RCC Curved beam

One of my students has asked me this question today :

Sir , how to find out the reinforcement for the curved beam ?

So , dear readers , let us solve this question today.

For the sake of understanding , I have assumed the following data for the curved beam.

Curved length of the RCC beam : 8560 MM.

Note :

In case , it is not possible , to measure it from the drawing , due to lack of clarity on the beam curvature , I suggest that first let the beam bottom be fixed at the position and then actually measure the beam curved length at the position. This shall give the most correct beam length at site.

Beam size :

Width :250 MM.

Depth : 650 MM.

Beam top bars : 2 Nos x 12 mm dia.HYSD bars [ Straight ]

Beam Main bars : 4 x 25 mm dia HYSD bars [ Straight ]

Bent up bars : 2 x 25 mm dia HYSD bars 

Stirrups : 8 mm dia HYSD bars @ 200 c/c.

We also know that :

Beam cover : 25 MM.

Stirrup hook length : 2 x ( 10 X dia of stirrup bar )

Development length for the top bars : 450 mm.

Development length for the bottom bars : 450 mm.

Picture22

Now with the above information , let us calculate the beam reinforcement as follows :

  1. Top bars : [ 8560- (25-25)+ (450+450) ] = [ 8560 – 50 = 900 ] = 9410 mm = 9.41 M.
  2. Bottom straight bars : 9.41M.
  3. Bent up bars : ( 8560-50 )+ 2 {0.41( 650-50)} + (450+450) ] = ( 8510 + 2 x 0.41 x 600 )+900  = ( 8510 +492+900 ) = 7902 mm = 7.902 M.
  4. Stirrups : Cutting length : 2 { ( 250 -50 ) +( 650 -50 )} + 2 X 10 x8 = 1600 + 160 = 1660 mm =1.660 M                                           No of stirrups : ( 8560/200 ) + 1 = 43.8 say 44 Nos.

Abstract for the weight :

  1. Top bars : 2 x 9.41 M x 0.89 Kg/M = 16.75 Kg.
  2. Bottom straight bars : 4 x 9.41 M .x 3.86 Kg/M = 145 Kg.
  3. Bent up bars : 2 x 7.902 M x 3.86 Kg/M = 61 Kg.
  4. Stirrups : Cutting length : 44 x 1.660 M x 0.39 Kg/M =   28.5 Kg.                                                                                                                                                                                                                                                                                                                                                  Total weight :  252 Kg.                           

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