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IS 800-2007 for tall buildings
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krane
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PostPosted: Wed Nov 28, 2012 6:17 pm    Post subject: IS 800-2007 for tall buildings Reply with quote

Dear Sefians,

Anybody implemented IS 800-2007 code tall steel buildings?

Does the provisions mentioned are adequate to design tall steel buildings?

Do we get any benefit over old code. Please share if somebody has the detail.

Regards,
KK Rane.

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sriprakash_shastry
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PostPosted: Thu Nov 29, 2012 4:02 am    Post subject: Reply with quote

Dear Mr. Krane,

I dont know if someone would have implemented the new code for tall buildings and I very much doubt it. However, one thing is to be kept in mind. THe new code is no magic compared to the old code. The designer is not going to be saving 20% on structural steel tonnage just by using the new code. THe old code had a lower Yield Stress and serviceability combinations for design whereas in the new code we are using Ultimate Stress and also increasing the loading with a factor of 1.5.

So one cannot expect magic to happen. In our comparisons we have seen that the maximum savings we get are to the tune of about 8% between the 2 codes.

With regard to the use of the new code in tall buildings one has to be extremely careful. There are so many conditions and stipulations for every aspect of design. I think the engineer has to know the code thoroughly before taking the leap into using this code for tall structures.

Warm Regards,
Sriprakash
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S.KANTHIMATHINATHAN
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PostPosted: Thu Nov 29, 2012 6:39 am    Post subject: IS 800-2007 for tall buildings Reply with quote

Dear Sefians,

I fave designed steel boiler supporting structure using IS 800-2007 code.

It is for member design.

We do not get any weight reduction in material when compared to pre-revised code.

With kind regards,
S.Kanthimathinathan
Structural Engineering Consultant,
Tiruchy Engineering Consultancy House,
1/1-A.Nariyan Street,
Srirangam, Tiruchy-620006
( Courses offered:- Design & Detailing of steel & R.C.C Structures)



Subject: [E-CONF] IS 800-2007 for tall buildings
From: forum@sefindia.org
Date: Thu, 29 Nov 2012 08:13:33 +0530
To: econf34289@sefindia.org

           Dear Sefians,

Anybody implemented IS 800-2007 code tall steel buildings?

Does the provisions mentioned are adequate to design tall steel buildings?

Do we get any benefit over old code. Please share if somebody has the detail.

Regards,
KK Rane.

Sent from BlackBerry® on Airtel

Posted via Email
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krane
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PostPosted: Thu Nov 29, 2012 5:30 pm    Post subject: IS 800-2007 for tall buildings Reply with quote

Dear Shastry Sir, It is quite surprising to note that even after 5 years from code release people are not following or not conversant with the latest code. I also observed many times that customers also ask for either old code or other country code. What care we need to actually take while using new code for tall buildings in steel. Pls let me know if you have any good reference for analysis and design for tall steel buildings considering the latest Indian code. Regards,K K RaneSent from BlackBerry® on Airtel
From: "sriprakash_shastry" <forum@sefindia.org>
Date: Thu, 29 Nov 2012 09:32:26 +0530
To: <econf34289@sefindia.org>
ReplyTo: econf34289@sefindia.org
Subject: [E-CONF] Re: IS 800-2007 for tall buildings

     Dear Mr. Krane,  I dont know if someone would have implemented the new code for tall buildings and I very much doubt it. However, one thing is to be kept in mind. THe new code is no magic compared to the old code. The designer is not going to be saving 20% on structural steel tonnage just by using the new code. THe old code had a lower Yield Stress and serviceability combinations for design whereas in the new code we are using Ultimate Stress and also increasing the loading with a factor of 1.5.   So one cannot expect magic to happen. In our comparisons we have seen that the maximum savings we get are to the tune of about 8% between the 2 codes.  With regard to the use of the new code in tall buildings one has to be extremely careful. There are so many conditions and stipulations for every aspect of design. I think the engineer has to know the code thoroughly before taking the leap into using this code for tall structures.  Warm Regards, Sriprakash
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PostPosted: Fri Nov 30, 2012 3:08 am    Post subject: IS 800-2007 for tall buildings Reply with quote

Sir,
A Typical 600MW boiler structure was used for comparison of LSD & WSD.

There is Weight reduction in Vertical bracing's (i.e., Members subjected to axial forces) and there is Increase in Weight for Boiler Columns (i.e., Members subjected to axial force and Bending Moment). Hence, there is Increase in Weight by around 3.7% when limit state method of design is adopted for Boiler Supporting structure( Consider Boiler Columns and Vertical bracing's Only).

Regards,
Harikrishna.T,
Engineer, FB/PE/SS.


kanthi nathan wrote:
Quote:
   Dear Sefians,

I fave designed steel boiler supporting structure using IS 800-2007 code.

It is for member design.

We do not get any weight reduction in material when compared to pre-revised code.

