Hello
i would like to ask if have point load (e.g 10 kn) in direction z and x how I can put its mass in Mass elements as lumped mass for Eigenvalue analysis
for 10 in direction z should I put in lumped mass Mz=1.019 only
for 10 in direction x should I put in lumped mass Mx=1.019 only
Thank you and regards,
reem
How assign lumped mass
Re: How assign lumped mass
Hi,
You don't need to define two different lmass elements, you can use just one in which you assign 1.019 in Mx and Mz directions and 0 in the others. Anyway, for details refer to the Help System of the program.
Regards
Federica Bianchi
You don't need to define two different lmass elements, you can use just one in which you assign 1.019 in Mx and Mz directions and 0 in the others. Anyway, for details refer to the Help System of the program.
Regards
Federica Bianchi
Re: How assign lumped mass
Dear reem,
inertia masses should be defined in the degree-of-freedom you are interested in. If you wish to obtain vibration modes/periods in the horizontal ‘x’ direction, then you have to define the mass in that very same horizontal 'x' direction, rather than in the vertical ‘z’ direction.
For further information you may refer to the Help System (and the structural dynamics textbooks cited in there).
fbianchi
inertia masses should be defined in the degree-of-freedom you are interested in. If you wish to obtain vibration modes/periods in the horizontal ‘x’ direction, then you have to define the mass in that very same horizontal 'x' direction, rather than in the vertical ‘z’ direction.
For further information you may refer to the Help System (and the structural dynamics textbooks cited in there).
fbianchi
Re: How assign lumped mass
quote:Originally posted by reem
Hello
if have point load (e.g 10 kn) in direction x what h should put in Mx , My,Mz , Mxx, Myy , Mzz to have period in x,y,z direction
Thank you and regards,
reem
Dear Reem,
Your questions are not really related to the use of SeismoStruct, but rather to a general understanding of Structural Dynamics. I thus strongly suggest you to read the many textbooks on that topic available in the literature.
Federica Bianchi
Hello
if have point load (e.g 10 kn) in direction x what h should put in Mx , My,Mz , Mxx, Myy , Mzz to have period in x,y,z direction
Thank you and regards,
reem
Dear Reem,
Your questions are not really related to the use of SeismoStruct, but rather to a general understanding of Structural Dynamics. I thus strongly suggest you to read the many textbooks on that topic available in the literature.
Federica Bianchi
-
fakharifar.mostafa
- Posts: 124
- Joined: 06 Jan 2010, 05:34
Re: How assign lumped mass
quote:Originally posted by fbianchi
Dear reem,
inertia masses should be defined in the degree-of-freedom you are interested in. If you wish to obtain vibration modes/periods in the horizontal ‘x’ direction, then you have to define the mass in that very same horizontal 'x' direction, rather than in the vertical ‘z’ direction.
For further information you may refer to the Help System (and the structural dynamics textbooks cited in there).
fbianchi
Hi,
Since the subject about direction for the lumped mass has been brought up in this comment, it arouse a question for me regarding typical cantilevered column tests with a concrete block as lumped mass on top.
I was reading and examining the two shake table column tests in the verification report (i.e. EXAMPLE 2 – Scaled bridge pier AND EXAMPLE 1 – Full-scale bridge column).
These two test are subjected a unidirectional excitation at base. Then:
1- While for the scaled bridge pier the mass element includes only Mx and Myy? (It is absolutely right, since the transnational mass inertia is in X axis and the rotational mass inertia is about Y axis.)
2- Why for the full scale bridge pier which was a blind prediction test, the lumped mass has the 3 components of Mx, My and Mz in addition to Myy (i.e. Mxx=Mzz=0).
Am I missing some of the assumptions of the test model? Though, I noticed that the top of the full scale bridge pier does have no restraint in the model, implying that My and Mz could contribute. Then how about Mxx and Mzz?
Could you please make a little bit more clarifications?
Dear reem,
inertia masses should be defined in the degree-of-freedom you are interested in. If you wish to obtain vibration modes/periods in the horizontal ‘x’ direction, then you have to define the mass in that very same horizontal 'x' direction, rather than in the vertical ‘z’ direction.
For further information you may refer to the Help System (and the structural dynamics textbooks cited in there).
fbianchi
Hi,
Since the subject about direction for the lumped mass has been brought up in this comment, it arouse a question for me regarding typical cantilevered column tests with a concrete block as lumped mass on top.
I was reading and examining the two shake table column tests in the verification report (i.e. EXAMPLE 2 – Scaled bridge pier AND EXAMPLE 1 – Full-scale bridge column).
These two test are subjected a unidirectional excitation at base. Then:
1- While for the scaled bridge pier the mass element includes only Mx and Myy? (It is absolutely right, since the transnational mass inertia is in X axis and the rotational mass inertia is about Y axis.)
2- Why for the full scale bridge pier which was a blind prediction test, the lumped mass has the 3 components of Mx, My and Mz in addition to Myy (i.e. Mxx=Mzz=0).
Am I missing some of the assumptions of the test model? Though, I noticed that the top of the full scale bridge pier does have no restraint in the model, implying that My and Mz could contribute. Then how about Mxx and Mzz?
Could you please make a little bit more clarifications?
-
seismosoft
- Posts: 1316
- Joined: 06 Jul 2007, 04:55
Re: How assign lumped mass
Dear fakharifar.mostafa,
No, no particular reason for such differences in modelling assumptions. Just remove My and see if it makes any difference in the results. Then do the same for Mz, and withdraw any relevant conclusions.
In future releases, we may certainly eliminate such apparent modelling assumptions inconsistencies, given that they seem to be giving rise to issues such as the ones you note.
Seismosoft Support
No, no particular reason for such differences in modelling assumptions. Just remove My and see if it makes any difference in the results. Then do the same for Mz, and withdraw any relevant conclusions.
In future releases, we may certainly eliminate such apparent modelling assumptions inconsistencies, given that they seem to be giving rise to issues such as the ones you note.
Seismosoft Support