Modification of Bridge Piers Scour Depth Equations using Genetic Algorithm

Abstract

One of the main reasons of bridge destruction is the bridge piers scour. A more accurate computation of scour depth would lead to a more solid design of bridge piers. Empirical equations can be applied to compute the scour depth. In this study, the coefficients of 17 empirical equations were optimized using genetic algorithm and fieldwork values. 80% of the field data were used to optimize the equations and the rest were used to verify them. The RMSE, MAE, E and R2 criteria were applied to evaluate the optimization method where the results showed the ability of genetic algorithm in empirical equations optimization. The (Froehlich 1988) equation had the highest degree of precision among the empirical equations, so the genetic algorithm has had the least effect on the optimization of this equation. The optimized (Neill 1964), (Melville 1975), (Laursen & Toch 1956), (Blench II 1962) and (Hancu 1971) equations with respectively, 75, 72, 71, 71 and 71 percent showed the highest reduction in RMSE error criteria. The optimized (Blench II 1962) equation with RMSE, MAE, E and R2 criteria equal to 0.57m, -0.085m, 62 percent and 0.65 respectively, presented the highest correlation coefficient and lowest error. In the end, more equations were proposed to predict the bridge piers scour depth.

Keywords

• scour
• optimization
• bridge pier
• genetic algorithm