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.
