Seismic response of a 40‐storey buckling‐restrained braced frame designed for the Los Angeles region

This study utilized nonlinear response history analysis to compare the seismic demand on three variations of a 40‐storey buckling‐restrained braced frame designed for high seismic hazard in the Los Angeles region. The three designs were referred to as a ‘code‐based design’, based on the 2006 International Building Code, a ‘performance‐based design’, based on criteria published by the Los Angeles Tall Building Design Council (LATBSDC) and a ‘performance‐based design plus’, based on newly developed criteria from The Pacific Earthquake Engineering Research Center (PEER). The response history analysis utilized spectrum‐matched ground motions as well as simulated ground motions for the Puente Hills fault. The spectrum‐matched motions were selected from the Next Generation Attenuation of Ground Motions (NGA) database, which is largely composed of recorded motions and scaled to five hazard levels. The simulated ground motions were broadband signals generated from a moment magnitude (M_w) 7.15 scenario rupture of the Puente Hills fault for two near fault regions and exhibit long period energy content that significantly exceeds the uniform hazard spectrum. Structural performance was assessed in terms of exceedance of a safe inter‐storey drift ratio (IDR). It was seen that the simulated ground motions impose higher IDR demands on the structures than the spectrum‐matched NGA ground motions. Furthermore, the number of instances of exceedance of a safe IDR, considered for this study as IDR = 0.03, is substantially higher for the simulated ground motions, pointing to the importance of considering such motions in the collapse prevention of tall buildings on a site‐specific basis. Copyright © 2010 John Wiley & Sons, Ltd.     

Comparative study of special and ordinary braced frames

The collapse probability of ductile and non‐ductile concentrically braced frames was investigated using nonlinear dynamic response analysis. Two buildings with three and nine stories located in Boston and Los Angeles, respectively, were designed and subjected to ground motions from the areas. In Boston area, three‐story and nine‐story buildings were designed as ordinary concentrically braced frame with response modification reduction factor R equal to 3 1/4 to be considered as non‐ductile structural systems; comparatively, in Los Angeles area, three‐story and nine‐story buildings were designed as special concentrically braced frame with response modification reduction factor R equal to 6 to be considered as ductile structural systems. In order to evaluate the performance of ductile and non‐ductile concentrically braced frames in moderate and severe seismic regions, ATC‐63 would be used as reference to assess the seismic behaviors. Evaluation approach recommended by ATC‐63 was adopted, and hundreds of nonlinear dynamic analyses were performed. Through alternating the scale factors of designated ground motions, median of structural collapse intensity was presented for each structure. By observing the results of statistical performance assessment, the seismic performance of the systems was evaluated, and some observations are made based on the study. Copyright © 2012 John Wiley & Sons, Ltd.     

Seismic design of outrigger systems using equivalent energy design procedure

An outrigger system is an effective structural scheme that is commonly used in high‐rise construction to increase the stiffness of concrete core walls and to reduce the moment demand within the walls. Despite the on‐going use of outrigger systems around the world, a formal seismic design procedure is yet available. This paper presents an equivalent energy design procedure (EEDP) to design outrigger systems for seismic applications. Three prototype outrigger‐wall buildings of various heights are designed for Vancouver, Canada. Detailed finite element models are developed to assess the seismic performance of the prototype buildings and to assess the safety using the FEMA P695 methodology. The result shows that EEDP is an efficient method to design outrigger systems which results in structures that can achieve sufficient margin of safety against collapse and satisfy multiple performance objectives at different seismic hazard levels.     

Comparative reliability of two 24‐story braced buildings: traditional versus innovative

The seismic reliability of two 24‐story buildings that have the same geometry and structural layout was evaluated and compared. The structural system of the first building consists of ductile steel braces and composite moment‐resisting frames (traditional building). The structural system of the second building consists of nonductile flexible steel frames stiffened through a system of buckling‐restrained braces (innovative building). Whereas the former was designed according to the Mexico City Building Code, the latter was designed according to a displacement‐based methodology. Both buildings were assumed to be located at the same site in the lake zone of Mexico City. The study shows that in spite of being considerably lighter, the innovative building exhibits higher levels of reliability. Copyright © 2011 John Wiley & Sons, Ltd.     

