Strap Footings Design
24
INPUT DATA Compressive strength of concrete Yield strength of reinforcement Height of soil above strap Density of backfill Density of concrete Design soil pressure c/c distance b/w columns Eccentricity of edge footing Enter %age diff. for DESIGN CHECKS 2 ft FOOTINGS DESIGN Service dead load from superstructure
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Transcript of Strap Footings Design
STRAP FOOTING DESIGN
INPUT DATA
Compressive strength of concrete
Yield strength of reinforcement
Height of soil above strap
Density of backfill
Density of concrete
Design soil pressure
c/c distance b/w columns
Eccentricity of edge footing
Enter %age diff. for DESIGN CHECKS
2 ft
FOOTINGS DESIGN
Service dead load from superstructure
Service live load from superstructure
Additional weight due to footing self weight
Strap self weight
Total service load
Total ultimate load
Column size along strap length
Column size in perpendicular direction
Ultimate soil reaction under footing
Service soil reaction under footings
Area required
Area provided
Length required
Width required
Select length
Select width
Select thickness
Select bottom cover
Select bar diameter
Effective depth
Actual soil pressure under footing
Actual soil pressuer/ft under each footing
REINFORCEMENT DESIGN
Load per running foot
Ultimate soil pressure
FOR THE TIME BEING INTERIOR FOOTING DESIGN IS BASED ON SQUARE FOOTING
Shear perimeter
One-way shear
One-way shear capacity
Two-way shear
Two-way shear capacity
Bending moment
Assume a
Rho
Calculated area of steel
Check a
Minimum area of steel
Selected area of steel
Main bars required
Main #4 bars required
Temp/Shrinkage area of steel
Temp/Shrinkage required
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.000 2 -46
-252
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186186
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Shear & Moment
Vu Mu
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.000 2 -46
-252
-96
88
186186
110
00 13
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-123
27 27
105
129
-102 -79
0
Shear & Moment
Vu Mu
STRAP FOOTING DESIGN
INPUT DATA units
3 ksi
60 ksi
5.50 ft
110 pcf
150 pcf
3.3 ksf
14.11 ft
2.00 ft
95%150
14.11 ft
9 in
5 ft 5.86 ft||||||||||||||||
35.2 k/ft176 11.99 ft
EXTERIOR units INTERIOR
111 kip 172
8 kip 13
2.2 kip 2.6
0.8 kip 0.8
122 kip 188
150 kip 231
9.0 in 20.0
24.0 in 12.0
176 kip 205
144 kip 167
44 ft² 51
44 ft² 53
4.75 ft -
8.71 ft -
5.00 ft 7.25
8.75 ft 7.25
15.0 in 15.0
3.0 in 3.0
0.750 in 0.750
10.9 in 10.9
4.0 ksf 3.9
35.2 k/ft 28.3
EXTERIOR units INTERIOR
35 kip/ft
4.0 ksf 3.9
FOR THE TIME BEING INTERIOR FOOTING DESIGN IS BASED ON SQUARE FOOTING
E41
FOR THE TIME BEING INTERIOR FOOTING DESIGN IS BASED ON SQUARE FOOTING
in 116
10 kip/ft 179
11 kip/ft 207
53
78
23 kip-ft/ft 110
in 0.7
0.00376
4.29 in² 2.32
in 0.7
2.84 in² 2.35
4.29 in² 2.35
9.75 5.34
21.45 11.75
1.62 in²
3.7
Di Vu Mu
0.00 0.0 0.0
0.38 13.2 2.5
0.38 -136.4 2.5
0.75 -123.2 -46.2
5.00 26.5 -251.6
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.000 2 -46
-252
-96
88
186186
110
00 13
-136
-123
27 27
105
129
-102 -79
0
Shear & Moment
Vu Mu
DON’T FORGET TO ITERATE!
E57
DON’T FORGET TO ITERATE!
