A robust method for reliability updating with equality information using sequential adaptive importance sampling

Reliability updating refers to a problem that integrates Bayesian updating technique with structural reliability analysis and cannot be directly solved by structural reliability methods (SRMs) when it involves equality information. The state-of-the-art approaches transform equality information into inequality information by introducing an auxiliary standard normal parameter. These methods, however, encounter the loss of computational efficiency due to the difficulty in finding the maximum of the likelihood function, the large coefficient of variation (COV) associated with the posterior failure probability and the inapplicability to dynamic updating problems where new information is constantly available. To overcome these limitations, this paper proposes an innovative method called RU-SAIS (reliability updating using sequential adaptive importance sampling), which combines elements of sequential importance sampling and K-means clustering to construct a series of important sampling densities (ISDs) using Gaussian mixture. The last ISD of the sequence is further adaptively modified through application of the cross entropy method. The performance of RU-SAIS is demonstrated by three examples. Results show that RU-SAIS achieves a more accurate and robust estimator of the posterior failure probability than the existing methods such as subset simulation.Comment: 38 pages, 6 tables, 9 figure

2-Dimensional Simulation of Deterioration Process for Life-cycle Performance Assessment of RC Structures in Marine Environment

The reliability-based durability design approach doesnt account for neither the surface deterioration of structures over service lives, nor the possible life-cycle maintenance. The paper employs the 2-dimentional (2D) simulation technique based on random field theory and Monte Carlo simulation method, to analyze the life-cycle performance of reinforced concrete structures under chloride attack, which is illustrated through the surface deterioration modelling of immersed tube tunnel segment of Hong Kong-Zhuhai-Macao (HZM) sea-link project. Then, the paper compares the maintenance demands imposed to different durability design specifications with different life-cycle performance target. The results may provide useful information in future durability design and aid the decision making process

Seismic Fragility Analysis of Precast RC Shear Wall-Frame Structures with Connection Defects

As observed in many evidences during past earthquakes, the quality of precast concrete (PC) connections is one of the main factors that affect the seismic reliability of PC structures. In the context of Chinas rapid development of PC structures in high seismic regions, it is important to assess the effect of connection deficiency on their seismic performance. This paper proposes a framework for seismic fragility analysis of PC shear wall-frame structures whose wall panels are assembled through grout sleeve connections that are susceptible to insufficient grouting. The uncertainties associated with the defected sleeve connections are taken into account, and then the probabilistic response of shear wall model is estimated through Point Estimate (PE) method. Then, a generic shear wall-frame building is modeled on platform of OpenSees. Seismic fragility analysis is performed to the structures with different degrees of connection deficiency, showing that the seismic performance is significantly affected by connection deficiencies, and great effort should be taken for the quality control of grout sleeve connections in construction site

Evaluating Seismic Performance of Water Supply System with Multiple-Functionality-Based Measurement

Water supply system (WSS) is an essential part of the infrastructure system of a city and plays an important role in resisting and recovering from natural disasters. Disruption of WSS due to seismic damage of pipelines would impair its city functionalities including fire suppression, water supply of critical facilities and domestic water supply. Some metrics have been proposed in existing literatures to evaluate the performance of WSS subjected to disaster events. Nevertheless, these metrics, aiming at a specific functionality of WSS, e.g. fire suppression or domestic water supply, cannot give a comprehensive evaluation with its multiple functionalities included. In this regard, this paper proposes an economic loss-based metric to evaluate integratedly the consequence of disruption of two functionalities, fire suppression and domestic water supply, of WSS subjected to hazard event. The direct economic losses associated with the two broken functionalities are estimated and compared through the case study of a water distribution network of a city in South-West China subjected to earthquake. It is found that the two functionality losses have small correlation and the strategy to improve the seismic performance should consider both of them integratedly

Mathematical Formulation of Tools for Assessment of Fragility and Vulnerability of Damaged Buildings

Performance-Based (PBE) and Consequence-Based (CBE) are new approaches to seismic design, evaluation and risk assessment, in which design criteria are devised to achieve stated performance objectives, and regional losses to civil infrastructure are mitigated through selective interventions for critical components of a civil infrastructure. These new approaches give engineers more flexibility in achieving performance goals but require substantial additional computational resources to fully achieve performance goals. As a step toward making such approaches feasible, this dissertation develops a number of computationally efficient methods for performing finite element-based structural system dynamic response analysis and reliability assessment. The Enhanced Uncoupled Modal Response History Analysis (EUMRHA) procedure developed herein is an efficient response analysis procedure to make the analysis of dynamic structural response to earthquakes in the nonlinear range less time-consuming. This technique is used to investigate the potential for aftershocks to cause additional damage to steel moment frame buildings, utilizing a technique designed to enhance the efficiency of Monte Carlo simulation in estimating low-probability events. Relatively simple probabilistic tools are proposed for purposes of rapid structural evaluation and condition assessment of damaged buildings. Finally, an analysis-based inspection scheme based on an associated probability model of connection damage is proposed for assessing the safety condition of existing buildings, and a procedure to assess the likely performance of an un-repaired building during a future earthquake is developed.Ph.D.Committee Chair: Ellingwood, Bruce R; Committee Member: Craig, James I.; Committee Member: DesRoches,Reginald; Committee Member: Goodno, Barry; Committee Member: Haj-Ali,Rami