ANALYSIS OF THROUGH DAMAGE OF REINFORCED CONCRETE BEAMS IN THE SUPPORT ZONES UNDER LOAD

Abstract

This paper presents the results of a numerical study of the effect of through opening of various diameters, contents, and spacing on the stress-strain state of reinforced concrete beams in tensioned and inclined areas. The relevance of the topic is determined by modern requirements for the optimization of structures in the construction and reconstruction of buildings, when it is necessary to lay engineering communications through the body of load-bearing elements without losing their reliability and strength.

The modeling was performed in the LIRA-CAD environment using a physically nonlinear formulation of the problem. Concrete is modeled using spatial volumetric elements of the KE 236 type, taking into account the 25th exponential deformation law, and reinforcement is modeled using finite elements of the KE 210 type with approximation of the σ–ε diagram by a piecewise linear dependence. This approach allows tracking the change in stress and deformation from the initial elastic stage to the formation and development of cracks in inclined and stretched areas.

The results obtained showed that the effect of the openings significantly depends on their geometric parameters and location. Also, holes with a diameter of 20 mm and a pitch of 2d create a local stress concentration in the tensile zone, but do not lead to a significant reduction in the stiffness of the structure. With an increase in diameter to 30 mm and an increase in pitch to 4d, the stress in the concrete decreases by 5–7%, and the area of detected crack opening expands but has a more uniform character. With an increase in the number of holes, there is a tendency for deformations to increase within the range of 3–6%, but the destruction remains plastic.

Studies of inclined sections have shown that vertically located damage near the zone of origin of inclined cracks affects the trajectory of their development, but at reasonable distances between holes does not cause a critical reduction in load-bearing capacity. On the contrary, in some combinations (smaller diameter, larger pitch), stress redistribution and a decrease in concentration at the crack tips were observed.

Thus, the results of the work confirm that the presence of through holes in the tension and inclined zones of reinforced concrete beams does not always have a negative effect. With a rational choice of diameter, pitch, and number of holes, it is possible to achieve a controlled effect on the working elements, avoiding brittle failure. The results obtained can be used in the design of structures with holes for engineering networks, ensuring safe operation without a significant reduction in load-bearing capacity.