RCC footing : Reinforcement

Exercise :

There is a sketch of a RCC footing.on which we need to work today.

Picture59

This is a hand drawn sketch of a trapezoidal footing.

The dimensions and the reinforcement details have been given in the sketch.

First thing is to ask several questions and seek the answers :

  1. What is the size of the footing in plan ? { 4 m x 3 M }
  2. What is the depth of the raft ? { 300 mm }
  3. What is the vertical depth of the sloping portion of the footing ? { 900 mm }
  4. What is the size of the column in plan ? { 1000 mm x 1000 mm }
  5. What is the main steel of the footing ? {16 mm Tor @ 200 mm c/c both ways }
  6. What is the reinf. in column ? { 8 bars of 25 mm dia Tor }
  7. Column stirrups ? {10mm bars @ 200 mm c/c }
  8. Height of the column { 5000 mm }.
  9. Cover for  the footing bars : 50mm
  10. Cover for the column bars : 40 mm
  11. Weight of 16 mm bars : 1.58 Kg/M
  12. Weight of 25 mm bars : 3.86 kg/M
  13. Weight of 10 mm bars : 0.62 Kg /M.

Thus we know the basic details.

Now let us calculate the weight of the reinforcement .

}1.MAIN BARS OF THE COLUMN: NOS X 25TOR

}TOTAL HEIGHT:

Vertical height + sloping height + Raft height 

5000 + 900 + 300 = 6200

}CUTTING LENGTH:

}TOTAL HEIGHT (6200) – BOTTOM COVER (50) -TOP COVER (40) + development length ’’L’’(300)

6200-50-40 + 300 = 6410= 6.41M

WEIGHT:

}25TOR : 8NOS X 6.41M* 3.85KG/M=  197.43KG

}2.STIRRUPS:  10 TOR@200 C/C

}CUTTING LENGTH:

}920*4 = 3680+ Hook length 120 = 3800 = 3.8M

NO OF STIRRUPS: 6110/200+1=32NOS

WEIGHT: 10 TOR:  32 NOS*3.8M*0.62=75.39KG

}

}

}3.RAFT BARS: 16TOR@200C/C BOTH WAYS

}A. LONG SIDE ( 4M):

}CUTTING LENGTH:

}4000-50-50+ development length ( 200+200) =4300= 4.3M

}NO OF BARS:

}(3000/200) +1= 16NOS

WEIGHT:

}16TOR:16NOS*4.3M@1.58KG/M=108.7KG

}

}

}3.RAFT BARS: 16TOR@200C/C BOTH WAYS

}B.SHORT SIDE( 3M):

}CUTTING LENGTH:

}3000-50-50+development length ( 200+200) =3300= 3.3M

}NO OF BARS:

}4000/200+1= 21NOS

}WEIGHT:

}16TOR:21NOS*3.3M @1.58KG/M=109.49KG

}16TOR:TOTAL:108.7KG+109.49KG=218KG

}

}

}

}10 TOR:    76   KG

}16TOR:   218   KG

}25TOR :  198   KG

}

}TOTAL WEIGHT:       492 KG

}

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