topic Re: SEISMIC ISOLATED BUILDING in Robot Structural Analysis Forum

SEISMIC ISOLATED BUILDING

StefanoPasquini6790 — Fri, 23 Feb 2018 11:18:28 GMT

Good morning at all,

I'm designing a seismically isolated building with the seismic devices placed in the top of the column of the ground floor. Well, the model it works perfectly, I made all the manual checks to validate it.

My question is: the storeys that are placed over the base isolation devices have a displacement of about 300 mm, how can I keep in count the effect of this displacement as load eccentricity in the top of the rc column?

Thank in advance!

Re: SEISMIC ISOLATED BUILDING

StefanoPasquini6790 — Fri, 23 Feb 2018 13:22:33 GMT

Hi again,

to be more clear in this topic, here attached two pics of a little part of the model, where it can be understood the geometry of the problem.

Detail of the modelDisplacement in seismic condition

Re: SEISMIC ISOLATED BUILDING

Romanich — Fri, 23 Feb 2018 15:50:42 GMT

Ciao Stefano,

The first solution is to shift the RC column in the direction of the biggest displacement and connect the device and column using a rigid link.

Re: SEISMIC ISOLATED BUILDING

t.sautierr — Tue, 07 Aug 2018 08:31:50 GMT

Second,third, fourth solution (but more time consuming) :
Second : second order analysis with peudo static forces of your seismic cases
Third : use the deformed shape update macro on your model and redo a calculation for statics vertical forces
Fourth : retrieve displacement and effort on the column and apply a moment or an excentric nodal force (keep in mind to equilibrate it at the bottom to have only moment effect) to each column in a new load case via api.

Re: SEISMIC ISOLATED BUILDING

StefanoPasquini6790 — Tue, 07 Aug 2018 08:45:15 GMT

Hi everybody, and thank you for your effort.

I soved in a "SAFE WAY" adding a concentrated moment in the top of the rc column that have the magnitude equal to the maximum displacement in the considered direction * SLS QPR vertical force value.... I've done for the four seismic condition and added in combination....

Excellent result!

Thank you

Re: SEISMIC ISOLATED BUILDING

Artur.Kosakowski — Tue, 07 Aug 2018 08:53:43 GMT

Hi @StefanoPasquini6790

Thank you for sharing the solution with others.