FUZZY RANDOM TIME-DEPENDENT RELIABILITY ANALYSIS OF EXISTING REINFORCED CONCRETE BRIDGES

摘要

Bridges deteriorate with time due to reinforcement corrosion, concrete carbonization and ever-increasing traffic toads. This results in reduction of their reliability. The factors influencing their reliability represent uncertainty. Binary state assumption indicates that the structure demonstrates only two crisp states, i.e. fully functioning or fully failed. The structure will be realized in one of the two states at any time. This is not practical in the real world. The structural failure criterion should be fuzzy. Based on conventional study on random time-dependent reliability, the fuzziness is incorporated in this paper. The fuzzy random time- dependent probabilistic (FRTDP) models of reinforcement strength and its sectional area and concrete strength are founded by fuzzy random variable and fuzzy stochastic process theory. A FRTDP model of resistance is deduced. Due to the difference between existing and constructing reinforced concrete (RC) bridges in analysis background, service life and information, the load models should be re-studied. A FRTDP model is substituted the dead load, and a FRTDP model is applied to the live load by incorporated fuzziness. The JC method is improved to compute the fuzzy random time-dependent (FRTD) reliability indices subjected to FRTD resistance, live load, dead load and fuzzy failure criterion. The total analytical method and process are demonstrated by an example of a fabricated RC bridge.