Since the maximum pressures at each transducer rarely all occurred at the same 

 instant in time, the choice of peak condition, or time zero, was subjective. 

 In all cases, that instant at which maximum pressures were occurring at the 

 greatest number of cells was chosen as time zero. 



50. Results of this analysis are presented in Tables 8 and 9 and 

 Plates 53-100. These data reinforce the fact that the shock pressure phenom- 

 enon is characterized by impulsive loadings and that, especially under extreme 

 wave conditions, the pressure distribution profile can change drastically in a 

 very short time. 



51. Comparison of corresponding temporal distributions for Plans R4S2 

 and R4S3 does not indicate any significant effects due to the difference in 

 the geometric shape of the modified recurve; however, pressure distribution 

 profiles for Plan R4S3 generally show slightly greater pressures near the top 

 of the seawall, due to concentration of wave energy in that area by the 2-ft 

 overhang. 



52. On completion of testing, results indicated probable selection of 

 the modified recurved seawall as the most suitable design; however, because of 

 the previously mentioned variability of the shock pressures, SAW requested 

 that additional wave pressure data be collected. Pressures were measured for 

 100 individual waves (instead of the previous 7 to 12 waves) for the two most 

 critical breaking wave conditions at wave periods of 12 and 14 sec and +8.6 ft 

 swl. This provided sufficient data to allow the execution of a simple 

 statistical analysis. 



53. the results of this additional testing are included in Tables 10 

 and 11. During this test series, provisions were made to increase the sam- 

 pling rate to 280 samples/sec. This provided a more comprehensive temporal 

 distribution of the wave pressures. Although all pressures for the individual 

 waves listed in Tables 10 and 11 did not occur at the same instant, the time 

 interval over which the maximum pressure occurred at all eight transducers 

 never exceeded 0.43 sec in the prototype. These data again show variability 

 of the shock pressures for consecutive waves of the same conditions and 

 clearly indicate that the maximum pressures occur at the top of the modified 

 recurved seawall. Secondary pressures were consistent throughout the tests. 

 Maximum secondary pressures occurred near +8.6 ft swl and demonstrated typical 

 magnitudes and durations of 5.5 psi and 2.5 sec (prototype), respectively. 



28 



