Experimental investigation of tsunami-borne debris impact force on structures: Factors affecting impulse-momentum formula

This study investigates factors affecting tsunami-borne debris impact force on structures. Debris collision accelerations were measured at the contact point on the structure's seaward wall using disc- and box-shaped smart debris devices; the equation of motion was used to estimate the debris impact forces from the measured accelerations. Also, the impact force was measured at the base of the structure using a multi-axis load cell, and compared with the forces determined using the smart debris devices. The basic impulse-momentum formula was modified by the addition of coefficients, taking into account the added mass and the debris velocity. Debris shape also influenced the impact force. Deformability of the debris and flexibility of the structure both reduced the debris impact force. •A smart floating debris device is used for direct measurement of the impact force at the contact point of the collision. Validity of the measurement technique using the smart debris device is shown.•The acceleration of the collision depends on the debris velocity, duration of the debris contact with the structure, debris mass, and shape of the debris.•The basic impulse-momentum formula is modified by the addition of coefficients, taking into account the added mass, the contact duration of the impact, and the debris velocity.