10.86 26.5 -96.2
13.65 105.4 88.0
14.49 128.9 185.6
14.49 -102.4 185.6
15.32 -78.9 110.1
18.11 0.0 0.0
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.000 2 -46
-252
-96
88
186186
110
00 13
-136
-123
27 27
105
129
-102 -79
0
Shear & Moment
Vu Mu
STRAP FOOTING DESIGN
RESULTS
Clear length of strap
Distance b/w footing reactions
Total footing area required
Total footing area provided
Centroid of loads from property line
Centroid of footings from propery line
Net eccentricity
Ultimate soil pressure
14.11 ft
5.86 ft
11.99 ft
STRAP DESIGN
Select width
Select height
Select top cover
Select bar dia
Select bar area
Select bar weight
Effective depth
Maximum shear force
Shear Capacity
Critical section distance
Moment for rectangular section
rho
Calculated area of steel
Minimum area of steel
Selected area of steel
Main bars required
Moment for T-Section
Effective flange width
Assume a
Calculated area of steel
Check a
Minimum area of steel
Selected area of steel
Main bars required
#4 bars required
Main bars required
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.000 2 -46
-252
-96
88
186186
110
00 13
-136
-123
27 27
105
129
-102 -79
0
Shear & Moment
Vu Mu
DON’T FORGET TO ITERATE!
PROVIDING ALL BARS UPTO THE POINT WHERE HALF OF MAX. B.M. OCCURS + DEVELOPMENT LENGTH
PROVIDING ONLY THESE BARS FROM POINT WHERE HALF OF MAX. B.M. OCCURS TO POINT OF INFLECTION + DEVELOPMENT LENGTH
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.000 2 -46
-252
-96
88
186186
110
00 13
-136
-123
27 27
105
129
-102 -79
0
Shear & Moment
Vu Mu
PROVIDING ALL BARS UPTO THE POINT WHERE HALF OF MAX. B.M. OCCURS + DEVELOPMENT LENGTH
PROVIDING ONLY THESE BARS FROM POINT WHERE HALF OF MAX. B.M. OCCURS TO POINT OF INFLECTION + DEVELOPMENT LENGTH
STRAP FOOTING DESIGN
RESULTS units
5.86 ft
11.99 ft
94 ft²
96 ft²
8.57 ft
11.94 ft
3.37 ft
4.0 ksf
231
14.11 ft
20 in
7.25 ft||||||||||||||||||||
28.3 k/ft205
STRAP DESIGN units
9.0 inTHIS BAR IS USED AS MAIN RFT BOTH FOR STRAP AND FOOTINGS
30.0 in
2.5 in
0.750 in
0.44 in²
0.668 lb/ft
25.88 in
27 kip
19 kip
4.25 ft
262 kip-ft
0.01110
2.59 in²
0.78 in²
2.59 in²
5.9
252 kip-ft
42 in
1.2 in
2.2 in²
1.2 in
0.78 in²
2.21 in²
THIS BAR IS USED AS MAIN RFT BOTH FOR STRAP AND FOOTINGS
BASED ON 2 LAYERS WITH 1" CLEAR SPACING
H29
THIS BAR IS USED AS MAIN RFT BOTH FOR STRAP AND FOOTINGS
H32
BASED ON 2 LAYERS WITH 1" CLEAR SPACING
5.0
11.1
5.9
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.000 2 -46
-252
-96
88
186186
110
00 13
-136
-123
27 27
105
129
-102 -79
0
Shear & Moment
Vu Mu
DETAILING PHILOSOPHYCONTINUING MINIMUM REINFORCEMENT UPTO CONTRAFLEXURE POINT + DEVELOPMENT LENGTH
PROVIDING ALL BARS UPTO THE POINT WHERE HALF OF MAX. B.M. OCCURS + DEVELOPMENT LENGTH
PROVIDING ONLY THESE BARS FROM POINT WHERE HALF OF MAX. B.M. OCCURS TO POINT OF INFLECTION + DEVELOPMENT LENGTH
K66
DETAILING PHILOSOPHY CONTINUING MINIMUM REINFORCEMENT UPTO CONTRAFLEXURE POINT + DEVELOPMENT LENGTH
0.00 2.00 4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.000 2 -46
-252
-96
88
186186
