Etabs model checking
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Author: rendel_©
Last Post: concreteok
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Etabs model checking
#1
I just want to share how I check my model in etabs and correct me if I'm wrong or advice the proper way:

1.)Gravity

make a safe model for slab which is the thickness
= no. of storey x slab thicknness in etabs model

Apply the area load
=no. of storey x average area load apllied in etabs
(THE CONCEPT OF THIS IS I COMBINED ALL THE SLAB AND MODEL IT IN SAFE AS 0NE SLAB)

Reaction in etabs should almost equal to the reaction of safe.

Or, roughly compute the reaction at base manually(by tributary area method) then compare to etabs reaction result




2.) Wind

Go in show deformed shape then choose the Wx and Wy(one at a time) then click the top corner of the building then right click to see the point displacement. This value should less than to the allowable lateral deflection, in ubc H/500, H is the total height of the building.


3.) Earthquake

Actual drift should be less than to allowable drift

allowable drift= 0.7 x R x 0.020 x story height
(with the period of less 0.7second)

= 0.7 x R x 0.025 x story height
(with the period of equal or more than 0.7second)
R= overstrenght coefficient form table 16-N of UBC 97 PART 2

Based in UBC 97 code

I have less experience in high rise..I not yet try to check the drift, Anybody can discuss how to get the actual drift and what load combination used in UBC 97 code in getting the actual drift.
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#2
Hi,

The basic checks are correct, I do the area method to check the gravity loads, will try your method also.

For the drift the EQ in X & Y direction are to be checked by the formulae you mentioned.

Also check the base shears for the eqrthquake, and if you are defining spectrums check the proportion values.

I think that should do to carry on the designing part.

Regards
"Be like a postage stamp. Stick to one thing until you get there."
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#3
(08-04-2009, 09:26 AM)reynand_d Wrote: I just want to share how I check my model in etabs and correct me if I'm wrong or advice the proper way:

1.)Gravity

make a safe model for slab which is the thickness
= no. of storey x slab thicknness in etabs model

Apply the area load
=no. of storey x average area load apllied in etabs
(THE CONCEPT OF THIS IS I COMBINED ALL THE SLAB AND MODEL IT IN SAFE AS 0NE SLAB)

Reaction in etabs should almost equal to the reaction of safe.

Or, roughly compute the reaction at base manually(by tributary area method) then compare to etabs reaction result




2.) Wind

Go in show deformed shape then choose the Wx and Wy(one at a time) then click the top corner of the building then right click to see the point displacement. This value should less than to the allowable lateral deflection, in ubc H/500, H is the total height of the building.


3.) Earthquake

Actual drift should be less than to allowable drift

allowable drift= 0.7 x R x 0.020 x story height
(with the period of less 0.7second)

= 0.7 x R x 0.025 x story height
(with the period of equal or more than 0.7second)
R= overstrenght coefficient form table 16-N of UBC 97 PART 2

Based in UBC 97 code

I have less experience in high rise..I not yet try to check the drift, Anybody can discuss how to get the actual drift and what load combination used in UBC 97 code in getting the actual drift.

interstory drift = 0.7*R*(ETABS results) < 0.020*story ht or 0.025*story ht

juice
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#4
remeber to check drift modifiers of members before running and checking drift model for ETABS. divide property modifiers of all members by 0.7 , ex. beam = 0.35/0.7 = 0.5, col = 0.7/0.7 = 1
Responsibility = Liability
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#5
'Anybody can discuss how to get the actual drift and what load combination used in UBC 97 code in getting the actual drift.'

View from non (seldom) etabs user and 'british' region concrete designer;

Drift check

ULS to check p-delta effect
- through 'braced' and 'unbraced' frame categorisation

load combination : 1.4DL+1.4WL and 1.2DL+1.2LL+1.2WL

SLS to check tolerance of human to the drift
- through control of interstorey drift, different countries different limit, 1/500 common

load combination : 1.0DL+1.0WL and 1.0DL+0.8LL+0.8WL

All moment inertia of the members when running structural analysis have to be reduced as per aci 318 (this is a typical british problem, why don't they provide guidance?)
concrete solution advocate
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