Hi
I have assigned some load combinations(101 to 114) as serviceability load cases , and some (201 to 236) as strength load cases in load envelopes.
after that I have mentioned LOAD LIST ENVELOPE 1 2 before parameter 1. so now staad should perform serviceability checks for load combination 101 to 114 and strength checks for 201 to 236.
But when I am going to post processing > unity checks , it is showing deflection check is critical for load cases 201 to 236 .
please have a look at staad file and suggest corrections
.M703-IA-P0.std
Please refer to the attached modified model. Please note that Envelop 1 is created for serviceability check and envelop 2 is created for strength check.. Just before PARAMETER 1, LOAD LIST ENVELOPE 1 is used and after the parameter lists CHECK code command is used like DFF etc. It will tell the program to go for deflection checking and the output contains deflection checking results. Similarly, before PARAMETER 2, LOAD LIST ENVELOPE 2 is used and it tells the program to go for strength checking.
0602.M703-IA-P0.std
Hi DSANJU
I have reviewed staad model modified by you.
If we do like this then in post processing >unity check staad shows results only for parameter mentioned later i.e. parameter 2 (strength check).
but if we mention parameter 1 later (deflection check)as in the case of model attached with this comment by me, than in post processing >unity check staad shows results only for deflection checks.
That means staad is taking parameter which is mentioned later as critical , whereas what staad should have done is, checked utilisation ratios for both parameters and than should have mentioned ratio which is critical out of this two in
post processing >unity check.
please review model sent by me.
this problem is there in staad since many year , please have a look at the conversation with Sye and Kris Sathia in below link
communities.bentley.com/.../92737
communities.bentley.com/.../85977
4760.0602.M703-IA-P0.std
The deflection check which is a serviceability limit state is done for the un-factored load combination and the strength check for the factored load combination. To do this, you need to define a new load combination without factoring the primary load cases for the deflection check (serviceability check). The alternate way to get the design result and deflection check (un-factored load) check is by creating two load combinations. All you need to do is to use the LOAD LIST command in two different parameters. One for Design with factored load combination and another with un-factored load combination for the deflection check . For example The load case A to load case B are Primary cases. And the Load combinations are as follow. Load Combination C = 1.5 ( L/C A + L/C B)....(Factored), Load Combination D = (L/C A + L/C B) ............(Unfactored) LOAD LIST C PARAMETER 1 CODE AISC BEAM 1 ALL Factored RATIO 1 ALL TRACK 1 ALL CHECK CODE ALL
LOAD LIST D
PARAMETER 2
DFF 200 MEMB x y z..... Unfactored DJ1 4 MEMB x y z..... DJ2 5 MEMB x y z..... CHECK CODE ALL Although in the post-processing mode, you can see the utilization ratio of only the last PARAMETER block, but in the output file, you can see the unity ratios of both the individual parameters.
I ran the model M703-IA-P0.std that you attached when you initiated the discussion on this thread on Monday, Sept 14, 2015.
We agree that for those members for which deflection governs, like 7, 9, 10, 11, 14, etc., an incorrect value is listed for the L/C number in the table that appears on the right side of the screen in the Beam-Forces page of the post-processing mode. Fortunately, this appears to be just a reporting error. You can find the correct value of the L/C for those members by viewing the steel design output in the ANL file. See the screenshot below that shows the result for member 7.
We will get this corrected ASAP.
Hi Kris Sathia one more issue when I am not assigning any load envelopes .
all members are safe (all passed).
but when for same staad file if I assign load envelopes than some members are failing and that too in strength checks , if they would have been failing in deflection check , I can understand , because staad SS6 doesn't performs deflection checks automatically , unless serviceability envelope is defined. but strength check is performed by default , so I think this issue should not be there .
please have a look at attached staad file . in this STAAD file I have defined load envelopes .after running this file you can see some members are failing in strength checks. but when you remove load envelopes these members are not failing. please check by removing load envelopes for same attached staad file.
M703-IA-P1.std
Regarding your most recent post (Tuesday, Sept 15, 7:19 PM)
You wrote:
one more issue when I am not assigning any load envelopes .
when you remove load envelopes these members are not failing. please check by removing load envelopes for same attached staad file.
Our response:
The results I get don't match yours. What I find is that, when both the LOAD LIST ENV commands are removed, several members are failing - 101, 114, 115, 116, 119, 120, 126, etc.. Strength cases govern in all these failures.
The results of the second code check of the model with the load envelopes removed are identical to those for the second code check in the model containing those load envelopes from your aforementioned posting.