Abstract:
Bridges are crucial assets forming part of road infrastructure. One of the challenging
problems faced by bridge engineers and road asset managers is maintaining these
bridges in such a way that they do not only meet optimum condition requirements, but also
those requirements that are concerned with the functionality of the bridges. Various
indicators, such as the Priority Condition Index, are used to indicate the condition of
bridges and to develop a maintenance strategy for bridges, but similar indices for the
functionality of bridges are not available. This paper focusses on the need for a functional
index for bridges and presents a method to calculate a combined Bridge Functionality
Index (BFI) based on traffic volumes accommodated by the bridge and the functional
ratings of the detour route that would have to be used should the bridge fail. The proposed
BFI was tested on 10 bridges on the Gauteng provincial road network. The study
methodology involved identifying the bridges, determining the detour routes and analysing
traffic data for the roads over the bridges and for the detour routes. This was followed by
the development of the BFI, which is a weighted combination of a Traffic Volume Factor for
the road over the bridge and a Functional Index for the detour route. The Functional Index
for the detour route is a function of five factors, namely User Risk Factor; Road Capacity
Factor; Riding Quality Factor; Road Safety Factor; and Detour Length Factor.
