Design Procedure for Bridge Foundations Subject to Liquefaction-Induced Lateral Spreading

The response of piled bridge foundations to liquefaction-induced lateral soil deformation is an important design consideration in
seismically active regions. Recent research and case history data suggest that three-dimensional deformation of the approach
embankment can significantly influence the loads placed on the embedded foundations during a flow failure or lateral spreading
event. For example, the 2010 Maule earthquake in Chile caused widespread lateral spreading in the soil surrounding the
Mataquito River bridge. However, only insignificant structural damage was observed in the bridge itself. The discrepancy between
the amount of soil deformation and structural damage suggests that design procedures for this load case that do not make adequate
consideration for 3D soil deformation mechanisms may lead to overly conservative and expensive design solutions. In contrast,
observed lateral spreading and damage near the Llacolén bridge was more relevant and resulted in the collapse of one of the
approach sections. The Llacolén bridge approaches show lesser 3D effects on both sides of the bridge and therefore larger loads
on the structural components.

In this work, finite element models of the Mataquito River and Llacolén bridges are created using the OpenSees computational
framework to investigate possible reduction in foundation loads during lateral spreading implied by the observed structural damage
at the sites. These models include beam on nonlinear Winkler foundation models, dynamic effective stress models of the
bridge-foundation-soil system in plane strain, and 3D models of the bridge abutments, approach embankments, and
surrounding soils. This numerical work seeks to frame load reduction mechanisms in the context of a simplified analysis
procedure for the lateral spreading load case. The results of the numerical models for the Mataquito and Llacolén bridges,
along with a preliminary parameter study conducted using an independent set of 3D finite element models, indicate that 
consideration for the 3D geometry of the bridge site and structure may result in tangible reductions in foundation bending
demands and abutment displacements compared to those returned by a plane strain description of the problem or
simplified analysis using 1D models.

This analysis procedure is modified to better consider the findings of this work and it is recommended to use in the design
of bridge foundations subjected to lateral spreading. Finally, an approach is proposed to estimate the reductions in abutment
displacement and associated foundation bending demands for a given site geometry. The latter is based on results from a
preliminary parametric study and would require further development and validation to use in practice.

Publication Date: 
Thursday, April 20, 2017
Publication Number: 
WA-RD 874.2
Last modified: 
10/23/2017 - 07:37
Pedro Arduino, Christopher R. McGann, Alborz Ghofrani
Washington State Transportation Center (TRAC-UW)
Number of Pages: 
Bridge design, Guidelines, Bridge substructures, Bridge foundations, Pile foundations, Soil structure interaction, Case studies, Liquefaction, Dynamic loads, Deformation, Mathematical models, Finite element method, Earthquake resistant design, Earthquake engineering, Recommendations