Transverse assessment of a concrete box girder bridge

Abstract

This paper looks at the beneficial effects of geometric arching from haunches, web continuity and compressive membrane action in the design and assessment of box girder top slabs. The paper initially reviews tests relevant to arching action in box girders and then analyses recent tests on box girder slab strips. Finally, using the assessment of an existing box girder bridge as an example, a series of computer models is developed to illustrate a method for transverse analysis of a box girder top slab in which some of these arching effects can be utilised. For the analysis of tests and the assessment example, a three-dimensional frame model that considers the in-plane strength enhancement of the restrained slab is used. This simplified approach was verified by finite-element modelling and the results show good agreement. The analysis methods including arching action significantly reduce the required amount of reinforcement for the deck slab. The paper concludes that arching action from geometrical arching of haunches and frame action are significant and must be considered for any accurate analysis at both serviceability and ultimate limit states. It is also concluded that compressive membrane action may occur and can be used in the design and assessment of box girder structures within certain geometric parameters.