BHEL - 1500 MW CCPP PRAGATI-III
PE-DC-314-653-C001-PART-3
CW PUMP HOUSE - 3D ANALYSIS AND DESIGN
E.1
Part – 3 – Design of Columns, Isolated Footings, Tie Beams at EL (-) 4.500, Grade Beams , Corbel and RC Wall.
DESIGN OF CORBEL
( For crane girder support on CWPH Columns along Grid- A & C )
(i) Material Data
Strength of Concrete
fck
=
25 N/mm2
Strength of Steel
fy
=
500 N/mm2
0.45 x 25
=
11.25 N/mm2
tcmax
=
3.1 N/mm2
b
=
500 mm
520.08 x 10^3 /(11.25 * 500 )
=
92.46 mm
Let
=
500 mm
Bearing Strength of Concrete ( sbr ) 0.45 * Fck =
Maximum Shear Stress
( Table 20 of IS 456 )
(ii) Structure information / Dimension :
Width of Bearing Plate
Length of Bearing Plate (l),
Adopting
=
=
Fv / ( sbr * b )
l
500 x 500mm Bearing Plate
Width of Column
=
B
=
600 mm
Clear Cover
=
Cc
=
50 mm
Dia of Rebar
=
f
=
25 mm
(iii) Loading information :
The following loads are obtained as support reactions (with impact factor) from the Analysis and
Design of Crane girder. Refer Doc. no. PE-DC-314-653-C002.
Vertical Load on the Corbel
=
Fv
=
346.72 kN
Horizontal Load on the Corbel
=
Fh
=
22.46 kN
Longitudinal Load on the Corbel
=
Fl
=
15.46 kN
Factored Vertical Load on the Corbel
=
Fv,u
=
=
346.72 x 1.5
520.08 kN
Factored Horizontal Load on the Corbel
=
Fh,u
=
=
22.46 x 1.5
33.69 kN
Factored Longitudinal Load on the Corbel
=
Fl,u
=
=
15.46 x 1.5
23.19 kN
Factored Loads for Design:
file:///conversion/tmp/scratch/378948448.xls
BHEL - 1500 MW CCPP PRAGATI-III
PE-DC-314-653-C001-PART-3
CW PUMP HOUSE - 3D ANALYSIS AND DESIGN
E.2
Part – 3 – Design of Columns, Isolated Footings, Tie Beams at EL (-) 4.500, Grade Beams , Corbel and RC Wall.
CALCULATIONS :
Assume Shear Stress
=
tc
=
Depth of Corbel
d
=
= 520.08 x 10e3 / ( 2.5 x 600 )
Overall Depth of Corbel D
d + Cc + f
=
=
346.72+50+25 =
Adopting overall Depth of Corbel
d
Fv / ( tc * B )
346.72 mm
421.72 mm
=
700 mm
=
637.50 mm
=
300 mm
=
0.471
< 0.6
=
=
0.062
0.471
(z/d)
1
- 0.47/(0.47+0.062)
0.062/(0.47+0.062)*0.47^2
=
=
-0.884
0.026
(z/d)
=
0.854
0.854 x 638
=
=
D
2.5 N/mm2
700 - 50 - 25/2
Check for Strut Action:
For Struct action in the Corbel, (av / d) ratio should be less than 0.6.
Distance of load from the face of the Column
av / d
=
av
300 / 637.50
Hence the member acts as a Corbel with Strut action
Determination of Lever Arm:
To determine the Lever arm, the following quadratic equation is solved.
(z/d)2 - [r / (r+k)].(z/d) + [k / (r+k)].r2 = 0
k
r
=
=
(520.08x 1000) /(0.88*600*638*25)
av / d
The co-efficients of quadratic equation are,
Ax2 + Bx + C = 0
x
A
B
C
=
=
=
=
x = [ -B ± √(B2 - 4AC) ] / 2A
x
=
Lever Arm, z =
544.30 mm
Determination of Neutral Axis (Xu):
Location of Compressive force from top compressive edge of the cross-section '0.45Xu' shall be
written as,
(d - z)
=
0.45Xu
Depth of Neutral Axis (Xu)
file:///conversion/tmp/scratch/378948448.xls
=
=
(d - z) / 0.45
( 637.5 - 544.3 ) / 0.45
=
207.11 mm
BHEL - 1500 MW CCPP PRAGATI-III
PE-DC-314-653-C001-PART-3
CW PUMP HOUSE - 3D ANALYSIS AND DESIGN
E.3
Part – 3 – Design of Columns, Isolated Footings, Tie Beams at EL (-) 4.500, Grade Beams , Corbel and RC Wall.
Xu,max / d =
=
0.0035/(0.0055+0.87Fy/Es)
=
0.456
Xu,max
=
0.456 x 638
=
290.72 mm
Xu < Xu,max Hence ok.
