Performance‐based design of high‐rise coupled wall systems

Coupled core walls provide an efficient lateral load‐resisting system. Performance of coupled wall systems depends primarily on ensuring that coupling beams provide adequate stiffness and strength. Current design guidelines, which are based on a strength‐based design approach, often result in beams with unrealistic details. Previous studies have also demonstrated that coupled core walls behave differently from what is assumed in a traditional strength‐based design approach. Therefore, currently available strength‐based design methodology is inadequate to address a large class of coupled core wall systems, and alternative design approaches are necessary. In this paper, a rational approach based on a performance‐based design method is demonstrated through the design and analysis of a prototype 30‐story coupled core wall structure. Critical responses of the prototype structure at different limit states under representative ground motions are compared in order to evaluate the adequacy of the performance‐based design method. Copyright © 2006 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.     

Stochastic seismic collapse and reliability assessment of high‐rise reinforced concrete structures

To provide knowledge beyond the conventional engineering insights, attention in this work is focused on a comprehensive framework for the stochastic seismic collapse analysis and reliability assessment of large complex reinforced concrete (RC) structures. Three key notions are emphasized: the refined finite element modeling and analysis approach towards structural collapse, a physical random ground motion model, and an energy‐based structural collapse criterion. First, the softening of concrete material, which substantially contributes to the collapse of RC structures, is modeled by the stochastic damage constitutive model. Second, the physical random ground motion model is introduced to quantitatively describe the stochastic properties of the earthquake ground motions. And then the collapse‐resistance performance of a certain RC structure can be systematically evaluated on the basis of the probability density evolution method combining with the proposed structural collapse criterion. Numerical results regarding a prototype RC frame‐shear wall structure indicate that the randomness from ground motions dramatically affects the collapse behaviors of the structure and even leads to entirely different collapse modes. The proposed methodology is applicable in better understanding of the anti‐collapse design and collapse prediction of large complex RC buildings.     

Comparison of earthquake behavior of reinforced concrete minarets using fiber‐reinforced polymer composite

This paper presents the comparison of the earthquake behavior of reinforced concrete (RC) minarets using fiber‐reinforced polymer (FRP) composite. A Turkish‐style RC minaret with two balconies of a mosque located in Trabzon, Turkey, was selected as an application. A 3D finite element model of the minaret was created using ansys finite element program to determine the earthquake behavior. The earthquake behavior of the minaret was investigated using the 1992 Erzincan earthquake ground motion record. Also, the cylindrical body of the minaret (below the first balcony, between two balconies and above the second balcony) was wrapped by four layers of FRP, and earthquake behavior was determined. Total thickness of the FRP was selected as 6.0 mm. At the end of the study, earthquake responses of the RC minaret such as displacements and maximum–minimum principal stresses before and after using FRP composite were compared with each other. It was seen from the earthquake analyses that using FRP is very effective on the earthquake responses of the minaret. Copyright © 2011 John Wiley & Sons, Ltd.     

Fragility assessment of high‐rise reinforced concrete buildings considering the effects of shear wall contributions

The effect of shear wall configurations on seismic responses of high‐rise RC buildings is investigated in this paper using fragility analysis method. Four lower high‐rise RC buildings that have the same plan dimensions and height but are different in configurations in lateral force resisting systems, were firstly designed following the standard code procedure. To consider uncertainties in earthquake motions, 16 real ground motion pairs were selected and scaled, then applied orthogonally to the four RC building models during the Incremental Dynamic Analysis (IDA). Fragility relationships were therefore derived based on the IDA results for the three limit states including slight damage, moderate damage and collapse to show the probabilistic comparison of seismic responses among the four buildings in both x and y‐directions. It was observed that generally adding shear walls will improve buildings' seismic performance at all limit states. However, shear wall configuration also plays a significant role in seismic behavior of the lower high‐rise regular RC buildings' and internal shear walls are generally more effective than external shear walls in improving building's seismic resistance. Copyright © 2016 John Wiley & Sons, Ltd.     

