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Torsion Constant of RC Beam (ETABS)

 
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m_j_ipa
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PostPosted: Wed Feb 02, 2011 4:05 am    Post subject: Torsion Constant of RC Beam (ETABS) Reply with quote

Hello Selfindia members,

Is it necessary to modify the torsional constant of beam?

Based on what I've read, they set the torsional constant to .01 to

account cracking of beam, in this procedure the Torsional force Tu

will be greatly reduced unlikely if we use the default value of 1 which

will give you a higher value of Tu.

Hope you can help me, if you have any copy of documents or links

regarding Torsion Constant of RC Beam,please kindly post it.

Thanks

m_j_ipa
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Dr. N. Subramanian
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PostPosted: Wed Feb 02, 2011 4:25 am    Post subject: Re: Torsion Constant of RC Beam (ETABS) Reply with quote

Dear Er IPA,

You have to calculate the torsional constant for the beam in order to get the correct results. The torsional constant is Sigma(bt^3/3)

Take care
Best wishes
Subramanian

m_j_ipa wrote:
Hello Selfindia members,

Is it necessary to modify the torsional constant of beam?

Based on what I've read, they set the torsional constant to .01 to

account cracking of beam, in this procedure the Torsional force Tu

will be greatly reduced unlikely if we use the default value of 1 which

will give you a higher value of Tu.

Hope you can help me, if you have any copy of documents or links

regarding Torsion Constant of RC Beam,please kindly post it.

Thanks

m_j_ipa
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m_j_ipa
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Joined: 01 Feb 2011
Posts: 3

PostPosted: Wed Feb 02, 2011 5:59 am    Post subject: Re: Torsion Constant of RC Beam (ETABS) Reply with quote

drnsmani wrote:
Dear Er IPA,

You have to calculate the torsional constant for the beam in order to get the correct results. The torsional constant is Sigma(bt^3/3)

Take care
Best wishes
Subramanian

m_j_ipa
[/quote]

Assuming that i already computed the torsional constant, will cracking reduce the torsional stiffness of the beam, if yes, to what limit or percent reduction.

Thanks.
m_j_ipa
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ibarua
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PostPosted: Wed Feb 02, 2011 8:04 am    Post subject: Torsion Constant of RC Beam (ETABS) Reply with quote

3rd Feb 2011

Dear Dr Subramanian,

The procedure you have explained is routinely used to compute the torsional constant for PSC Tee-girders and RCC girders while estimating distribution of live loads on the longitudinal girders of a bridge deck.

Regards,

Indrajit Barua.

On Wed, 02 Feb 2011 10:04:06 +0530 "drnsmani" <forum@sefindia.org> wrote
Quote:
     Dear Er IPA,

You have to calculate the torsional constant for the beam in order to get the correct results. The torsional constant is Sigma(bt^3/3)

Take care
Best wishes
Subramanian

      m_j_ipa wrote:                Hello Selfindia members,

Is it necessary to modify the torsional constant of beam?

Based on what I've read, they set the torsional constant to .01 to

account cracking of beam, in this procedure the Torsional force Tu

will be greatly reduced unlikely if we use the default value of 1 which

will give you a higher value of Tu.

Hope you can help me, if you have any copy of documents or links

regarding Torsion Constant of RC Beam,please kindly post it.

Thanks

m_j_ipa     
     
Quote:





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Dr. N. Subramanian
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PostPosted: Thu Feb 03, 2011 5:16 am    Post subject: Re: Torsion Constant of RC Beam (ETABS) Reply with quote

m_j_ipa wrote:
Dear Er IPA,

Any Reinforced concrete member  will have cracks as soon as the shuttering is removed; cracks will be min in compression members. Cracking will surely reduce the stiffness. For reducing cracking you have to provide stirrups.

For a better understanding of torsion (Our IS code considers it in an app. manner, by taking it as an equivalent BM), you have to refer to the papers by Prof. Hsu of the Univ of Houston, USA.


Hsu, T.T.C., "Torsion of Structural Concrete - A Summary on Pure Torsion," Torsion of Structural Concrete, SP-18, American Concrete Institute, 1968, pp. 165-178.


Hsu, T.T.C., "Torsion of Structural Concrete - Plain Concrete Rectangular Sections," Torsion of Structural Concrete, SP-18, American Concrete Institute, 1968, pp. 203-238.


