基础隔震结构抗震可靠度简化分析方法

选用胡聿贤平稳地震地面运动模型作为基础隔震结构的随机地震动输入,采用Bouc-Wen模型描述隔震结构的层间滞变位移,将滞变体系动力特性矩阵随机等效线性化,并建立等价线性状态方程。引入左右特征向量系,对振动微分方程进行解耦,推导了基础隔震结构随机地震响应的统计矩解析解。采用变形失效准则,定义了上部结构和隔震层的功能状态极限函数。在此基础上,采用首次超越破坏模型,基于Possion分布假设和串联系统可靠度模型,建立了从整体上评价基础隔震体系抗震可靠度的简化分析方法。最后,通过一个基础隔震框架结构计算实例,说明了这种方法的运用。     

框架结构抗震设计的简化分析方法

在简化假设的基础上,导出了规则框架结构自振周期,振型,地震作用,楼和及水平位移等的解析表达式,并制成了图表。利用本文结果,可方便地进行规则框架的抗震设计和计算结果检验,算例表明,本文结果应用于非规则框架的抗震分析时,也具有令人满意的精度。     

抗震结构最优设防水平决策与全寿命优化设计的简化易损性分析方法

地震破坏状态概率分析是抗震结构最优设防水平决策与全寿命优化设计的关键问题之一,作者们曾根据"三水准"设防原则和地震烈度的危险性分析结果提出了二种实用分析方法.本文建立了结构破坏状态概率分析的地震易损性理论基础,提出了极限状态地震易损性和破坏状态地震易损性的概念.从地震易损性理论的角度,对二种地震破坏状态概率简化分析方法进行了深入分析,指出第1种方法是一种考虑结构宏观抗震能力不确定性的半理论半经验易损性分析方法,而第2种方法则是一种不考虑结构宏观抗震能力不确定性的简化易损性分析方法,根据地震破坏状态概率的计算结果对二种方法进行了对比分析,并提出了相关的建议.     

结构抗震设防标准及其决策分析

本文首先在文献[5]给出的一组代表性多层住宅砖房的地震易损性曲线的基础上，对多层住宅 砖房的抗震可靠度进行研究，然后通过基于造价－期望地震损失的决策分析，求得所选8度地区的最优设防烈度，并给出了与最优设防烈度相应的多层住宅砖房的抗震可靠度指标。     

考虑模糊可靠度的抗震结构优化设计

在结构优化的目标函数中，不仅应考虑结构造价，而且应考虑结构服役期的损失期望。为此，我们定义了抗震结构模糊可靠度的概念。利用抗震设计原则和地震危险性分析给出了一个计算模糊可靠度的方法。然后提出了三步优化法；第一步，寻求一系列对应于不同设防烈度的最小造价设计；第二步，同时考虑造价和地震引起的损失期望，寻求最优设防烈度；第三步，寻找相应于此最优烈度的最小造价设计。     

抗震结构最优可靠度的决策方法

由于结构的可靠度是保证结构整体正常工作的数量指标,因而从逻辑上来说,基于可靠度分析的优化设计是最合理的设计模式。但如何确定结构可靠度的限值却是一个尚待解决的重大决策问题。本文提出了抗震结构可靠度的决策方法,这个方法既考虑了结构的当前投资(造价),又考虑了长远的经济和社会效益。解决这个问题的关键,是给出了抗震结构的造价和可靠度间函数关系的估计方法。     

高层建筑结构的抗震可靠度分析与优化设计

本文根据我们在文献２中给出的等效随机地震静力作用模型，紧密结合规范和利用我们在文献６中提出的结构体系可靠度分析的最弱失效模式法，提出了结构构件和体系“小震不坏”和“大震不倒”及结构体系在设计基准期内的抗震可靠度分析方法；重新校准了结构构件的目标可靠度指标；综合考虑结构造价和损失期望，提出了结构体系抗震目标可靠度的优化决策方法；分别给出了满足构件抗震目标可靠指标与同时满足构件和体系抗震目标可靠指标的     

固体潮理论值一阶微商的解析表达式及拟合检验

本文采用全微分法,导出了直接而严密的固体潮理论值对时间一阶微商的解析表达式．将其应用于固体潮资料的拟合检验,确保了理论上的严谨性和计算精度．文中还介绍了部分拟合检验的应用实例,并与不同拟合方法进行了对比分析,表明全微分法在运算处理速度上与谐波展开法和数值微分法相比得到了成倍的提高,而与天顶距微分法的运算速度相同．     

Ground motion selection for simulation‐based seismic hazard and structural reliability assessment

