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mc_joah
Posts: 1
Registered: ‎09-11-2012

Direction of seismic excitation

556 Views, 4 Replies
09-11-2012 04:12 AM

Hi,

 

According to EN 1998-1:2004 4.3.3.1 (11), the seismic excitation must be applied to all relevant directions.

For some structures there might be more than 2 relevant directions, and these directions may deviate from the directions of the global X- and Y-direction in the Robot model.

 

In my understanding of Robot, this should be possible when using the button "direction definition" in the "EN 1998 Parameters" dialog box.

I have tried this to a simple model, but it does not seem to work properly.

 

Have anyone tried something similar, with good results?

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Romanich
Posts: 563
Registered: ‎09-29-2009

Re: Direction of seismic excitation

09-11-2012 05:15 AM in reply to: mc_joah

Hi,

you must use Quadratic or Newmark combinations:

seis.png

 

Also, you can read p.15.8 from Mr. Wilson book

   
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Active Contributor
MARIOS75
Posts: 26
Registered: ‎01-04-2010

Re: Direction of seismic excitation

09-11-2012 10:15 AM in reply to: mc_joah

Keep in mind that unlike Newmark combination rule, SRSS rule is not direction dependant.

Rotating the building + newmark rule i guess will do the job.

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Valued Contributor
mark.martin.se
Posts: 69
Registered: ‎05-19-2011

Re: Direction of seismic excitation

10-05-2012 04:13 AM in reply to: MARIOS75

Hi,....

 

 

....just to clarify,.... According to EC8 all the structure's members should "resist" 100% of the prescribed seismic forces in one direction plus 30%  of the prescribed forces in the perpendicular direction!


i.e.:

1Edx"+"0,3Edy

0,3Edx"+1Edy

when Z direction is disregarded.


So, what I need to check in the "Direction definition" is......

 

 

 

Am I wrong?

 

Regards

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Valued Mentor
tony.ridley
Posts: 652
Registered: ‎09-07-2011

Re: Direction of seismic excitation

10-07-2012 11:06 PM in reply to: mark.martin.se

You seem to have set it up correctly. 

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