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How to apply Vertical earthquake load in etabs

 
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Sandeepk
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PostPosted: Sun Dec 03, 2017 10:26 am    Post subject: How to apply Vertical earthquake load in etabs Reply with quote

How to apply vertical earthquake load in etabs as i am modeling building in zone IV and need to apply vertical earthquake load
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sagar_shinde
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PostPosted: Mon Dec 04, 2017 5:28 am    Post subject: Re: How to apply Vertical earthquake load in etabs Reply with quote

Sandeepk wrote:
How to apply vertical earthquake load in etabs as i am modeling building in zone IV and need to apply vertical earthquake load




You can apply static earthquake by defining EqZ. For dynamic analysis there is no such provision in ETABS. All you can do is Define Spec Z and give scale factor value maximum of Spec X and Spec Y. Although I would like to get expert opinion about this solution till ETABS is updated.
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aditya
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PostPosted: Tue Jun 18, 2019 5:10 pm    Post subject: Reply with quote

Dear Sefians,
Shall we distribute the vertical seismic base shear Vby=Av*W in each storey following the same formula as used for horizontal base shear as given in clause 7.6.3 (a) of IS 1893 Part 1: 2016? Please clarify since the code seems to be silent on this matter.
For example, vertical seismic force in storey i will be given by the following formula or not?
Qyi=Av*Wi*hi2/sum(Wi*hi2) where XZ is the horizontal plane and Y is the vertical direction, Av=design vertical seismic coefficient=(2/3)*Ah
with regards,
Aditya
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aditya
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PostPosted: Wed Jun 26, 2019 1:28 pm    Post subject: Reply with quote

Dear Er. S. Arun Kumar,
It seems nobody is interested or not using this clause. Can you help me on this topic related to how to apply vertical earthquake force at different floors in a multi-storeyed RC Building? Thanks in advance.
with best regards,
Aditya
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rahul.leslie
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PostPosted: Fri Jun 28, 2019 5:16 am    Post subject: Reply with quote

Find Av (6.4.6, IS:1893-2016) from

Av = (2/3)*(Z*I)/(2*R)*(2.5)

and define vertical earthquake EQv

EQv = Av*(DL+reduced.LL)

... use this EQv in place of 'ELz' in the combinations described in 6.3.4.1, IS:1893-2016
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hemal
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PostPosted: Sun Jun 30, 2019 6:30 am    Post subject: How to apply Vertical earthquake load in etabs Reply with quote

(1) Vz = Av*W'

Av = 2/3 * Ah-max = 2/3 * Z/2 * I/R' *2.5


R'=R as per indian code. However other codes have specified between 1 to 1.5 in absence of exact value.


W''=W as per indian code. However according to other codes it includes only dead load or it is less than that for horizontal load.


Distribution of Vz along height of structure is similar to that for horizontal loads.


This approach requires to apply vertical seismic loads globally.




(2) Some other codes allows to consider its effect on partial model (or elements) which can get significal forces due to such actions. For higher seismic zones (IV & V), vertical seismic effects may be considered globally. Otherwise its effects shall be limited to large cantilevers (>5m), large span beams (>20m), prestressed elements, elemens (beam, columns, walls) supporting vertical elements having inplane or out of plane offset etc. When effects are considered on partial model or on element, Av shall be multiplied with seismic weight of element and shall be applied on element as vertical seismic load as separate load case and shall be combined with other loads as per codal requirement.


Some other codes likes ASCE have simplied procedure to consider vertical seismic effects. It requires to amplify dead load effects (BM, SF etc) by certain factor. Such factor as per indian code may be 0.3ZI. Load factor for dead load in all seismic load combinations shall be amplified by factor (1+0.3*Z*I) or (1-0.3*Z*I) to account for vertical seismic load effects.


Chinese code requires to consider verical seismic effect globally in higher seismic zones, and for lower and moderate seismic zones it requires to consider vertical seismic effect as 10% of representative gravity load (75% of total gravity load) for cantilever elements and 20% for large span elements.


Also, when vertical seismic loads are combined with horizontal seismic loads, no of load combinations can be reduced drastically to reduce design time by using the sign of verical seismic load action wisely.


e.g. 1.5D+1.5EQh+0.3(1.5EQv)
1.2D+1.2L+1.2EQh+0.3(1.2EQv)
0.9D+1.5EQh-0.3(1.5EQv)


Hope this helps.


Hemal Mistry










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hemalmistry
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PostPosted: Thu Jul 04, 2019 7:30 am    Post subject: How to apply Vertical earthquake load in etabs Reply with quote

(1) Vz = Av*W'

Av = 2/3 * Ah-max = 2/3 * Z/2 * I/R' *2.5


R'=R as per indian code. However other codes have specified between 1 to 1.5 in absence of exact value.


W''=W as per indian code. However according to other codes it includes only dead load or it is less than that for horizontal load.


Distribution of Vz along height of structure is similar to that for horizontal loads.


This approach requires to apply vertical seismic loads globally. 




(2) Some other codes allows to consider its effect on partial model (or elements) which can get significal forces due to such actions. For higher seismic zones (IV & V), vertical seismic effects may be considered globally. Otherwise its effects shall be limited to large cantilevers (>5m), large span beams (>20m), prestressed elements, elemens (beam, columns, walls) supporting vertical elements having inplane or out of plane offset etc. When effects are considered on partial model or on element, Av shall be multiplied with seismic weight of element and shall be applied on element as vertical seismic load as separate load case and shall be combined with other loads as per codal requirement.


Some other codes likes ASCE have simplied procedure to consider vertical seismic effects. It requires to amplify dead load effects (BM, SF etc) by certain factor. Such factor as per indian code may be 0.3ZI. Load factor for dead load in all seismic load combinations shall be amplified by factor (1+0.3*Z*I) or (1-0.3*Z*I) to account for vertical seismic load effects. 


Chinese code requires to consider verical seismic effect globally in higher seismic zones,  and for lower and moderate seismic zones it requires to consider vertical seismic effect as 10% of representative gravity load (75% of total gravity load) for cantilever elements and 20% for large span elements. 


Also, when vertical seismic loads are combined with horizontal seismic loads, no of load combinations can be reduced drastically to reduce design time by using the sign of verical seismic load action wisely.


e.g. 1.5D+1.5EQh+0.3(1.5EQv)
       1.2D+1.2L+1.2EQh+0.3(1.2EQv)
       0.9D+1.5EQh-0.3(1.5EQv)


Hope this helps.


Hemal Mistry

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