This paper examines four methods by which ground motions can be selected for dynamic seismic response analyses of engineered systems when the underlying seismic hazard is quantified via ground motion simulation rather than empirical ground motion prediction equations. Even with simulation‐based seismic hazard, a ground motion selection process is still required in order to extract a small number of time series from the much larger set developed as part of the hazard calculation. Four specific methods are presented for ground motion selection from simulation‐based seismic hazard analyses, and pros and cons of each are discussed via a simple and reproducible illustrative example. One of the four methods (method 1 ‘direct analysis’) provides a ‘benchmark’ result (i.e., using all simulated ground motions), enabling the consistency of the other three more efficient selection methods to be addressed. Method 2 (‘stratified sampling’) is a relatively simple way to achieve a significant reduction in the number of ground motions required through selecting subsets of ground motions binned based on an intensity measure, IM. Method 3 (‘simple multiple stripes’) has the benefit of being consistent with conventional seismic assessment practice using as‐recorded ground motions, but both methods 2 and 3 are strongly dependent on the efficiency of the conditioning IM to predict the seismic responses of interest. Method 4 (‘generalized conditional intensity measure‐based selection’) is consistent with ‘advanced’ selection methods used for as‐recorded ground motions and selects subsets of ground motions based on multiple IMs, thus overcoming this limitation in methods 2 and 3. Copyright © 2015 John Wiley & Sons, Ltd.     

Methodology for the development of analytical fragility curves for retrofitted bridges

Fragility curves for retrofitted bridges indicate the influence of various retrofit measures on the probability of achieving specified levels of damage. This paper presents an analytical methodology for developing fragility curves for classes of retrofitted bridge systems. The approach captures the impact of retrofit on the vulnerability of multiple components, which to date has not been adequately addressed, and results in a comparison of the system fragility before and after the application of different retrofit measures. Details presented include analytical modeling, uncertainty treatment, impact of retrofit on demand models, capacity estimates, and component and system fragility curves. The findings indicate the importance of evaluating the impact of retrofit not only on the targeted response quantity and component vulnerability but also on the overall bridge fragility. As illustrated by the case study of a retrofitted multi‐span continuous (MSC) concrete girder bridge class, a given retrofit measure may have a positive impact on some components, yet no impact or a negative impact on other critical components. Consideration of the fragility based only on individual retrofitted components, without regard for the system, may lead to over‐estimation or under‐estimation of the impact on the bridge fragility. The proposed methodology provides an opportunity to effectively compare the fragility of the MSC concrete bridge retrofit with a range of different retrofit measures. The most effective retrofit in reducing probable damage for a given intensity is a function of the damage state of interest. Copyright © 2008 John Wiley & Sons, Ltd.     

Life‐cycle reliability of RC bridge piers under seismic and airborne chloride hazards

Over the last two decades, the probabilistic assessment of reinforced concrete (RC) structures under seismic hazard has been developed rapidly. However, little attention has been devoted to the assessment of the seismic reliability of corroded structures. For the life‐cycle assessment of RC structures in a marine environment and earthquake‐prone regions, the effect of corrosion due to airborne chlorides on the seismic capacity needs to be taken into consideration. Also, the effect of the type of corrosive environment on the seismic capacity of RC structures has to be quantified. In this paper, the evaluation of the displacement ductility capacity based on the buckling model of longitudinal rebars in corroded RC bridge piers is established, and a novel computational procedure to integrate the probabilistic hazard associated with airborne chlorides into life‐cycle seismic reliability assessment of these piers is proposed. The seismic demand depends on the results of seismic hazard assessment, whereas the deterioration of seismic capacity depends on the hazard associated with airborne chlorides. In an illustrative example, an RC bridge pier was modeled as single degree of freedom (SDOF). The longitudinal rebars buckling of this pier was considered as the sole limit state when estimating its failure probability. The findings show that the life‐cycle reliability of RC bridge piers depends on both the seismic and airborne chloride hazards, and that the cumulative‐time failure probabilities of RC bridge piers located in seismic zones can be dramatically affected by the effect of airborne chlorides. Copyright © 2011 John Wiley & Sons, Ltd.     

A recursive decomposition algorithm for network seismic reliability evaluation

A new probabilistic analytical approach to evaluate seismic system reliability of large lifeline systems is presented in this paper. The algorithm takes the shortest path from the source to the terminal of a node weight or edge weight network as decomposition policy, using the Boolean laws of set operation and probabilistic operation principal, a recursive decomposition process then could be constructed. For a general weight network, the modified Torrieri method (NTR/T method) is introduced to combine with the suggested algorithm. Therefore, the recursive decomposition algorithm may be applied to evaluate the seismic reliability of general lifeline systems. A series of case studies, including a practical district electric power network system and a large urban water supply system, show that the suggested algorithm supplies a useful probabilistic analysis means for the seismic reliability evaluation of large lifeline systems. Copyright © 2002 John Wiley & Sons, Ltd.     

