Strength of eccentrically tensioned reinforced concrete structures with small eccentricities by normal sections

It is implemented the method of normal rectangular sections slab (shell) reinforced concrete elements strength calculating with flat eccentric tensile strength using the deformation m ethod. The results of the calculation are analyzed for the case of eccentric tension with small eccentricities with varying next parameters: the height of the cross section and the reinforcement coefficient. It is investigated the character of diagrams condition change of section “N – εc(1)” at gradual change of the stress-strain state from eccentric to the central tension. It is revealed that when the eccentricity of external forces decreases, the compressed zone of concrete decreases until its complete disappearance, and at rather small values of eccentricities of force application the balance between external and internal forces cannot be found by the method of current norms. An equilibrium is found between internal and external forces only at a two-digit diagram of the distribution of relative longitudinal deformations (in the case of a compressed zone). Variants of the given problem decision without considerable loss of calculations accuracy are offered, the most expedient of which is transition to algorithm of calculation by a method of limiting efforts. It was accepted as the basic in the previous building norms. The results of numerical calculations performed in the software complex “Lira-CAD” and the corresponding mathematical modeling confirmed the rationality and allowable accuracy of further calculations by this method.