Evaluation of Partial Safety Coefficients in the Concrete Tank Design by a Semi-Probabilistic Approach

Traditionally, the optimization of civil engineering structures is conducted by a deterministic approach based on global safety coefficients recommended by the dimensioning codes, such as the Algerian seismic code and the Eurocodes. These coefficients are applied to take into account the uncertainties related to live loads in order to protect the structures against unpredictable variations in the mechanical performance of the materials. In reality, the use of these safety factors still do not lead to an optimal solution, as they can lead to an over-dimensioning of the structure when it does not lead to a lack of robustness. This approach gives to the dimensioning a reliability without having to perform a reliability analysis. The use of these coefficients aims to introduce a sufficient margin of safety in order to increase the safety of the structure design and to reduce the role of the uncertainties on the performances of the optimized structure. This research aims to evaluate the partial safety factors associated with the internal tensile stress developed in the upper beam of a tank, as well as its resistance. The evaluation of the partial safety factors is presented with a semi-probabilistic calculation. Two random variables were considered, the live load, as well as the compressive strength of concrete, modeled by distribution normal laws. In addition, the target reliability index is taken in a range of performance of the civil engineering structure.