DEFORMATION CHARACTERISTICS OF ECCENTRICALLY LOADED R.C. COLUMNS

Abstract

Attempts have been made from time to time to find out methods to predict actual colipse loads of R.C. Structures by calculations only. Ordinary calculations based on the elastic theory fail near collapse loads as the behaviour, of both the materials used in. R.C. Structures i.e. concrete and steel, is far from elastic in this region. When a section developes moment equal to or near to its ultimate moment of resistance, the section goes on rotating on further loading without taking any further moment and thus acts as a hinge which is called PLASTIC HINGE. In redumdant structures, on further loading, more sections become plastic hinges and a redistribution of moments takes place. In case of highly ductile materials like steel, plastic hinges can take large rotations without reaching the ultimate strains and the steel structures collapse when the system developes sufficient number of plastic hinges to attain one degree of freedom. In case of R.C. Structures, the reinforced concrete plastic hinges have a limited rotation capacity and knowledge of amount of rotation which the section undergoes, is necessary in order to apply the redistribution principles for analysis of such structures. An attempt has been made in this work to study the load and deformation characteristics of rectangular symmetri-cally reinforced sections subjected to axial load and bending moment with respect to one axis. The assumptions made in this work are comparatively simple and more near to reality, The results of analysis have been presented in form of P-M and P-4 interaction curves which can be used for design of sections or for calculation of ultimate load and moment which a given section can carry. Also the curvature which the section will have at ultimate stage can be found out directly from the curves. Theoretical results have been supported by tests on twelve columns having steel area, concrete strength, dimensions and eccentricity of load as variables. The test results show quite .a good agreement with those obtained by theoretical