Author(s): R. Triatmadja; Kuswandi; M. Indriyani; A. Nurhasanah
Linked Author(s): Radianta Triatmadja
Keywords: Tsunami; Force; Debris; Simulation
Abstract: Tsunami force on structures can be devastating depending on the size of the tsunami surge and the strength of the structures. In addition to hydrodynamic force, debris force either single debris or in group may hit a building at smaller area and hence resulting in greater pressure impact. Such impact may be of significant if applied on columns of buildings. The type, size, characteristics and approached angles of debris vary considerably. It is important to understand the characteristics of debris flows under tsunami surge and their impact on structures based on simplified debris of basic shapes. Physical model simulations were carried out using a flume of 20.80 m long, 0.6 cm wide and 0.45 high. The flume was divided in to two parts using a gate that can be opened quickly. The upstream part was used as a basin to store water to a certain depth. When the gate was opened, the water in the basin surged downstream similar to tsunami surge on land and hit a column where a load cell was installed to measure the pressure. The speed of the surge was recorded based on the arrival time of the surge front at a number of stations. The surge height was varied by varying the basin depth. Debris of various sizes under similar tsunami surges were then placed in front of the column at various distances. The tsunami surge and debris speed as well as the debris force on the columns were measured and compared with clear water tsunami force. The results indicate that the debris velocity is slower than the front surge depending on the bed friction, ? and the degree of immersion. Although the debris hit the column at slower speed, its impact force is higher than the hydrodynamic force. Since debris requires time to gain speed as they are dragged by the surge, the distance between the columns and the initial location of the debris is an important parameter. The theoretical approach of debris (sphere) force on a rectangular column was shown to be comparable to the experimental results.