196 COLLAPSE OF TEXAS TOWER NO. 4 



But tlie tower, having a low frequency, as it did after it was made, 

 it was apparent to everyone that this was bad, so that it might well 

 have been interesting to and, perhaps, valuable to, make a dynamic 

 analysis, but certainly the first thing to do was to restore the initial 

 integrity of the tower, and they were doing it at the time we were out 

 there. 



Mr. French. But would it be reasonable to infer from your findings 

 that the static force of a single 35-foot wave might well be less than the 

 forces exerted by a series of 10-foot waves ? 



Mr. Brewer. Would you repeat that question ? 



Mr. French. Would it be reasonable to infer from your findings 

 that the static force of a single 35-foot wave might well be less than the 

 forces exerted by a series of 10-foot waves ? 



Mr. Brewer. That is possible with the low natural frequency, but 

 actually we know that tuning did not take place, but if you have multi- 

 ple impacts on three legs which gave forces roughly comparable to the 

 30-foot wave, and this is borne out by a diagram which is in one of 

 our reports which shows this to be the case, but this is not a resonant 

 phenomenon. It could be though if the tower had an even lower 

 natural frequency ; it could be conceivable that it could get resonance 

 with the waves and have some really tremendous stresses and motions. 

 But we have no evidence that suggests that that occurred. 



Senator Saltonstall. Mr. Chairman, would Mr. French permit an 

 interruption ? 



Senator Stennis. Mr. French, I think you have used your time at 

 this point. I yield to the Senator. 



Senator Saltonstall. I want to understand, Mr. Brewer, as a lay- 

 man, what you said about a diving board. I think I understand it. 



"V\Tiat you are saying is that if a person out at the end of a diving 

 board is in time with the up and down motion he can produce more 

 dynamic stress than if that person on the end of the diving board 

 gets out of time with the up and down motion. 



Mr. Brewer. That is correct. 



Senator Saltonstall. And, therefore, it becomes less of a stress. ^ 



Mr. Brewer. That is right. His stress still is greater, however, than 

 if he just stands quietly at the end of the board. 



Senator Saltonstall. His stress is still greater when he stands 

 quietly ? 



Mr. Brewer. No. 



Senator Saltonstall. No. That is what I understand. 



static, IMPTJLSrSTE, AND RESONANT LOADING CONDITIONS 



Mr. Brewer. There are three things we are speaking of. If you 

 stand quietly at the end of the board you have a stress on the board 

 that is called a static condition. 



If he jumps once on the board, that is called impulsive loading on the 

 board, and that would be greater than a static case. 



If he repeats the jumping and gets it just exactly right, depending 

 on the mechanical properties of the board, then he can get an even 

 greater loading, and that is a third thing called a resonance. 



We have then a static loading, impulsive loading, and then we have 

 a resonant loading condition. These are the three things that occur. 



