Resistance of masonry and reinforced concrete members to diagonal splitting

Abstract

The issue of ensuring the integrity of masonry and reinforced concrete load-bearing members of the structural systems of buildings under the action of a load whose resultant force is directed diagonally in the plane of the member is considered. The most common is the case of the combined action of vertical and horizontal forces, which in seismic construction areas significantly affect the bearing capacity of structures. Special attention is paid to small-sized members, which include masonry, and reinforced concrete as a composite material. This is due to the complexity of their stress-strain state when performing diagonal splitting (simultaneous shear in compressed areas and tear in the tension zone). The failure of load-bearing structures leads to accidents and the collapse of objects as a whole or their parts, threatens the safety of people and the environment, and the loss of material values. One of the ways to increase safety is a justified clarification of the definition of the bearing capacity of structures, which creates conditions for effective design. Taking into account that significant plastic strains occur during an earthquake, the expediency of applying the theory of plasticity to design the ultimate load of masonry walls, short reinforced concrete corbels, key joints of beams with slabs and columns, and wall panels in which loss of bearing capacity through diagonal splitting is possible. Masonry and concrete are considered as a rigid-plastic body. Plastic strains are localized on the failure surface, adjacent areas are considered rigid. The principle of virtual velocities is applied, and the mathematical apparatus of the theory of plasticity is adapted to masonry and concrete, taking into account the specifics of their strength and strain properties.  The bearing capacity of structures is determined from the condition of minimum capacity of plastic strain. Normal and tangential stresses on the shear surface in the compressed zones correspond to the strength condition. The results obtained by the variation method found experimental confirmation. Recommendations on constructive measures to improve serviceability are provided.