implemented. Structures with 4, 8 and 12 stories have been designed using this methodology, and in order to validate it, seven accelerograms have been used for nonlinear time‐history analysis of the above structures. The results demonstrate the efficiency of this procedure. Copyright © 2012 John Wiley & Sons, Ltd.     

消能摇摆钢框架结构抗震性能的影响因素与设计方法

消能摇摆钢框架结构包含主体钢框架结构、摇摆结构和耗能阻尼器三部分。刚度较大的摇摆结构可以使主体钢框架在地震作用下发生均匀的层间变形,抑制薄弱层产生。布设于摇摆结构底部的阻尼器,能够耗散地震动能量,减小整体结构的地震反应,提高结构的抗震性能。文中对消能摇摆钢框架结构抗震性能的影响因素进行参数分析,并基于我国建筑抗震设计规范的原则提出了抗震设计方法。根据消能摇摆钢框架结构的受力机理,提出简化分析模型,通过弹塑性地震反应分析,验证简化模型的有效性。基于简化分析模型对无量纲参数进行参数分析,根据各参数的影响规律得到无量纲参数的建议范围。结合我国“三阶段”抗震设防要求,提出消能摇摆钢框架结构的设计方法,并结合算例进行验证。研究表明,消能摇摆钢框架结构抗震性能良好,设计合理的摇摆结构与阻尼器能够抑制钢框架的薄弱层、减小结构的地震反应。     

Equivalent viscous damping in direct displacement‐based design of steel braced reinforced concrete frames

Performance‐based design method, particularly direct displacement‐based design (DDBD) method, has been widely used for seismic design of structures. Estimation of equivalent viscous damping factor used to characterize the substitute structure for different structural systems is a dominant parameter in this design methodology. In this paper, results of experimental and numerical investigations performed for estimating the equivalent viscous damping in DDBD procedure of two lateral resistance systems, moment frames and braced moment frames, are presented. For these investigations, cyclic loading tests are conducted on scaled moment resisting frames with and without bracing. The experimental results are also used to calibrate full‐scale numerical models. A numerical investigation is then conducted on a set of analytical moment resisting frames with and without bracing. The equivalent viscous damping and ductility of each analytical model are calculated from hysteretic responses. On the basis of analytical results, new equations are proposed for equivalent viscous damping as a function of ductility for reinforced concrete and steel braced reinforced concrete frames. As a result, the new equation is used in direct displacement‐based design of a steel braced reinforced concrete frame. Copyright © 2012 John Wiley & Sons, Ltd.     

Alternative approach to compute shear amplification in high‐rise reinforced concrete core wall buildings using uncoupled modal response history analysis procedure

The seismic response of the high‐rise reinforced concrete (RC) wall structures is really complicated as several vibration modes other than the fundamental mode normally contribute significantly to the response—commonly recognized as ‘higher mode effects’. Response spectrum analysis (RSA) procedure, which can account for higher mode effects, is usually employed to compute the seismic design demand for the high‐rise structures. Recent studies show that the inelastic seismic force demands obtained from the rigorous nonlinear response history analysis procedure are much larger than the seismic force design demands obtained from the code‐based RSA procedure for the high‐rise RC wall structures. Though, the nonlinear response history analysis procedure is widely accepted for its ability to provide the most accurate estimate of nonlinear seismic responses, the obtained responses are generally so complex that it is quite difficult for engineers to grasp the overall picture of the responses and gain some insight into them and use them to understand the cause of high seismic demands. Another important issue related to the nonlinear seismic response prediction of the high‐rise RC wall structures is the realistic and accurate numerical modeling of RC walls. In this study, a simplified but reasonably accurate procedure called the uncoupled modal response history analysis procedure is used to interpret the complex nonlinear behavior of high‐rise RC wall structures. Moreover, a finite element model based on modified compression field theory is employed for accurate numerical modeling of RC walls by incorporating the axial‐flexure‐shear interaction. This study, by making use of a better computer modeling approach and an in‐depth analysis by modal decomposition, aims to resolve some of the unanswered questions regarding realistic prediction of nonlinear seismic demands of high‐rise structures.     

