I'm working on a STAAD model having several load cases and combinations, some of which include seismic loads. Project specifications allow a 1/3 increase in allowables for seismic loads. I'd like to set my model up so the Utilization Ratio table in the STAAD report shows the correct Allowable Ratio based on load combination. Is this possible? So far I've been unable to make it happen.
I've tried using the LOAD LIST command in the following manner:
...
LOAD LIST <combo #1 without seismic>
PARAMETER
RATIO 1.0 ALL
LOAD LIST <combo #2 with seismic>
RATIO 1.33 ALL
CHECK CODE ALL
But, this doesn't seem to work. The Utilization Ratio table shows the controlling load combo, #1 or #2, but the Allowable Ratio is shown as 1.33 for all members. Is there a way to make the table show 1.0 allowable for members where combo #1 controls? I'd like the report to indicate that the 1/3 increase is only being applied to the appropriate cases/combos. Thanks for any input.
You need to use the design command in the following manner:
PARAMETER 1
-----------------
---------------
PARAMETER 2
You need to refer the output file for the design result. The design results obtained from the post-processing mode would be for the last CHECK CODE command which is for the PARAMETER 2 used in the design
Answer Verified By: shaymore
My hope was to get all of the analysis results to print out in the STAAD Report (nice formatting, good for presenting to customer). It appears that the Report is behaving the same as the Post-Processing mode GUI by only showing the results from the most recent CHECK CODE.
So, my follow-up question: Is there a way to change the Report so it shows the multiple code-check output tables, or better yet a consolidated table? (If not, the Report becomes useless when checking code more than once.)
If you have multiple CHECK CODE command in different Parameter list, you post-processing mode would display the results of last CHECK CODE command. in your case, you have to look into the STAAD Output file to get the results for all the CHECK CODE command. Unfortunately, the post-processing mode is not able to display all the result. If you are interested to get the result from post-processing mode ( results in tabulated form as you mentioned), you can save the model a different name. In one file use RATIO 1.33 command and in the other file use RATIO 1.0 in the parameter list. The post-processing mode of the two files would display your required result.
Mr. Sanju,
In lieu 0f increasing the ratio to 1.33, it would be better in my view to multiply all the loads of the cmbination containing the seismic load with a factor 3/4. It may serve the purpose. Please comment.
Answer Verified By: Unknown
The code is suggesting to increase the allowable stresses induced for the seismic load combination by 33%. If we increase the factor of safety imposed on the load combination and use them in steel design, we would eventually design with higher loads. The stresses induced in the members for this load combination would be higher. But, by doing this we are not increasing the allowable stresses in the members. Our objective should be to increase the allowable stress in the member. By default, the ratio computed from the stresses induced from axial load and bi-axial bending to the allowable one for the same should be less than or equal to 1. This ratio has to be increased by 33%. This can be achieved in STAAD.Pro by using RATIO 1.33 parameter.