Strength / Serviceability Member Design

For AISC 360-10, here is the procedure.

Let us say that the load list for steel design (deflection checks and strength checks) is 101 to 185

Also, let us assume that load cases 101 to 120 are the ones for deflection checks and the remaining are for strength checks.

The load cases that are required for deflection checks should be included in a load envelope that is defined as a ‘Serviceability’ case:-

. DEFINE ENVELOPE

. (load case and combination numbers) ENVELOPE (envelope number) TYPE SERVICEABILITY

. END DEFINE ENVELOPE

During code checking per AISC 360-10, cases 101 to 120 will be used only for deflection checks, the remaining will be used for strength checks.

Regarding the crashes you are experiencing, try using the latest build - 20.07.09.31. The number of reported cases in this new version is far less than in the previous builds.

Thank you - but I am asking about member selection not code check.

What I would like is that STAAD determines what is the governing case (strength or serviceability) and select the appropriate member. Strength should be based on ULS envelope and serviceability on SLS envelope.

Is proposed solution applicable to member selection?

Yes, the method I suggested is applicable for member selection too.

Ok - here is the simple example:

STAAD PLANE

START JOB INFORMATION

ENGINEER DATE 29-Apr-13

END JOB INFORMATION

INPUT WIDTH 79

UNIT METER KN

JOINT COORDINATES

1 0 0 0; 2 8 0 0;

MEMBER INCIDENCES

1 1 2;

DEFINE MATERIAL START

ISOTROPIC STEEL

E 2.05e+008

POISSON 0.3

DENSITY 76.8195

ALPHA 1.2e-005

DAMP 0.03

END DEFINE MATERIAL

MEMBER PROPERTY CANADIAN

1 TABLE ST W130X24

CONSTANTS

MATERIAL STEEL ALL

SUPPORTS

1 PINNED

2 FIXED BUT FX MY MZ

*

*

*

LOAD 1 LOADTYPE Dead  TITLE D

MEMBER LOAD

1 UNI GY -20

*

*

*

LOAD 2 LOADTYPE Live TITLE L

MEMBER LOAD

1 UNI GY -100

*

*

*

LOAD COMB 3 1.25D+1.5L

1 1.25 2 1.5

LOAD COMB 4 0.85D+1.5L

1 0.85 2 1.5

LOAD COMB 5 1.0L

2 1.0

*

*

*

PERFORM ANALYSIS

*

*

*

DEFINE ENVELOPE

3 4 ENVELOPE 1 TYPE STRENGTH

5 ENVELOPE 2 TYPE SERVICEABILITY

END DEFINE ENVELOPE

*

*

*

PARAMETER 1

CODE AISC UNIFIED 2005

MAIN 1 ALL

DFF 800 ALL

DJ2 2 ALL

DJ1 1 ALL

TRACK 2 ALL

CHECK CODE ALL

*

*

*

SELECT ALL

*

*

*

PERFORM ANALYSIS

*

*

*

PARAMETER 2

CODE AISC UNIFIED 2005

MAIN 1 ALL

DFF 800 ALL

DJ2 2 ALL

DJ1 1 ALL

TRACK 2 ALL

CHECK CODE ALL

*

FINISH

I tried to use AISC 2010 but for some unknown reason I got output in imperial units, which I dont want to use, so I switch to 2005.

If you look the output file - deflection controls but the load case is 3 (Strength) instead 5 (Serviceability).

So how to limit deflection check to Serviceability envelope?

sasa3k,

As I wrote, the method I suggested works only for AISC 360-10

I forgot to mention that you need to add the line

LOAD LIST ENV 1 2

before PARAMETER 1 in order for the serviceability and strength checks to be based solely on the load cases contained in the respective envelopes.