The state of bridge loading in south africa

Abstract

Bridges in South Africa are designed in accordance with TMH7, which was first published in 1981 and revised in 1989. Since the publication of the code, there have been revisions to traffic legislation and the nature of the vehicles that currently occupy our roads has changed over the past forty years with respect to gross vehicle weight, axle weigh, number of axles, axle spacing and dynamic amplification. This paper evaluates the current code provisions by comparing load effects of NA loading to those obtained from modern WIM data for normal traffic. This paper does not address abnormal loading. The shortcomings of TMH7 are presented and an alternative load model is presented that is both up to date and calibrated to international ISO norms. New research in dynamic amplification is presented and a simplified model for multiple lane presence is outlined. A model is presented that is not only modern, but also simpler to apply than the current code, which is seen as cumbersome.