Bridge pier failure probabilities under combined h

Authors: Zach Liang George C Lee

Publish Date: 2013/06/21

Volume: 12, Issue: 2, Pages: 241-250

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Abstract

In many regions of the world a bridge will experience multiple extreme hazards during its expected service life The current American Association of State Highway and Transportation Officials AASHTO load and resistance factor design LRFD specifications are formulated based on failure probabilities which are fully calibrated for dead load and nonextreme live loads Design against earthquake load effect is established separately Design against scour effect is also formulated separately by using the concept of capacity reduction or increased scour depth Furthermore scour effect cannot be linked directly to an LRFD limit state equation because the latter is formulated using forcebased analysis This paper in two parts presents a probabilitybased procedure to estimate the combined hazard effects on bridges due to truck earthquake and scour by treating the effect of scour as an equivalent load effect so that it can be included in reliabilitybased failure calculations In Part I of this series the general principle for treating the scour depth as an equivalent load effect is presented In Part II the corresponding bridge failure probability the occurrence of scour as well as simultaneously having both truck load and equivalent scour load effect are quantitatively discussed The key formulae of the conditional partial failure probabilities and the necessary conditions are established In order to illustrate the methodology an example of dead truck earthquake and scour effects on a simple bridge pile foundation is represented

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