ABSTRACT
The 2016 edition of ASCE 7, Minimum Loads and Associated Criteria for Buildings and Other Structures, contains a new Chapter 6 on Tsunami Loads and Effects. This new chapter applies to the tsunami design of all Risk Category III (critical and high occupancy) and IV (essential) buildings located in the mapped 2500-year tsunami design zone (TDZ). Based on their specific tsunami risk and evacuation planning, local communities may require that tsunami design also be required for taller Risk Category II (hotel, office, residential, etc.) buildings in the TDZ. The upper floors in these buildings could then provide a “refuge of last resort” to folk stranded in the evacuation zone with insufficient time to evacuation horizontally. One of the primary factors affecting the decision about whether or not to require tsunami design for taller Risk Category II buildings will be the likely additional construction cost. This study looked at two prototypical coastal buildings; a 6-story office building with reinforced concrete moment frame system, and a 7-story flat slab residential building with reinforced concrete shear walls providing lateral load resistance. Both buildings were tall enough to provide safe refuge above the anticipated flow depth at any location along the Western US coastline, including Alaska and Hawaii. The buildings were considered in four locations, namely; Hilo, Hawaii; Monterey, California; Seaside, Oregon; and Waikiki, Hawaii. Each building was designed for the wind and seismic requirements at each location. The buildings were then evaluated for their resistance to the tsunami loads required by the new tsunami design chapter in ASCE 7–16. This paper reports on the structural adjustments that were required to columns and walls in the 7-story residential building so as to satisfy the new tsunami design requirements. The financial consequences of these adjustments are compared with the overall cost of the building without tsunami design so as to illustrate the cost implications of requiring tsunami design for taller Risk Category II buildings.
