mass source

susan · Post by **susan** » Fri Jun 27, 2008 5:16 am

Hello

How can we define mass source from loads? (e.g. DEAD+0.02LIVE)
Should we use load command or mass command?

Thanks.

silvia · Post by **silvia** » Fri Jun 27, 2008 6:37 am

both.
mass if for inertial mass. load is for gravity weight.

esi_opensees · Post by **esi_opensees** » Sun Jun 29, 2008 3:28 am

Hi
I have the same question.For define mass source from loads that susan said, we should use dead weight of elements (p*A*L) for "mass" command and use external loads (DEAD+20%LIVE) for "load" command.
Is it true??

im_pce · Post by **im_pce** » Sun Jun 29, 2008 3:42 am

I think we should use mass command for dead weight of elements (p*A*L)+DEAD+20%LIVE; and
we use load command for DEAD+100%LIVE.

Dear silvia, which opinion is correct? me or esi_opensees?

tnx

silvia · Post by **silvia** » Sun Jun 29, 2008 7:08 am

no, you have to define both mass and load -- mass only if you need intertial loads, such as dynamic analysis

imancivil · Post by **imancivil** » Mon Jun 30, 2008 2:41 am

Dear Dr.silvia

I'm sorry, I do not understand which reply is true. esi_opensees or im_pce ?

silvia · Post by **silvia** » Mon Jun 30, 2008 7:49 am

neither, i guess.
a mass has two effects: weight, due to gravity forces, and inertial mass in dynamics, due to inertial.
you decided which and how you model them, i guess.

basir · Post by **basir** » Wed Apr 22, 2009 10:34 am

i have the same question
i have a model and i want to perform below analysis
1- nonlinear dynamic time history analysis
2- adaptive pushover analisys
3- modal analysis
i want to calculate modal shape and frequency for load pattern of pushover analysis
and i have to assign gravity load on beams
now i dont know how should i define mass
do i have to assign mass( wich is calculated from dead loads) on nodes and assign distibuted gravity deal and live loads on beam?
i think the wieght we assign on beams will be change in mass too ,to calculate lumpd mass
please help

silvia · Post by **silvia** » Fri Apr 24, 2009 9:12 am

they are handled independently.

basir · Post by **basir** » Sat Apr 25, 2009 4:53 am

thanks for reply
i think i should assign mass only in horizental direction that we apply ground motion excitation in the transient analysis not in the same direction as gravity loads
am i right?
and also does this method ( i mean assigning mass only in horizental direction ) affect the eignvalues ?
thanks again dr silivia

jndlsmt · Post by **jndlsmt** » Wed Dec 08, 2010 8:49 pm

can anybody ans for my question????
i am modeling a single shear wall supported by shallow foundation
i have a 3 nodes of structure , 1 is attached to the centre of foundation, 2nd is the node where i applied a lateral load, and 3rd is the last n ode of wall is equal to the height of wall
tell me for gravity analysis??
how to define a mass for the structure at nodes, total mass is assume something ( is we define the half half load on 2 and 3rd node??)
tell me for lateral cyclic loading???
how to define a loads

vesna · Post by **vesna** » Thu Dec 09, 2010 9:53 am

please look at the example manual:
http://opensees.berkeley.edu/wiki/index ... les_Manual

You will find the answer to your question there.

The OpenSees Community

mass source

mass source

assign mass and load

mass source