Experimental study on seismic performance of steel‐reinforced recycled concrete frame with infill wall

In order to investigate the seismic performance of steel‐reinforced recycled concrete (SRRC) frame with infill wall, low cyclic loading tests on four frames with infill wall and one frame without infill wall were conducted. The failure modes, hysteresis loops, skeleton curves, bearing capacity, ductility, stiffness degradation, and energy dissipation capacity of specimens were analyzed. The seismic performance of SRRC frames with and without infill wall was compared. The influence of the aspect ratio of infill wall, the axial compression ratio of column, and the distance of horizontal reinforcements of infill wall were investigated. Test results show that compared to the SRRC frame without infill wall, the SRRC frame with infill wall had higher bearing capacity and initial stiffness, but faster stiffness degradation and worse energy dissipation capacity. With the increase of aspect ratio of infill wall and axial compression ratio of column, the bearing capacity and initial stiffness of SRRC frame with infill wall increased, whereas the ductility decreased. With the decrease of distance of horizontal reinforcements of infill wall, the initial stiffness and energy dissipation capacity of SRRC frame with infill wall increased. After the infill wall fails under earthquake, the remaining SRRC frame has good seismic performance.     

Comprehensive nonlinear seismic performance assessment of MR damper controlled systems using virtual real‐time hybrid simulation

Magnetorheological (MR) dampers have gained significant attention in seismic mitigation of structural systems due to their distinguished characteristics such as inherent stability and minimum power requirements. Their performance in control of nonlinear structural response, however, has not been widely investigated. This paper provides comprehensive nonlinear seismic performance assessment of a three‐story benchmark structure equipped with a large‐scale MR damper using virtual real‐time hybrid simulation to efficiently capture the nonlinear behavior of the damper. The framework is first verified by means of available experimental results of an actual RTHS on the same structural system. A set of 12 earthquake ground motions, each one scaled to have 12 different intensities are then utilized to perform nonlinear dynamic analyses. An energy‐based adaptive passive‐on control strategy is proposed, and its performance is compared with passive‐on, passive‐off, and uncontrolled response of the structure in terms of interstory drifts shown by fragility curves, residual drifts, MR damper control force, and the ability to maintain a uniform interstory drift along the height of the structure.     

后加混凝土-砌体组合墙体抗震性能试验研究

根据某实际工程,设计1∶2缩尺的纵向和横向两种组合墙体试件进行低周反复荷载试验。针对后加混凝土构件-砌体组合墙体的承载力、延性、滞回特性、耗能能力及破坏模式、混凝土构件的应变和钢筋的应变发展过程等进行研究。结果表明:拉结(剪切)钢筋+植筋的连接节点具有可靠的连接性能,可以保证既有砌体结构与后加混凝土构件的协同工作;后加混凝土-砌体组合墙体具有更高的承载力及变形能力;通过等效黏滞阻尼系数对比分析可知,后加混凝土墙体提高了砌体墙的耗能能力;提出了后加混凝土-砌体组合墙体受剪承载力计算式,且与试验结果吻合较好。     

竖向不规则钢筋混凝土框架结构基于性能的抗震设计方法

考虑结构在地震作用下不同反应阶段的动力特性,采用振型反应谱法,建立结构在不同地震作用水平下的弹塑性需求曲线族,即结构的层间剪力一位移需求曲线.结合结构的能力曲线,提出以楼层为研究对象的层间能力谱法.由结构的性能目标与位移延性的关系,建立性能目标与层间需求曲线的关系,从而得到考虑结构延性的层间需求曲线.通过计算分析表明,层间能力谱法可以有效的用于对竖向不规则结构进行基于性能的抗震设计,可以方便地对不同地震作用水平、不同性能目标的结构进行地震作用计算和配筋计算,并能控制结构在不同地震作用下的变形性能、塑性铰出现顺序及部位,与时程分析方法相比偏于保守,且比直接基于位移的设计方法具有明显的优势.     

