ACCELERATION AND IMPACT OF STRUCTURES MOVED BY 

 TSUNAMIS OR FLASH FLOODS 



by 

 Fvederiok E. Camfield 



I . INTRODUCTION 



A high velocity flow of a wall of water surging over land, such as 

 found in some tsunamis or flash floods, may carry forward structures 

 which will impact with other structures. The resulting impact forces, 

 combined with the force of the surging water, may result in serious 

 damage of structures which would otherwise withstand the surging water. 

 Therefore, a means of estimating the forces on a structure resulting 

 from the impact of other structures is needed. 



II. ACCELERATION AND IMPACT OF STRUCTURES 



Camfield (in preparation, 1978)^ shows that the distance, x, a 

 structure will move, as a function of time, t, is given as 



X = ut - - £n (aut + 1] (1) 



where u is the velocity of the water and a is a constant defined by 



C/?A 



2 V(l + Cm) 



A = cross-sectional area of the submerged part of the structure 

 transverse to the direction of motion 



V = volume of water displaced by the structure 



C-Q = coefficient of drag given in the Table 



C^ = mass coefficient given in Figure I for rectangular struc- 

 tures (from Riabouchinski , 1920) . 



Example solutions of equation (1) are shown in Figure 2. 



(2) 



^CM4FIELD, F.E., "Tsunami Engineering," U.S. Army, Corps of Engineers, 

 Coastal Engineering Research Center, Fort Belvoir, Va. (in preparation, 

 1978). 



^RIABOUCHINSKI, D. , "Sur la Resistance des Fluides," International 

 Congress of Mathematics , Strasbourg, 1920, pp. 568-585. 



