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Coefficients in ASCE 41-17
- Thread starter cmrdata
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The equivalent table in ASCE 41-13 had a V term that was defined as "the design shear force calculated using limit-state analysis procedures in accordance with Section 10.4.2.4.1". Section 10.4.2.4.1 says in part:
This is consistent with the definition of VyE that Agent666 found (in the commentary of ASCE 41-17). They can't keep their symbols consistent, but if you look up Vp in Chapter 1 of ASCE 41-17, it gives a pretty good definition:
The other thing I have wondered is what axial load should be applied to the column when determining the plastic moment of the column, which in turn determines the plastic shear. Since you are comparing VyE to VcolOE and VcolOE is calculated based on axial compression only from gravity loads, that is what I use to determine my plastic shear. Below is a snip from 10.4.2.3.1:
This is consistent with the definition of VyE that Agent666 found (in the commentary of ASCE 41-17). They can't keep their symbols consistent, but if you look up Vp in Chapter 1 of ASCE 41-17, it gives a pretty good definition:
The other thing I have wondered is what axial load should be applied to the column when determining the plastic moment of the column, which in turn determines the plastic shear. Since you are comparing VyE to VcolOE and VcolOE is calculated based on axial compression only from gravity loads, that is what I use to determine my plastic shear. Below is a snip from 10.4.2.3.1:
- Thread starter
- #4
Thank you, Agent666 and Chris3eb, for your input.
Chris3eb, regarding the application of NUG when determining the plastic moment of the column, what you described is also what I did. In theory, a different PMM curve should be developed for the top and bottom of the column to obtain the necessary plastic moment for each load combination. This is illustrated in the design example in
“SEAOC Design Guide, vol. 1”,
That said, both of you might already have had a lot experiences in dealing with ASCE 41, and I would like to solicit your general opinion if I may:
I just came off a project using ASCE 41-17 Linear Static Procedure to evaluate a multi-story concrete building in Washington state that was built in the ‘50s. Currently there is no widely available commercial software that would do such evaluation systematically (calculating “m” values for each components, checking D/C ratio, etc.), so tremendous efforts were devoted to a more “manual” operations with numerous spreadsheets. Of course, CSI’s Perform-3D would do this more “automatically”, but it is geared for nonlinear analysis only, which is a whole new ball game.
After jumping through all these hoops, I become more appreciative of what commented in this article:
It was first published in 2008, before 31 and 41 were merged, however, I think their concepts and arguments are still valid. I therefore have to wonder if ASCE 41 is really any better than using the 75% approach, as prescribed in section 303.3.2 of IEBC, which allows us to proceed in accordance with ASCE 7. I understand the concern on the issue that “simply reducing the ground motion demand by a factor of 0.75 does not result in a spatially uniform hazard”, as noted in ASCE 41 Commentary, but we can tweak the hazard level to obtain a more appropriate ground motion demand based on the specific site.
Any thoughts? Thumbs up or thumbs down for 41? Thanks.
Chris3eb, regarding the application of NUG when determining the plastic moment of the column, what you described is also what I did. In theory, a different PMM curve should be developed for the top and bottom of the column to obtain the necessary plastic moment for each load combination. This is illustrated in the design example in
“SEAOC Design Guide, vol. 1”,
That said, both of you might already have had a lot experiences in dealing with ASCE 41, and I would like to solicit your general opinion if I may:
I just came off a project using ASCE 41-17 Linear Static Procedure to evaluate a multi-story concrete building in Washington state that was built in the ‘50s. Currently there is no widely available commercial software that would do such evaluation systematically (calculating “m” values for each components, checking D/C ratio, etc.), so tremendous efforts were devoted to a more “manual” operations with numerous spreadsheets. Of course, CSI’s Perform-3D would do this more “automatically”, but it is geared for nonlinear analysis only, which is a whole new ball game.
After jumping through all these hoops, I become more appreciative of what commented in this article:
It was first published in 2008, before 31 and 41 were merged, however, I think their concepts and arguments are still valid. I therefore have to wonder if ASCE 41 is really any better than using the 75% approach, as prescribed in section 303.3.2 of IEBC, which allows us to proceed in accordance with ASCE 7. I understand the concern on the issue that “simply reducing the ground motion demand by a factor of 0.75 does not result in a spatially uniform hazard”, as noted in ASCE 41 Commentary, but we can tweak the hazard level to obtain a more appropriate ground motion demand based on the specific site.
Any thoughts? Thumbs up or thumbs down for 41? Thanks.
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