Strengthening Of Determinate Pratt Steel Truss By The Application Of Posttensioning Along Its Bottom Chord

Abstract

Majority of the truss bridges in India and abroad are either structurally deficient and/or functionally obsolete. There is a desperate need to enhance the performance of these existing bridges by an appropriate technique which should be economical and with minimum disturbance to the traffic. The aim of the present analytical work is to know the effect of posttensioning   on the member forces and deflections of a statically determinate Pratt type of the truss. Pratt type of truss has been considered in our study, as it is one of the most commonly used truss configuration in truss bridges. Because of its relative economy and less disturbance to the traffic, posttensioning technique has been adopted to upgrade the performance of the truss. Bottom chord of the truss is post tensioned with high tensile steel cable and the profile of the cable is straight. The truss is analysed for member forces and deflections using direct stiffness approach of matrix analysis. From the obtained analytical results, it is seen that there is a noticeable improvement in the performance of the structure: Member forces have been reduced significantly in the entire bottom chord members and there is reduction in deflections at all the joints after posttensioning