Which members are intended to be included in the parameters FLEX and AXIAL for a braced bay when using Direct Analysis Method? Does this include just the braced columns, beams and bracing or the entire frame (including gravity only beams/columns)? I'm a little confused by the definition provided by STAAD. The definition STAAD provides is as follows:
FLEX, identification of members whose flexural stiffness is considered to contribute to the lateral stability of the structure, along with the initial value of τb that should be used. Members listed with FLEX will have their EI factored by 0.80 times τb while performing the global solution. The final member forces and code check will be with 100% of the flexural stiffness.
AXIAL, identification of members whose axial stiffness is considered to contribute to the lateral stability of the structure. These members will have their EA factored by 0.80 while performing the global solution. The final member forces and code check will be with 100% of the axial stiffness.
I am currently trying to model Example 2.1 in AISC Guide 28 in STAAD and analyze it using direct analysis method and compare the results to those provided in the example. I think it may be worth noting that the example usese effective length method, where I am using direct analysis method. Currently, my results for the moment in the beams and axial loads in the columns match that of the example (or are within 0.50%) except for the axial loads in the columns for combinations 5, 6 and 7. The results for these combinations have been up to 30% off. These are the only combinations that include the wind load; which is why I think the error might be coming from the columns in the braced bay. Any help is appreciated, thanks!
Lauren