Problem with DFF command not check in steel design with STAAD Pro SS6 built 20071150 (Latest built)

What different of command?.
LOAD LIST 101 TO 107 and LOAD LIST ENVELOPE 1
which Envelope 1 include load no. 101 to 107 ?
I remember that I ever use this command in SS4 without define any envelope.
STAAD can check code and check the deflection.

Does it's mean in the SS6 we must define and evelope for check deflection limit

and for steel design code check we must define envelope or not for the correct result ?.

With most of my code only use LOAD LIST ... TO ... command.

Regard.

I have attached a modified file with SERVICE and STRENGTH envelopes which has subsequently been used to do a CODE CHECK.

Here are some points which should be noted.

1. For both service and strength and checks to be carried out, you have to have 2 separate envelopes. In the attached model, you will find 2 separate envelopes namely service ( cases 101 to 107 ) and strength ( cases 201 to 207 ).

2. The LOAD LIST ENV 1 2 has been used just before the design so that the design accounts for both envelopes during design.

3. DFF has to be specified as part of the design parameters if deflection check is to be carried out. This is in addition to defining the service envelope. Since you specified DFF for members 3 10 and 13, the deflection check will be carried out for these members only. If you need to check other members for deflection, specify DFF for those too.

4. Since you need the same combos to be checked for service and strength (ASD), you need to add the combos 201 to 207 which are basically same load combos as 101 to 107 but still needed as STAAD.Pro cannot consider same load combos for both service and strength envelopes.

I hope this helps.

2330.Structure1_rev.std

Hi all,
Im using SS6 20.07.11.70 version. I used DFF and service envelope in my design. But still it is not performing deflection check.

I have clearly defined service envelope then why STAAD showing the below warning.

**WARNING- Deflection check of member # 4 will not be performed as service envelope not provided.

Here is the code.

STAAD SPACE
START JOB INFORMATION
ENGINEER DATE 07-Apr-16
END JOB INFORMATION
INPUT WIDTH 79
UNIT METER KN
JOINT COORDINATES
1 0 0 0; 2 5 0 0; 3 0 3 0; 4 5 3 0; 5 0 0 3; 6 5 0 3; 7 0 3 3; 8 5 3 3;
MEMBER INCIDENCES
1 1 3; 2 2 4; 3 3 4; 4 3 7; 5 4 8; 6 5 7; 7 6 8; 8 7 8;
DEFINE MATERIAL START
ISOTROPIC STEEL
E 2.05e+008
POISSON 0.3
DENSITY 76.8195
ALPHA 1.2e-005
DAMP 0.03
TYPE STEEL
STRENGTH FY 253200 FU 407800 RY 1.5 RT 1.2
END DEFINE MATERIAL
MEMBER PROPERTY EUROPEAN
1 TO 8 TABLE ST IPE500
CONSTANTS
MATERIAL STEEL ALL
*
SUPPORTS
1 2 5 6 PINNED
*
LOAD 1 LOADTYPE Dead TITLE LOAD CASE 1
SELFWEIGHT Y -1
LOAD 2 LOADTYPE Live TITLE LOAD CASE 2
MEMBER LOAD
3 TO 5 8 CON GY -50
LOAD COMB 3 GENERATED AISC GENERAL 1
1 1.0
LOAD COMB 4 GENERATED AISC GENERAL 2
1 1.0 2 1.0
LOAD COMB 5 GENERATED AISC GENERAL 3
1 1.0 2 0.75
LOAD COMB 6 GENERATED AISC GENERAL 4
1 0.6
PERFORM ANALYSIS
*
DEFINE ENVELOPE
1 3 TO 6 ENVELOPE 1 TYPE SERVICEABILITY
1 3 TO 6 ENVELOPE 2 TYPE STRESS
END DEFINE ENVELOPE
*
LOAD LIST ENV 1 2
*
PARAMETER 1
CODE AISC UNIFIED 2005
DFF 500 MEMB 3 TO 5 8
FYLD 248213 MEMB 3 TO 5 8
FU 413688 MEMB 3 TO 5 8
CHECK CODE MEMB 3 TO 5 8
FINISH

You have created Service and Strength envelop with the same load case / combination. Please refer to the attached model.

2465.a1.std

The load cases that are assigned to the serviceability load envelope happen to be the same as the ones that are assigned to the strength envelope. Thus, both envelopes have the same set of load cases. The AISC 360 design module in STAAD is current not set up to handle this situation currently. In other words, the load cases in those two envelopes need to be distinct and have no commonality. This limitation is expected to be removed in a future version.

So, here is what you can do presently. For each of the cases 1 and 3 to 6, create load combinations that are simply 1.0 times the respectives cases (Load combination 11 = 1 * LC1, Load combination 13 = 1 + LC3 and so on). Then, assign those combination cases to one of those envelopes.

The load cases that are assigned to the serviceability load envelope happen to be the same as the ones that are assigned to the strength envelope. Thus, both envelopes have the same set of load cases. The AISC 360 design module in STAAD is current not set up to handle this situation currently. In other words, the load cases in those two envelopes need to be distinct and have no commonality. This limitation is expected to be removed in a future version.

So, here is what you can do presently. For each of the cases 1 and 3 to 6, create load combinations that are simply 1.0 times the respectives cases (Load combination 11 = 1 * LC1, Load combination 13 = 1 + LC3 and so on). Then, assign those combination cases to one of those envelopes.

I can answer the part on why the limitation has been set - In general the codes have distinct load combinations for Serviceability and Strength Limit States - this is true for all the codes I can think of - Indian, Eurocode or BS. Refer to clause 2.5 of BS 5950-1:2000 for an example.

For the part of the said inappropriate message, we will advise the developers to put in a more reasonable one.

You can try the following:

DEFINE ENVELOPE

1 3 TO 6 ENVELOPE 1 TYPE STRESS
1 3 TO 6 ENVELOPE 2 TYPE SERVICEABILITY
END DEFINE ENVELOPE
*
LOAD LIST ENV 1 2
*
PARAMETER 1
CODE AISC UNIFIED 2010
DFF 500 MEMB 3 TO 5 8
FYLD 248213 MEMB 3 TO 5 8
FU 413688 MEMB 3 TO 5 8
TRACK 2 ALL
CHECK CODE MEMB 3 TO 5 8

a1t.zip