平面不规则钢筋混凝土框架结构基于性能的抗震评估方法

从现行规范对平面不规则结构的限制条件出发,推导扭转角与扭转位移比的关系式,结合钢筋混凝土框架结构在不同地震作用水平下的层间位移角限值,建立平面不规则结构的层间扭转角需求曲线;依靠现有有限元分析程序计算结构构件的扭转角和扭转角能力曲线,提出平面不规则钢筋混凝土框架结构基于性能的抗震评估方法--扭转角能力谱法.通过算例对扭转角能力谱法的使用方法和原理进行阐述,建立平面不规则结构的评估曲线,分析结构不同楼层各构件的扭转变形性能.结果表明,扭转角能力谱法既可以一目了然地判别出楼层与楼层之间的扭转变形关系,又可以准确地判别出同一楼层各抗侧力构件的扭转变形性能,从而全面的实现各构件基于性能的抗震评估.     

Experimental study on seismic performance of T‐shaped partly precast reinforced concrete shear wall with grouting sleeves

Prefabricated structure has prominent advantages such as easy control of construction quality, saving fabricating time and natural resources, and reducing environmental pollution and construction noise. The mostly used structural system in high‐rise buildings is reinforced concrete shear wall structure, which has high load capacity and lateral stiffness. Focusing on the connection of reinforcements, three T‐shaped partly prefabricated reinforced concrete shear walls and one cast‐in situ specimen in same dimensions as a control group are tested under low‐frequency cyclic loading to analyze their seismic performances in this paper. During the experiment, the axial compression ratio of specimens is fixed at 0.3, 0.4, and 0.5. Through the observation of phenomena and data analysis, hysteretic curve, skeleton curve, stiffness degradation, ductility, and load bearing capacity are compared and analyzed. The results show that partly prefabricated reinforced concrete shear wall has similar load bearing capacity with the cast in situ specimen, and it also has excellent ductility, stiffness, and energy‐dissipating capacity. The experimental results and analysis indicate that partly prefabricated reinforced concrete shear wall has outstanding seismic performances; under effective and reliable design, it can be used in building structures to play the same role as cast in situ components.     

钢筋混凝土短肢剪力墙抗震性能试验研究

采用1∶2缩尺模型,设计了6个T形短肢剪力墙试件和6个L形短肢剪力墙试件,以及2个T形普通剪力墙试件。通过低周反复加载试验,研究钢筋混凝土短肢剪力墙构件的抗震性能,并与普通剪力墙进行对比。观测了短肢剪力墙受力-变形-损伤-裂缝-屈服-破坏的全过程;分析了短肢剪力墙的破坏特征、滞回曲线、骨架曲线、刚度退化曲线、位移延性及截面变形规律等。研究表明：T形和L形短肢剪力墙试件在水平荷载作用下,强度和刚度退化曲线呈明显的非对称特点;在开裂之后刚度退化较快;在退化过程中刚度退化速度减缓不明显,后期的刚度退化也不趋于稳定; 大偏心破坏范围内,增大轴压比可以提高试件的承载力;延性并不随轴压比一致变化,控制轴压比试件延性才能发挥到最好,减小剪跨比可增大试件延性;翼缘侧受压时的顶点位移比腹板侧受压时的要小;剪力滞后现象比较显著;破坏的主要形式为弯剪破坏;截面积相同时,T形截面比L形截面短肢剪力墙试件的承载力大,抗震性能优良;高厚比为6.5的T形短肢剪力墙试件相比其它高厚比的短肢剪力墙试件综合性能更佳。     

Experimental study on seismic performance of L‐shaped partly precast reinforced concrete shear wall with cast‐in‐situ boundary elements

