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 With the majority of existing bridge networks designed for superseded design vehicular loading, the necessity to utilise more rigorous analysis methods to assess the load effects of bridges is indispensable.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.

Modular Bayesian damage detection for complex civil infrastructure

“…7. An alternative and more comprehensive vehicular load case could be implemented on the basis of appropriate modelling ratios as presented by Jamali et al [21].…”

Reliability-based load-carrying capacity assessment of bridges using structural health monitoring and nonlinear analysis

“…Tier 1 assessment is the most basic tier and usually serves as the first-pass check, which includes carrying out Axle Spacing Mass Schedule (ASMS) approach or simple beam-line analysis of the bridge compared against design loading with or without live load distribution factors. 5,22 These approaches are considered as ''one size fits all,'' which means ratings will be very conservative. This tier determines if further assessment is required and whether or not the bridge has sufficient capacity for the nominated vehicular loading.…”

“…Process of numerical model creations, with advantages and limitations of each modeling technique, is detailed in the authors' previous works. 22,24,27 The hidden reserved capacity of the bridge is masked if the numerical model is not calibrated with existing bridge information. Nonlinear analysis can be carried out on the calibrated numerical model of the bridge using information gained from SHM data.…”

“…representing the previous major design vehicle. 22 These vehicular loadings were scaled down by a factor of 10, in order to be applicable to the Box Girder ''carriageway.'' As can be seen from Table 3 with reference to relative percentage difference (RPD), ultimate LCC of the Box Girder is changed significantly prior (Tiers 1 and 2) and after considering as-is condition (Tiers 3 and 4).…”

“…Process of numerical model creations, with advantages and limitations of each modeling technique, is detailed in the authors’ previous works. 22,24,27…”