Design of prestressed concrete beams using system reliability and optimization

In this paper, second moment reliability methods for components and systems are integrated with optimization tools in the design of prestressed concrete (PC) beams. Loading, material properties, prestressing force levels, as well as the models used to predict flexural behavior are all treated as random variables. The performance functions considered are related to the stresses at initial and final stages as well as the flexural strength of the beam. System reliability methods are used to compute the probabilities of unsatisfactory performance of PC beams at these limit states. Reliability-based design examples of double tee PC beams commonly used in the construction industry are presented to illustrate the proposed approach. Additionally, design charts are proposed to make easier the implementation of the proposed method.