Civil Engineering Association

Here's another tip to newbie ETABS user; always make a rough estimate of your seismic weight and compare this to what ETABS is giving you. :idea:

Mass source :

Full dead load

some percentage of live load as per code.

(02-05-2009, 01:20 PM)aslam Wrote: [ -> ]Mass source :

Full dead load

some percentage of live load as per code.

hi aslam, try to make an estimate of your seismic weight outside of ETABS' results for you to get a good feel on what ETABS had outputted.

ETABS newbies: check your definition of seismic mass source; it may be doubling your self-weight. :D

My Opinion :

Separated your DEAD LOAD become Self Weight Dead Load and Super Imposed Dead Load.

The Dead Load for mass source is Super Imposed Dead Load (exclude Self Weight Dead Load).

I think double value of self weight because you do not separate the DEAD LOAD for calculate the mass source.

Please correct me if I wrong..

Regards,
robertsasmita

Look at http://www.youtube.com/watch?v=JRvoU-35SL8

yes..
any other opinion from other member ?

regards,
robertsasmita

Yups... that's right any additional dead load besides the selfweight needs to be separated to prevent double calculating of selfweight in mass source. Additional dead load which known as superimposed load should be added when third option of mass source is used with load factor 1 and life load should be added with load factor according to the spesific code (Usually 0.3).

CMIIW,
regards

I usually use the second option (from loads). All the coeficients are those given in the seismic codes (1 for dead loads and permanent loads and 0.4/0.3 for live loads). The third option can also be used (in this case only the dead load is 0, the rest of the loads have the same coeficients).