ANALYSIS OF R.C. MULTIBEAM BRIDGES FOR I.R.C. LOADS

Abstract

Bridges, which are most important structures in present day life, may be of short span or long span. A multibeam deck bridge proves to be economical for relatively shorter spans. A multibeam deck 4has longitudinal girders supported over supports alongwith cross beams at supports and, sometimes, at intermediate positions also. Various methods are available for analysis of multibeam bridge decks. Among all the methods available, grillage analogy method is a popular computer oriented method, since it is easy to comprehend and use, relatively inexpensive and is reasonably accurate for a variety of bridges. In grillage analogy, the bridge deck is idealised into a grid which has members in longitudinal as well as transverse directions. The load has also to be converted into equivalent nodal loads. A comprehensive computer program has been developed which has a data base for IRC live loads. The program generates IRC vehicle and moves it on the deck gradually in longitudinal direction. The program also finds design forces for a member and corresponding other forces for same placing of load. A study for effect of transverse stiffness on distribution of bending moment among longitudinals, torsion in end longitudinals and deflection at mid-span is carried out. It is observed that a uniform distribution of load among longitudinals is observed for more stiffer transverse system of deck. With increasing transverse stiffness the torsion in.end longitudinals and deflections in the deck decreases. The effect of distribution of transverse stiffness, is very less on above effects of bridge deck.