Performance‐based seismic design of an irregular tall building in Istanbul

Structural design of a 50‐story tall reinforced concrete residential building, which was planned to be constructed in Istanbul and given up afterwards by the investor, has been completed in accordance with the draft version of Seismic Design Code for Tall Buildings in Istanbul that adopts performance‐based seismic design as the basic approach as Tall Buildings Initiative Guidelines do. Seismic design of the building has formed the main part of the structural design process due to high seismicity of the proposed location and extremely irregular floor plan not conforming to usual tall building structures. The building consists of two individual buildings linked through sky floors at the top 12 stories whose design was one of the most challenging works. The building has been designed for design basis earthquake by elastic response spectrum analysis, and its seismic performance has been checked for maximum considered earthquake by nonlinear time‐history analyses carried out using PERFORM‐3D. Copyright © 2015 John Wiley & Sons, Ltd.     

中美超限高层建筑性能化抗震设计方法对比分析

为了系统比较中美超限高层建筑基于性能的抗震设计方法,介绍了美国太平洋地震工程研究中心主导实施的“高层建筑推进计划”项目,探讨了该项目的主要成果（PEER-2010）《高层建筑基于性能的抗震设计指南》,并结合算例将其建议的基于性能抗震设计方法与中国GB 50011-2010《建筑抗震设计规范》和GB 50010-2010《高层建筑混凝土结构技术规程》中规定的基于性能抗震设计方法进行对比。研究结果表明:PEER-2010与我国规范中分别建议的超限高层建筑性能化抗震设计方法在性能目标划分、地震动选择、荷载输入及对地基与结构相互作用的考虑上均存在差异。PEER-2010对性能目标的划分相对更宽松,建议的下一代选波方法能够考虑长周期超高层建筑的选波问题,并对考虑地基与上部结构相互作用有着较为明确的规定。     

The effect of design drift limit on the seismic performance of RC dual high‐rise buildings

Current building codes aim to ensure the acceptable performance of structures implicitly. Because these provisions are empirically developed for low‐ to medium‐rise buildings, their applicability to high‐rise building warrants further investigation. In this paper, the effect of design drift limit on the seismic performance of reinforced concrete dual high‐rise buildings is considered. Nine buildings are designed for 3 drift limits: the code limit (i.e., 2%), one that is lower than the code limit (i.e., 1.5%), and one that is higher than the code limit (i.e., 3%). For each drift limit, buildings of 3 heights (20, 25, and 30 stories) are designed. Finite element models are constructed in OpenSees, and incremental dynamic analysis is performed. The results are used to develop probabilistic seismic demand models, where model parameters are determined using maximum likelihood estimation to incorporate equality and censored data. Reliability analysis using probabilistic demand models is conducted to derive seismic fragility and demand hazard curves. In addition, the collapse performance of the drift limits is evaluated using the Federal Emergency Management Agency (FEMA) P695 procedure. The study results show that the design drift limit affects the building's seismic performance, and the effect depends on the performance level considered. Moreover, from a structural integrity perspective, a larger design drift limit does not induce a significantly higher risk and might yield a more cost‐effective design.     

Seismic retrofit of a high‐rise steel moment‐resisting frame using fluid viscous dampers

The Tall Building Initiative project of Pacific Earthquake Engineering Research Center has been expanded to investigate the seismic performance and possible retrofit of existing tall buildings. A candidate 35‐story steel building with representative details from the early 1970s was analyzed following several guidelines, which revealed a wide range of potential inadequacies. Thus, a two‐level retrofit approach was examined that focused on achieving the collapse prevention limit state under the major basic safety earthquake (BSE‐2E) hazard level prescribed by ASCE 41. This paper focused on a Level‐2 retrofit that used fluid viscous dampers to augment Level‐1 retrofits. For this approach, feasible damper locations and overall effective damping ratios were first evaluated through a series of preliminary studies, and then a two‐phase design method was used to refine the distribution and mechanical properties of the dampers. Thorough assessments of the refined design were carried out following several design guidelines, including ASCE 41, FEMA 351, and FEMA P‐58. The results indicated that the proposed retrofit method of using fluid viscous dampers could achieve the retrofit goal and provide a cost‐effective means of improving the structural behavior and reducing economic losses in a major seismic event.     

Performance‐based seismic evaluation of the Icon Hotel in Dubai,United Arab Emirates

The Icon Hotel, which is part of the Dubai Promenade in Dubai, is a new waterfront development and represents cutting edge architecture. This building has a unique ‘donut shape’ with significant design and buildability challenges in the field of structural engineering. The wheel shape tower is 160 m high with an external diameter of 165 m, an internal diameter of 78 m and a depth of 35 m. It was designed to accommodate hotel and residential occupancies. The building's primary structural system is composed of two concrete core walls placed 96 m apart on either side and partially coupled by mega steel trusses at upper mechanical floor as well as long‐span steel arches located at the top to accommodate the required shape of the building. This paper presents the structural engineering design approach used to evaluate the seismic behaviour of this building by implementing performance‐based design methodology. The analysis results show that the building will behave in a desired manner during future anticipated earthquakes. Copyright © 2010 John Wiley & Sons, Ltd.     

