Reliability-based design of prestressed concrete beams

A reliability-based procedure for the design of prestressed concrete (PC) beams is presented. Loading, material properties, prrestressing force levels, as well as the models used to predict structural behavior at initial, final, and ultimate stages are all treated as random variables. System reliability methods are used to compute the probabilities of unsatisfactory performance of PC beams at initial and final stages. The design of PC beams is solved by integrating second-moment reliability methods for components and systems with an automated design optimization package using the feasible directions method. A number of reliability-based design examples of PC beams commonly used in the United States construction industry for offices and retail buildings are presented to illustrate the proposed approach. Additionally, design charts are provided to make easier the implementation of the proposed approach.