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Tall building - Loads

 
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cckeshav
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PostPosted: Tue Dec 04, 2012 1:23 pm    Post subject: Tall building - Loads Reply with quote

Dear SEFIans:

I have always had a doubt regarding the live loads specified in codes. The questions are: 1. What kinds of loads are included under live loads? 2. Whether live load distribution effects are considered? 3. Whether impact effects due to live loads are considered? 4. Whether the live load reduction factors consider these effects?

These questions are important as the total load worked out is based on the live loads. The slabs should be designed for entire live load as both distribution and impact effects are present. However, the beams have these effects to a lesser extent and the columns to a much lower extent. This means that the actual live load on the columns is much less than that designed for. Or on the other hand, the slabs are actually designed for a lower load effects than they are subjected to. I am not sure which argument is correct.

C. Channakeshava

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gautam chattopadhyay
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PostPosted: Tue Dec 04, 2012 4:22 pm    Post subject: Tall building - Loads Reply with quote

in buildings live loads are mostly stationary, not moving. live load includes dwellers and the loads due to furniture.we consider effect of impact in case of moving load only where momentum of the moving load is imparted to the structure. hence i feel on impact factor need be considered in building structures for residential purposes. However in commercial buildings like malls, lounge of airport terminal buildings where LMUs are operated for passengers and goods impact factor may be felt important. Yet the LMUs have very nominal dead load and passenger together may be 1500 kgs at maximum. If we consider the speed at 40 kmph, one may find the impact percentage will be negligible hardly 7 to 8%.

On Tue, Dec 4, 2012 at 8:09 PM, cckeshav <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
           Dear SEFIans:

I have always had a doubt regarding the live loads specified in codes. The questions are: 1. What kinds of loads are included under live loads? 2. Whether live load distribution effects are considered? 3. Whether impact effects due to live loads are considered? 4. Whether the live load reduction factors consider these effects?

These questions are important as the total load worked out is based on the live loads. The slabs should be designed for entire live load as both distribution and impact effects are present. However, the beams have these effects to a lesser extent and the columns to a much lower extent. This means that the actual live load on the columns is much less than that designed for. Or on the other hand, the slabs are actually designed for a lower load effects than they are subjected to. I am not sure which argument is correct.

C. Channakeshava
     



     



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Manoharbs_eq
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PostPosted: Wed Dec 05, 2012 4:07 am    Post subject: Reply with quote

Impact load for Live load as such is not considered in codes.

Reduction of live load is applicable for supporting elements like column and footing only on the basis that no building will have full live load for all the floor at a time, hence supporting elements and for load calculation reduction is acceptable.


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R_Shenoy
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Joined: 20 Mar 2012
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PostPosted: Wed Dec 05, 2012 9:27 am    Post subject: Tall building - Loads Reply with quote

IS 875 caters to this to some extent by prescribing reduction in LL based on influence area on the beam and for columns based on number of floors supported.

On Tue, Dec 4, 2012 at 8:09 PM, cckeshav <forum@sefindia.org (forum@sefindia.org)> wrote:
Quote:
           Dear SEFIans:

I have always had a doubt regarding the live loads specified in codes. The questions are: 1. What kinds of loads are included under live loads? 2. Whether live load distribution effects are considered? 3. Whether impact effects due to live loads are considered? 4. Whether the live load reduction factors consider these effects?

These questions are important as the total load worked out is based on the live loads. The slabs should be designed for entire live load as both distribution and impact effects are present. However, the beams have these effects to a lesser extent and the columns to a much lower extent. This means that the actual live load on the columns is much less than that designed for. Or on the other hand, the slabs are actually designed for a lower load effects than they are subjected to. I am not sure which argument is correct.

C. Channakeshava
     



     



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cckeshav
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PostPosted: Wed Dec 05, 2012 10:15 am    Post subject: Tall Buildings - Loads (Slab Loads) Reply with quote

Dear Mr Goutham Chattopadhyay:

The code specified live loads, even for a residential building, is much higher than that obtained through calculation by including loads due to furniture + people, etc.  The only justification for this load is the distribution and impact effect.

With Regards
C.Channakeshava
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