Regression-based method for calculation of the punching shear capacity of the slab

Introduction. At slab-column joints, where significant force is concentrated on a relatively small area of the support, punching shear failure of the slab may occur. This type of failure is accompanied by formation of the spatial failure surface called punching cone. The main factors influencing punching shear capacity are: energetic size effect, percentage of longitudinal reinforcement in the tensile zone of the slab, span to depth ratio, column perimeter to depth ratio. Lack of consideration for these factors in a calculation method may result in low accuracy. The purpose of this work is to develop a calculation method which takes into account the main factors affecting the punching shear capacity of the slab.

Materials and methods. The paper presents a comparison of the punching shear strength obtained in laboratory tests with domestic (CP 63.13330) and foreign (Eurocode 2, ACI 318-11, Model Code 2010) building codes. It is important to develop a more accurate method for calculation of punching shear strength of a slab. Coefficients of the method can be obtained by the least squares regression analysis using Levenberg – Marquardt algorithm based on the experimental data.

Results. As a result of the regression analysis, a calculation method for punching was obtained. The comparison of the punching shear strength obtained in laboratory tests with the described method is given.

Conclusions. The comparison showed that the obtained method has a higher compliance with the experimental data than the methods presented in a number of building codes. The developed method can be used to assess the punching shear strength of slabs and foundation with and without transverse reinforcement.

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