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[swanand_deo]

Dear SEFI Team,

I need technical clarity on following points:

1. How is the building height considered for calculation of wind forces?  (Note: there is expansion joint between tower and podium at podium level)
   1. Is it considered from Ground to terrace?
   2. Ground to LMR/OHT top?
   3. Basement to Terrace? or
   4. Basement to LMR/OHT top? 
2. Under what circumstances is the LMR or OHT height included in the for wind calculation? 
   1. Does it depend on how elevated is the LMR or OHT above the terrace or
   2. The width of the LMR/OHT with respect to building width. or any other parameter?

Regards,
Swanand S Deo

Posted via Email

[sangramiitk]

Wind flow above Ground level.Hence height calculation to be from ground level.
Based on height wind intensity keeps on increasing.


Regards
-sangram kesari das


On Thu, 18 May, 2023, 6:02 pm swanand_deo, <forum@sefindia.org (forum@sefindia.org)> wrote:

[vikram.jeet]

Since roof level water tank is in smaller width compared to building,,
Height of building be taken from Ground surface level to top of parapet for working out wind force   external pr coeff based on ht at resp level  PLUS force on water tank be taken as per it's elevation at roof,,

The ht above Ground surface is for working out external wind pressure,,
For internal wind pressures the basement also comes into picture,,

But it is seen that for rcc buildings,,  EQ is critical vs Wind,  but for Industrial Steel buildings like steel plants, Tps buildings,  wind is very potent force vis a vid EQ

[swanand_deo]

In my case, the LMR bottom is 6m above the terrace slab top while the width of the LMR is almost 80% of building width in Y direction.

Even though there is a 1.5m gap after the LMR upto the OHT which is 3m further high. All these contribute to around 10m above the terrace.

The OHT is around 50% of building width.

Thus, in such case, should the LMR and OHT also be considered as an obstruction?

[vikram.jeet]

All obstructions contribute to wind force  and roof water tank  is face wind loaf as per it's height from Ground surface level,,

Taking tank in building height if it's width is substantial is right.
But forces on building  ,i think, will be same .

[pvgraju]

Dear Sir,

For Building wind load is to be calculated from GL to top of terrace.
For projections above buildings relevant table from the wind code is to be taken. But while calculation of wind load for  projection height is to be taken as terrace top level.
For example building height is 40m, projection height is 10m then wind load for projection is to be calculated for height 40m to 50m.

Regards,

P.V.Gavarraju.