Hydrostatic Loading . Additional studies are required to improve 

 procedures for designing against hydrostatic load. OTEC structures will 

 be pressure-resistant hulls for the entire life of the structure. Risk 

 analysis places hydrostatic loading as a critical item because if failure 

 occurs the probability of catastrophic loss of the entire structure is 

 high. The effect of large penetrations, out-of-roundness , and axial and 

 hoop stiffeners on the implosion strength of cylindrical hulls needs to 

 be studied. The effect of pressure gradient needs to be studied but this 

 topic depends on whether OTEC structures will be oriented horizontally or 

 vertically. 



Computer Design Methods . Improvements to computer analysis, such 

 as finite element or finite difference methods, should be made by incor- 

 porating valid constitutive relations for the construction material. The 

 constitutive relations for concrete materials needs to account for applied 

 multiaxial loading effects while the concrete is partially and fully sat- 

 urated with seawater. 



Design for Shear . Guides need to be developed to design for shear in 

 large shell structures. For example, the cold water pipe at the base of 

 the structure is under high bending and shear forces due to currents act- 

 ing along the length of the pipe. The pipe will be prestressed in the 

 axial and hoop direction. An allowable design shear strength is required 

 for the concrete in the shell. This shear strength should be based on 

 appropriate experimental data on saturated concrete. 



Design for Impact . Guides need to be developed to design for impact 

 loading of concrete structures. Local and large area impact loads need to 



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