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hemalmistry ...
Joined: 01 Jul 2009 Posts: 70
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Posted: Wed Mar 14, 2018 6:49 pm Post subject: clause 7.3.14_modelling building with podium |
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Clause 7.3.14 requires to model multiple tower with single podium separately and integrally (fig 1B). Do we also need to model single tower with podium (fig. 1A) separately and integrally? Clause 8.1.3 applies to both fig 1A and 1B but modelling requirement is mentioned in cl. 7.3.14 and in cl. 8.1.3.3.3 (a) for fig. 1A only. |
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ahujavipul General Sponsor
Joined: 26 Jan 2003 Posts: 230
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Posted: Wed Mar 21, 2018 12:30 pm Post subject: clause 7.3.14_modelling building with podium |
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I think this issue has been answered by the moderators.
Though a bigger question still lingers. In a combined tower model what empirical time period should be taken & base and what should be the procedure for scaling.
I would propose that for the purpose of diaphragm calculation, a static equivalent load be applied in opposite directions (or in various permutations) & then the stresses studied. The natural time period will only produce minimal response.
Regards
Vipul Ahuja |
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hemalmistry ...
Joined: 01 Jul 2009 Posts: 70
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Posted: Wed Mar 21, 2018 2:51 pm Post subject: Re: clause 7.3.14_modelling building with podium |
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Dear vipul sir,
Clause 8.1.3.3.3 (c) (2) says "equivalent static seismic forces can be used, provided they are scaled to match base overturning moments obtained from response spectrum analysis".
Above clause need explanation as it required to do reverse of what we are doing for individual tower model. Does this clause requires to use response spectrum method only as impirical time period for multitower model to be used for static method is not available ? And so if static method is to be used its base overturning moment (why not base shear) is to be matched with that of response spectrum method.
Also, clause 8.1.3.3.3 (c) (1) needs explation. How load combinations as required by this clause can be generated?
Regards
Hemal
ahujavipul wrote: | I think this issue has been answered by the moderators.
Though a bigger question still lingers. In a combined tower model what empirical time period should be taken & base and what should be the procedure for scaling.
I would propose that for the purpose of diaphragm calculation, a static equivalent load be applied in opposite directions (or in various permutations) & then the stresses studied. The natural time period will only produce minimal response.
Regards
Vipul Ahuja |
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ahujavipul General Sponsor
Joined: 26 Jan 2003 Posts: 230
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Posted: Fri Mar 23, 2018 12:16 pm Post subject: clause 7.3.14_modelling building with podium |
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I agree, the basis for matching overturning moment rather than base shear is unclear, when the stretching force in the ground floor diaphragm (between--say two towers) is less dependent on overturning & more on the base shear of the two acting in opposite directions.
Regards
Vipul Ahuja |
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