Seismic Risk Assessment Using Stochastic Nonlinear Models

Abstract

The basic input when seismic risk is estimated in urban environments is the expected physical damage level of buildings. The vulnerability index and capacity spectrum-based methods are the tools that have been used most to estimate the probability of occurrence of this important variable. Although both methods provide adequate estimates, they involve simplifications that are no longer necessary, given the current capacity of computers. In this study, an advanced method is developed that avoids many of these simplifications. The method starts from current state-of-the-art approaches, but it incorporates non-linear dynamic analysis and a probabilistic focus. Thus, the method considers not only the nonlinear dynamic response of the structures, modeled as multi degree of freedom systems (MDoF), but also uncertainties related to the loads, the geometry of the buildings, the mechanical properties of the materials and the seismic action. Once the method has been developed, the buildings are subjected to earthquake records that are selected and scaled according to the seismic hazard of the site and considering the probabilistic nature of the seismic actions. The practical applications of the method are illustrated with a case study: framed reinforced concrete buildings that are typical of an important district, the Eixample, in Barcelona (Spain). The building typology and the district were chosen because the seismic risk in Barcelona has been thoroughly studied, so detailed information about buildings' features, seismic hazard and expected risk is available. Hence, the current results can be compared with those obtained using simpler, less sophisticated methods. The main aspects of the method are presented and discussed first. Then, the case study is described and the results obtained with the capacity spectrum method are compared with the results using the approach presented here. The results at hand show reasonably good agreement with previous seismic damage and risk scenarios in Barcelona, but the new method provides richer, more detailed, more reliable information. This is particularly useful for seismic risk reduction, prevention and management, to move towards more resilient, sustainable cities.Sustainability 2020, 12, 1308 2 of 21 software useful for estimating the stochastic response of multi degree of freedom systems (MDoF) systems by considering uncertainties in the seismic hazard and in the main features of the structures. Uncertainties were considered in relation to the geometry of the structure, the mechanical properties of the materials and the seismic action, amongst many other variables. In that study, thousands of non-linear dynamic analyses (NLDA) were executed using thousands of structural models and earthquake records. The procedure for combining the structural models and the earthquake records was based on the Latin hypercube and Monte Carlo sampling methods.From the NLDA results presented in Vargas-Alzate et al. 2019 [2], a simplified methodology was proposed to estimate maximum inter-story drifts ...

Assessment of Enhanced Dempster-Shafer Theory for Uncertainty Modeling in a GIS-Based Seismic Vulnerability Assessment Model, Case Study—Tabriz City

“…There are studies on estimating physical and social seismic vulnerabilities in urban areas in the literature ([e.g., References [3][4][5][6][7][8][9]). Some of the studies in the literature use existing analytical relations or vulnerability indices in a spatial decision support system (SDSS) framework where the pre-defined vulnerability codes for buildings are available for estimating buildings' damages ([e.g., References [8,[10][11][12][13][14][15][16][17]). However, a few studies have considered estimating building damage as a decision making problem concerning the necessity of PSVA in earthquake prone areas that lack required data for defining mathematical vulnerability relations/ indices (the mentioned data include details of structural properties of existing buildings and/or the statistical data of building damage from previous earthquakes) [18][19][20][21].…”

New insights into the relationship between seismic intensity measures and nonlinear structural response

“…For instance, if a specific structure is analysed, uncertainties related to the mechanical properties of the materials and seismic action are the ones carrying more variability into the response (Vamvatsikos and Fragiadakis 2010;Jalayer et al 2015;Vargas-Alzate et al 2019a). In the case of urban environments, information related to the geometrical distribution of buildings belonging to the emplacement are also required (Silva et al 2015;Vargas-Alzate et al 2020). It is worth mentioning that the quantification of statistical properties in simulations that consider random sources of high variability can lead to identifying new properties of the IMs, as in the case of steadfastness.…”

An investigation of the structural nonlinearity effects on the building seismic risk assessment under mainshock–aftershock sequences in Tehran metro city

“…In this case, the consideration of nonlinearity of structures during the time history analysis of all buildings in a region can be significantly time-consuming. This fact was implied by Vargas-Alzate et al (2020) in assessing the seismic risk of buildings in the city of Barcelona, as well as Lu et al (2020) study where they attempted to propose a new approach for considering the effects of aftershock in the regional seismic risk assessment via nonlinear dynamic time history analysis.…”