I always go with the equivalent static method, calculate the seismic response coeff. factor and input in AutoPipe as seismic loads in the X/-X & Z/-Z directions. Now I have a project the client wants to do a dynamic response spectrum analysis to confirm the system is ok. We all know the equivalent static method is using more stringent seismic load. I started defining the .SPC file using IBC 2006 method for the same location I initially calculate the equivalent static seismic load, so I have the acceleration vs. period load from the IBC 2006. In the equivalent static method the seismic response coefficient is SDS*Ie/R now I have to define the scale factor for each seismic load Ri, the default value is 1.0, if I go with the default value it will give a higher result than the equivalent static method as it is likely design for the equivalent full SDS, the scale factor I believe needs to be less than 1.0 but how to calculate or estimate is not provided by any AutoPipe example or descriptions in the help file. we need simple examples to show comparison and how to use each method available in the software and ensure that the software is correctly formatted and useful like what STAAD pro team do.
Good day to you Mibrahim,
It appears that you are asking how to factor response spectrum loads in accordance with IBC (ASCE7) specifications. In STAAD users must manually specify the factors outlined in Chapter 12 of the code, as described in the following wiki:
In AutoPIPE, you will define the Response Spectrum load as a 100% and then when you configure the (1) Dynamic analysis Response spectrum, on the (2) Define dialog, one can (3) specify different spectrums for each of the axis directions and also apply a respective (4) scale factor.
Regards,Mike DattilioBentley Product Advantage Group Senior AnalystBentley Systems Inc=============================================================================
AutoPIPE's New Feature:Support Optimizer
Working From Remote Location/ Home with AutoPIPE
Note: Licensing: (PDF file)For all Bentley V8i versions and lower.Bentley SELECTServer will be deprecated
I know all what you are talking about, i defined the REG.spc and don't have problem with it, the problem is in the scale factor, if you put 2 or 2.5 or even 1 you will get the output way bigger compared with ELF method, the scale factor should be less than 1 and if we do response spectrum in 4 cases X/-X Z/-Z we need to define the proper scale factor in each direction. in ELF we design according to Sds *I/R in response spectrum we don't have single value Sds but a set variable with time, in scale factor you still need to consider I/R when you do the analysis in order to get output in the same effect of ELF.
Please note that the values and other settings given in my screen shots above are fictitious and are not intended to be an example for modeling a Static Seismic with matching Dynamic Response Spectrum load. You are correct about AutoPIPE help does not contain any information about how to calculate the "Response Spectrum - Support Groups" X-Y-Z scale factors. The help advises the user to "enter a scale factor by which the corresponding response spectrum will be multiplied. The default is 1.00.". Therefore it is intended for the user to input a value of their choosing.
As you know, this scale factor is applied to the entire spectrum and does not vary with time. It is a constant factor. This factor maybe calculated based on a specified code that takes into consideration multiple sub-subsections and variables or it could be dictated by project documentation, etc...
Suggest the following:
1. Configure the Response Spectrum - Support Group dialog with a defined spectrum file as needed for X-Y-Z axis directions. And, enter a respective scale factor for each axis direction.
2. Manually scale each row of a spectrum SPC file as needed. When using the "Response Spectrum - Support Group" dialog enter a scale factor of 1 because the scale factor had already been applied to each row of the spectrum file.
Regards, Mike Dattilio Bentley Product Advantage Group Senior AnalystBentley Systems Inc=============================================================================