Design and Durability of Highway Overpasses

The scope of this paper is to compare durability of different types of concrete overpasses constructed on Croatian highways in past forty years. Bridge condition assessment was conducted due to new categorization of the roads in Republic of Croatia and in accordance with State Bridge Management System. During examinations, some characteristic damages on prefabricated overpasses were noticed: rapid construction degradation around the expansion joints and damages on drainage system. In order to minimise maintenance expenses, it is necessary to optimize construction in the course of design phase by choosing more adequate types of construction and details. Considering overpasses are one of the major bridge group, viewed in elevation by those traveling on a road bellow, the structure type, span lengths, and proportions as viewed in elevation should be carefully considered.

The purpose of this paper is to describe and to compare most frequent structural solutions implemented in design of concrete overpasses on Croatian highways in last thirty years. Emphasis is placed on durability of each type of structure, construction time and costs and maintenance costs. Great part of all overpasses in Croatia is constructed with prefabricated concrete elements, as a result of fast construction requirement. Fewer overpasses were constructed with continuous solid slab. Recently, on new highways, construction of integral bridges is planned. The pros and cons of different structures considered are discussed. Improvements applied in design, based on rebound information of structural behaviour and durability will be presented.