Performance-based seismic design of nonstructural building components:The next frontier of earthquake engineering

With the development and implementation of performance-based earthquake engineering,harmonization of performance levels between structural and nonstructural components becomes vital. Even if the structural components of a building achieve a continuous or immediate occupancy performance level after a seismic event,failure of architectural,mechanical or electrical components can lower the performance level of the entire building system. This reduction in performance caused by the vulnerability of nonstructural components has been observed during recent earthquakes worldwide. Moreover,nonstructural damage has limited the functionality of critical facilities,such as hospitals,following major seismic events. The investment in nonstructural components and building contents is far greater than that of structural components and framing. Therefore,it is not surprising that in many past earthquakes,losses from damage to nonstructural components have exceeded losses from structural damage. Furthermore,the failure of nonstructural components can become a safety hazard or can hamper the safe movement of occupants evacuating buildings,or of rescue workers entering buildings. In comparison to structural components and systems,there is relatively limited information on the seismic design of nonstructural components. Basic research work in this area has been sparse,and the available codes and guidelines are usually,for the most part,based on past experiences,engineering judgment and intuition,rather than on objective experimental and analytical results. Often,design engineers are forced to start almost from square one after each earthquake event: to observe what went wrong and to try to prevent repetitions. This is a consequence of the empirical nature of current seismic regulations and guidelines for nonstructural components. This review paper summarizes current knowledge on the seismic design and analysis of nonstructural building components,identifying major knowledge gaps that will need to be filled by future research. Furthermore,considering recent trends in earthquake engineering,the paper explores how performance-based seismic design might be conceived for nonstructural components,drawing on recent developments made in the field of seismic design and hinting at the specific considerations required for nonstructural components.

Peak displacement patterns for the performance-based seismic design of steel eccentrically braced frames

Performance-based seismic design(PBSD) aims to assess structures at different damage states. Since damage can be directly associated to displacements, seismic design with consideration of displacement seems to be logical. In this study, simple formulae to estimate the peak floor displacement patterns of eccentrically braced frames(EBFs) at different performance levels subjected to earthquake ground motions are proposed. These formulae are applicable in a PBSD and especially in direct displacement-based design(DDBD). Parametric study is conducted on a group of 30 EBFs under a set of 15 far field and near field accelerograms which they scaled to different amplitudes to adapt various performance levels. The results of thousands of nonlinear dynamic analyses of EBFs have been post-processed by nonlinear regression analysis in order to recognize the major parameters that influence the peak displacement pattern of these frames. Results show that suggested displacement patterns have relatively good agreement with those acquired by an exact nonlinear dynamic analysis.

Optimization for performance-based design under seismic demands, including social costs

Performance-based design in earthquake engineering is a structural optimization problem that has, as the objective, the determination of design parameters for the minimization of total costs, while at the same time satisfying minimum reliability levels for the specifi ed performance criteria. Total costs include those for construction and structural damage repairs, those associated with non-structural components and the social costs of economic losses, injuries and fatalities. This paper presents a general framework to approach this problem, using a numerical optimization strategy and incorporating the use of neural networks for the evaluation of dynamic responses and the reliability levels achieved for a given set of design parameters. The strategy is applied to an example of a three-story offi ce building. The results show the importance of considering the social costs, and the optimum failure probabilities when minimum reliability constraints are not taken into account.

Probabilistic Performance-Based Optimum Seismic Design Framework: Illustration and Validation

In the field of earthquake engineering,the advent of the performance-based design philosophy,together with the highly uncertain nature of earthquake ground excitations to structures,has brought probabilistic performance-based design to the forefront of seismic design.In order to design structures that explicitly satisfy probabilistic performance criteria,a probabilistic performance-based optimum seismic design(PPBOSD)framework is proposed in this paper by extending the state-of-the-art performance-based earthquake engineering(PBEE)methodology.PBEE is traditionally used for risk evaluation of existing or newly designed structural systems,thus referred to herein as forward PBEE analysis.In contrast,its use for design purposes is limited because design is essentially a more challenging inverse problem.To address this challenge,a decision-making layer is wrapped around the forward PBEE analysis procedure for computer-aided optimum structural design/retrofit accounting for various sources of uncertainty.In this paper,the framework is illustrated and validated using a proof-of-concept problem,namely tuning a simplified nonlinear inelastic single-degreeof-freedom(SDOF)model of a bridge to achieve a target probabilistic loss hazard curve.For this purpose,first the forward PBEE analysis is presented in conjunction with the multilayer Monte Carlo simulation method to estimate the total loss hazard curve efficiently,followed by a sensitivity study to investigate the effects of system(design)parameters on the probabilistic seismic performance of the bridge.The proposed PPBOSD framework is validated by successfully tuning the system parameters of the structure rated for a target probabilistic seismic loss hazard curve.The PPBOSD framework provides a tool that is essential to develop,calibrate and validate simplified probabilistic performance-based design procedures.

