Abstract:

In this research a study on design of high strength prestressed concrete bridge girders have been performed. The grillage analysis of standard National Highway Authority (NHA) Pakistan  two-lane bridges with all the eight types (type A – type H)  of standard NHA cross sections of I-girders is carried out using STAAD Pro.2007. The significance of the research is to have better understanding of using high strength concrete and evaluating its incremental effect on the span of girders. Observations made. From this research shows that By increasing specified concrete compressive strengths (fc‘) from 41 MPa (6000 psi) to 69 MPa (10000 psi) having girder spacing of 2.5m center to center and the average increase in span length is 25 %. From these results it is obvious that that by increasing concrete strength of girders the span length increases for all the eight types of girders.The maximum increase in span range is for girder “Type G” i.e. 31%.According to NHA the span range specified is from 29m to 37m, concrete strength used is 5000 Psi and the depth of the section is 2400mm.But if we use high strength concrete from 6000 Psi to 10000 Psi the same girder depth of NHA can be use for span length up to 48.5m.