Experimental study on the behaviour of reinforced concrete thin-walled open section compression members

Abstract

Reinforced cement concrete wall panels are load bearing integral structural elements of a building system. The conventional walls panels are heavy, reinforced at least with minimum percentage of compression steel and possess handling and erection problems. The main objective of the investigation is to study the behaviour of reinforced concrete thin-walled open section compression members with web stiffener in terms of load bearing capacity, lateral deflection and failure mode and formulate suitable design equations if the existing popular equations are not compatible. Regression analysis based on experimental data is carried out to suggest minimal changes to the existing design equations of IS 456 2000 and ACI 318 1989. The entire study is carried out in four phases. In the first phase of investigation, literature survey was carried out covering the analytical and experimental works so far conducted in the area of the research. In the second phase of investigation, test specimens were cast. Forty-eighty numbers of channel section specimens and thirty-six numbers of trapezoidal section specimens were cast. In the third phase, the effect of vertical web stiffener, increase in wall thickness, slenderness ratio and height to flange width ratio were examined and quantified in terms of lateral deflection, first crack load, failure load, stiffness and ductility factors. In the fourth phase, comparison of the experimental failure load was made with the existing equations of concrete wall design. All the three proposed equations are simple to use and yield reliable estimation of ultimate load. Out of the three suggested equations, the proposed empirical equation is the most reliable, very simple to use with buckling coefficient and nominally conservative in estimating the ultimate failure load. The maximum limits of slenderness ratio, height to flange width ratio, height to thickness ratio and web width to flange width ratio are suggested to exploit the section efficiency and material strength effectively.