study and photographs of an AVP during slamming,'^ it is estimated that the part of the bottom 

 structure extending from the keel to the turn of the bilge in the forward quarter length of the 

 ship may be subjected to occasional localized slamming or pounding pressures. In some 

 locations within this area, the pressure attains values of the order of 300 psi. For the pur- 

 pose of design calculations, the time variation of the pressure is such that it may be assumed 

 to act statically. The following design loads are given as an interim recommendation: 



a. For the design of bottom panels: Assume that the pressure attains a maximum value 

 which varies linearly from 300 psi at the bow to 30 psi at a distance of 0.25 L from the bow: 



Po = 300 - 1080 |- , A < 0.25 



where p is the design pressure for plates, 



X is the location of the plate measured from the bow in feet, and 

 L is the length of the ship in feet. 



b. For the design of transverse framing: Assume that a static uniform pressure of inten- 

 sity p„/2 acts on the bottom over a strip one frame space in width. 



c. For th^ design of longitudinal stiffeners or framing: Assume that a static pressure 

 acts on the bottom plating supported by the longitudinal equal to Pq/2. 



If the bottom plating is to be designed to keep the stresses within the elastic limit, 

 then the simple formulas and tables of Reference 10 may be conveniently used for the calcula- 

 tion of the maximum stresses and deflections in plates loaded transversely. The ultimate load 

 for transversely loaded panels may be estimated by utilizing the simple method given by 

 Greenspon.^^ 



DISCUSSION 



The data of Tables 2 through 6 furnish a basis for working up distributions of motion 

 and hull bending moment for assigned service missions of ships of this type. In the present 

 instance, these basic data have been utilized to predict wartime service conditions for opera- 

 tion in the North Atlantic; the procedure for making this prediction is carried out in Tables 8 

 through 11, as a guide for similar analyses of other missions. It should be pointed out that 

 the prediction for "Wartime North Atlantic" service is greatly influenced by the estimated 

 operational speeds provided by the U.S. Coast Guard. Inspection of Table 1 indicates that 

 the estimates of service operating speeds made by COMAIRPAC vary considerably from those 

 provided by ships in service in Atlantic waters. 



It should be emphasized that the sea state is a variable which is most difficult to de- 

 fine. In the present case, variability of the sea conditions, for a given sea state, has been 



27 



