Study on the Methodology for Reliability-based Bridge Design Considering the Equivalent Scour Load

Study on the Methodology for Reliability-based Bridge Design Considering the Equivalent Scour Load

Owing to the frequent occurrence of worldwide hydraulic hazards, scour has become the major cause of failure for cross-water bridges in many countries. Currently, the effect of scouring on bridges is not considered as an external loading; as a result, current bridge design codes are merely used to verify the stability of structures with specific scour exposure conditions. In order to design bridges while considering the scour effect, along with external and other loadings of hazardous events, developing a load model to represent the change of structural characteristics under different scour conditions is required. This study introduces a methodology that applies an innovative idea which conceptually transforms the reduction of capacity of a bridge due to the effects of scouring into an equivalent scour load which can be used as a demand load for structural design. A series of lateral loading tests of a pile model were conducted to revise the equivalent scour load formula in the literature. The proposed formula was used to establish a load model that considers the lateral failure mode and calculates the failure probability by applying conditional failure probability and introducing an acceptable failure condition factor. The experimental results are employed to construct the parametric scour fragility curves through the application of equivalent scour load formulae. The scour depths observed from the flume experiments are used to develop a scour fragility curve that can be applied to evaluate the vulnerabilities to scouring of piled bridge piers in preliminary studies. This study presents a feasible methodology for constructing a scour fragility curve from flume experiments.