110
00 13
-136
-123
27 27
105
129
-102 -79
0
Shear & Moment
Vu Mu
PROVIDING ALL BARS UPTO THE POINT WHERE HALF OF MAX. B.M. OCCURS + DEVELOPMENT LENGTH
PROVIDING ONLY THESE BARS FROM POINT WHERE HALF OF MAX. B.M. OCCURS TO POINT OF INFLECTION + DEVELOPMENT LENGTH
K75
PROVIDING ALL BARS UPTO THE POINT WHERE HALF OF MAX. B.M. OCCURS + DEVELOPMENT LENGTH
K78
PROVIDING ONLY THESE BARS FROM POINT WHERE HALF OF MAX. B.M. OCCURS TO POINT OF INFLECTION + DEVELOPMENT LENGTH
STRAP FOOTING DESIGN
DESIGN CHECKS
1-Area provided => Area required
2-Area F1 => Area required
3-Area F2 => Area required
5-F1 soil pressure = F2 Soil pressure
6-Shear capacity of F1 is adequate
7-Shear capacity of F2 is adequate
SummaryExterior footing: 5 ft x 8.75 ft x 15 inMain rft: 10 Temp/Shrinkage rft: 4
Interior footing: 7.25 ft x 7.25 ft x 15 inMain rft: 6 both ways
Strap: 9x30 with 6 bars
Concrete price: 13456
Steel price: 13119
Total price: 26575
Concrete
Exterior footing Concrete (cu ft)
Interior footing Concrete (cu ft)
Strap concrete (cu ft)
Total concrete (cu ft)
Select factor for wet volume
Wet volume
Cement Ratio
Sand Ratio
Crush Ratio
No. of cement bags
Volume of sand
Volume of crush
Price of cement bag
Price for 1 cu ft of sand
Price for 1 cu ft of crush
Steel
Exterior footing steel weight (KG)
Interior footing steel weight (KG)
Strap steel weight (KG)
Total stirrups needed
Stirrups steel weight (KG)
Total weight (KG)
Price of steel per KG
Shear reinforcement design of strap
Shear reinforcement required?
Minimum shear reinf required?
Select shear reinf bar dia
Select shear reinf bar area
Select bar weight lb/ft
Spacing of shear reinforcement
Select spacing
Detailing of bars
Point of contraflexure (ft)
Development length required (in)
No. of minimum bars required
Length of these bars required (ft)
Half of the main bars provided
Area of these bars (in²)
a (in)
Bending moment (kip-ft)
Distance where this moment occurs (ft)
Tota cut-off distance of these bars (ft)
No. of bars required for max bending moment
DETAILING PHILOSOPHYCONTINUING MINIMUM REINFORCEMENT UPTO CONTRAFLEXURE POINT + DEVELOPMENT LENGTH
PROVIDING ALL BARS UPTO THE POINT WHERE HALF OF MAX. B.M. OCCURS + DEVELOPMENT LENGTH
PROVIDING ONLY THESE BARS FROM POINT WHERE HALF OF MAX. B.M. OCCURS TO POINT OF INFLECTION + DEVELOPMENT LENGTH
Length of these bars (ft)
No. of bars b/w these two sections
Length of these bars (ft)
Total length of main bars (ft)
Weight of bottom 2#4 strap bars (KG)
PROVIDING ALL BARS UPTO THE POINT WHERE HALF OF MAX. B.M. OCCURS + DEVELOPMENT LENGTH
PROVIDING ONLY THESE BARS FROM POINT WHERE HALF OF MAX. B.M. OCCURS TO POINT OF INFLECTION + DEVELOPMENT LENGTH
STRAP FOOTING DESIGN
DESIGN CHECKS
OK
OK
OK
OK
OK
OK
Summary
Concrete price: 13456
Steel price: 13119
Total price: 26575
Concrete
55
66
20
141
1.54
216
1
2
3
29
72
108
265
20
40
Steel
73
59
53
13
16
202
65
Shear reinforcement design of strap
YES
YES
0.375
0.11
0.376
6.0
6.0
Detailing of bars
12.69
33
2
15.50
3
1.32
3.5
143
3.29
6.25
4.0
6.25
1
9.25
65.25
9
