A possible design formula for estimating tsunami pressure forces 

 per unit length on vertical walls is given by Equation (D-26) in Appendix 

 D, which is restated here in the form 



(i) F = Cp (| PgdJ) (5M 



(ii) C ^ Ik 

 P 



Equation (5^i) expresses the force in terms of the hydrostatic pressure 

 force for the surge depth dg above the toe of the structure (see Figure 

 D-1 , Appendix D). The factor C-p, a pressure coefficient, represents the 

 number of times the dynamic force exceeds the static. Based upon an 

 average value of K from the total results of Table X and upon experimental 

 indications that the vertical jet height at the wall is from 1.5 to 2 

 times the velocity head of the surge, C^ appears to average about lU. 



3. The Ability of Structures to Withstand Tsunamis 



In the coastal cities and villages that suffered tsunami damage, 

 the houses were generally old, one-story, wooden-frame buildings. Such 

 houses had a poor capacity for withstanding the tsunami forces. One 

 design detail, usually lacking, which should be emphasized in future 

 design, was adequate connection between the wooden- frame structure and 

 the footings. This weakness caused many houses to be floated off their 

 foundations, and was probably the main cause of tsunami damage to wooden 

 buildings close to the maximum runup. This is true not only for smaller 

 buildings but also for larger ones like the two-story Odd Fellows building 

 in Crescent City. 



Houses and buildings that were floated off their foundations and 

 survived the attrition of tsunamis and impacts from other floating debris 

 or the impacts of stranding, were razed during cleaning-up operations. 

 It is therefore impossible to tell to what extent these structures would 

 have been able to withstand the tsunamis had they been adequately con- 

 nected to their foundations . Many of the older and smaller wooden 

 structures like the houses in many small villages , were completely 

 demolished by the tsunami. 



The few concrete-block and reinforced-concrete structures in tsunami- 

 inundated areas withstood the waves rather well. Such buildings Include 

 the concrete-block, steel-frame engine house in Seward, some concrete- 

 block buildings in downtown Kodiak and on the Kodiak Naval Station, and 

 the reinforced-concrete, five-story hotel on Front Street in Crescent City. 

 Some of these buildings, however, were damaged from the impacts of floating 

 boats and debris. 



Floating timber caused much of the damage at Crescent City. Huge logs 

 acted as battering rams in punching through walls, and functioned as drag- 

 nets in concentrating pressure. During a tsunami the floating timber has 



366 



