Reliability-based condition assessment of deteriorating concrete bridges considering load redistribution

A wide variety of models have been proposed for estimating the reliability of highway bridges. For reinforced concrete bridges subjected to environmen tal attack, time-variant reliability methods have to be used. In this study , the condition of reinforced concrete girder bridges is assessed using a t ime-variant system reliability approach in which both load and resistance a re time-variant quantities. Several system models are considered, including failure of any girder (series system) and failure of a specified number of adjacent girders (series-parallel system). Adaptive importance sampling is used to determine the cumulative-time system failure probability. An exist ing reinforced concrete T-beam bridge located near Pueblo, Colorado, is inv estigated. The influence of resistance degradation and post-failure load re distribution is included. A comparison of reliability estimates for several system models is given, including the influence of correlation among initi al girder strengths. The results can be used as a guide for the selection o f system models for bridge reliability analysis, identification of critical girders in a bridge system, and for the development of optimal reliability -based maintenance strategies for reinforced concrete highway bridges. (C) 1999 Elsevier Science Ltd. All rights reserved.