Analysis of the Northridge earthquake response of a damaged non-ductile concrete frame building

The response of a seven-story reinforced concrete building recorded during the Northridge earthquake is analysed in this paper. The building was designed in 1965 to the lateral force requirements of 1964 Los Angeles City Building Code. Non-ductile concrete moment frames and interior slab-column frames form the lateral resisting system of the building. The building suffered severe damage during the Northridge earthquake and was ‘red tagged’. This building was instrumented by as many as 16 sensors during the earthquake. These accelerogram records were analysed using system identification techniques to obtain important building response information. This also provided the opportunity to see if certain analytical techniques that are commonly used by practising engineers and/or researchers and many of which are currently being incorporated in various upcoming documents dealing with seismic evaluation of existing buildings could have predicted the observed performance of the building.     

阻尼墙在金柏年财富广场消能设计中的应用研究

江苏金柏年财富广场位于地震高烈度区的江苏宿迁市,为大底盘双塔框剪结构,地上25层,高94.95m,是目前国内最高的首栋采用粘滞阻尼墙消能设计建筑,整栋结构共布置121片阻尼墙,使结构整体附加阻尼比提高了2.5%.分析结果表明:该消能结构在多遇地震作用下,层间位移能满足<建筑抗震设计规范>要求,在罕遇地震作用下也有一定安全可靠度,具有较好抗震性能.     

Development of new Los Angeles seismic analysis criteria for tall buildings—site-specific considerations

Many tall buildings are planned and constructed in the city of Los Angeles. Significant building code changes as a result of recent earthquakes will complicate the design and plan checking for new buildings, not only in Los Angeles, but throughout all seismic regions in the United States and around the world. This paper reports on new efforts to develop seismic analysis criteria for Los Angeles. The initial efforts have been in the areas of the design basis ground motions, near-source effects on ground motions and building design, and the first yield limit state. A study of the design basis ground motions in the Los Angeles area indicates that the present code-defined level of ground motion may underestimate the seismic forces in design. Near-source effects would affect practically all of the heavily populated and built-up portions of Los Angeles due to the many known and suspected active seismic sources in the region. Studies of the group motions suggest that a return period of about 40 years may be reasonable to estimate the earthquake demand for the first yield limit state.     

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.     

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.     

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.     

Effect of vertical structural irregularity on seismic design of tall buildings

Many tall buildings are practically irregular as an entirely regular high‐rise building rarely exists. This study is thus devoted to assessing the approach and coefficients used in the seismic design of real‐life tall buildings with different vertical irregularity features. Five 50‐story buildings are selected and designed using finite element models and international building codes to represent the most common vertical irregularities of reinforced concrete tall buildings in regions of medium seismicity. Detailed fiber‐based simulation models are developed to assess the seismic response of the five benchmark buildings under the effect of 40 earthquake records representing far‐field and near‐source seismic scenarios. The results obtained from a large number of inelastic pushover and incremental dynamic analyses provide insights into the local and global seismic response of the reference structures and confirm the inferior local response of tall buildings with severe vertical irregularities. Due to the significant impacts of the severe irregularity types on the seismic response of tall buildings, the conservative code approach and coefficients are recommended for design. It is also concluded that although the design coefficients of buildings with moderate irregularities are adequately conservative, they can be revised to arrive at more consistent safety margins and cost‐effective designs.     

Life‐cycle cost assessment of mid‐rise and high‐rise steel and steel–reinforced concrete composite minimum cost building designs

The traditional trial‐and‐error design approach is inefficient to determine an economical design satisfying also the safety criteria. Structural design optimization, on the other hand, provides a numerical procedure that can replace the traditional design approach with an automated one. The objective of this work is to propose a performance‐based seismic design procedure, formulated as a structural design optimization problem, for designing steel and steel–reinforced concrete composite buildings subject to interstorey drift limitations. For this purpose, eight test examples are considered, in particular four steel and four steel–reinforced concrete composite buildings are optimally designed with minimum initial cost. Life‐cycle cost analysis (LCCA) is considered as a reliable tool for measuring the damage cost due to future earthquakes that will occur during the design life of a structure. In this study, LCCA is employed for assessing the optimum designs obtained for steel and steel–reinforced concrete composite design practices. Copyright © 2011 John Wiley & Sons, Ltd.