258 COLLAPSE OF TEXAS TOWER NO. 4 



Now, these pins cost money. We weren't trying to get a cheap 

 tower, but we thought it was the best connection we could devise. 



Mr. Kendall. Do I understand that you don't consider it essential 

 that the undersea braces be as rigid as possible ? 



Mr. Kuss. Yes, sir; in the sense I'm talking about. We did not 

 want to have bending moments at the end of the struts where they 

 connect to the legs, because that introduced unknown stresses which 

 would be repeated with every motion of the tower. 



Mr. Kendall. Wasn't it essential that the undersea braces be as 

 rigid as possible ? 



Mr. Kuss. Sir, I'm talking about the individual braces. Rigidity 

 does not mean strength, sir, necessarily. Strength is one thing and 

 rigidity is another. 



Mr. Kendall. Well, didn't j'ou want to establish as great a rigidity 

 as possible in the undersea braces ? 



Mr. Kuss. No, sir. We were purposely avoiding rigidity at the ends 

 of the members. 



Mr. IvENDALL. What do you mean, at the ends of the members? 



Mr. Kuss. Where each member connects to the legs or where they 

 connect to one another. 



Mr. Kendall. Where did you want to achieve your rigidity? 



FUNCTION OF TRUSSED SYSTEM 



Mr. RuTLEDOE. Sir, the truss system, as in any truss, provides the 

 rigiditj^ of the structure. Mr. Kuss is discussing the joint. The over- 

 all rigidity is provided by the truss. This is similar to a very large 

 bridge. To our knowledge, in the main connection joints in a large 

 bridge, completely welded connections have never been used. The 

 connections or major members are either pinned or riveted or bolted. 



Mr. Kendall. I am anxious to get the distinction, Mr. Rutledge. 



Mr. Rutledge. I beg your pardon ? 



Mr. Kendall. I am anxious to get the distinction that you have 

 mentioned. 



Mr. Rutledge. Well, the rigidity — we need rigidity in the overall 

 structure against lateral forces. The system of bracing members pro- 

 vides that rigidity. 



On the other hand, the joint where these members come together, 

 if they are completely rigidly connected at the joint and there is a 

 very small deflection, it tends to bend each of the members at the 

 joint, which puts in what is called the secondary stresses. 



Mr. Kendall. Now, as the architect-engineer, were all the changes 

 which deviated from the original design approved by your firm? 



CHANGES APPROVED BY ARCHITECT-ENGINEER 



Mr. Rutledge. They w^ere approved as they affected the ultimate 

 structure. 



Mr. Kendall. Was the elimination of piling approved ? 



Mr. Rutledge. Yes, sir. 



Mr. Kendall. The elimination of the temporary platform? 



Mr. Rutledge. Yes, sir. 



Mr. Kendall. The increases in pin tolerances ? 



