Structural Performance of Highway Bridges under Given Foundation Settlements

This paper presents a study of structural performance of highway bridges under given foundation settlements.The ultimate objective of this research is to analyze and develop acceptable levels of bridge foundation settlements under ultimate and service limit states, which are not adequately addressed in current bridge design standards.In order to design modern bridges to accommodate any expected foundation settlements, structural engineers need to consider foundation movements and quantify their impacts on the performance of bridge superstructures.In this paper, one type of widely used highway bridges, cast-in-place posttensioned concrete box girder bridges, is considered and settlement analyses are performed to study the induced bridge girder stresses due to foundation or pier settlements.Two sets of bridge examples are studied with different bridge skew angles and horizontal curve radii, to investigate the effects of these parameters.A state-of-art bridge analysis finite element (FE) program is used to analyze various bridge responses.It is shown that the bridge girder curvature and skew angle can impact the girder stresses due to foundation or pier settlements, and the trends are plotted using a numerical parametric study.Based on the evaluation of stress increase due to settlements, an acceptable pier settlement limit can be further determined based on allowable girder stresses in the next stage of the study.