CALCULATION OF THE BEARING CAPACITY OF A KEYED JOINT IN THE CASE OF FAILURE OF THE SEAM BY A COMPRESSED STRIP

The key joint with the seam of precast and precast- cast-in-place reinforced concrete structures is considered. The bearing capacity of the joint is proposed to be calculated using the method based on the variational method in the theory of concrete plasticity. In experimental studies, the destruction of the same along the inclined compressed strip was recorded. Diagonal splitting is considered as a theoretical model in this case. A kinematically possible scheme is proposed, which takes into account the specificity of the stress-strain state of the element in the limit state. The scheme includes 4 rigid discs formed with a failure surface: two wedges under the loading platforms, and two discs formed with the surfaces of the wedges and the tearing-off plane connecting their tops. The wedges approach each other, the other two move away perpendicular to the tearing-off plane. The failure surface consists of areas of shear with compression, on which directional plastic strain is localized and limit normal and tangential stresses with values according to the accepted condition of concrete strength, as well as areas of tension with principal stresses. The unknowns when solving the problem of the strength of a compressed strip under diagonal splitting are the two angles of inclination of the shear sections of the wedges to the splitting plane (  1 2 , ), the ratio of the speeds of the rigid disks k V V = 1 2 / and the limit load. After determining the jumps of the normal and tangential components of velocities on the sections of the failure surface, as well as their areas, the functional of the method is recorded, which is examined for a steady state. As a result, a formula for determining the limit load was obtained, which takes into account the strength characteristics of concrete and reinforcement, the geometric parameters of the joint (height and depth of the key, the angle of inclination of the support platform of the key, the width of the seam), the amount of reinforcement. To determine the values of the load, this function is examined for the extremum.