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f 



h w 



, 



Flow Direction 





h 



i 1 



Tsunami surge flowing post elevated structure 



h = surge height 



h w = wetted height on structure 



L - length measured perpendicular to the 

 sections shown above and below 



L/d = l/(2h„) 



Flow Direction 



■2h v 



■- 2h 



Equivalent body used for determining coefficient of Drag Cq 

 Flow is assumed symmetrical about the dashline 



Figure 67. Determination of C„ when flow 

 passes under a structure. 



SOLUTION : 



(a) It can be assumed, for purposes of determining the coefficient 

 of drag, that the structure is equivalent to a structure 14 meters 

 wide and 2.0 meters high with both underflow and overflow (Fig. 67). 

 From Table 6, for a flat plate normal to the flow direction where 

 L/d = 7, the coefficient of drag C^ - 1.25. 



(b) The structure is higher than the depth of flow so there would 

 be neither underflow or overflow. This corresponds to an infinitely 

 high structure where L/d = °°. From Table 6, C_ = 2.0. 



180 



