Partial factors for shear capacity assessment of in-service RC T-girder bridges

摘要

As the infrastructure age, their assessment to carry the loads they are subjected to becomes increasingly important. Also, assessment is needed as part of a regular monitoring programme. Before carrying out a rigorous probabilistic analysis for assessment, it is often required to make a preliminary assessment using simplified procedures, such as that developed using semi-probabilistic approach, in which partial factors are used. In this article an attempt has been made to evolve a framework to determine the partial factors for safety assessment of the in-service T-girder bridges in India against the limit state of shear. Limit state of shear is considered because it is one of the important ultimate limit states for bridge girder that results in brittle failure. The partial factors are derived using first order reliability method. In order to suggest a simple method for safety assessment, statistical properties of modelling error associated with the simplified equation of shear capacity estimation are estimated using test data of 185 beams reported in the literature. To demonstrate the usefulness of the framework developed, an attempt has been made to determine partial factors for assessment for a typical T-girder bridge designed according to the relevant Indian codes. The loading considered corresponds to actual traffic loads on a typical Chennai flyover. The study reported here gains importance as: (i) general guidelines to assess the reliability of in-service bridges are non-existent in the Indian context and (ii) the partial factors suggested for two consequence classes can be used for quick assessment of the safety of existing similar flyover girders against limit state of shear in a more rational way.