Review of South African live load models for traffic loading on bridge and culvert structures using weigh-in-motion (WIM) data

Abstract

Includes bibliographical references.This thesis uses the axle weights and axle spacings of heavy vehicles recorded by weigh-in-motion (WIM) sensors to calculate the load effects on single lane, simply supported structures spanning up to 30m. The main objective was to compare the load effects caused by the recorded vehicles with those calculated using TMH7 Part 2 and the alternative live load models proposed in subsequent research. Through the probabilistic analysis of the truck survey data, the thesis predicts the magnitude of extreme events that may occur within a bridge structure's design life. The results reinforce the deï¬ ciencies of TMH7 Part 2's NA loading curve to cater for normal traffic conditions on spans of 10m and less. They also highlight the conservative assumptions made in the conï¬ guration of vehicle convoys used to simulate serviceability loads in 20m to 30m spans. The ï¬ ndings of the thesis support the need for the rational calibration of the partial factors used in limit state design. The WIM data was analysed to highlight the extent of overloading. The results provide evidence that the overloading of individual axles and axle sets is prevalent and that overloading has a greater impact on 5m and 10m spans than 30m spans. Research was carried out into the basis of the bridge live load models in TMH7 Part 2 and those recently developed in Europe, the United States and Canada. The thesis documents the advancement of rationally based live load models derived from actual vehicle data. Alternative live load models were calibrated against the extreme events predicted by the WiM data. The results independently validate the alternative live load model proposed by the latest research commissioned by the Department of Transport. This live load model takes a similar form to the one proposed in the Eurocode - ENV 1991-3