Time-dependent reliability analysis of CFST arches for out-plane stability considering concrete creep

CFST arches have been widely used in bridge engineering worldwide due to their light weight, high compressive strength, convenience of construction, and aesthetic appearance. However, studies on the reliability of this type of bridges have been limited, especially on the time-dependent reliability. The concrete creep under a long-term sustained load could cause time-dependent displacements of CFST arches which lead to the deterioration of the stability bearing capacity. Therefore, time-dependent reliability levels for the out-plane creep stability bearing capacity of CFST arch ribs, the main members of CFST arch bridges, are investigated in this paper. The time-dependent limit state function for out-plane creep stability of CFST arches considering concrete creep is firstly established, in which random process of the resistance is expressed as an implicit time-dependent function. The time integrated approach and the finite element reliability method (FERM) are then combined to solve the reliability indices during different time intervals. It has been shown by the numerical results that with the deterioration of the out-plane stability bearing capacity induced by concrete creep, the reliability of CFST arches decreases significantly. For a loading level of 50%, the reliability index of CFST arches varies from 9.68 similar to 8.96 without considering load uncertainty, while varies from 6.04 similar to 5.51 with considering load uncertainty. With the consideration of load uncertainty, the sensitivity index of creep coefficient increases while other sensitivity indices decrease. For different basic random variables, the load has the most important influence on the reliability index, and it is followed by the diameter of the steel tube, the strength of steel, the elastic modulus of concrete,