基于抗震性能的框架—剪力墙结构优化设计

根据我国现行建筑抗震设计规范对结构最大层间位移角限值的要求,以地震作用最小为目标,用计算机VC语言编写出框架—剪力墙结构的优化程序,并计算出满足要求的剪力墙数量,简单实用,适用于地震区高层建筑结构的初步设计阶段。     

谈底框—抗震墙结构房屋抗震设计要点

针对底框—抗震墙结构房屋抗震整体性能差这一问题,重点从结构方案、结构抗震计算和结构构造等方面总结了该结构房屋抗震设计时的一些要点,指出虽然在结构设计中有一定局限性,但只要遵循其内在规律,就能使设计达到安全、合理的目的。     

Performance‐based plastic design and collapse assessment of diagrid structure fused with shear link

A diagrid structure fused with shear link (DSSL) is an innovative earthquake resilient structural system. The DSSL combines the steel diagrid structural system with shear links to dissipate the earthquake energy with the goal to minimize structural repair and downtime after strong earthquake shaking. The SLs are placed between diamond‐shaped grid units and decoupled from the gravity system. To facilitate the design of the proposed DSSL system, the performance‐based plastic design (PBPD) procedure is extended to design a prototype building utilizing DSSL. Detailed finite element model is developed to simulate the non‐linear dynamic response of the structure under a range of earthquake shaking intensities. The results of non‐linear dynamic analyses show that the DSSL has excellent seismic performance and can be efficiently designed using PBPD. Lastly, detailed collapse risk assessment of the prototype building is performed using the FEMA‐P695 methodology. The result shows that the PBPD‐designed DSSL has adequate margin against collapse. Hence, it can be used as an effective seismic force resisting system.     

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.     

关于框架加少量剪力墙结构抗震设计的探讨

通过对框架加少量剪力墙结构层间位移角的分析,指出层间位移角的控制应采用分级控制值,即层间位移角的控制值根据剪力墙所承担的地震倾覆力矩的比值来确定,为框架—剪力墙结构的抗震设计提供了参考。     

An introduction to the structural design of rocking wall‐frames with a view to collapse prevention,self‐alignment and repairability

The purpose of this article is to present a new method of analysis for the structural design of pin‐supported rocking wall‐moment frames with supplementary devices and post‐tensioned stabilizers. The function of the wall is to prevent soft story failure, impose uniform drift and provide support for the supplementary equipment. The proposed methodology lends itself well to several seismic design strategies, ranging from severe damage avoidance, to collapse prevention, to structural self‐alignment and repairability. Repairability means avoiding major damage to columns and foundations. The success of the resulting solutions is due to the single degree of freedom behavior of the combined system and the fact that its overall performance is not significantly affected by minor changes in the stiffness of the wall. The sensitivity of the response to wall rigidity is addressed by comparing the maximum elastic slope of the wall with a fraction of the specified uniform drift. The limitations of rocking wall‐moment frames, as viable lateral resisting systems, have been addressed. Several worked examples have been presented to provide insight and technical information that may not be readily available from electronic output. The proposed solutions are exact within the bounds of the theoretical assumptions and are ideally suited for manual as well as spreadsheet computations. Copyright © 2015 John Wiley & Sons, Ltd.     

Reliability‐based optimum seismic design of RC frames by a metamodel and metaheuristics

The present study is devoted to reliability‐based optimum seismic design (RBOSD) of reinforced concrete (RC) moment frames within the context of performance‐based design. A chaotic enhanced colliding bodies optimization (CECBO) metaheuristic algorithm is proposed to achieve the optimization task. In the framework of CECBO, chaotic maps are employed to achieve randomness that results in better convergence rate in comparison with its standard version. For reliability assessment of structures during the optimization process, the Monte Carlo simulation method is employed. In order to reduce the prohibitive computational burden of the MCS in the optimization setting, a metamodel is proposed to accurately evaluate the required deterministic and probabilistic structural seismic nonlinear responses. Efficiency of the proposed methodology for implementation of RBOSD process for RC frames is illustrated by presenting two numerical examples.     

