seismic weight and base shear output in SAP?

[drokapil041]

Dear all,

please someone tell how the seismic weight of structure and base shear can be shown. For it, i summed up the support reactions for 1.5(DL+LL) load combination and divide it by 1.5. This total reaction is near to the manual seismic weight calculation. but the base shear (which i presumed as in structure output for EQX or EQY load case) is almost half the manually calculated base shear.
how does sap calculates seismic weight for each diaphragm level and way to display it.

regards

 

[unodinoi]

It depends on your mass source combination (Define > Mass Source). You can make a new load combination with those coefficients, for example like 1.0(DL)+0.5(LL) - depends on the factors you've used for the masses, usually the live load is taken with a factor less than 1. Then you can easily view the base reactions from Display > Show Tables, where you need to mark the earthquake load combination from Output Cases and then mark Structure Output > Base Reactions.

If you want to see the story shears, you have to make section cuts, which can be done by marking joints and elements and adding them to a group (Assign > Assign to Group), Define > Section Cuts and selecting the groups and then displaying the results from Display > Show Tables > Structure Output > Other Output Items > Section Cut Forces.

 

[drokapil041]

Thanks unodinoi for your response and answer.

please do clear my next confusion. i have assign the beam with dimension of 300mm x 300mm and the slab with 110m. i also assign beam with top center in cardinal insertion point. my confusion is does it mean the t beam is now of depth equal to 300 + 110/2 = 355 mm.

regards

 

[unodinoi]

Not exactly. It means that you have a 110/2=55 mm overlapped space consisting of half of your slab and the upper part of your beam. It is no problem because such programs calculate the stiffness matrix for nodes and just sum up the slab and beam stiffness in coinciding nodes. Basically it won't affect the global response of your building in a significant way but some differences might be present on a lower scale if you are focused on the T-beam response.