Critical Aspects in Design and Construction of Open Type Shallow Highway Girders Across Railways

Abstract

A highway bridge across railways in-lieu of the level crossing will surely be smoothening the road traffic and the rail traffic. Hence, it is essential to bridge across the railways at all the level crossing locations in a developing country. Due to the introduction of a bridge across a busy railway track, the necessity to negotiate the level difference happens. This level difference is more with the usage of the conventional type of girders. By this, the delay of the project due to land acquisition is considerable. The most suitable superstructure for such highway bridge is the deck with shallow open type pre-stressed girders. When multiple shallow, open-type girders are placed adjacently and integrated with a deck slab above these, the load distribution and sharing between girders are to be refined based on experimental studies and authors discussed the same within this paper. An experimental study on two Double-T cross-section pre-stressed model girders and deck assembly revealed the structural behaviour between girders. The results from the two-point load testing helped in developing various design methodologies in this study. An escalation of 17% in the design forces need to be considered on the results obtaining from the grillage analysis, to cater the unbalanced forces on the individual web of the open-type girder, during the eccentric loading condition. The Authors elaborated the design of shear friction reinforcement. The self-managing capacity of the spreading tendency of the webs of this type of girders is due to the counteracting of radial pressure generated from the pre-stressing force. The critical aspects of construction also dealt with in this paper without which the usage of open-type girders with ends closed cannot be encouraged. The authors developed conceptual designs for the removable internal shutter, launching scheme and demolishing of the bridge superstructure, in this study. The dismantling of the bridge is a rare requirement arises only when the number of track increases. The reuse of girder-deck assembly is also found possible and suggested in this paper.