CASE STUDY OF TSUNAMI BORE IMPACT ON RC WALL

The Tohoku Tsunami of March 11, 2011 caused tremendous damage to many coastal buildings, bridges and port facilities. During field surveys following this event, the authors documented a number of structures that were damaged to a near-collapse condition as a result of hydrodynamic loading. Analysis of survivor videos provided information on the tsunami flow characteristics at these locations, allowing for an assessment of current hydrodynamic loading expressions under full-scale conditions. Based on laboratory experiments performed at Oregon State University, the lead author and colleagues developed a new hydrodynamic loading expression for a broken bore striking a vertical wall [1]. This expression was applied to a case study of a large vertical reinforced concrete (RC) wall damaged by an incoming bore strike during the Toholcu Tsunami. The damaged wall is on the seaward side of a high-bay building in the Minami Gamou Sewage Treatment plant near the Sendai coastline. A non-linear finite element model of the building was subjected to the hydrodynamic pressure distribution derived from the laboratory experiments. It is shown by structural analysis of the wall that using this loading expression generates the same yielding response in the wall as observed in the field, as reflected in the deflected shape measured by LiDAR. Similar analysis using current Japan Tsunami design provisions indicates that these provisions are considerably more conservative from a structural perspective than is necessary to resist hydrodynamic loading from a tsunami bore. This paper presents the application of hydrodynamic loading by the leading edge of a bore, determined based on laboratory experiments, to the non-linear analysis of a reinforced concrete building damaged during the Toholcu Tsunami.