Economic Preliminary Design of Bridges with Prestressed I-Girders

Abstract

This work provides the design engineer with a direct and simple method for the optimal economic design of standard prestressed I-girders. The bridge considered is single span, with a cast-in-place reinforced concrete deck that acts compositely with the girders under super imposed dead load and live load. A computer program has been developed, based on a linear programming model, to construct two charts, which can then be used for the preliminary design of standard pretensioned I-girder sections. The first chart is used to obtain the most economic girder type and its corresponding spacing. The other chart is used to obtain the required prestressing force. The linear programming model is applied to perform a sensitivity study to evaluate the effect of changing the design variables on the value of the maximum girder span and the necessary prestressing force.