(b) the force accelerating the building at the moment of impact; 

 and 



(c) the momentum of the building at the moment of impact. 



SOLUTION : 



(a) The submerged cross-sectional area of the building, transverse 

 to the direction of the surge, is given as 



A = width X submerged depth = 40 x 10.5 = 420 square feet (39 square 

 meters) and the submerged volume (the displaced water) is 



V = width X length x depth = 40 x 14.4 x 10.5 = 6,048 cubic feet 

 (171 cubic meters). 



The coefficient of drag can be approximated by assuming the side of the 

 building is a flat plate. To determine an equivalent flat plate, using 

 the Table, assume that the submerged depth for underflow and overflow 

 (a totally submerged plate) is twice the depth of the building, or 



L 40 ^ ^_9 



and from the Table 



From Figure 1 , where 



d 2 X 10.5 



1.1 



a _ 14.4 _ 



b --^0-- °-2^ ' 



then 



Cm = 4.0 , 



and equation (2) gives 



CM 1.1 X 420 



2V (1 + Cm) 2 X 6,048 (1 + 4.0) 



= 0.0076 . 



The relationship between distance and time is shown in Figure 2, which 

 for a distance of 20 feet gives 



t = 2.40 seconds . 



13 



