Robot Structural Analysis

## Robot Structural Analysis

Distinguished Contributor
Posts: 120
Registered: ‎09-17-2012
Message 1 of 24 (780 Views)

780 Views, 23 Replies
10-04-2012 12:02 AM

Dear Sir

-  Which mass type (global mass & dynamic mass ) shall I use it for my model (concrete tower 21 floor )?

Shall I activate the mass in three directions (X,Y,Z) or only (X,Y) Because my building height = 75m ?

Refaat

Valued Mentor
Posts: 606
Registered: ‎09-07-2011
Message 2 of 24 (778 Views)

# Re: Load to mass conversion

10-04-2012 12:09 AM in reply to: refaat

Most accurate is consistent I believe.  But we normally use lumped with rotations.

If you disregard density there will be no mass participating in the modal analysis. Unless you add it back in via load to mass conversion.

I would NOT disregard density, and also add 30% live load (or whatever percentage) to the load to mass conversion.  Normally can ignore Z direction.  If you add mass to global or dynamic the mass will be added to all dynamic cases.  If you specify the modal case only, it will only be added to that case.

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Posts: 3,709
Registered: ‎04-26-2010
Message 3 of 24 (772 Views)

# Re: Load to mass conversion

10-04-2012 12:10 AM in reply to: refaat
Refaat

-  Which mass type (global mass & dynamic mass ) shall I use it for my model (concrete tower 21 floor )?

Rafal Gaweda
Distinguished Contributor
Posts: 120
Registered: ‎09-17-2012
Message 4 of 24 (751 Views)

# Re: Load to mass conversion

10-04-2012 02:28 AM in reply to: Rafal.Gaweda

Dear Sir

I got confused about base shear coeff. ( as i see in the attached capture 01) you got this coeff. (1.74) by dividing (automatic / inactive ). Did you mean that the inactive case is the static linear case ?? (because as we know that the base shear scale is the ratio (0.85Vstatic/Vdyanmic) . as I used it in the capture 02 ,is it true or not ?

Thanks

Refaat

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Posts: 120
Registered: ‎09-17-2012
Message 5 of 24 (749 Views)

# Re: Load to mass conversion

10-04-2012 02:29 AM in reply to: Rafal.Gaweda

Dear Sir

Pls , give me more explanation (  3 Selecting Global mass - converted masses will be applied to all dynamic cases and also can be used in inertia   forces (of course if such forces are applied on model)

In my case , I will use (global mass ) in my model is Keya ?

Thanks

Refaat

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Registered: ‎04-26-2010
Message 6 of 24 (743 Views)

# Re: Load to mass conversion

10-04-2012 03:32 AM in reply to: refaat

Pls , give me more explanation (  3 Selecting Global mass - converted masses will be applied to all dynamic cases

Example:

Rafal Gaweda
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Posts: 3,709
Registered: ‎04-26-2010
Message 7 of 24 (738 Views)

# Re: Load to mass conversion

10-04-2012 03:39 AM in reply to: refaat
Refaat,

I got confused about base shear coeff. ( as i see in the attached capture 01) you got this coeff. (1.74) by dividing (automatic / inactive ). Did you mean that the inactive case is the static linear case ??

Inactive means that results come directly from seismic calculation without base shear.

as I used it in the capture 02 ,is it true or not ?

Yes, true.

One more remark: do not use "Use normalized values" checkbox.

Rafal Gaweda
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Posts: 120
Registered: ‎09-17-2012
Message 8 of 24 (721 Views)

# Re: Load to mass conversion

10-04-2012 04:23 AM in reply to: Rafal.Gaweda

Dear Sir

Do you mean that ( Dynamic = globle + modal ) ? , and i have to use dynamic

Thanks

Rrfaat

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Posts: 120
Registered: ‎09-17-2012
Message 9 of 24 (715 Views)

# Re: Load to mass conversion

10-04-2012 04:35 AM in reply to: Rafal.Gaweda

Dear Sir

As appears in the attached capture

As I understand (T= structure period ) and what  about (reduction coeff.)?

Thanks

Refaat

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Posts: 3,709
Registered: ‎04-26-2010
Message 10 of 24 (712 Views)

# Re: Load to mass conversion

10-04-2012 04:35 AM in reply to: refaat
Do you mean that ( Dynamic = globle + modal ) ? , and i have to use dynamic

Global means that converted masses will be considered in ALL dynamic cases in model (modal and footfall ones; other dynamic cases need to be run after modal case so they consider masses from precedent modal).

Rafal Gaweda

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