Optimum Design of Howe Steel Truss Bridges

The optimization process is an important topic that assists with minimizing the cost of designed structures. However, the weight of the entire structure should be smaller amongst all cases studied to obtain the optimum design. In the current study, optimum design considering the height to span ratio of Howe-truss is carried out. Simply supported truss with different span lengths (24m, 32m, and 40m) and varying bays lengths (2, 3, 4, and 6 m) were examined assuming one traffic lane. The weight-height envelopes were obtained for all cases studied for the decision of the optimum height. Finite element analysis was used for the analysis using SAP2000 and the design was performed as per the AISC and AASHTOO requirements. The results showed that the optimum height of the truss depends on the span length of the truss bridge. However, span-to-height ratios between 9 to 10 are the optimum ratio in which a lower weight of truss can be obtained. Furthermore, changing the bay length of the truss has a considerable effect on the optimum ratio decided and using a heigh to bay ratio of 1 contributed to obtaining the optimum weight. The deflection limitations seem to have a considerable effect on the optimum height of the bridge truss.