Based on reliability analysis, a parametric study is conducted on typical prestressed concrete I-girders and spread box beams to investigate their structural safety. The effects of changes in initial prestress, section size and allowable concrete stresses on the required number of strands and on the reliability index are considered. It is shown that current bridge design specifications result in non-uniform safety for different spans and girder spacings. Therefore, code calibration at ultimate must take into account the allowable stresses criterion.
