Effect of Debris Forces on the Stability of Pile Foundation Bridges

Effect of Debris Forces on the Stability of Pile Foundation Bridges

The purpose of present study is to investigate the stability of cross-river bridges subjected to hydraulic loads and debris accumulations under extreme flood events. Steep riverbed and rapid flow are the common characteristics of Taiwan’s rivers. The heavy rain brought by Typhoon often induces local scouring around bridge foundations, and make the exposure of foundations more serious. According to past reconnaissance reports on typhoons or floods, the collapse of many bridges can be contributed to debris accumulation. The debris not only increases the effective area of substructure components, but also reduces the flow area and cause backwater upstream and increased velocities through the bridge opening. However, this effect of debris accumulation is not included in the current bridge design code in Taiwan. In order to have better understanding of bridge behavior in an extreme flood event, the hydraulic loads have to be calculated precisely, especially the hydraulic loads under the condition of debris accumulation. Therefore, a stability analysis of a cross-river bridge under flood water and debris loads was conducted using the pushover analysis procedure. The inelastic behavior of its substructures and piles underflowing water with high velocity was also discussed.