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RE: PENNSYLVANIA BUILDING CODE - Historic Live Load Specification

[Subject Prev][Subject Next][Thread Prev][Thread Next] Bill P. wrote, "...it is not likely that the basic methodology of prestressed concrete design is that different currently compared to the 1960s, at least not in the simple case that I'm looking at.In fact, as far as I know P/S design is the "last bastion" of allowable stress design in the concrete world. Outside of a rudimentary check for "flexural strength," it's all stress and service deflection analysis."

  Bill,
I've only been doing prestressed design for 20 years, so I do not know how it was approached in the 60's, but since 1985, I and the engineers with whom I have worked have always designed by ACI ultimate strength design, with careful checks for stresses during stripping, yarding, shipping, erection and service. If there is a rudimentary check it is the service deflection analysis, as once the section is chosen, there is not a lot that can be done to stiffen it up - what can be done is increase the original camber which diminishes any sag under live load. Maybe Texas engineers have done it differently, but I know some that I think did not. When I'm in the office, tomorrow, I'll look for old BOCAs for old LLs, but I think nothing goes back to the 60's.
  Jim Getaz
  Winchester, Virginia



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