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P Large Delta using storey magnifier method as per IS 800-20

 
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Rameshwar Prasad
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Joined: 25 Feb 2010
Posts: 16

PostPosted: Tue Nov 05, 2013 6:26 am    Post subject: P Large Delta using storey magnifier method as per IS 800-20 Reply with quote

Hi All,

If i were to take into account P-Large delta using storey magnifier method  the formula mentioned on pg 276 in design of steel structures by Dr. N Subramanian gives the value of the "maximum end moment"
based on maximum first order end moment for a storey.

1. My main point of contention is whether all the columns in a particular storey are to be of the same size to apply this formula.

2. Are all the columns in a single storey to be designed for the same approximated "maximum second order end moment"?
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Dr. N. Subramanian
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Joined: 21 Feb 2008
Posts: 5302
Location: Gaithersburg, MD, U.S.A.

PostPosted: Wed Nov 06, 2013 4:33 am    Post subject: Re: P Large Delta using storey magnifier method as per IS 80 Reply with quote

Dear Er Prasad,

I do not have the paper by Chen and Lui(1985) with me now.Chen, W.F, and Lui,   E.M., Stability design criteria for steel members and frames in the United   States, Journal of Constructional Steel Research, Vol. 5, 1985, pp.   31-74, Discussion by Vandepitte, Vol. 6, No. 1, 1986, pp. 76-79.

However, to answer to your question (1): it is not necessary that all the columns in a particular storey are to be of the same size to apply this formula.

For question (2) You will have the first order end moment from the linear analysis computer program for different columns. You need to multiply those values by the moment amplification factor in order to get the moment including P-Delta effect.

Best wishes,
NS
Rameshwar Prasad wrote:
Hi All,

If i were to take into account P-Large delta using storey magnifier method  the formula mentioned on pg 276 in design of steel structures by Dr. N Subramanian gives the value of the "maximum end moment"
based on maximum first order end moment for a storey.

1. My main point of contention is whether all the columns in a particular storey are to be of the same size to apply this formula.

2. Are all the columns in a single storey to be designed for the same approximated "maximum second order end moment"?
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Rameshwar Prasad
SEFI Member
SEFI Member


Joined: 25 Feb 2010
Posts: 16

PostPosted: Wed Nov 06, 2013 12:54 pm    Post subject: Doubt Solved!! Yet another raised... Reply with quote

Hi Dr. N

You know its kind of a privilege when the person, whose book you are referring solves your query. Thank You. If you dont mind i posted another doubt on the forum regarding P-small delta approximation for a beam column. i am pasting the URL of the link. Can you please sort that out too?

http://www.sefindia.org/forum/viewtopic.php?t=15233

Regards
Rameshwar Prasad

PS You are a source of inspiration for many. Keep Inspiring!!!
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