DETERMINATION OF DEFLECTIONS OF CONTINUOUS REINFORCED CONCRETE BEAMS UNDER REPEATED LOADS

Abstract

For bending elements of constant cross-section without prestressing of reinforcement in areas where the bending moment does not change sign, it is allowed to calculate the curvature for the most stressed section, and for other sections of this section to consider its change proportional to the value of the bending moments.It is known that most structures are operated under repeated loads, which is not taken into account by current standards. In addition, repeated loads can affect the change in the elastic-plastic characteristics of concrete, which is also ignored by regulatory documents. The aim of the work is to improve the method for determining the deflections of continuous beams under repeated short-term loads, taking into account the change in the elastic-plastic modulus of concrete. When determining the deflections of continuous beams under repeated loading, it is necessary to take into account the change in the sign of the bending moment, the transverse force, the curvature of the beam axis and the change in the elastic-plastic modulus of concrete due to repeated loading. Considered a two-span continuous beam of rectangular profile, loaded with concentrated forces, which are applied repeatedly. The standards recommend that statically indeterminate structures be designed taking into account theredistribution of forces. For this case, provided that the support and span sections are of equal strength, the moments will be the same. Since the beam is considered without pre-tensioning of the reinforcement, cracks will appear in its stretched zones, the maximum opening width of which will be above the support and under the forces in the spans. The presented improved method for determining the deflections of continuous beams from bending and shear deformations takes into account the change in the elastic-plastic characteristics of concrete due to repeated loading. The derived formulas can be used to determine the deflections of continuous beams under repeated loads.