desgin steel members using AISC ASD89

[ELSARWAN]

hi every one,
I have to check sap model for truss members with span 42 meters, I have two questions:
1- I want to ask about design parameters, in the model that I have all design parameters are program calculated "the designer didn't make design over right for any thing" is this right?!!


2- I think that I have to enter design parameters such as " unbraced length ratio " and "effective length factor k" if I member divided into several segment I attach snap to illustrate my point.

I really need help in this topic ,I asked a lot of people about this issue but no one have clear answer.
thanks in advance.

 

[Jatfuentes]

Dear ELSarwan,

I Think ( and I allways do), you must check the "k" values used by SAP and the effective unbraced lengths. For me, SAP is my assistant, I work as if I were doing the calculation by hand. For the bottom chord of your truss, you have two lengths. In the plane of the truss, "lx" is the distance between joints. In the plane perpendicular to the truss "ly" is the distance between your transverse bracings, if you dont have transverse bracings, "ly", for each element is the total length of your truss. Suppose that the length of each element is "a", the total length should be "5a", then for each element "a" you must input in SAP2000, l33 = 1, and l22 = 5 ( in the case that you dont have lateral bracing).

Regards

 

[ELSARWAN]

Dear Jatfuentes,
thanks a lot for your kind answer ,
I agree with you in all your points ,I always do this when I using staad pro. put I don't have big experience in sap2000
again thx alot