With kind regards,
S.Kanthimathinathan
Structural Engineering Consultant,
Tiruchy Engineering Consultancy House,
1/1-A.Nariyan Street,
Srirangam, Tiruchy-620006
( Courses offered:- Design & Detailing of steel & R.C.C Structures)


Subject: [E-CONF] IS 800-2007 for tall buildings
From: forum@sefindia.org (forum@sefindia.org)
Date: Thu, 29 Nov 2012 08:13:33 +0530
To: econf34289@sefindia.org (econf34289@sefindia.org)

Dear Sefians,

Anybody implemented IS 800-2007 code tall steel buildings?

Does the provisions mentioned are adequate to design tall steel buildings?

Do we get any benefit over old code. Please share if somebody has the detail.

Regards,
KK Rane.

Sent from BlackBerry® on Airtel









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Dr. N. Subramanian
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PostPosted: Fri Nov 30, 2012 1:35 pm    Post subject: Reply with quote

Dear Er Sriprakash,

I appreciate your points. We have already discussed about this in our regular forum and many have written that the code is economical only in a few cases. Limit state method is supposed to provide the required level of safety in all load cases, which is doubtful while using WSD. Hence the main point here is safety and not economy, though it is also imp.

IS 800 was revised after about 25 years! It is now on par with other international code. Of course AISC still used WSD but the formulae have been modified to give uniform results in both the cases. It uses LSD also.
Thus the designer has the choice to use both.

Regards,
NS

sriprakash_shastry wrote:
Dear Mr. Krane,

I dont know if someone would have implemented the new code for tall buildings and I very much doubt it. However, one thing is to be kept in mind. THe new code is no magic compared to the old code. The designer is not going to be saving 20% on structural steel tonnage just by using the new code. THe old code had a lower Yield Stress and serviceability combinations for design whereas in the new code we are using Ultimate Stress and also increasing the loading with a factor of 1.5.

So one cannot expect magic to happen. In our comparisons we have seen that the maximum savings we get are to the tune of about 8% between the 2 codes.

With regard to the use of the new code in tall buildings one has to be extremely careful. There are so many conditions and stipulations for every aspect of design. I think the engineer has to know the code thoroughly before taking the leap into using this code for tall structures.

Warm Regards,
Sriprakash


Last edited by Dr. N. Subramanian on Sat Dec 01, 2012 4:40 am; edited 1 time in total
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Yogesh.Pisal
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PostPosted: Sat Dec 01, 2012 4:28 am    Post subject: Reply with quote

Dear Er Krane,

We have implemented IS800: 2007 in our design for industrial structures. I think there should not be any harm in implementing the same for the Tall buildings also.

One really need to closely study AISC to interprete IS800 2007 correctly. Following are some of the points.

1. Vertical bracing configuration: Indian code has very limited / generalized provisions - One has to closely interact with AISC before finalizating the design. Further, we need to go for X-bracing or double storey X-bracing or Zipper columns.

2. Utilization ratio - If we will be keeping margin in our design of members then it will result into the higher consumption of material into the connection. Main reason - Our conenctions are based on capacity instead of actual forces.

3. Design of base plates specially for braced frames: Its always debatable to design the base plate for capacity. But, one need to finalize the philosophy very carefully. e.g. Mainly in the braced frame we should design the base plates for the braced bays for the capacity.

4. Optimization - It is expected by most of engineers that IS800 2007 will result into the lower consumption of steel. But, it is incorrect to conclude the same. Further, consumption of material in connection can be as high as 18 to 20% instead of 10 to 12% as per previsous code. Hence, it is really difficult to have overall economy, but definitely we will be having more safely.

Further, I personally feel that - In no case we should not use IS800 1984.

Regards,
Yogesh Pisal
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S.KANTHIMATHINATHAN
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Joined: 09 Jun 2012
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PostPosted: Sat Dec 01, 2012 7:03 am    Post subject: IS 800-2007 for tall buildings Reply with quote

Dear Sir,
My view on
Point number 2:- Connections are to be designed based on actual forces and moments with respect to moment connections of steel frames. Even for shear connections it is better to design based on actual forces.

Point number 3:- I understand that Mr.Yogesh Pisal , opines that the base plates are to be designed based on the capacity of column resting on that. This is acceptable for hinged base. But with respect to moment carrying columns, the stiffened base plates are designed for actual forces and moments. Use of moment coefficients depending on the edge/boundary condition of each segment of base plate (considering the stiffeners are restraining the base plate) is followed and the maximum thickness is adopted in practice.

Point number 4:- It is expected by most of engineers that IS800 2007 will result into the lower consumption of steel. But it is not so.

I am not able to understand "In no case we should not use IS800 1984." mentioned by Mr.Yogesh Pisal      

With kind regards,
S.Kanthimathinathan
Structural Engineering Consultant,
Tiruchy Engineering Consultancy House,
1/1-A.Nariyan Street,
Srirangam, Tiruchy-620006
( Courses offered:- Design & Detailing of steel & R.C.C Structures)



Subject: [E-CONF] Re: IS 800-2007 for tall buildings
From: forum@sefindia.org
Date: Sat, 1 Dec 2012 09:58:38 +0530
To: econf34289@sefindia.org

           Dear Er Krane,

We have implemented IS800: 2007 in our design for industrial structures. I think there should not be any harm in implementing the same for the Tall buildings also.

