LONG TERM BEHAVIOUR OF STEEL CONCRETE COMPOSITE BRIDGES

Abstract

Long term behaviour of steel concrete composite bridges is a major problem as the deflection and slip values increase with respect to time, creep and shrinkage of concrete depends on various material properties, there is no correlation between creep and shrinkage and structural response, presence of steel element with concrete in composite member makes it a very difficult task. Slip occurs at the interface of steel and concrete element makes prediction of long term behaviour even difficult, short term deflections can be predicted from fundamental structural mechanics. To meet this objective, various modelling techniques were examined to model steel concrete composite bridge considering partial interaction using SAP 2000, link stiffness was calculated to simulate partial interaction properly. Creep shrinkage effects were considered with help of construction scheduler for the modelled bridge. Study on effect of creep coefficient on deflection values was done by comparing codes and obtaining deflection values from SAP 2000 for the modelled beam. Obtained results indicate that the long-term deflection due to creep and shrinkage is generally 1.5 to 2 times its short-term deflection, the composite beam with a partial interaction shows larger deflection values than that of full interaction beams for both the short-term and long-term deflections. Central deflection values of the girders increases with respect to time because of creep and shrinkage effects, rate of increase of deflection decreases with respect to time. As the creep coefficient increases with respect to time for particular time of loading, modulus of elasticity of concrete decreases thereby increasing deflection values