NUMERICAL SIMULATION OF THE CRACK FORMATION MOMENT IN REINFORCED CONCRETE STRUCTURES WITH USING SE "SAPFIR"

Abstract

This article is devoted to the analysis of the influence of the calculation method of the crack formation moment M_crc in frames of nonlinear deformation model on the crack resistance of cross section and the width of cracks’ opening according to foreign and Ukrainian building codes. The considered stress-strain state is flat eccentric compression / tension.

The first method is to take the value of the longitudinal force equal to the external force N, and calculate the crack formation oment M_crc at which the criterion of crack formation is achieved. With this method of calculation, the longitudinal force is assumed to be static.

The second method is to take the eccentricity of the external forces e₀ constant and calculate the limiting forces of crack formation N_crc, M_crc. In this case, the eccentricity e₀ is assumed to be static.

To achieve this goal, a numerical study of the typical rectangular cross-section of the reinforced concrete rod element was performed, taking into account the physical nonlinearity of the materials for different types of load combinations. The section is reinforced with 4 rods of Ø14 mm. Reinforcement class is A400C, concrete class - C16/20. The methods of calculating the crack formation moment M_crc and the eccentricity of the external forces e₀ from 0.25∙h to 8∙h were varied.

For the numerical study of this problem was chosen "Cross Sections’ Designer" SE "SAPFIR-3D". To determine the degree of influence of the method of calculating the crack formation moment M_crc on the width of cracks’ opening according to foreign building codes, stresses after the cracks’ formation σ_s,crc were additionally calculated.