Debris Force on Rectangular Column Due to Tsunami.

Tsunami caused significant causalities and structural damages. Debris, especially that of relatively large size that is driven by tsunami may produce even higher force resulting in more fatalities. Therefore research on debris movement due to tsunami surge and its effect on structures need to be studied. This research is aims at understanding the speed of simple ball-shape debris under tsunami surge attack and its impact on vertical column structures. The debris was made of concrete that was injected into thin plastic balls. The research was held in Hydraulic and Hydrology Laboratory of Gadjah Mada University Indonesia. A channel of 17,5m x 0,6m x 0,45m in dimension was used for the simulation. Tsunami waves were generated using a dam break system with quick release mechanism. Agate that was located 5.25 m from the upstream of the channel was connected to a load of 100 kg. The gate may be opened quickly by dropping the load. The rectangular column of 4.7 cm by 4.7 cm for the test was connected to a load cell. The debris was spread evenly across the flume width and along 1 m of the channel with the nearest distance to the building was varied. These were 0cm, 50cm, and 100cm. The results indicated that the maximum debris velocity is less than the tsunami surge. The debris velocity increases from still to a maximum speed where the drag force equals the frictional force on the debris. The maximum force on the rectangular column varied due to the layout of the debris as they hit the rectangular column