| In Japan, road bridges are designed taking into account various uncertainties. For example, the measures for dealing with uncertainties such as fail-safes are installed considering events that have a large impact on the bridge but cannot be specifically considered in the design calculations because of their high uncertainty. Uncertainties which can be evaluated probabilistically are considered by partial factors in the semi-probabilistic method, and the reliability level required by the design standard is satisfied. On the other hand, uncertainties that are difficult to evaluate probabilistically are treated in various ways in the design process. Measures for dealing with uncertainties are, for example, application of fail-safes, designing structural systems to be redundant, providing plastic deformation capacity even in areas that do not plasticize in calculation, and designing foundations in both liquefiable and non-liquefiable conditions in consideration of liquefaction uncertainty if the ground in which the foundation locate is judged to have a possibility of liquefaction. The measures to deal with uncertainties other than those expressed by partial factors is often determined by engineering judgment based on past disaster experience, and the level of reliability required for these measures is not clear. Therefore, to improve the accountability of treatment of uncertainties and to deal with uncertainties more reliably and efficiently in the design of road bridges, this study proposes a framework for treatment of uncertainties in the seismic design of road bridges. First, the authors reviewed existing studies on uncertainties and risks in design of road bridges, including their types and way of evaluation. Second, we proposed a framework for treatment of uncertainty in seismic design in road bridges. Finally, the applicability of the framework is discussed through case studies. |
