FLEXURAL BEHAVIOUR OF CONTINUOUS STEEL CONCRETE COMPOSITE BRIDGE GIRDERS

Abstract

Steel concrete composite bridges are becoming very popular as they are efficient and economical and provide a section which is lower in weight as compared to concrete bridge girders of similar span length and subjected to similar loading. The construction time of the continuous composite bridge girders is far less than concrete bridge girders. The continuous composite girder has several advantages over the simply supported girders such as having lower span deflections for similar cross-sectional properties and for similar load conditions. The current practice of neglecting the concrete in the negative bending zone of the girder has been studied and an alternate model has been proposed which takes the tension stiffening of cracked concrete into account. Different spans and interaction ratios were studied, and comparisons were drawn. A lower mid-span deflection and lower moment in steel girders in the negative bending zone was observed in the tension stiffened Steel Concrete Composite girder as compared to the girders which were analysed without considering concrete in the negative bending zone. A 2-D model was created to simulate and study the behaviour of the steel concrete composite girders. The model was validated against theoretical models which are in practice. The validation was done for a Steel Concrete Composite with rigid connection and for partial interaction with inter layer slip. The model was also validated against the current practice of neglecting concrete in the negative zone of the composite girder. The results so obtained were in accordance with the already present numerical models. The effective moment of inertia was also used to understand the effects of using the residual strength of the concrete after cracking. To simulate the behaviour of the Steel Concrete Composite girder under negative bending, a cracked model which incorporated the effective moment of inertia of the concrete was developed. The percentage decrease in the span deflections were reported showing a considerable amount of decrease in deflections as compared to sections with complete cracked properties. The moment decrease in the steel girder at the negative moment zone was also reported