Full-scale Field Test Extraction of Natural Frequency and Acceleration of Bridge using Modal Test and Operational Modal Analysis

Abstract

Vibration in bridges occurred due to several factors such as structural design, environmental loadings, and loading characteristics (speed parameter, loading patterns, and configuration of axles). If this problem is prolonged for several years, this may lead to stages of failure such as structural cracking, fatigue on structural members, excessive deformation, and local stress concentration on structural connections. In response to this issue, an investigation was carried out in this study by utilising numerical modelling of Finite Element Analysis (FEA) to explore the effect of the Intermediate Diaphragm (ID) on the RC bridge deck. The FEA is then validated and confirmed from the full-scale field-test, which consists of a modal test for both frequency and mode shape comparisons, and operational modal analysis for extraction of deck acceleration. The results show that the current natural frequency of the bridge does not reach the minimum frequency requirement from the BS5400 Code of Practice, while the acceleration based on a 24-tonnes moving truck is within the allowable acceleration limit. In comparison, frequency, mode shape and acceleration between the FEA numerical analysis and field test had shown insignificant differences and minimum error between the two.