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16" Wall Footing Design Guide

This document provides the design calculations for a 16-inch wide concrete wall footing. It calculates the factored loads on the footing, checks the bearing pressure, designs the main and secondary reinforcement, and verifies the strength of the wall and footing at the bearing interface. The main reinforcement designed is #4 bars spaced at 32 inches. The secondary reinforcement is 2 #5 bars spaced at 14 inches. Both the wall and footing strengths exceed the factored loads at the bearing interface.

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92 views1 page

16" Wall Footing Design Guide

This document provides the design calculations for a 16-inch wide concrete wall footing. It calculates the factored loads on the footing, checks the bearing pressure, designs the main and secondary reinforcement, and verifies the strength of the wall and footing at the bearing interface. The main reinforcement designed is #4 bars spaced at 32 inches. The secondary reinforcement is 2 #5 bars spaced at 14 inches. Both the wall and footing strengths exceed the factored loads at the bearing interface.

Uploaded by

biniam
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as XLS, PDF, TXT or read online on Scribd
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PROJECT: Page:

CLIENT:
SUBJECT: 16" WALL FOOTING JOB NO: Designed:
TITLE: WF16 Checked:
'file:///conversion/tmp/scratch/490161191.xls'#$WF
INPUT
Wall width, D: 8 in 8 in
Axial dead load, Wd: 1.20 Klf (unfactored)
Axial Live Load,WL: 0.46 Klf (unfactored)
Axial wind load, Ww: (unfactored)
Surcharge, Ws: 0.00 Klf
Clear cover to footing, 3 in 1.33 Ft. 0.33 Ft. 0.33 Ft.
Bar size(Transverse): 2#4 2.33 Ft.
Bar size(Longitidunal):3#5 1.00 Ft.
Depth from grade, h: 2.33 Ft.
Wall stress; 1500 Psi
Ftg. Conc. Stress, fc': 3000 Psi 1.33 Ft.
Steel Stress, fy: 60000 Psi
Soil Density 120 pcf
Allowable Soil pressur 2.00 Ksf
Width of Footing, L: 1.33 Ft.
Thickness of ftg.,Df: 1.00 Ft.
Codes:
ACI 318-2002 Section 9.2.1
Eq. 9-1 through 9-7

Check bearing pressure:


Weight of footing-Eart = 1.33 x 1.00 x 0.15 = 0.20 Ksf
Weight of soil, Ws = 1.33 x 0.66 x 0.12 = 0.11 Ksf
Total Load, 1.20 + 0.46 + 0.00 + 0.00 + 0.20 + 0.11 = = 1.97 K
Footing Area, A 1.965 / 2.00 = 0.98 ft. OK

Factored Loads:
Pu= 1.2 Wd + 1.6( WL+Ww+Ws)= 1.2 x 1.20 Klf + 1.60 x 0.46 Klf = 2.18 Klf
Factored net soil pressure(max.), pn= = 2.18 / 1.33 = 1.64 Ksf

Oneway shear:
Effective Depth, d: Df-c-bar diam./2= 12 -3 - 0.1 = 8.9 in
phi: 0.75 (As per ACI 318-02, 9.3.2.3)
One way shear capacity, phixVcb: 0.75 x 2.00 x 54.77 x 12.00 x 8.88 = 8750 Lbs or 8.75 K
where Vcb=2 * (fc' )2 * b * d

Oneway shear force, Vcb_actual= pn * [(L-D)/2 -d]= 1.64 Ksf *(0.33 - 0.740 )= -0.67 K
phi * V cb > Vcb_actual OK

Design of main reinforcement;


Ultimate Moment, Mu =[ P xBx((L-D)/2)2 /2]= 1.64 Ksf x 1.00 x 0.33 x 0.33 / 2 = 0.09 ft-K/ft or 1.08 in-K/ ft
phi: 0.9 (As per ACI 318-02, 9.3.2.1)
Dessign Moment=Mu/phi= 1.19983 in-K/ ft
Reinf. Area, As nominal= =Mn/(fy x 0.9 x d)= 0.003 sq.in /ft
a=As x fy/ ( 0.85*fc'*B)= 0.0 in
As=Mn/(fy x (d-a/2))= 1.20 / [ 60 x ( 8.9 - 0.00 /2) ]= 0.002 sq.in /ft

Check for min. reinforcement;


As min.= 0.0018*12*h= 0.0018 x 12 0.022 sq.in /ft
Use As min since As min>As req.
Spacing of rebar=As required/As of # 4 0.20 / 0.022 = 9 ft Use---> # 4 @ 32 in

Net tensile Strain Compatibility Check;


Depth of neutral axis, c=a/0.85= 0.0 in /0.85= 0.0 in
es=ec*(d-c)/c= 0.003 x ( 9.0 - 0.0 ) / 0.0 = 4.672 > 0.005 OK

Design of secondary reinforcement;


As min.= 0.0018*12*h= 0.0018 x 12 x 12.0 = 0.259 in2
Spacing of rebar=As required/As of # 5 0.31 / 0.26 = 14.35 in Use---> 2 #5

Check for bearing at interface;


Strength of wall at bearing; 8x 12 x 1500 = 144.00 K > 2.18 K OK
Strength of footing at bearing; 8x 12 x 3000 = 288.00 K > 2.18 K OK

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