DIRECT ANALYSIS AISC 360-10

Re: DIRECT ANALYSIS AISC 360-10

Sye — Thu, 05 Dec 2013 06:21:49 GMT

Unfortunately it is not possible to do that from a single DIRECT ANALYSIS. However you may actually consider carrying out a separate PDELTA 35 ANALYSIS with the serviceability cases for checking the column drifts and then do a DIRECT ANALYSIS for the strength cases.

Re: DIRECT ANALYSIS AISC 360-10

MAHESH KUMAR K — Wed, 04 Dec 2013 10:08:14 GMT

Exactly, the displacement i have compared are the nodal displacement to check the drift of the structure. Is it possible to get the displacement of the nodes with full EI after analysis to check the serviceability (drift) limits, i believe that the reduced stiffness are to be used for calculating the required strength only as per Cl. C2.3 Adjustments to Stiffness (Chapter C AISC 360-10). Please advice.

Re: DIRECT ANALYSIS AISC 360-10

Sye — Tue, 03 Dec 2013 23:33:57 GMT

Although I could not see the images, but I am guessing that you are looking at the nodal displacements as opposed to section displacements. The REDUCEDEI 0 ensures that displacements at intermediate locations within the member are computed using the full E and I. The section displacements are the ones that are used for checking whether the member satisfies deflection limits ( L/240, L/360 etc ). The displacements at the nodes on the other hand comes from the analysis with reduced E and I.

Re: DIRECT ANALYSIS AISC 360-10

MAHESH KUMAR K — Tue, 03 Dec 2013 13:17:37 GMT

I am getting the same displacement by changing the REDUCEDEI also, please refer to the below and advice,

The displacement results shows that the full EI is used for calculating the deflections? please advice

The below results with command,

PERFORM DIRECT ANALYSIS LRFD TAUTOL 0.01 DISPtol 0.002 -
ITERDIRECT 10 REDUCEDEI 0 PDiter 15

The below results with command,

PERFORM DIRECT ANALYSIS LRFD TAUTOL 0.01 DISPtol 0.002 -
ITERDIRECT 10 REDUCEDEI 1 PDiter 15

The below results with command,

PERFORM DIRECT ANALYSIS

Re: DIRECT ANALYSIS AISC 360-10

MAHESH KUMAR K — Tue, 03 Dec 2013 13:03:32 GMT

While using the REDUCEDEI 1 or 0, there is no change in the deflection values (i.e. getting the same deflection values while running with REDUCEDEI 0 or 1 ), please advice (may i assume that the deflections are calculated with full EI in all the cases and reduced EI is used for arriving the member internal forces {REQUIRED STRENGTHS} alone to account for the stability analysis as outlined in Chapter C AISC 360-10?) .

The below results with command

PERFORM DIRECT ANALYSIS LRFD TAUTOL 0.01 DISPtol 0.002 -
ITERDIRECT 10 REDUCEDEI 1 PDiter 15

The below results with command,

PERFORM DIRECT ANALYSIS LRFD TAUTOL 0.01 DISPtol 0.002 -
ITERDIRECT 10 REDUCEDEI 0 PDiter 15

The below results with command,

PERFORM DIRECT ANALYSIS

Re: DIRECT ANALYSIS AISC 360-10

Sye — Tue, 03 Dec 2013 04:01:31 GMT

Yes STAAD does follow the analysis procedure outlined in Appendix 7 of the AISC 360-05 code which has now been moved to Chapter C of 360-10 code.

I created a wiki item based on your second query and you can find the answer at

communities.bentley.com/.../10599.aspx