Loading for SAP 2000

[Respawn]

I am running a response spectrum modal analysis for a reinforced concrete parking structure. I defined the mass source to include self weight and additional mass. The self weight multipliers are 1 for dead, 0 for live and MEP, under load patterns. I applied the MEP load and live load to each slab as a two way gravity load. I also defined four load cases from the CBC code. My response spectrum is based on IBC 12 and the ground accelerations are used by zip code. I made sure to include gravity in both U1 and U2 directions (Units are correct). Did I approach my loading correctly?

 

[Agent666]

Check your masses, sounds like you are counting the dead load twice if you have it selected and also have it defined as an additional load case with 1.0 load factor.

Why zero live load and MEP loads? Some proportion in accordance with your code will be present during an earthquake unless you're never fitting out or occupying the structure.

Get someone you're working with to check your model. Very hard to tell from our perspective with just a description (and I don't work to those codes so can't be of much help in judging those aspects).

 

[milkshakelake]

MEP should be part of the dead load, not a separate load. It should be included in seismic weight. I would do a quick hand calculation to make sure the model has the correct seismic weight.

@Agent666 If you include only dead load in the seismic mass in SAP2000, it won't be counted twice. Also, ASCE-7-10 load combinations: you don't need to account for live loads in seismic weight.

12.7.2 Effective Seismic Weight
The effective seismic weight, W, of a structure shall include the dead load, as defined in Section 3.1, above the base and other loads above the base as listed below:
1. In areas used for storage, a minimum of 25 percent of the floor live load shall be included.
EXCEPTIONS:
a. Where the inclusion of storage loads adds no more than 5% to the effective seismic weight at that level, it need not be included in the
effective seismic weight.
b. Floor live load in public garages and open parking structures need not be included.