Stiffness of vertical keyed joints of large panel buildings before cracking

The object of the research is the linear stiffnesses of vertical keyed joints of wall panels of multi-story buildings before the moment of cracking. This work aims to propose and substantiate methodology for calculating the linear stiffnesses of two-node special finite elements used for modeling vertical joints in calculation software. Methods. To obtain the axial stiffness it is proposed to consider the properties of the joint concrete, the geometry of the joint and the parameters of the finite element calculation scheme of the building using Hooke's law. To obtain the relation for calculating the shear stiffness in the plane of the panels, when considering keys, the joint is considered as a set of elements, that are connected in series and in parallel, which stiffness is calculated accordingly. To obtain the dependence for calculation the shear stiffness in and out of the plane of the panels, without considering keys, the relations of the theory of elasticity are used. Results. A method for calculating the stiffnesses of vertical key joints of large-panel buildings in the three orthogonal directions before the moment of cracking is proposed and substantiated, the expediency of considering the work of shear in the joint when calculating its stiffness is shown. It is substantiated, that there is only slight influence of the geometry of keys on the results of calculating the stiffnesses in the linear stage of the work of the joint. The scope of application of the proposed methodology is determined. The comparison between the calculation results of a 5-storey large-panel building from a 9-point seismic impact with setting the stiffnesses of two-node finite elements according to the proposed methodology and according to the methodology currently used in design practice is carried out. The influence of reinforcement in the vertical joint on the results of calculating its stiffnesses before the moment of cracking is estimated.