Extended sandwich model for reinforced concrete slabs: Shear strength with transverse reinforcement

In this paper, the description of the shear strength of orthogonally reinforced concrete slabs with transverse reinforcement by the newly developed extended sandwich model is presented. Based on a sandwich model, the slab element is subdivided into two cover elements and a core element. The applied in-plane forces on the cover elements are treated with the cracked membrane model. Regarding shear transfer, rotating crack faces that are able to transfer shear stresses by aggregate interlock are assumed in the core, whereas the crack orientation relative to the slab plane is determined by the crack pattern of the covers. The introduction of stressed crack faces in the core enables a subdivision of the applied shear force into a concrete and a steel contribution, allowing the determination of the required minimum transverse reinforcement ratio that enforces a ductile flexural failure. A brittle shear failure is eliminated by providing a transverse reinforcement even if it is a minimum transverse reinforcement that is not able to resist the applied shear force by itself. In addition, the extended sandwich model enables a general treatment of the deformation behavior. Verifications against experimental data generally show a good agreement. The influences of a deviation of the principal shear and moment direction from the direction of the in-plane reinforcement as well as the transverse reinforcement ratio on the shear strength and the deformation capacity are demonstrated.