A BRIDGE FOR AIRCRAFT RUNWAY

Abstract

Analysis and design of a 200 m wide and 1000m long bridge for the landing of aircrafts has been carried out using the commercial software package STAAD Pro. The bridge is an extension of a 1 km long runway. For this purpose the modeling and analysis of the concrete-steel composite deck, concrete piers with cap to support the deck have been done in STAAD Pro. Three alternative designs have been examined for the bridge by varying the cantilever projection of the deck, with suitable and corresponding changes in spacing of the main beams, grid beams and ribs. The analysis has been carried out for all the possible loading conditions, for the deck and the piers. in case of the deck, only live and dead loads and their combinations are considered. The earthquake load is important for the design of piers. The effect of the wind load is ignored in the analysis since it is much smaller than the earthquake load. To consider the earth-quake load the dynamic analysis is performed for the piers in the STAAD Pro by the response spectrum method and the base shears and moments are obtained for the design of piers. Due to large length and width (1000 m x 200 m) of the super structure, temperature effects are important and have been considered in the design of the expansion joints provided at every pier location, as well as for the design of bearings The weight of the superstructure had to be minimized to reduce the seismic forces and arrive at smallest possible size of the piers which are very large (684) in number. A practical spacing of the piers have been considered as 18 m c/c and it has been found that a cantilever projection of 1.5 m in the 18 m x 18 m deck panels with 15 m main span ,meets all design requirements including minimum size of expansion joints. iii