Fuzzy theory based approach for three-dimensional nonlinear analysis of reinforced concrete two-blade bridge piers

A modern conceptual design of a bridge structure should be open to wide criteria to endow the structure with static, dynamic and ductile characteristics sufficient to tackle the seismic events. The fulfillment of these requirements, as well as the exploration and the verification of innovative structural schemes, can be achieved only by using refined analysis formulations and effective numerical tools. The structural scheme considered in this paper is based on two-blade slender bridge piers. This kind of pier is a structural element subdivided into two parts, each with different geometric and mechanical properties. The first part has a box section and it is very stiff while the second part is made of two flexible blades connected at the top. This scheme has two purposes: the transmission of vertical loads to the foundation structures and the possibility to allow horizontal displacements (due to thermal effects, concrete shrinkage, etc.) without the use of cinematic mechanisms. In order to evaluate the structural performance of such a bridge pier, with regards to its stiffness, strength and ductility, a nonlinear analysis is clearly required. A proper evaluation of such performance is essential in order to achieve an optimized structure, with respect to the vertical and the horizontal loads. In the present study, the structural performances of the pier are evaluated using a solid finite element formulation. In this kind of analysis one cannot forget that the real world is affected by uncertainty, and one has to keep it into account. In general, there are several ways to reach this goal, for example one can use a probabilistic approach or a fuzzy approach. In this paper the uncertainty, involved in the reliability assessment, is modeled using a fuzzy criterion.