Reliability-Based Partial Safety Factors in Cantilever Construction of Concrete Bridges

One of the most important aspects of the construction of concrete bridges using the balanced cantilever method is the limit state of the loss of stability by overturning. This problem is especially relevant because of the lack of guidance in most structural codes about the actions involved and the safety factors to be used. First, the main assumptions, actions, and the methodology involved in the construction of such bridges are presented. The result of the reliability-based calibration process is the definition of a set of partial safety factors to apply in the design of the elements used for ensuring stability during the construction of bridges using this method. The bridges covered in this study are those with main spans between 80 and 140 m. This range includes most of the concrete bridges constructed with the cantilever method. The derived partial safety factors are also valid for a wide range of estimated live loads and wind forces on the deck during consruction. Finally, an example is presented comparing the design values of the stabilizing elements for a bridge with a main span of 120 m, obtained using the proposed safety factors and those computed with a global safety factor of 1.5.