Hsu, T.T.C., "Torsion of Structural Concrete - Behavior of Reinforced Concrete Rectangular Members," Torsion of Structural Concrete, SP-18, American Concrete Institute, 1968, pp. 261-306.


Hsu, T.T.C., "Ultimate Torque of Reinforced Rectangular Beams," Journal of Structural Division, ASCE, Vol. 94, No. ST 2, February, 1968, pp. 485-510.


Hsu, T.T.C., "Torsion of Structural Concrete - Interaction Surface of Torsion, Shear and Bending in Members Without Web Reinforcement," Journal of the American Concrete Institute, Proc., Vol. 65, No. 1, January, 1968, pp. 51-60.


Hsu, T.T.C., "Torsion of Structural Concrete - Uniformly Prestressed Rectangular Beams Without Web Reinforcement," Journal of the Prestressed Concrete Institute, Vol. 13, No. 2, April, 1968, pp. 34-44.

Hsu, T. T. C., "Nonlinear Analysis of Concrete Torsional Members," Structural Journal of the American Concrete Institute, Vol. 88, No. 6, Nov.-Dec. 1991, pp. 674-682.

Also see his book Torsion of Reinforced Concrete, Van Nostrand Reinhold, 1984, 544pp,  and his recent book "unified Theory of Concrete Structures" by T.T.C. Hsu and Y.L. Mo, Wiley, 2010, 500pp,


Best wishes
Subramanian


m_j_ipa[/quote][/quote]

Assuming that i already computed the torsional constant, will cracking reduce the torsional stiffness of the beam, if yes, to what limit or percent reduction.

Thanks.
m_j_ipa[/quote]
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m_j_ipa
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PostPosted: Fri Feb 04, 2011 9:35 am    Post subject: Re: Torsion Constant of RC Beam (ETABS) Reply with quote

[quote="drnsmani"][quote="m_j_ipa"]Dear Er IPA,

Any Reinforced concrete member  will have cracks as soon as the shuttering is removed; cracks will be min in compression members. Cracking will surely reduce the stiffness. For reducing cracking you have to provide stirrups.

For a better understanding of torsion (Our IS code considers it in an app. manner, by taking it as an equivalent BM), you have to refer to the papers by Prof. Hsu of the Univ of Houston, USA.


Hsu, T.T.C., "Torsion of Structural Concrete - A Summary on Pure Torsion," Torsion of Structural Concrete, SP-18, American Concrete Institute, 1968, pp. 165-178.


Hsu, T.T.C., "Torsion of Structural Concrete - Plain Concrete Rectangular Sections," Torsion of Structural Concrete, SP-18, American Concrete Institute, 1968, pp. 203-238.


Hsu, T.T.C., "Torsion of Structural Concrete - Behavior of Reinforced Concrete Rectangular Members," Torsion of Structural Concrete, SP-18, American Concrete Institute, 1968, pp. 261-306.


Hsu, T.T.C., "Ultimate Torque of Reinforced Rectangular Beams," Journal of Structural Division, ASCE, Vol. 94, No. ST 2, February, 1968, pp. 485-510.


Hsu, T.T.C., "Torsion of Structural Concrete - Interaction Surface of Torsion, Shear and Bending in Members Without Web Reinforcement," Journal of the American Concrete Institute, Proc., Vol. 65, No. 1, January, 1968, pp. 51-60.


Hsu, T.T.C., "Torsion of Structural Concrete - Uniformly Prestressed Rectangular Beams Without Web Reinforcement," Journal of the Prestressed Concrete Institute, Vol. 13, No. 2, April, 1968, pp. 34-44.

Hsu, T. T. C., "Nonlinear Analysis of Concrete Torsional Members," Structural Journal of the American Concrete Institute, Vol. 88, No. 6, Nov.-Dec. 1991, pp. 674-682.

Also see his book Torsion of Reinforced Concrete, Van Nostrand Reinhold, 1984, 544pp,  and his recent book "unified Theory of Concrete Structures" by T.T.C. Hsu and Y.L. Mo, Wiley, 2010, 500pp,


Best wishes
Subramanian


Subramanian,

Thanks Sir for the references.

m_j_ipa.
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