In order to promote industrial production of reinforced concrete shear wall, a typical partly precast reinforced concrete shear wall with both end boundary elements cast‐in‐situ and the other part precast is experimentally studied. In this paper, three L‐shaped specimens of this kind and one completely cast‐in‐situ specimen as a control group are tested under low‐frequency cyclic loading to investigate their safety, applicability, and different characteristics. For the partly precast specimen, the vertical distributed reinforcements of precast part are equivalently spliced by grouting sleeves arranged along the center line of the wall whereas the horizontal reinforcements are directly anchored into the cast‐in‐situ boundary elements. During the test, the axial compression ratio of these specimens is fixed at 0.2, 0.3, and 0.5, respectively. Such test phenomena and test data including failure modes, yielding load and displacement, the skeleton curve, energy dissipation, stiffness degradation, ductility, and so on are observed, analyzed, and compared. Chinese code and American Concrete Institute code are adopted to estimate the bearing capacity. Results show that the partly precast specimens have good integrity. With the increase of axial compression ratio, the bearing capacity of these partly precast specimens increases whereas the ductility decreases. It is also found that the partly precast specimens have slightly lower bearing capacity compared with the cast‐in‐situ specimen as well as excellent deformation capacity and ductility, which indicates the tested partly precast shear wall has good and reliable seismic performance and can be used as a structural element in building construction.     

Dynamic responses of industrial reinforced concrete chimneys strengthened with fiber‐reinforced polymers

Industrial reinforced concrete (RC) chimneys are tall and slender structures that need repair and strengthening in their service lives. Fiber‐reinforced polymers (FRPs) are continuously becoming a popular material that is used for strengthening purposes of RC structures. The purpose of this study is to determine the effect of FRP strengthening on dynamic responses of industrial RC chimneys. A 75‐m‐high industrial RC chimney with an opening on the body was selected for FRP strengthening. First, three‐dimensional finite element model of the chimney and its modal analyses were performed in ANSYS software. Then, linear transient analyses of the chimney were carried out by using 1992 Erzincan Earthquake ground motion record. After that, body of chimney was strengthened with FRP composite, and dynamic analyses were performed. Finally, dynamic responses of chimney before and after FRP strengthening, such as displacements and maximum–minimum principal stresses, were compared. At the end of the study, it was seen that displacements increased along the height of the chimney, maximum and minimum principal stresses occurred at the region of opening and base for all analysis, respectively. Also, it was seen from this study that FRP strengthening is effective on the dynamic response of industrial RC chimneys. Copyright © 2014 John Wiley & Sons, Ltd.     

Approximate method of estimating seismic performance of high‐rise buildings with oil‐dampers

When subjected to long‐period ground motions, many existing high‐rise buildings constructed on plains with soft, deep sediment layers experience severe lateral deflection, caused by the resonance between the long‐period natural frequency of the building and the long‐period ground motions, even if they are far from the epicenter. This was the case for a number of buildings in Tokyo, Nagoya, and Osaka affected by the ground motions produced by the 2011 off the Pacific coast of Tohoku earthquake in Japan. Oil‐dampers are commonly used to improve the seismic performance of existing high‐rise buildings subjected to long‐period ground motion. This paper proposes a simple but accurate analytical method of predicting the seismic performance of high‐rise buildings retrofitted with oil‐dampers installed inside and/or outside of the frames. The method extends the authors' previous one‐dimensional theory to a more general method that is applicable to buildings with internal and external oil‐dampers installed in an arbitrary story. The accuracy of the proposed method is demonstrated through numerical calculations using a model of a high‐rise building with and without internal and external oil‐dampers. The proposed method is effective in the preliminary stages of improving the seismic performance of high‐rise buildings.     

