Effect of Asynchronous Earthquake Motion on Complex Bridges. I: Methodology and Input Motion

Based on observed damage patterns from previous earthquakes and a rich history of analytical studies, asynchronous input motion has been identified as a major source of unfavorable response for long-span structures, such as bridges. This study is aimed at quantifying the effect of geometric incoherence and wave arrival delay on complex straight and curved bridges using state-of-the-art methodologies and tools. Using fully parametrized computer codes combining expert geotechnical and earthquake structural engineering knowledge, suites of asynchronous accelerograms are produced for use in inelastic dynamic analysis of the bridge model. Two multi- degree-of-freedom analytical models are analyzed using 2,000 unique synthetic accelerograms with results showing significant response amplification due to asynchronous input motion, demonstrating the importance of considering asynchronous seismic input in complex, irregular bridge design. The paper, Part 1 of a two-paper investigation, presents the development of the input motion sets and the modeling and analysis approach employed, concluding with sample results. Detailed results and implications on seismic assessment are presented in the companion paper: Effect of Asynchronous Motion on Complex Bridges. Part II: Results and Implications on Assessment.

[1]  Kyriazis Pitilakis,et al.  Inelastic dynamic analysis of RC bridges accounting for spatial variability of ground motion, site effects and soil–structure interaction phenomena. Part 2: Parametric study , 2003 .

[2]  P. Paultre,et al.  Multiple-support seismic analysis of large structures , 1990 .

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

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

[5]  Amr S. Elnashai,et al.  Inelastic Dynamic Response of RC Bridges Subjected to Spatial Non-Synchronous Earthquake Motion , 2000 .

[6]  A. Kiureghian,et al.  Response spectrum method for multi‐support seismic excitations , 1992 .

[7]  Paul C. Jennings,et al.  Spatial variation of ground motion determined from accelerograms recorded on a highway bridge , 1985 .

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

[9]  J. Penzien,et al.  Ground motion modeling for multiple-input structural analysis , 1991 .

[10]  Kyriazis Pitilakis,et al.  Inelastic dynamic analysis of RC bridges accounting for spatial variability of ground motion, site effects and soil–structure interaction phenomena. Part 1: Methodology and analytical tools , 2003 .

[11]  R T Severn,et al.  SEISMIC RESPONSE OF MODERN SUSPENSION BRIDGES TO ASYNCHRONOUS LONGITUDINAL AND LATERAL GROUND MOTION. , 1989 .

[12]  H. L. Wong,et al.  Response of a rigid foundation to a spatially random ground motion , 1986 .

[13]  Giorgio Monti,et al.  Seismic design of bridges accounting for spatial variability of ground motion , 2005 .

[14]  R T Severn,et al.  SEISMIC RESPONSE OF MODERN SUSPENSION BRIDGES TO ASYNCHRONOUS VERTICAL GROUND MOTION. , 1987 .

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

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