I am not able to analyse structure with joist girders with ASCE properties assigned in STAAD. When I searched it is told that you cant carry out analysis with those properties assigned for joist, you have to model joist as an equivalent beam. Can any one tell me how to find an equivalent section ( I section or whatever it may), to carry out anaylsis and design?
The joists modeled in STAAD.Pro can be used for transferring gravity loads to the supporting members only and these are not accounted for in the stiffness analysis. If you would like to consider these members in the stiffness analysis, the only way would be to come up with the analysis properties. This is not possible without knowing the actual configuration of the truss used by the manufacturer. So here is the best option I can think of. You can refer to the deck manufacturer’s catalog and find out moment of inertia. You would also need to come up with an equivalent cross sectional area based on the weight per unit length and the material density. You can then define these as a general section with cross sectional area and moment of inertia as inputs. Alternately after figuring out the moment of inertia and cross sectional area, you can use the Section Wizard program which has an equivalent section calculator that can come up with approximate section dimensions based on properties ( like say A , I ) and cross section type. See picture below