Rod models of strength of compressed concrete strips of the conjugation between beams and columns of prefabricated monolithic frames

Introduction. The existing methods of calculation of reinforced concrete structures are not universal. Each calculation model is suitable only for a limited class of elements. The construction of a general design model that adequately describes the resistance of structures to shear forces in combination with bending is one of the most difficult tasks of reinforced concrete theory. Therefore, in practical calculations of shear strength, contingent models are used. Aim. Construction of bar models of concrete compressive strength of inclined strips of concrete. Materials and methods. The proposed rod models of inclined compressed concrete strips of beam support zones with small shear spans a ≤ h01 between load and support pads are based on modeling their physical performance, copying major crack trajectories and failure schemes. Results. Experimental and theoretical studies have revealed possible schemes of failure of the support zones of beams at the conjugation with columns under the action of concentrated forces with the ratio of the shear span a = h01 (where h01 is the work height of the console). Two schemes of failure of compressed concrete strips have been experimentally obtained, the first scheme from compression when the main compressive stresses reach the axial compression strength of concrete and the second scheme from the combined action of compression and shearing when the tangential stresses reach the strength limit. Analytical evaluation of the obtained schemes of failure of compressed concrete strips is given. Limit states are revealed, calculated dependences of strength are developed. Conclusions. The proposed rod models and calculation dependencies for determining the strength of compressed concrete strips are based on analogies of their physical work, have simplicity of application and allow calculations with a sufficient degree of reliability.