谈建筑结构中剪力墙结构的优化设计

为了更好地适应市场经济的发展,对建筑结构中剪力墙结构的优化设计进行了探讨,介绍了剪力墙结构的设计及计算方法,同时分析了剪力墙结构应用于工程中需注意的事项,促使建筑结构得到完善和优化。     

Design and specification compilation of a modular‐prefabricated high‐rise steel frame structure with diagonal braces part II: Elastic–plastic time‐history analysis and joint design

The use of modular‐prefabricated steel structures has distinct advantages, such as rapid construction, industrial production, and environmental protection. Although this type of structure has been extensively employed around the world, it is primarily used for low‐rise buildings; its application in high‐rise buildings is limited. This paper proposes a new type of modular‐prefabricated high‐rise steel frame structure with diagonal braces. An elastic–plastic time‐history analysis of a 30‐storey building during rare earthquakes was performed. The base shear, storey drift, stress, damage characteristics, and other performances of the structure were investigated. According to the mechanism analysis, finite element simulation, and model test, the formulas for the elastic and elastic–plastic design of the truss–column connection, column–column flange connection, and diagonal brace–truss connection are proposed in this paper. The control parameters for the structural design are also discussed. This study provides an important reference for the research and design of this type of modular‐prefabricated high‐rise steel structure. The design method has been compiled into a design specification named Technical Specifications for Prefabricated Steel Frame Structure with Diagonal Bracing Joints, which is unique for this type of structure.     

剪力墙平面布置对异形柱框剪结构地震响应的影响分析

通过调整某异形柱框架-剪力墙结构的剪力墙布置方案,进行改进后模型的模态分析和弹性时程分析,研究剪力墙和异形柱不同平面布置对地震响应的影响。分析发现,改进后模型的抗震性能显著提高,底部剪力变化不大,最大楼层位移和结构自振周期得到明显改善,最大楼层位移值减小14.4%,自振周期减小4.34%。     

A modified response spectrum analysis procedure to determine nonlinear seismic demands of high‐rise buildings with shear walls

The standard response spectrum analysis (RSA) procedure prescribed in various design codes is commonly used by practicing engineers to determine the seismic demands for structural design purpose. In this procedure, the elastic force demands of all significant vibration modes are first combined and then reduced by a response modification factor (R) to get the inelastic design demands. Recent studies, however, have shown that the response of higher vibration modes may experience much lower level of nonlinearity, and therefore, it may not be appropriate to reduce their demand contributions by the same factor. In this study, a modified RSA procedure based on equivalent linearization concept is presented. The underlying assumptions are that the nonlinear seismic demands can be approximately obtained by summing up the individual modal responses and that the responses of each vibration mode can be approximately represented by those of an equivalent linear SDF system. Using 3 high‐rise buildings with reinforced concrete shear walls (20‐, 33‐, and 44‐story high), the accuracy of this procedure is examined. The inelastic demands computed by the nonlinear response history analysis procedure are used as benchmark. The modified RSA procedure is found to provide reasonably accurate demand estimations for all case study buildings.     

Performance‐based plastic design method for tall hybrid coupled walls

The research presented herein involves a performance‐based design method for a tall hybrid coupled wall (HCW) system. For this study, HCW structures were designed with a performance‐based plastic design (PBPD) method. This approach directly accounts for inelastic structural behavior and considers design lateral force distribution at ultimate limit state. The design concept uses a pre‐selected target drift and yield mechanism as key performance limit states. The yield mechanism consists of shear yielding in the coupling beams and flexural yielding of reinforced concrete walls at the bases. HCW structures with varying heights and coupling ratios (CRs) were designed and subjected to a series of nonlinear dynamic analyses. The results indicated that the CR strongly influences the response of the structure. The structures could also be under‐designed when the inelastic distribution of lateral forces owing to higher modes was not properly considered. Finally, a design method to account for higher mode effects within the PBPD framework was presented. The method was validated using the results from nonlinear analyses. Copyright © 2016 John Wiley & Sons, Ltd.