keywords: Reinforced concrete, Panelled beams, reliability analysis, uncertainties, sensitivity analysis
This study presents reliability assessment of a large span reinforced concrete panelled-beams floor system designed in accordance with BS 8110 (1997). Deterministic designs against flexure, shear and deflections of the panelled-beams were carried out in consistent with the provisions of the code and also submissions in the literature. The performance functions of the respective failure modes of flexure, shear and deflections were then developed. The reliability assessment of the floor system using the performance functions derived were implemented based on stochastic approach where basic design variables were treated as random variables with their statistical characteristics obtained from JCSS code (2000) and executed using First Order Reliability Method (FORM). The results obtained showed that safety index decreases with increase in load ratio in all the modes of failure considered. In deflection, the safety indices indicated that the design is only safe with a load ratio of 0.8 to 1.0 and a failure at load ratios 0.9 to 1.0 having beta (β) values of 3.02 and 2.87 with corresponding approximate probability of failure of 1.28E-03 and 2.04E-03, respectively. Sensitivity assessments showed that the reliability index (β) values for design of reinforced concrete panelled-beams are mostly influenced by the characteristic compressive strength of concrete, span and depth of the beams. It was also noted that safety index increases with increase in variables such as characteristics compressive strength, and depth, while it decreases with increase in span of the beams and applied load.