Research on performance-based seismic design criteria

The seismic design criterion adopted in the existing seismic design codes is reviewed. It is pointed out that the presently used seismic design criterion is not satisfied with the requirements of nowadays social and economic development. A new performance-based seismic design criterion that is composed of three components is presented in this paper. It can not only effectively control the economic losses and casualty, but also ensure the building's function in proper operation during earthquakes. The three components are: classification of seismic design for buildings, determination of seismic design intensity and/or seismic design ground motion for controlling seismic economic losses and casualties, and determination of the importance factors in terms of service periods of buildings. For controlling the seismic human losses, the idea of socially acceptable casualty level is presented and the 'Optimal Economic Decision Model' and 'Optimal Safe Decision Model' are established. Finally, a new method is recommended for calculating the importance factors of structures by adjusting structures service period on the base of more important structure with longer service period than the conventional ones. Therefore, the more important structure with longer service periods will be designed for higher seismic loads, in case the exceedance probability of seismic hazard in different service period is same.

Performance-based global reliability assessment of a high-rise frame-core tube structure subjected to multi-dimensional stochastic earthquakes

When evaluating the seismic safety and reliability of complex engineering structures,it is a critical problem to reasonably consider the randomness and multi-dimensional nature of ground motions.To this end,a proposed modeling strategy of multi-dimensional stochastic earthquakes is addressed in this study.This improved seismic model has several merits that enable it to better provide seismic analyses of structures.Specifically,at first,the ground motion model is compatible with the design response spectrum.Secondly,the evolutionary power spectrum involved in the model and the design response spectrum are constructed accordingly with sufficient consideration of the correlation between different seismic components.Thirdly,the random function-based dimension-reduction representation is applied,by which seismic modeling is established,with three elementary random variables.Numerical simulations of multi-dimensional stochastic ground motions in a specific design scenario indicate the effectiveness of the proposed modeling strategy.Moreover,the multi-dimensional seismic response and the global reliability of a high-rise frame-core tube structure is discussed in detail to further illustrate the engineering applicability of the proposed method.The analytical investigations demonstrate that the suggested stochastic model of multi-dimensional ground motion is available for accurate seismic response analysis and dynamic reliability assessment of complex engineering structures for performance-based seismic resistance design.

Development of Performance-Based Tunnel Evaluation Methodology and Performance Evaluation of Existing Railway Tunnels

The concept of performance-based design, which mainly focuses on mechanical performance, has become the international standard, as in the case for ISO. The standardization of tunnel design has not been achieved because it requires integration of separate specialized fields, such as geotechnical engineering, structural engineering and concrete engineering. It is also required to clarify performance-based criteria for tunnel structures to suit specific use purposes (objectives), establish the concept of survey, planning, design, construction and maintenance based on such criteria, and develop proper management systems for operation and maintenance to suit specific tunnel use purposes. To this end, it is vital to develop a methodology for evaluating and verifying the performance of existing tunnels. This paper presents a new concept of performance requirements for tunnel structures and describes the method of quantitatively evaluating the total performance of existing tunnels in relation to the required performance, assuming the total performance to be based on the Analysis Hierarchy Process.

An evaluation of force-based design vs.direct displacement-based design of jointed precast post-tensioned wall systems

The unique features of jointed post-tensioned wall systems, which include minimum structural damage and re-centering capability when subjected to earthquake lateral loads, are the result of using unbonded post-tensioning to attach the walls to the foundation, along with employing energy dissipating shear connectors between the walls. Using acceptance criteria defined in terms of inter-story drift, residual drift, and floor acceleration, this study presents a multiplelevel performance-based seismic evaluation of two five-story unbonded post-tensioned jointed precast wall systems. The design and analysis of these two wall systems, established as the direct displacement-based and force-based solutions for a prototype building used in the PREcast Seismic Structural Systems （PRESSS） program, were performed at 60% scale so that the analysis model could be validated using the PRESSS test data. Both buildings satisfied the performance criteria at four levels of earthquake motions although the design base shear of the direct displacement-based jointed wall system was 50% of that demanded by the force-based design method. The study also investigated the feasibility of controlling the maximum transient inter-story drift in a jointed wall system by increasing the number of energy dissipating shear connectors between the walls but without significantly affecting its re-centering capability.

Application of consequence-based design criteria in regions of moderate seismicity

Current design criteria and prineiples of earthquake engineering design are reviewed,including safety factors, probabilistic approach,and two-level and muhi-level functional design ideas.The modern multi-functional idea is discussed in greater details.When designing a structure,its resistance to and the intensity of the earthquake action are considered. The consequence of failure of the structure is considered only through a rough and empirical factor of importance,ranging usually from 1.0 to 1.5.This paper suggests a method of'consequence-based design,'which considers the consequences of malfunctioning instead of simply an importance factor.The main argument for this method is that damage to a structure located in different types of societies may have very different consequences,which are depeudant on its value and usefulness to the society and the seismicity in the region.

Prediction of column failure modes based on artificial neural network

To implement the performance-based seismic design of engineered structures,the failure modes of members must be classified.The classification method of column failure modes is analyzed using data from the Pacific Earthquake Engineering Research Center(PEER).The main factors affecting failure modes of columns include the hoop ratios,longitudinal reinforcement ratios,ratios of transverse reinforcement spacing to section depth,aspect ratios,axial compression ratios,and flexure-shear ratios.This study proposes a data-driven prediction model based on an artificial neural network(ANN)to identify the column failure modes.In this study,111 groups of data are used,out of which 89 are used as training data and 22 are used as test data,and the ANN prediction model of failure modes is developed.The results show that the proposed method based on ANN is superior to traditional methods in identifying the column failure modes.

