SP-357—8: Punching-shear strength of reinforced concrete slabs subjected to concentric transverse loads and in-plane tensile forces

Reinforced concrete slabs can be subjected simultaneously to transverse loads and in-plane tensile forces, as it occurs in top slabs of continuous box girder bridges at intermediate supports, or in flat slabs supported on columns, subjected to horizontal loads. To study the effects of in-plane forces in the slab punching-shear strength, an experimental and theoretical investigation was carried out, which is described in this paper. Five square slabs of 1650 mm (42”) side and 120 mm (4.7”) thickness were tested under a centered transverse point load and different degrees of uniaxial in-plane tensile force. Numerical predictions using non-linear finite element analyses were performed to help in the experiments design. Furthermore, the punching-shear mechanical model, Compression Chord Capacity Model (CCCM), was extended to incorporate the effects of in-plane tensile forces. The experimental results showed that the punching strength linearly decreases with the level of applied tensile force and, if cracking in the slabs is produced by the tensile force, yielding of the reinforcement and further reduction may take place. Excellent agreement was found between theoretical predictions and tests results. Furthermore, the CCCM was verified with available results of punching tests with uniaxial and biaxial tensile forces, obtaining very good results.
This work has been carried out within the framework of research projects BIA-2015-64672-C4-1-R, and BIA2015- 64672-C4-3-R financed by the Ministry of Economy and Competitiveness (MINECO) of Spain, and also with the financial support of the Government of Catalonia through the contract for research and innovation in infrastructures E1-INF-18500. The authors want to deeply thank also the personnel of the Structural Technology Laboratory of the Universitat Politècnica de Catalunya.
Postprint (author's final draft)