ABSTRACT
This paper reports the investigation on the reliability levels implicit in the BS8110 requirements, probability-based optimum design and sensitivity tests for singly reinforced continuous beams. These are accomplished with the aid of the modern reliability analysis (First-Order Reliability Integration Scheme- F0RM5, Gollwitzer, et al,1988) and a Nonlinear Programming Algorithm. The design variables a r e the geometrical dimensions, material strengths and loading with their respective probabilistic nature considered. The limit state equations based on Ultimate and Serviceability limit states are derived and the implied safety levels for the various states computed. The results show that the criterion for bending is satisfactory with safety levels falling within an economical range earlier proposed (Moses, et al, 1990). However, the criterion for shear is inadequate yielding very low safety levels, while deflection requirement is unduly conservative. In the optimum design the objective function was taken to be the total expected cost subjected to bending and shear constraints. Numerical values for the design variables at optimum points a r e proposed and the influence of the variabilities in concrete quality and live load on the objective function and the design variables is noted. It is established that valid estimates of the design parameters can be ensured if the relevant data is under control.