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m_j_ipa SEFI Member
Joined: 01 Feb 2011 Posts: 3

Posted: Wed Feb 02, 2011 4:05 am Post subject: Torsion Constant of RC Beam (ETABS) 


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 General Sponsor
Joined: 21 Feb 2008 Posts: 5457 Location: Gaithersburg, MD, U.S.A.

Posted: Wed Feb 02, 2011 4:25 am Post subject: Re: Torsion Constant of RC Beam (ETABS) 


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 SEFI Member
Joined: 01 Feb 2011 Posts: 3

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


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 General Sponsor
Joined: 26 Jan 2003 Posts: 1039

Posted: Wed Feb 02, 2011 8:04 am Post subject: Torsion Constant of RC Beam (ETABS) 


3rd Feb 2011
Dear Dr Subramanian,
The procedure you have explained is routinely used to compute the torsional constant for PSC Teegirders 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

Posted via Email 

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Dr. N. Subramanian General Sponsor
Joined: 21 Feb 2008 Posts: 5457 Location: Gaithersburg, MD, U.S.A.

Posted: Thu Feb 03, 2011 5:16 am Post subject: Re: Torsion Constant of RC Beam (ETABS) 


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, SP18, American Concrete Institute, 1968, pp. 165178.
Hsu, T.T.C., "Torsion of Structural Concrete  Plain Concrete Rectangular Sections," Torsion of Structural Concrete, SP18, American Concrete Institute, 1968, pp. 203238.
Hsu, T.T.C., "Torsion of Structural Concrete  Behavior of Reinforced Concrete Rectangular Members," Torsion of Structural Concrete, SP18, American Concrete Institute, 1968, pp. 261306.
Hsu, T.T.C., "Ultimate Torque of Reinforced Rectangular Beams," Journal of Structural Division, ASCE, Vol. 94, No. ST 2, February, 1968, pp. 485510.
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. 5160.
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. 3444.
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. 674682.
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 SEFI Member
Joined: 01 Feb 2011 Posts: 3

Posted: Fri Feb 04, 2011 9:35 am Post subject: Re: Torsion Constant of RC Beam (ETABS) 


[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, SP18, American Concrete Institute, 1968, pp. 165178.
Hsu, T.T.C., "Torsion of Structural Concrete  Plain Concrete Rectangular Sections," Torsion of Structural Concrete, SP18, American Concrete Institute, 1968, pp. 203238.
Hsu, T.T.C., "Torsion of Structural Concrete  Behavior of Reinforced Concrete Rectangular Members," Torsion of Structural Concrete, SP18, American Concrete Institute, 1968, pp. 261306.
Hsu, T.T.C., "Ultimate Torque of Reinforced Rectangular Beams," Journal of Structural Division, ASCE, Vol. 94, No. ST 2, February, 1968, pp. 485510.
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. 5160.
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. 3444.
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. 674682.
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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