Tensile force along Horizontal Direction,
Ft
Fv / 2
=
=
Fv ( av / z )
520.08 x ( 300 / 544.30 )
=
286.65 kN
=
520.08 / 2
=
260.04 kN
=
286.65 kN
Ft should be atleast Fv/2
Here,
\
Ft > (Fv /2)
Ft
Determination of Area of Tension Steel:
Strain in tension Steel, es
=
0.0035 ( d - Xu ) / Xu
=
0.0073
>
0.87fy / Es
=
Hence Steel reaches yield.
Stress in Steel
=
fs
Area of Steel required, Ast
=
( Fv,u +Fh,u ) / fs
Ast
= ( 286.65 + 33.69 ) x 1000 / 435
=
=
0.87 x 500
435 N/mm2
=
710.60 mm2
=
0.40%
Check for Minimum & Maximum Area of Steel:
Minimum Percentage of Steel in Corbels
Astmin
=
0.40% x 600 x 637.50
=
1530 mm2
Ast < Astmin, Hence Provide Minimum reinforcement
Maximum Percentage of Steel in Corbels
=
1.30%
=
4972.5 mm2
Hence Area of Steel required
=
1530 mm2
Diameter of Rebar provided
=
25 mm
Provided Number of 25mm dia. Bars
=
5 nos.
Hence reinforcement provided, Astprov.
=
2454.37 mm2
Astmax
=
1.30% x 600 x 637.50
As < Ast,max, Hence ok
Astprov.
>
Astmin
HENCE SAFE
Hence provide 5 nos. of 25mm dia. Bars for Main Reinforcement
file:///conversion/tmp/scratch/378948448.xls
0.0022
BHEL - 1500 MW CCPP PRAGATI-III
PE-DC-314-653-C001-PART-3
CW PUMP HOUSE - 3D ANALYSIS AND DESIGN
E.4
Part – 3 – Design of Columns, Isolated Footings, Tie Beams at EL (-) 4.500, Grade Beams , Corbel and RC Wall.
Area of Horizontal(Longitudinal) Shear Steel:
Asu
Fl,u / fs
=
=
23.19 / 435 x 1000
=
53.31 mm2
=
355.30009 mm2
Hence Area of Steel required
=
355.30009 mm2
Diameter of Rebar provided
=
12 mm
Provided Number of 12mm dia. Bars
=
4 nos.
Hence reinforcement provided, Astprov.
=
452.39 mm2
2454.37x100/(600 x 638)
=
0.64%
tc
=
0.54 N/mm2
Minimum Area of Shear steel
Astprov. / 2
=
Astprov.
>
Astmin
HENCE SAFE
Hence provide 4 nos. of 12mm dia. Bars
( in the upper two-third depth)
Shear capacity of Section
Shear capacity of Concrete
Percentage of Main Steel
=
Nominal Shear Stress
Enhancement factor
for Shear Stress, f
t c1
=
2 x d / av
=
2 x 637.50 / 300.0
=
4.25
=
=
f x tc
4.25 x 0.54
=
2.29 N/mm2
tc1
<
tc,max
HENCE OK
tc1 * b * d
Shear Capacity of concrete =
=
( 2.29 x 600 x 638 ) / 1000
=
877.29 kN
Shear capacity of Steel:
Diameter of stirrups provided
Number of legs
Spacing of Stirrups provided, sv
=
=
=
=
12 mm
2 nos.
(700-50-50)/5
120 mm
Area of Shear reinforcement provided, Asv
=
226.19 mm2
Shear Capacity of Steel
Total Shear Capacity (Vu)
Vu
file:///conversion/tmp/scratch/378948448.xls
=
(0.87 fy.Asv.d) / sv
=
(0.87x500x226.19x637.5)/120 =
=
877.29 + 522.71
>
Fvu = 520.08kN
522.71 kN
=
1400.01 kN
BHEL - 1500 MW CCPP PRAGATI-III
PE-DC-314-653-C001-PART-3
CW PUMP HOUSE - 3D ANALYSIS AND DESIGN
E.5
Part – 3 – Design of Columns, Isolated Footings, Tie Beams at EL (-) 4.500, Grade Beams , Corbel and RC Wall.
HENCE SAFE
file:///conversion/tmp/scratch/378948448.xls
BHEL - 1500 MW CCPP PRAGATI-III
PE-DC-314-653-C001-PART-3
CW PUMP HOUSE - 3D ANALYSIS AND DESIGN
E.6
Part – 3 – Design of Columns, Isolated Footings, Tie Beams at EL (-) 4.500, Grade Beams , Corbel and RC Wall.
OUTPUT RESULTS :
(i) Materials
Concrete
Steel
=
=
Width of Corbel
Depth of Corbel
=
=
M25
Fe 500
(ii) Dimensions :
(iii) Steel Details :
Tension Reinforcement
Provide
5 - 25 mm
Horizontal Shear Reinforcement
Provide
file:///conversion/tmp/scratch/378948448.xls
4 - 12 mm
f Bars as Tension Reinforcement
600 mm
700 mm