Effects of spatially variable ground motions on the seismic response of a skewed, multi-span, RC highway bridge

Abstract This paper presents a study of the influence of spatially variable ground motions on the longitudinal seismic response of a short, three-span, 30-degree skewed, reinforced concrete highway bridge. Linear and nonlinear finite element models are created for the bridge and linear elastic and nonlinear inelastic time history analyses conducted. Three different types of illustrative excitations are considered: The first utilizes spatially variable ground motions incorporating the effects of variable soil conditions, loss of coherency and wave passage as input motions at the structures' supports. The time history with the smallest peak displacement and the one with the largest peak displacement from the spatially variable ones are then used as uniform input motions at all bridge supports. The comparative analysis of the bridge model shows that the uniform ground motion input with the largest peak displacement cannot provide conservative seismic demands for all structural components—in a number of cases it results in lower response than that predicted by spatially variable motions. The present results indicate that there is difficulty in establishing uniform input motions that would have the same effect on the response of bridge models as spatially variable ones. Consequently, spatially variable input motions need to be applied as excitations at the bridge supports.

[1]  John E. Goldberg,et al.  The effect of ground transmission time on the response of long structures , 1965 .

[2]  Aspasia Zerva,et al.  Response of multi-span beams to spatially incoherent seismic ground motions , 1990 .

[3]  Wai-Fah Chen,et al.  Bridge Engineering Handbook , 1999 .

[4]  E. Vanmarcke,et al.  Stochastic Variation of Earthquake Ground Motion in Space and Time , 1986 .

[5]  M. Feng,et al.  Fragility analysis of bridges under ground motion with spatial variation , 2003 .

[6]  P. C. Jennings,et al.  Simulated earthquake motions , 1968 .

[7]  R Purasinghe,et al.  USE OF VISCO-ELASTIC DAMPERS AT EXPANSION JOINTS TO SUPPRESS SEISMIC VIBRATION OF BRIDGES , 1997 .

[8]  John F. Stanton,et al.  STATE-OF-THE ART ELASTOMERIC BRIDGE BEARING DESIGN , 1991 .

[9]  Aspasia Zerva,et al.  On the spatial variation of seismic ground motions and its effects on lifelines , 1994 .

[10]  Weijun Wang,et al.  Response of indeterminate two-span beam to spatially varying seismic excitation , 1990 .

[11]  J B Mander,et al.  OBSERVED STRESS-STRAIN MODEL FOR CONFINED CONCRETE , 1988 .

[12]  A. M. Abdel-Ghaffar,et al.  3-D NONLINEAR SEISMIC BEHAVIOR OF CABLE-STAYED BRIDGES , 1991 .

[13]  Giorgio Monti,et al.  Nonlinear Response of Bridges under Multisupport Excitation , 1996 .

[14]  Marc O. Eberhard,et al.  EFFECTS OF SPATIALLY VARYING GROUND MOTIONS ON SHORT BRIDGES , 1998 .

[15]  Ronald S. Harichandran,et al.  RESPONSE OF LONG-SPAN BRIDGES TO SPATIALLY VARYING GROUND MOTION , 1996 .

[16]  J. Mander,et al.  Theoretical stress strain model for confined concrete , 1988 .

[17]  Ahmed M. Abdel-Ghaffar,et al.  Suspension Bridge Response to Multiple-Support Excitations , 1982 .

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