Investigation of the Influence of Local Low Strength Concrete on the Bearing Capacity of Bending Reinforced Concrete Beams

Reinforced concrete beams can experience local low concrete strength under certain conditions, for example, poor construction practices can cause problems such as concrete voids, surface cavities, block cracking, surface sinks and create areas of low concrete strength. This study presents the response of flexural hinge-supported reinforced concrete beams with different local areas of low concrete strength along the span. Modified models are adopted to describe the concrete properties and an ideal elastic-plastic model is adopted for the steel properties. The beam was divided into three main parts: one sensitive to bending moment, the second sensitive to shear, and the third sensitive to bond. The variables included two types of concrete strength and one reinforcement diameter. The results show that the most critical region with low concrete strength along the span of the beam is the confluence zone near the supports, which is reflected in the ductility of the load-deflection curves. A new generalized empirical model is developed to predict the effect of bearing capacity reduction from local low-strength concrete

On the Stability of Eccentrically Compressed Reinforced Concrete Elements with a Small Eccentricity, Taking into Account the Rheological Properties of Concrete

In the practice of modern construction, flexible centrally and eccentrically compressed reinforced concrete elements are becoming more common. In this regard, the relevance of studying their work and the mechanism of bearing capacity exhaustion increases. There are two directions in determining the bearing capacity of these elements: calculation for stability and calculation for strength. The loss of stability in a number of cases, obviously, can cause the destruction of not only centrally, but also eccentrically compressed rods with small eccentricities, since under certain conditions they can practically turn out to be close in their work. The stability of these eccentrically compressed rods is calculated by multiple integration. Such a calculation is especially laborious for reinforced concrete elements. This article is devoted to the study of the stability of centrally and eccentrically compressed reinforced concrete rods with small eccentricities, taking into account the creep of concrete. An eccentrically compressed rod with a small eccentricity of length l is replaced by a centrally compressed rod of length l0 so that the bending arrow includes the eccentricity. The numerical values of the rheological coefficients are determined from the boundary values of the reduced stiffness, which varies along the length of the rod. Complicated integration is replaced by the solution of the differential equation of the bent axis of the rod in the form of a sinusoid half-wave