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Staad Response spectrum Help need Please

 
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rukmangad.garud
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Joined: 18 Apr 2010
Posts: 3

PostPosted: Sat Mar 26, 2011 4:28 am    Post subject: Staad Response spectrum Help need Please Reply with quote

Hello Friends,
I have a case study example for a G+10 storey TOWER Building modeled in staad V8i, I have to do a response spectrum analysis. I have given parameters and lumped mass for Static EQ loading and need to know whether separate lumped mass is to be given for response spectrum case. Is it necessary to give lumped mass in y direction also for response spectrum load.
I have calculated the lumped mass for each floor by assigning pin supports at floor nodes and analysed for Dead Load + 0.5 Live Load case and assigned the support reactions as lumped in all 3 directions. Is this the correct way or do Staad Pro V8i version have any other way of specifying Lumped mass for response spectrum case, as we can give floor and member loading in case of static IS 1893 method.
I have created separate primary load cases for X and Z direction, do i have to assign lumped mass for each case of response spectrum in  X and Z direction.
can you please elaborate the procedure. thanks
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Yogesh.Pisal
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Joined: 18 May 2008
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PostPosted: Sat Mar 26, 2011 8:47 am    Post subject: Reply with quote

Dear Friend,

You have too many questions in single paragraph. It will be better if you will ask them point wise. I will answer some of them.

1. We need to lump masses separately for Static analysis and Response spectrum analysis.

2. If you want to apply seismic force in vertical direction then you need to lump the mass in vertical direction also. (You can check applicability of vertical seismic force in IS 1893 Part 1)

3. You can either apply joint loads or apply applicable seismic forces / mass in all applicable directions.

4. We need to have different primary load cases for each direction earthquake force.

5. Mass lumping has to be done in first primary load case only.

Regards,
Yogesh Pisal
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rukmangad.garud
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Joined: 18 Apr 2010
Posts: 3

PostPosted: Mon Mar 28, 2011 10:18 am    Post subject: Reply with quote

Dear Mr Pisal Thanks for your cooperation and replying.
My question was
1. Lumped mass is given in the form of Joint weight, member weight, floor weight for IS 1893 Seismic definition for Static analysis.
Lumped mass is given as Joint Load for response spectrum analysis
can the lumped mass be given in the form of member load, floor load for response spectrum as in case of static analysis.
2. Is the ratio of Vb static/ Vb response obtained in the output file need to be changed once the first analysis has been made.

3. the value of damping in IS 1893 definition for static method gets written in input staad file as 0.05 (5%) for concrete, but the same value specified for seismic response spectrum case gets written as 5.0. I dought  wether staad analysis engine recognizes both of them correctly and takes appropriate values as 5%

thanks.
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sukanta.adhikari
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PostPosted: Mon Mar 28, 2011 12:04 pm    Post subject: Reply with quote

Mr Yogesh has given a good reply to ur querry.I will add few more..

Pointwise reply.
1. Lumped mass is given in the form of Joint weight, member weight, floor weight for IS 1893 Seismic definition for Static analysis.
Lumped mass is given as Joint Load for response spectrum analysis
can the lumped mass be given in the form of member load, floor load for response spectrum as in case of static analysis

Yes lumped mass can be given in form of member load,floor load provided the sequence is followed,ie,self weight,Joint load,member load,floor load/plate load etc. for Response spectrum analysis also.

2. Is the ratio of Vb static/ Vb response obtained in the output file need to be changed once the first analysis has been made.

No if both Equivalent static and Response spectrum method is carried out in one file.No need to change any value .Base shear comparision Vb static/Vb response will be done automatically and its value will be adjusted accordingly keeping base shear obtained by Equivalent static method as Lower bound
3. the value of damping in IS 1893 definition for static method gets written in input staad file as 0.05 (5%) for concrete, but the same value specified for seismic response spectrum case gets written as 5.0. I dought  wether staad analysis engine recognizes both of them correctly and takes appropriate values as 5%

You need to enter the value of damping as 0.05 for RCC both in Equivalent static and Response spectrum method.

Regards,
S.Adhikari



rukmangad.garud wrote:
Dear Mr Pisal Thanks for your cooperation and replying.
My question was
1. Lumped mass is given in the form of Joint weight, member weight, floor weight for IS 1893 Seismic definition for Static analysis.
Lumped mass is given as Joint Load for response spectrum analysis
can the lumped mass be given in the form of member load, floor load for response spectrum as in case of static analysis.
2. Is the ratio of Vb static/ Vb response obtained in the output file need to be changed once the first analysis has been made.

3. the value of damping in IS 1893 definition for static method gets written in input staad file as 0.05 (5%) for concrete, but the same value specified for seismic response spectrum case gets written as 5.0. I dought  wether staad analysis engine recognizes both of them correctly and takes appropriate values as 5%

thanks.
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lokeshm
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Joined: 28 Oct 2011
Posts: 10
Location: Davangere, Tumkur

PostPosted: Wed Mar 28, 2012 11:06 am    Post subject: check this Reply with quote

i am tried for floor loading in staad but its not working... so plz help me.. i dont kow properly how to place column..... i am fresher..
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anshugoel
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Joined: 22 Jan 2010
Posts: 341

PostPosted: Wed Mar 28, 2012 2:16 pm    Post subject: Re: check this Reply with quote

lokesh2325 wrote:
i am tried for floor loading in staad but its not working... so plz help me.. i dont kow properly how to place column..... i am fresher..


Please don't take offense, just to lighten up the day, not at your expense though.

Everyone has their share of bad days (Mine is almost every other day).

In a lighter vein, you can never be tried for floor loading in staad.

Or were you tried and then found guilty of providing incorrect loading ?

Or maybe you were just tired of floor loading, was it just the loading that tired you or was it all the work ?

If you were tried, how can you be helped ?

If you "dont kow" properly, then who would know ?

If you kowed properly to place column, then would you be a fresher ?
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