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dimensions of isolated footing for crane supporting columns

 
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achaljain
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PostPosted: Wed Mar 16, 2011 6:29 am    Post subject: dimensions of isolated footing for crane supporting columns Reply with quote

dear sirs,

I am designing a workshop building which has 2 cranes of 150/40 tonnes in tandem operation. the height of the crane hook is 20 m  and the frames are spaced at 8m and the transverse span is of 30m.
the sbc is quite good of 5t/m2 as it is rocky.
the column is not having any intermediate support.
i am getting very high eccentricity cos of wind loads.
please guide me as to what could be the dimensions of the footing.
i m currently getting a footing size of 8 x 5 m which is very high.
there is another restriction that the footing size in transverse direction(in direction of eccentricity) cannot be increased.
is there any other method...
please help..!!!!
thank you in advance
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P.K.Mallick
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PostPosted: Wed Mar 16, 2011 1:40 pm    Post subject: Re: dimensions of isolated footing for crane supporting colu Reply with quote

achal_jain wrote:
dear sirs,

I am designing a workshop building which has 2 cranes of 150/40 tonnes in tandem operation. the height of the crane hook is 20 m  and the frames are spaced at 8m and the transverse span is of 30m.
the sbc is quite good of 5t/m2 as it is rocky.
the column is not having any intermediate support.
i am getting very high eccentricity cos of wind loads.
please guide me as to what could be the dimensions of the footing.
i m currently getting a footing size of 8 x 5 m which is very high.
there is another restriction that the footing size in transverse direction(in direction of eccentricity) cannot be increased.
is there any other method...
please help..!!!!
thank you in advance



If the soil is rocky,the sbc can not be so low.Attach a sketch while explaining your problem.

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achaljain
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Joined: 12 Oct 2010
Posts: 3

PostPosted: Wed Mar 16, 2011 2:36 pm    Post subject: Reply with quote

please find attached a sketch of the frame such frames are spaced at 8 m interval.
the total length between expansion joints is 94 m .
the soil bearing capacity is 50 t/m2 instead of 5 ,sorry for it...!!
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P.K.Mallick
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PostPosted: Wed Mar 16, 2011 3:15 pm    Post subject: Reply with quote

Check your load combination,once again. The size of footing appears to be on higher side for sbc of 50t/sqm
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achaljain
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PostPosted: Wed Mar 16, 2011 3:38 pm    Post subject: Reply with quote

dear Mr. Mallick,

the load case is just dead+live+wind load+crane load, actually the footing size is increasing bcos of highly eccentric loading due to moment generated by the wind force and a small moment due to the crane but since the column is not supported at intermediate level(almost free standing) the m/p ratio is close to 3.5 .
and no loss of contact is allowed between soil and the footing under the gross bearing pressure.
the gross bearing pressure is well above the pressure exerted by the foundation.

what cud be a reasonable size of footing..?
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abhio
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Joined: 08 Mar 2010
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PostPosted: Thu Mar 17, 2011 9:56 am    Post subject: Reply with quote

Dear Er Jain,

You could reduce the size of footing required drastically by allowing some uplift.

Regards,

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A S Oundhakar,
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Invictus Consultancy Services,
Mumbai
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anandjha
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PostPosted: Mon Apr 11, 2011 5:44 am    Post subject: Reply with quote

Dear Er. Jain,

Refer Steel Designers Manual  Chapter ,"Foundation ", for the design of isolated footing with negative pressure.

Regards

A. Jha


abhio wrote:
Dear Er Jain,

You could reduce the size of footing required drastically by allowing some uplift.

Regards,
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