Civil Engineering - RCC Structures Design - Discussion


A prestressed rectangular beam which carries two concentrated loads W at L/3 from either end, is provided with a bent tendon with tension P such that central one-third portion of the tendon remains parallel to the longitudinal axis, the maximum dip h is


Answer: Option C


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Sushmitha said: (May 1, 2015)  
Please give the explanation.

Piyush Singh said: (Sep 3, 2015)  
w         |         w           
A (L/3) B (L/6) | (L/6) C (L/3) D

Reaction Ra = W.

Reaction Rb = W.

Bending Moment at Center of the Beam = [W * (L/3 + L/6) ]-[W* (L/6) ].

= WL/3.

Now Moment due to prestressing force = P*h (h= maximum dip).

Dip required => P*h = WL/3.

Therefore h = WL/3P.

Arun said: (Oct 4, 2016)  
Thanks @Piyush.

Lokesh said: (Dec 5, 2016)  
Good and thanks @Piyush Singh.

Mamun Biswal said: (Apr 2, 2017)  
Thanks @Piyush.

Chandru M said: (Apr 16, 2017)  
Thank you @Piyush Singh.

Rajesh said: (May 11, 2017)  
Thank u@piyush.
Done very cleverly....

Manohar said: (Aug 18, 2017)  
Thanks @Piyush.

Somnath Gorain said: (Sep 14, 2017)  
Thanks @Piyush.

Mriganka Roy said: (Sep 22, 2017)  
Thank you @Piyush.

Subhra said: (Oct 25, 2017)  
Thanks @Piyush.

Raj Chavda said: (Nov 15, 2017)  

Now moment at centre=[W*2L/3-W*L/3] = WL/3.
Now moment due to prestressing = P*h.
Now moment P*h should be > = for dip required.
P*h> = WL/3.
h> = WL/3P.
Generally h>or = WL/3P.

Saravanaraja said: (Dec 18, 2017)  
Bending Moment at Center of the Beam = [W * (L/3 + L/6) ]-[W* (L/6) ]. How this come? Please tell me, I am not understanding.

Explain me briefly @Piyush Singh.

Saikiran said: (Jan 14, 2018)  
L/3+L/6 is L/2.

Multiply reaction with L/2 and subtract moment due to load ( load(W)*distance from load to center(L/6)).

Lakhan Bhavnani said: (Jan 18, 2018)  
Thanks @Piyush.

Anil Kum said: (Jan 25, 2018)  
Good, Thanks @Piyush.

Bidyut said: (Mar 1, 2018)  
Thanks for the explanation.

Ayesha said: (Jun 26, 2018)  
Caluculate : W(L/3+L/6)-W(L/6) = WL/3.
M = WL/3,
M= h*P.
Equate both you got h value @Saravanaraja.

Umesh said: (Dec 24, 2018)  
Very nice explanation Thanks.

Srihari said: (Apr 26, 2019)  
Dip means?

Sanat Kumar Rout said: (Sep 11, 2019)  
Thanks for explaining @Piyush.

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