In statically indeterminate systems, forces are distributed between individual elements depending on the ratio of their stiffnesscharacteristics. In reinforced concrete structures, the stiffness depends on the formation of cracks. The calculation of statically indeterminate reinforced concrete structures is usually carried out using iterations. In this case, it often turns out that the iterative process does not converge. This is due to the fact that after the first iteration, the most rigid element has the highest forces. Therefore, the rigidity of this element decreases at the next iteration. As a result, in this element, the efforts also decrease. As a result, the iterative process often does not converge. The article proposes a method for iterative calculationof reinforced concrete structures. The essence of the method is that when cracks form, the stiffness in the element under consideration decreases once and for all. Further, at the next iteration, this stiffness does not increase, even if the bending moment is less than the cracking moment. In this case, external iterations should be carried out to increase the load. Due to the small step of increasing the load, the once reduced stiffness no longer increases. Thanks to this technique, the iterative process converges stably, and the number of iterations is significantly reduced. It is shown that when calculating reinforced concrete cross-rod systems, it is important to take into account changes in torsional stiffness. This fact must be taken into account when designing. Several factors affect the difference between the calculation without taking into account the change in torsional stiffness and taking into account this change. This is the ratio of the initial flexural stiffness to the stiffness after cracking; the ratio of the initial bending stiffness to the yield stiffness of the reinforcement; similar torsional stiffness ratios; the ratio of changes in torsional stiffness to changes in bending stiffness; load level.
Author Biographies
T. N. Azizov, Pavlo Tychyna Uman State Pedagogical University, Uman
Doctor of Engineering, Professor
D. V. Kochkarоv, National University of Water and Environmental Engineering, Rivne