地震荷载作用下相关性对结构可靠度的影响

当一个结构系统承受偶发的不确定地震荷载时,其结构单元或元素失效无效的相关性在系统可靠度评估中的十分重要,该相关性的产生,是由于结构系统同时受某一基本随机变量的影响,如地震峰值地面加速度,荷载效应转换或构件承载力等,本文分析了考虑该相关的必要性,此外,还给出了一个考虑相关性的简单方法,可用于估计一个等关联性和等可靠度单元的并联系统的失效概率,该方法由拉斯渐进副近积分法导出。     

Seismic fragility and reliability of structures isolated by friction pendulum devices: seismic reliability‐based design (SRBD)

The paper deals with the seismic reliability of elastic structural systems equipped with friction pendulum isolators (friction pendulum system). The behavior of these systems is analyzed by employing a two‐degree‐of‐freedom model accounting for the superstructure flexibility, whereas the friction pendulum system device behavior is described by adopting a widespread model that considers the variation of the friction coefficient with the velocity. With reference to medium soil condition, the uncertainty in the seismic inputs is taken into account by considering a set of artificial records, obtained through Monte Carlo simulations within the power spectral density method, with different frequency contents and characteristics depending on the soil dynamic parameters and scaled to increasing intensity levels. The sliding friction coefficient at large velocity is also considered as random variable modeled through a uniform probability density function. Incremental dynamic analyses are developed in order to evaluate the probabilities exceeding different limit states related to both r.c. superstructure and isolation level defining the seismic fragility curves through an extensive parametric study carried out for different structural system properties. Finally, considering the seismic hazard curves related to a site near L'Aquila (Italy), the seismic reliability of the r.c. superstructure systems is evaluated, and seismic reliability‐based design abacuses are derived with the aim to define the radius in plan of the friction pendulum devices in function of the structural properties and reliability level expected. Copyright © 2016 John Wiley & Sons, Ltd.     

Probability-based seismic reliability assessment method for substation systems

Power systems play a key role in emergency rescue after an earthquake. Substations are among the most important components of a power system, so it is necessary to study their seismic reliability after an earthquake. Most studies, however, have focused on the seismic behavior of major electrical equipment or the reliability of the substation under ordinary operational conditions. The seismic reliability of substations as a system has not been thoroughly studied. This study proposes a new probability-based method to evaluate the seismic reliability of complex engineering systems such as substations. The proposed method developed the state tree to construct a greatly simplified system model that enables the failure probability to be calculated for the whole system, with explicit consideration of correlations among various components. A typical 220/110/10-kV substation was studied with this method, and the most critical components were identified.     

Simplified seismic fragility analysis of structures with two types of friction devices

This paper presents a method and results of seismic fragility estimation of frame structures with friction devices and with friction devices and restrictors. The seismic intensity parameter, defined as the mean value of the pseudovelocity spectrum in a specified periods band, is proved to allow the use of linear regression analysis of the response parameters of the considered non‐linear structures on seismic intensity. A simplified method of fragility estimation is proposed, based on the concept of ‘mean seismic excitation’ and linear regression of the seismic response parameters on seismic intensity parameter. The key risk contributors for the system with friction devices and for the system with friction devices and restrictors are identified on the basis of the fragility analysis, and recommendations for improvement of the seismic response of the respective systems are derived. The results of the fragility study show that when the initial ‘bare’ frame is retrofitted by rigidly connected bracings the effect is much lower than in the case of connecting the bracings by friction devices and especially by friction devices and restrictors. Copyright © 2000 John Wiley & Sons, Ltd.     

基于改进云图法的结构概率地震需求分析

概率地震需求分析是美国太平洋地震工程研究中心(Pacific Earthquake Engineering ResearchCenter,PEER)提出的新一代"性能化地震工程(Performance-Based Earthquake Engineering,PBEE)"理论框架的重要一环。传统的概率地震需求分析方法称为"云图法",这种方法针对确定性结构进行一系列地震动作用下的非线性动力分析,从而得到地震动强度参数与结构地震需求的"云图"。然而,传统的云图法只能考虑地震动的不确定性,而无法考虑结构的不确定性。为此,结合拉丁超立方体抽样技术,提出一种能综合考虑地震动不确定性和结构不确定性的改进云图法,并将传统的概率地震需求分析内容拓展为概率地震需求模型、概率地震需求易损性分析、概率地震需求危险性分析三个层次。以一榀五层三跨钢筋混凝土框架结构为例,分别采用传统云图法和改进云图法对其进行概率地震需求分析,得到了该结构的概率地震需求模型、地震需求易损性曲线和地震需求危险性曲线。分析结果表明:提出的方法可以有效地考虑地震动与结构的不确定性,避免不考虑结构的不确定性而低估结构的地震风险性。