Studying the Effect of Fundamental Structural Period on the Seismic Fragility Curves of Two-Span Integral Concrete Box G
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RESEARCH PAPER
Studying the Effect of Fundamental Structural Period on the Seismic Fragility Curves of Two‑Span Integral Concrete Box Girder Bridges Payam Amirian1 · Abdolrasoul Ranjbaran1 Received: 10 June 2019 / Accepted: 22 October 2019 © Shiraz University 2019
Abstract The main step in deriving fragility curves of structures is to develop their probabilistic seismic demand model (PSDM). PSDMs can be expressed as the linear regression of engineering demand parameters and intensity measure suitable pairs in the log-transformed space. However, extracting PSDMs can be costly, computationally challenging, and time-consuming. For these reasons, this study proposes a practical method to estimate the two coefficients of the regression fit line of PSDM based on the fundamental periods of two-span integral concrete box girder bridges. Moreover, the effect of geometrical properties on the fundamental period has been investigated and an equation has been derived for the estimation of the fundamental period. For statistical analyses, 220 bridges are modeled using Latin hyper-cube sampling while 35,200 nonlinear time history analyses are done using OpenSees software to generate PSDMs. Keywords ANOVA · Box girder bridges · Fragility curve · Fundamental structural period · PSDM
1 Introduction In the past, large-magnitude earthquakes have had significant effects on road network systems and considerable disastrous impacts on buildings, human life, and economy. Some examples for such catastrophic events are the San Fernando earthquake in 1971, the Kobe earthquake in 1995, the Loma Prieta earthquake in 1989, the Northridge earthquake in 1994 and more recent events such as the earthquakes in Italy and New Zealand in 2009 and 2011, respectively. Bridges play a crucial role in ensuring the efficiency of roads and the interconnection between cities and their strategic facilities. Probabilistic seismic demand models (PSDMs) are powerful tools for describing the seismic demand of different bridge components in terms of measurements of ground motion intensity. Researchers (Nielson and Desroches 2006; Padgett and Desroches 2008; Ramanathan 2012) commonly use PSDMs to analyze fragility to characterize bridge conditional reliability. Several researches (Padgett * Abdolrasoul Ranjbaran [email protected] Payam Amirian [email protected] 1
Department of Civil and Environmental Engineering, Shiraz University, Shiraz 7134851154, Iran
and DesRoches 2007; Dukes et al. 2012) performed sensitivity studies to define the parameters that affect the bridge reaction considerably. Nielson and DesRoches (2006) and Padgett and DesRoches (2008) researched a specific type of bridge, three spans simply supported steel girder bridge with normal column heights and balanced frame in Central America. Dukes et al. (2012) demonstrated a sensitivity analysis on a two-span integral concrete box girder bridge in California and reported the effect of five design parameters listed as the longitudinal and transverse reinforcement ratio, column height to
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