Transcript Concrete Structures - An-Najah National University

Concrete Structures
DR. Nabil Dmaidi
Units of Measure
Concrete
:
Cubic Yard
Steel
:
Lb or tons
Formwork :
Square feet per contact area
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Types of Concrete construction
1.
Foundations
2.
Columns
3.
Slabs and beams
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Foundations
Isolated
footing
Combined
footing
Shallow
Deep
Strap
footing
Wall
footing
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Raft
foundation
Shallow Foundation
Isolated
Footing
Combined
Footing
Strap
Footing
Raft
Foundation
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Continuous
Wall Footing
Deep Foundation
Caissons
Piles
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Columns
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Shapes
–
–
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Square - Rectangle - Circular
Others
Reinforcement
–
Ordinary - Spiral
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Slabs and Beams: One-Way slabs
One-Way Slab, Beam, and Girder
One-Way Slab, Supported
by Beams or Walls
One-Way Joist Slab
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Slabs and Beams: Two-Way Slabs
Flat Plate
Waffle Slab
Flat Slab
Two-Way Slab
Supported by Beams
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Estimating Issues
1.Formwork is the largest cost item that
represents 40% to 60% of concrete structure
cost.
Distribution of costs for cast-in-place concrete slab wall:
Slab
Concret e
21%
Reinforcing
28%
Concret e
Placing
3%
Wall
Concret e
Mat erials
30%
formwork
Mat erials
10%
Formwork
Labor
38%
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Formwork
Labor
52%
Concret e
Labor
7%
Formwork
Mat erials
11%
2.Waste allowance from 2% to 10% should be
added for concrete and concrete formwork.
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1. Center Line Method
30’10”
30’
Building size: 30’ x 40’
40’0”
40’10”
Calculations:
1. Length = 30’10” - 1’6”
= 29’4”
2. Width = 40’10” - 1’6”
= 39’4”
3. Perimeter = 29’4” + 29’4” + 39’4” +39’4”
= 137”4”
4. Volume of concrete = 137.33’ x 1’ x 1.5’ = 206 ft3
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2. Sectional Method
Calculations:
1.Length = 10.833’+40.833’ = 81.67’
2.Width
= 27.833’+27.833’ = 55.67’
3.Perimeter
= 81.67’+55.67’
= 137.34 Total Linear ft
4.Volume = 137.34’x1’x1.5’ = 206 Cubic feet
= 7.6 Cubic Yards
30’10”
27’10”
5.volume in CY = 206/27
40’10”
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COST OF OTHER COMPONENTS OF
CONCRETE WORK
1.Reinforcement Steel
2.Forms
3.Concrete Mix
4.Finishing
5.Curing
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Table 1.
DIMENSIONS & WEIGHT OF WELDED WIRE FABRIC
SPACING
WIRE GAUGE
POUNDS/100 SF
4" X12"
NO. 6 XNO. 6
41.6
4" X12"
NO. 8 XNO. 8
29.6
6" X12"
NO. 4 XNO. 4
43.8
6" X12"
NO. 6 XNO. 6
31.8
6~ X6"
NO. 6 XNO. 6
42.8
6" X6"
NO. 8 XNO. 8
30.0
6" X6"
NO. 9 XNO. 9
25.8
6" X6"
NO. 10 XNO. 10
20.7
4" X4"
NO. 6 XNO. 6
61.9
4" X4"
NO. 8 XNO. 8
44.1
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Table 2
SIZES & WEIGHTS OF REINFORCING BAR
BAR NUMBER
SIZE (IN.)
WEIGHT (LB./FT.)
2
3
1/4 ROUND
3/8 ROUND
0.167
0.367
4
5
6
1/2 ROUND
5/8 ROUND
3/4 ROUND
0.668
1.043
1.502
7
8
7/8 ROUND
1ROUND
1SQUARE
1- 1/8 SQUARE
1- 1/4 SQUARE
2.044
2.670
3.400
4.303
5.313
9
10
11
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EXAMPLE:
How many pounds of rebar are required for the
concrete floor area below?
6” Concrete slab with #4 rebar 15”
on center each way
40’
20’
60’
30’
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Step #1: Calculate the total SF of area involved.
20'0" X 30'0"
= 600 SF
30'0" X 40'0"
= 1 200 SF
Total
= 1,800 SF floor area
Step #2: Calculate the pounds of rebar per SF of floor based on the unit
spacing of the rebar at any point of intersection.
Unit area:
15" X 15"
= 1.25' X 1.25'
= 1.56 SF
Unit rebar length: 1.25' + 1.25'
= 2.5 LF
Lbs. of rebar/unit:= 2.5 LF X .668 lbs/ LF = 1.67 lbs
It is now known that there are 1. 67 lbs of rebar per 1.56 SQ FT of floor
area.
1.67 / 1.56
= 1.07 lbs/SF of floor area.
SO: 1.07 lbs/ SF X 1,800 SF
= 1,926 lbs of #4 rebar required.

DR. Nabil Dmaidi