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[yatindoshi]

I am analyzing the High rise building ( 34 floors) with transfer floor above podium level. The structural framing system is shear wall frames for typical floor cantilevered out from transfer floor. The podium is supported on big columns. The shear walls at typical floor do not go upto foundation due to architectural , functional difference between podium and typical floors.
The building is location in seismic zone 3.

What are the precautions do be taken in analysis and design of such buildings.

Calculations for heat of hydration in transfer floor .?

How to go about the seismic design of such buildings.?
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[ibarua]

23RD August 2009

I'd be very hesitant NOT to continue the shear walls up to the foundations. From what you have described, the building will behave like a water tank on a staging -- stiff superstructure and flexible or soft substructure & foundation.

The shear walls are dispensed with where they are needed most for ensuring structural stability of the building.

Please educate your architect on about the dangers of such planning.

One should not try to defy the laws of nature.

Indrajit Barua.

On Sun, 23 Aug 2009 yatindoshi wrote :

[ahujavipul]

The stiffness of any floor of your building should not suddenly reduce as you go down the building--especially check the floor where you are stopping shear walls--see IS 1893 for relevant clauses.

Will your floor slab at the transfer level be able to accommodate rotations from the columns above to the columns below even though they are not in line--for gravity & seismic.

You can probably justify for gravity but how about seismic. This will not be a ductile detail. You will find that some columns/walls will need to go through.

Regards,

Vipul Ahuja

[Dr. N. Subramanian]

Dear Er Doshi,

Both Er Indrajit Barua and Vipul Ahuja have rightly said that you should educate the Architect and stress the need for continuing the shear wall upto the foundation. It is better you give a copy of the book "Seismic conceptual Design of Buildings- Basic principles for engineers, architects, building owners, and authorities", by Prof. Hugo Bachmann, which has been reprinted by NICEE, in which Prof. Bachmann has beautifully explained the EQ protection methods to be adopted by us in a simple and easy manner with lot of diagrams and photographs of collapsed buildings. This book will also be useful to many SEFIans.

Best wishes,
Subramanian  

[thirumalaichettiar]

Yes! Indeed the reference book referd by Dr.N.S is available at the cost of Rs200/= which contains very good substances. Should be given or recommended for not only to Architects but also to those interested in EQ design.

T.Rangarajan.

[B.S.VIRDI]

What I understand that shear wall not going up to foundation level , how base shear of 32 stories will be transferred to foundations. In this case is it useful to have shear walls at all.

B.S.VIRDI

[thirumalaichettiar]

Er.Yatindoshi,

Hope that still you wait some response from Sefi and so the following are for you information.

Please go through the following likns in the Sefi Forum:

1.http://www.sefindia.org/forum/viewtopic.php?p=725&sid=de6914c8a3f494b97c09ecacbf1b28d2


2.http://www.sefindia.org/forum/viewtopic.php?p=725&sid=de6914c8a3f494b97c09ecacbf1b28d2

In thabove some guidance is given for the analysis and use ofsoftware.

As you propose the Shear wall to start from FF is not at all recommended for Seismic forces s the building is 32 storey.

I have some information regarding the SHEAR Wall which I want to share.

Shear wall is classified as SHORT, SQUAT AND CANTILEVER.
SHORT   1< H/D WHERE H ID THE HEIGHT OF THE WALL & d IS THE
                     LENGTH OF THE WALL. The action is in shear.
SQUAT 1 <H/D<3. The action is Bending and shar.
CANTILEVER  H/D>3. The action is Bending.
Shear wall design is a complicated one with respect to its loaction in Plan, against the various forces as listed below:
1.DL+LL. It is difficult to estimate exactly the LL actiong on various floors. The reduction allowed in the code may lead to underestimate the same. It is the one helping t counteract against the overturning moment due to Lateral loads.
2.WIND LOAD: It is assumed that wind load is i in 50 years and even the worst case is the Gust force. It is the force When the building is from 10 to 30 storey height then Shear wall is proposed in addition to the frem-COlumns and Beams and the WL is prominnent when the height gets more.
3.SEISMIC FORCES: If the site is in Seismic zone it needto be designed for it. So need to analysis for it and it still makes the design more complicated in detailing and arrangements of the locations in a building.Reference is to be made on the book "REINFORCED CONCRETE AND MASONRY STRUCTURES By Prestley-chapter on STRUCTURAL WALL.
4. ENVIRONMENTAL LOAD-SHRINKAGE,CREEP:It is impotant to take care of these in the case of Tall Buildings with Shear wall.
5.TEMPERATURE: Need to consider this also.
6.FIRE LOAD:
iT IS IMPORTANT LOAD NEED TO BE THOUGHT OF IN DECIDING THE THICKNESS AND SIZE OF THE SHEAR WALL.
As per the TABLE 2 of the book "DESIGN OF SHEAR WALL BUILDINGS-CIRIA R-102, THE THICKNESS OF WALL IS AS GIVEN BELOW AS PER CP (110):

1. UNREINFORCED DENSE AGGREGATE SECTION OR LESS THAN 0.4% REINFORCEMENT:
               1/2 H      1 H    1.5H
               150        150    175mm
2.REINFORCED WITH DENSE AGGREGATE -0.4% TO 1% .
              1/2H      1H     1.5 H    2H    3H      4H
              100      120     140      160   200    240
3.REINFORCED WITH MORE THAN 1% STEEL
               1/2H     1H      1.5H    2H     3H     4H
                -          -        100     100    150    180MM
IN CP(110)  wala re defined as STOCKY when he/t is less than 12. The design of walls which are more slender than this should take into account- out of plane moment transfered from the slab and destabilising  moment from eccentricity of axial load.
In this regard I would like to draw the comments posted by Er.Vikram jeet and it is true that this aspect is very important.
The Min. steel 0.2% for HYS is for Shrinksge and temperature and Max is 4% is specified in CP (110).

Hope many Seniors and Experienced Sefians will put more information on the SHEAR WALLS.

T.Rangarajan.

[suraj]

Multistoreyed Structure
Learned architect should follow new guidelines set by National Disaster Management Authority.
Soft floors have to be avoided in such situations.
Configration should not change as planned.
SE has to competenctly advise architect.
Shear walls must continue to foundations.
It is understood that learned architect did not attend one week course being conducted by government for architects about seismic knowledge updating.
Regards

[pathre_v]