Effect of the angle of seismic incidence on the fragility curves of bridges

SUMMARY This study examines the effect of the angle of seismic incidence θ on the fragility curves of bridges. Although currently, fragility curves of bridges are usually expressed only as a function of intensity measure of ground motion (IM) such as peak ground acceleration, peak ground velocity, or Sa(ω1), in this study they are expressed as a function of IM with θ as a parameter. Lognormal distribution function is used for this purpose with fragility parameters, median cm and standard deviation ζ to be estimated for each value of θ chosen from 0 < θ < 360°. A nonlinear 3D finite element dynamic analysis is performed, and key response values are calculated as demand on the bridge under a set of acceleration time histories with different IM values representing the seismic hazard in Los Angeles area. This method is applied to typical straight reinforced concrete bridges located in California. The results are validated with existing empirical damage data from the 1994 Northridge earthquake. Even though the sample bridges are regular and symmetric with respect to the longitudinal axis, the results indicate that the weakest direction is neither longitudinal nor transverse. Therefore, if the angle of seismic incidence is not considered, the damageability of a bridge can be underestimated depending on the incidence angle of seismic wave. Because a regional highway transportation network is composed of hundreds or even thousands of bridges, its vulnerability can also be underestimated. Hence, it is prudent to use fragility curves taking the incident angle of seismic waves into consideration as developed here when the seismic performance of a highway network is to be analyzed. Copyright © 2012 John Wiley & Sons, Ltd.

[1]  Oscar A López,et al.  The critical angle of seismic incidence and the maximum structural response , 1997 .

[2]  Julio J. Hernández,et al.  Critical response of structures to multicomponent earthquake excitation , 2000 .

[3]  Fumio Yamazaki,et al.  A simplified method of constructing fragility curves for highway bridges , 2003 .

[4]  Anne S. Kiremidjian,et al.  Statistical Analysis of Bridge Damage Data from the 1994 Northridge, CA, Earthquake , 1999 .

[5]  Reginald DesRoches,et al.  Seismic fragility of typical bridges in moderate seismic zones , 2004 .

[6]  Armen Der Kiureghian,et al.  A stochastic ground motion model with separable temporal and spectral nonstationarities , 2008 .

[7]  Masanobu Shinozuka,et al.  Mechanistic quantification of RC bridge damage states under earthquake through fragility analysis , 2008 .

[8]  Kevin R. Mackie,et al.  Nonlinear Modeling of Bridge Structures in California , 2010 .

[9]  Ricardo A. Medina,et al.  Influence of angle of incidence on seismic demands for inelastic single-storey structures subjected to bi-directional ground motions , 2007 .

[10]  H Y Kim,et al.  STATISTICAL ANALYSIS OF FRAGILITY CURVES , 2000 .

[11]  B. Borzi,et al.  Deformation-based vulnerability functions for RC bridges , 2004 .

[12]  Mervyn J. Kowalsky,et al.  SHEAR AND FLEXURAL BEHAVIOR OF LIGHTWEIGHT CONCRETE BRIDGE COLUMNS IN SEISMIC REGIONS , 1999 .

[13]  George Deodatis,et al.  Non-stationary stochastic vector processes: seismic ground motion applications , 1996 .

[14]  Craig E. Taylor,et al.  REDARS 2 Methodology and Software for Seismic Risk Analysis of Highway Systems , 2006 .

[15]  Youwei Zhou,et al.  Effect of seismic retrofit of bridges on transportation networks , 2003 .

[16]  Michael H. Scott,et al.  Plastic Hinge Integration Methods for Force-Based Beam¿Column Elements , 2006 .

[17]  Reginald DesRoches,et al.  A Hertz contact model with non‐linear damping for pounding simulation , 2006 .

[18]  Fumio Yamazaki,et al.  Earthquake Damage Assessment of Expressway Bridges in Japan , 1999 .

[19]  H. Matlock.  Correlation for Design of Laterally Loaded Piles in Soft Clay , 1970 .