One really need to closely study AISC to interprete IS800 2007 correctly. Following are some of the points.

1. Vertical bracing configuration: Indian code has very limited / generalized provisions - One has to closely interact with AISC before finalizating the design. Further, we need to go for X-bracing or double storey X-bracing or Zipper columns.

2. Utilization ratio - If we will be keeping margin in our design of members then it will result into the higher consumption of material into the connection. Main reason - Our conenctions are based on capacity instead of actual forces.

3. Design of base plates specially for braced frames: Its always debatable to design the base plate for capacity. But, one need to finalize the philosophy very carefully. e.g. Mainly in the braced frame we should design the base plates for the braced bays for the capacity.

4. Optimization - It is expected by most of engineers that IS800 2007 will result into the lower consumption of steel. But, it is incorrect to conclude the same. Further, consumption of material in connection can be as high as 18 to 20% instead of 10 to 12% as per previsous code. Hence, it is really difficult to have overall economy, but definitely we will be having more safely.

Further, I personally feel that - In no case we should not use IS800 1984.

Regards,
Yogesh Pisal

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S.KANTHIMATHINATHAN
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PostPosted: Sat Dec 01, 2012 7:10 am    Post subject: IS 800-2007 for tall buildings Reply with quote

Sirs,
I agree that IS:800:2007-L.S.M is now on bar with other international code and Limit state method is supposed to provide the required level of safety in all load cases.

Does it amount to the structures deigned using IS"800:1084 is not that safe. THis question is being asked by many design engineers.


With kind regards,
S.Kanthimathinathan
Structural Engineering Consultant,
Tiruchy Engineering Consultancy House,
1/1-A.Nariyan Street,
Srirangam, Tiruchy-620006
( )



Subject: [E-CONF] Re: IS 800-2007 for tall buildings
From: forum@sefindia.org
Date: Fri, 30 Nov 2012 19:05:07 +0530
To: econf34289@sefindia.org

           Dear Er Sriprakash,

I appreciate your points. We have already discussed about this in ourvregular forum and many have written that the code is economical only in a few cases. Limit state method is supposed to provide the required level of safety in all load cases, which is doubtful while using WSD. Hence the main point here is safety and not economy, though it is also imp.

IS 800 was revised after about 25 years! It is now on bar with other international code. Of course AISC still used WSD but the formulae have been modified to give uniform results in both the cases. It uses LSD also.
Thus the designer has the choice to use both.

Regards,
NS

      sriprakash_shastry wrote:                Dear Mr. Krane,

I dont know if someone would have implemented the new code for tall buildings and I very much doubt it. However, one thing is to be kept in mind. THe new code is no magic compared to the old code. The designer is not going to be saving 20% on structural steel tonnage just by using the new code. THe old code had a lower Yield Stress and serviceability combinations for design whereas in the new code we are using Ultimate Stress and also increasing the loading with a factor of 1.5.

So one cannot expect magic to happen. In our comparisons we have seen that the maximum savings we get are to the tune of about 8% between the 2 codes.

With regard to the use of the new code in tall buildings one has to be extremely careful. There are so many conditions and stipulations for every aspect of design. I think the engineer has to know the code thoroughly before taking the leap into using this code for tall structures.

Warm Regards,
Sriprakash

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Yogesh.Pisal
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PostPosted: Sat Dec 01, 2012 7:34 am    Post subject: Reply with quote

Dear Sir,

Regarding Point No 2

OCBF : Refer Cl 12.7.3.1

We should design the connection for minimum of 1.2 times bracing capacity, actual loads as per enhanced Load combinations and maximum force that can be transferred by the system.

SCBF : Refer Cl 12.8.3.1

We should design the connection for minimum of 1.1 times bracing capacity and maximum force that can be transferred by the system.

Here, code clearly guide us to follow minimum force from above estimations and hence we can not go directly for actual forces. Further, this has also been supported by AISC also.

Regarding Point No 3

Refer Cl 12.12.1 & EL12.12.2

We should design the Pinned as well as Fixed base plates for the capacities and not for the actual forces.

My point was about the structure which is braced in either direction - In this case, we need not to design each and every column of the braced frame for the shear capacity of column. Rather, we should design base plate for the brace capacity. All the other columns can be designed for actual forces. Further, note that IS800: 2007 does not specify such detailed provision.

Now my interpretation regarding codal provision: I think this is applicable to the non braced frames only - Consider Portal frame : Only for the demonstration purpose

Support condition - Pinned base : We have to design the base plate for the shear capacity of column.
Support condition - Fixed base : We have to design the base plate for moment as well as shear capacity of column.

Lastly, "In no case we should not use IS800 1984." was a typing mistake. I want to say "Now we should not follow IS800:1984 in any situation"

Regards,
Yogesh Pisal
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