Modelling techniques for structural evaluation for bridge assessment

Abstract

Load assessment of existing bridges in Australia is evaluated mainly using beam line model and the grillage analogy to examine the structural integrity of bridge components due to live loadings. With the majority of existing bridge networks designed for superseded design vehicular loading, the necessity to utilise more rigorous analysis methods to assess the load effects of bridges is indispensable. In this paper, various vehicular loading cases on a grillage model of a box girder bridge and its equivalent finite element model (FE) are considered, and their applicability for bridge assessment using structural health monitoring (SHM) as defined in the new revision of AS 5100.7 is studied. Based on numerical analyses, it was observed that component-level load effects in the two models have notable differences, irrespective of vehicle speed, position and loading. However, when global-level load responses are compared, the discrepancy in analysis outputs drops dramatically. The modelling ratios developed in this paper are practical and will be applicable with any modelling techniques for bridge assessment under vehicular loading on both a global and component-response basis. It was also observed that FE is more efficient in terms of model updating and damage simulation, and hence more appropriate for implementation of SHM techniques. The proposed flowchart suggested for heavy load assessment incorporates detailed and simple modelling approaches aligned with experimental data obtained by SHM techniques, which can be used for periodic and long-term monitoring of bridges. It can enhance the proper determination of bridge condition states, as any conservative estimation of bridge capacity may result in unnecessary load limitations.