Practical modelling of high‐rise dual systems with reinforced concrete slab‐column frames

This paper discusses practical modelling issues pertinent to the design of an irregularly shaped reinforced concrete (RC) high‐rise building currently under development in New York City. The structure analysed consists of a 60‐storey residential tower and a 25‐storey hotel building structurally connected to each other. For the seismic force resistance, a dual system combining ordinary RC shear walls and intermediate slab–column moment frames was used at the upper portion, while a building frame system of ordinary RC shear walls was used at the lower portion of the structure. A variety of models were used to simulate the behaviour of various elements of the structure, with special attention given to overall systemic effects of different member stiffnesses considered to account for distinct stress levels under service and ultimate loads. The models used for slab–column frames and shear walls were verified by comparing with other available models or laboratory tests. The in‐plane flexibility of floor diaphragms at the interface between the two substructures with different geometries was simulated to identify the most critical wind conditions for each structural member. Finally, building dynamic analyses were performed to demonstrate the modelling issues to be considered for the lateral force design of irregular high‐rise buildings. Copyright © 2009 John Wiley & Sons, Ltd.     

ISCS method for the performance‐based seismic design of vertically irregular reinforced concrete frame structures

The procedure to obtain the inelastic demand curves for the multi‐degree‐of‐freedom system, composed of inter‐story shear versus inter‐story displacement curve is introduced. The demand curves are established by using mode spectrum method, and the dynamical characteristic of structure under different earthquake hazard levels is taken into account. The relation of structure performance object and displacement ductility is adopted to deduce the relation of structure performance object and inter‐story demand curve. Therefore, the inter‐story demand curves take into account the inelastic behavior of structure under earthquake action adequately. Then, considering the seismic responding characteristic and the capacity curve of the frame structure, a new method named Inter‐Story Capacity Spectrum (ISCS) is put forward for the performance‐based seismic design of vertically irregular frame structures. Examples are presented to demonstrate the applicability and the utility of the proposed method. It is concluded that the new method can control the inter‐story drift, the order and position of hinges of vertically irregular structures under different earthquake hazard levels. Comparing with time‐history analysis method, it leans to safe and is superior to direct displacement‐based design method. Copyright © 2011 John Wiley & Sons, Ltd.     

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.     

Axial behavior of concrete‐filled carbon fiber‐reinforced polymer composite columns

Concrete‐filled carbon fibre‐reinforced polymer (CFRP) composite columns without longitudinal and transverse reinforcing steels were tested to perform both experimental and analytical investigations of the axial behaviour of circular columns confined with CFRP composite tubes. The tubes were manufactured by wrapping the CFRP sheets with 90° + 90°, 90° ± 75°, 90° ± 60°, 90° ± 45°, 90° ± 30° wrapping angles with respect to longitudinal axis of the tube. Monotonic axial loads were applied to the gauge‐instrumented concrete‐filled CFRP tubes. The effects of fibre‐wrapping angle, thickness of tube, as well as transverse dilation on stress–strain relationships of the confined columns, were identified and discussed. Proposed models to predict both the strength and the ductility of columns confined with CFRP composite tubes show good agreement with the test results. Copyright © 2009 John Wiley & Sons, Ltd.     

阻尼填充墙加固震损框架抗震性能试验研究

提出先对震损框架进行局部修复,再采用阻尼填充墙对其进行加固的阻尼填充墙加固震损框架方法,设计制作震损修复框架（CRF）、阻尼填充墙加固震损框架（CRDIWF）以及阻尼填充墙框架（DIWF）三榀足尺试件,对其进行拟静力加载试验,对比研究三个试件的滞回性能、承载能力、耗能能力与延性、破坏特征等。试验结果表明：对震损框架先进行局部修复,再采用阻尼填充墙对其进行抗震加固的方法是可行的;试件CRDIWF的抗侧刚度、承载能力、耗能能力、位移及延性与DIWF基本相当,且均比试件CRF高;阻尼填充墙实现了既定的滑移耗能机制,释放了对框架的刚度效应和约束效应;试件CRDIWF、试件DIWF的破坏特征与试件CRF一致,破坏时层间位移角为1/37,满足《建筑抗震设计规范》中罕遇地震作用下层间位移角1/50的要求,具有良好的抗倒塌能力;为保证阻尼填充墙工作机制与耗能机制的实现,阻尼填充墙砌体单元的砂浆剪切强度应大于SBS阻尼层的剪切强度。