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SUMMARY: Critical issues in emergency management after a seismic event are assessing the functionality of the main infrastructures (hospitals, road network, etc.) and deciding on their usability just after the mainshock. The use of a pure analytical tool to assess the aftershock risk of a structure can be contrasted with the limited time available to make a decision about the usability of a structure. For this reason, this paper presents a method for evaluating post-earthquake bridge practicability based on a rational combination of information derived from numerical analyses and in situ inspections. In particular, we propose an effective tool to speed up the decision-making process involved in evaluating the seismic risk of mainshock-damaged bridges in the context of aftershocks. The risk is calculated by combining the aftershock hazard using the Omori law and the fragility curves of the structure, which are calculated using the regression analysis of a sample of results obtained with data randomly generated by the Latin Hypercube Sampling technique and updated based on the results of in situ inspection. Different decision criteria regarding the practicability of bridges are discussed, and a new criterion is proposed. This tool was applied to an old highway RC viaduct. There are two main findings, including the high sensitivity to Bayesian updating (especially when the damage predicted by numerical analysis does not match the real damage) and the criteria used to decide when re-open bridges to traffic. © 2013 John Wiley & Sons, Ltd

Catastrophic failure of the above ground steel storage tanks was observed during past earthquakes, which caused serious economic and environmental consequences. Many of the existing tanks were designed in the past with outdated analysis methods and with underestimated seismic loads. Therefore, the evaluation of the seismic vulnerability of these tanks, especially ones located in seismic prone areas, is extremely important. Seismic fragility functions are useful tools to quantify the seismic vulnerability of structures in the framework of probabilistic seismic risk assessment. These functions give the probability that a seismic demand on a given structural component meets or exceeds its capacity. The objective of this study is to examine the seismic vulnerability of an unanchored steel storage tank, considering the uncertainty of modeling parameters that are related to material and geometric properties of the tank. The significance of uncertain modeling parameters is first investigated with a screening study, which is based on nonlinear static pushover analyses of the tank using the abaqus software. In this respect, a fractional factorial design and an analysis of variance (ANOVA) have been adopted. The results indicate that the considered modeling parameters have significant effects on the uplift behavior of the tank. The fragility curves of two critical failure modes, i.e., the buckling of the shell plate and the plastic rotation of the shell-to-bottom plate joint, are then developed based on a simplified model of the tank, where the uplift behavior is correctly modeled from the static pushover analysis. The uncertainty associated with the significant parameters previously identified are considered in the fragility analysis using a sampling procedure to generate statistically significant samples of the model. The relative importance of different treatment levels of the uncertainty on the fragility curves of the tank is assessed and discussed in detail.

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Catastrophic failure of above ground storage tanks was observed due to past earthquakes causing serious economic and environmental consequences. Therefore, the evaluation of the seismic vulnerability of existing liquid storage tanks located in seismic prone areas is an important task. Seismic fragility functions are useful tools in order to quantify the seismic vulnerability of structures. These functions give a probability that a seismic demand on a structural component meets or exceeds its capacity, and are generally derived by a variety of approaches, e.g., field observations of damage, static structural analyses, judgment, or analytical fragility functions. Unlike the other methods, the analytical fragility functions are developed from a coupling of the structural response analysis and a probabilistic seismic demand model. The objective of this study is to investigate the seismic vulnerability of above ground steel storage tanks using different analytical methods of the fragility function. A comparison of the well-known cloud method and the incremental dynamic analysis is performed at different limit states for two existing cylindrical steel storage tanks. The first tank represents a slender geometry with a fixed-roof and the second one is a broad tank, unanchored, and provided with a floating roof.

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The need of enhanced seismic analysis and design rules for petrochemical piping systems is widely recognized, where the allowable stress design method is still the customary practice. This paper presents an up-to-date performance-based seismic analysis (PBSA) of piping systems. The concept of performance-based analysis is introduced and a link between limit states and earthquake levels is proposed, exemplifying international code prescriptions. A brief review on seismic design criteria of piping systems is then provided by identifying the main critical issues. Finally, the actual application of the performance-based approach is illustrated through nonlinear seismic analyses of two realistic petrochemical piping systems