Modeling shear and flexural response of hollow core slabs using truss analogy

The truss analogy provides one of the most useful design methods for shear critical concrete structures and gives a better understanding of the force flow in cracked reinforced concrete members, with struts representing the flow of compressive stresses and ties representing the flow of tension stresses. Prestressed, precast hollow core slabs are used extensively for floor and roofs in precast concrete construction. For these prestressed concrete members without web reinforcement, shear can be critical for certain load configurations and truss analogy provides a tool for predicting the flexural and shear capacity of these slabs. This paper presents a new strut-and-tie model developed to predict the ultimate load carrying capacity of prestressed precast hollow core slabs and also to indicate the associated mode of failure. It is important to incorporate concrete tension elements (concrete ties) in the truss model to carry the diagonal tension forces in these members. The results obtained from the proposed model have been compared with experimental results of full scale load tests conducted on 14 hollow core slabs, 5 meters and 2.5 meters in length with depths of 200 mm, 250 mm and 300 mm. The proposed strut-and-tie model provides good agreement with the experimental results and can be employed for the analysis and design of hollow core slabs.