I am fairly new to SAP and am trying to do a seismic analysis on a three-story building with a braced frame seismic force resisting system using a response spectrum analysis. I can run the response spectrum analysis, but once I have I cannot figure out how to get story shear out of the model.
When I have SAP output the "Base Shear" I get 211kips in the y-direction.
When I then have SAP output the "Element Joint Forces-Frames" and then sum up the values for all of the points at the base (so the bottoms of the first-floor columns and the x-braces) I get 241 kips in the y-direction.
When I then have SAP output the "Element Joint Forces-Frames" for all frames and sum of the values for all of the points at each floor wherever there is a column (so from every element framing into a column at the floor), I get a total of 79kips at the roof, 267 kips at the 3rd floor, and 427kips at the 2nd floor.
I believe that the base shear should equal the output at the second floor, which is the sum of all of the story shears (so the second story shear is 427-267=160kips, the third-story shear is 267-79=188kips, and the roof shear is just 79 kips). However, clearly this is not matching up. It is also confusing to me that the "base shear" output directly by SAP and the base shear I compute from "Element Joint Forces-Frames" do not line up. I know that the story shear is contained within SAP somewhere, but I can't figure out how to get SAP to tell it to me!
Can anyone tell me how to output story shear from a modal analysis? Thank you!
As a side note, the reason I need the story shear is to compute accidental torsion. If anyone knows a better way to apply accidental torsion to a building using modal/response spectrum analysis that would be helpful, too!
When I have SAP output the "Base Shear" I get 211kips in the y-direction.
When I then have SAP output the "Element Joint Forces-Frames" and then sum up the values for all of the points at the base (so the bottoms of the first-floor columns and the x-braces) I get 241 kips in the y-direction.
When I then have SAP output the "Element Joint Forces-Frames" for all frames and sum of the values for all of the points at each floor wherever there is a column (so from every element framing into a column at the floor), I get a total of 79kips at the roof, 267 kips at the 3rd floor, and 427kips at the 2nd floor.
I believe that the base shear should equal the output at the second floor, which is the sum of all of the story shears (so the second story shear is 427-267=160kips, the third-story shear is 267-79=188kips, and the roof shear is just 79 kips). However, clearly this is not matching up. It is also confusing to me that the "base shear" output directly by SAP and the base shear I compute from "Element Joint Forces-Frames" do not line up. I know that the story shear is contained within SAP somewhere, but I can't figure out how to get SAP to tell it to me!
Can anyone tell me how to output story shear from a modal analysis? Thank you!
As a side note, the reason I need the story shear is to compute accidental torsion. If anyone knows a better way to apply accidental torsion to a building using modal/response spectrum analysis that would be helpful, too!