Performance-Based Design for Large Crowd Venue Control Using a Multi-Agent Model

Performance-based design is more holistic and flexible than prescriptive design for providing safety in large complex buildings. Here, a multi-agent method to model the egress patterns of evacuees is combined with a microscopic pedestrian simulation model used to analyze the forces between individuals in a densely populated enclosed space in a crowd crushing and trampling analysis （CroC＆Ts）. The system is used to model egress patterns in a typical crowd evacuation simulation. The simulations indicate that some individuals will die from crushing in 2 m and 4 m wide exits in emergencies. The simulations also show that the fatality probability increases when barriers obstacled the path and when the egress distances were lar- ger. The simulations validate the conclusions of the stranded crowd model （SCM） and provide quantitative predictions of the crowd crushing and trampling risk. Therefore, the CroC＆Ts can provide performancebased egress designs for large pubic buildings and improve crowd safety management and emergency planning.

某高层混合结构核心筒偏置抗震设计与分析

此项目为79m高层酒店建筑,采用型钢混凝土柱-钢框架梁-钢筋混凝土核心筒的混合结构体系。具有核心筒偏置立面收进的建筑特征,属于不规则超限工程。首先调整框架梁柱截面及剪力墙厚度,减弱偏置对质心与刚心的偏离程度,减小结构扭转及位移比偏大的不利影响。随后对结构进行抗震性能化设计,通过小震弹性,中震验算,罕遇地震下的动力弹塑性时程分析,确定结构的薄弱部位并分析关键构件的损伤情况,最后对楼板开大洞及跃层柱进行专项分析,最终结果表明结构在中大震下均能满足性能目标的要求。

黄浦江过江隧道的动力抗震分析

借鉴日本东京湾的隧道分析方法 ,提出了适合于本课题的隧道分析的计算模型 ,即用等效质量 -弹簧系统代替地基切片 ,隧道用能承受剪力、弯矩和轴力的梁代替 .数值仿真表明 ,隧道与风井接头处的轴力、角位移、剪力较大 .如果总体设计允许的话 ,建议各段隧道的长度不宜相差太大 ,以减小地震波作用下隧道接头的动力相对位移和内力 .

对石墙抗震性能的研究和设计取值的建议

本文总结石结构抗震课题组在料石墙砌体的拟动力抗剪试验方面的成果,并以此为基础,提出料石砌体的设计计算公式.

重视抗震概念设计提高工程设计质量

依据高层建筑混凝土结构技术规程(JGJ3-2002)和建筑抗震设计规范(GB50011-2001)中有关加强概念设计的部分内容,阐述了抗震概念设计的含义、产生及一般原则。从结构的简单性、整体性、规则性、均匀性、结构的刚度和抗震能力等方面加以论述。目的是使工程技术人员重视抗震概念设计,提高建筑工程设计质量。

土钉土体系统动力模型的建立及地震响应分析

建立了土钉土体系统动力计算模型,这种模型将土体对土钉的作用处理成一个线性弹簧和一个与速度有关的阻尼器,把面板对上钉的惯性作用简化为集中于土钉头上的等效质量加以考虑.以此为基础,建立土钉土体系统地震动力作用下的阻尼微分方程,求解了在简谐地震作用下土钉动力响应的解析解.最后,结合一案例进行了分析,并用大型非线性有限元软件ADINA对此计算模型进行了验证,结果表明这种计算模型对土质较均匀的边坡动力设计和分析是安全、可靠、合理的.

油气长输管道的抗震问题

介绍了美国与日本的油气长输管道抗震研究概况。分析了我国油气长输管道抗震的发展和存在的问题,根据分析结果提出了我国油气长输管道抗震需要开展研究的一些问题。

应用SATWE和TAT软件的几个问题

总结了在设计中应用钢筋混凝土框架结构三维空间分析软件SATWE和TAT时应注意的问题。通过对结构上采用平动计算与耦连计算的比较、侧刚计算与总刚计算的比较、对多塔计算的分析、底层层高合理取值的分析、上下抗侧移刚度比值的分析 ,说明在设计中 ,应根据工程实际情况并结合程序的计算原理进行设计前的详细分析 ,以使计算结果更趋合理。

建筑结构的控制与减震设计及其研究

对建筑结构控制与减震设计的一些较为实用方法给予简要介绍，并结合对近期一些研究成果的评述，探讨结构的动力优化设计及具有发展前景的研究方向。

澜沧——耿马地震民用建筑震害

1988年11月6日云南澜沧—耿马相继发生7.6级和7.2级地震。本文介绍这次地震损失较重的澜沧、耿马、沧源和双江四个县的民用建筑震害,初步分析了震害的原因,研究了各类房屋的震害特征,总结了从震害中应吸取的经验教训,为地震灾区重建家园和房屋抗震设计提供依据。