This document summarizes the design of a single reinforced concrete corbel according to ACI 318-05. The corbel is 300mm wide and 500mm deep with 35MPa concrete and 415MPa steel reinforcement. It was designed to resist a vertical load of 370kN applied 100mm from the face of the column. The design includes checking the vertical load capacity, calculating the required shear friction and main tension reinforcement, and designing the horizontal reinforcement. The provided reinforcement of 3 No.6 bars for tension and 3 No.3 link bars at 100mm spacing was found to meet all design requirements.

1. DAR GROUP
Project
The Pearl
Job Ref.
Q09079
Section
PA
Sheet no./rev.
1
Calc. by
Eng.MS
Date
09-July-06
Chk'd by
Eng.AE
Date App'd by Date
RC SINGLE CORBEL DESIGN TO ACI 318-05
Vu
Nuc
a
d h
Framing
bars
Main
tension
bars
Horizontal
bars
Steel angle
mind/2
Shd
2
3
Sh
Sh
Corbel geometry
Width of corbel; b = 300 mm
Total thickness of corbel; h = 500 mm
Depth to main reinforcement; d = 450 mm
Material properties
Yield strength of reinforcement; fy = 415 MPa
Compressive strength of concrete; f’c = 35 MPa
Type of concrete; Normal weight
Unit weight of concrete;  = 1.00
Corbel construction; Monolithic
Coefficient of friction;  = 1.4   = 1.40
Design load data
Factored vertical load; Vu = 370.00 kN
Distance of vertical load from face of column; a = 100 mm
Horizontal force acting on corbel; Nuc = 75.00 kN
Strength reduction factor;  = 0.750
Vertical load capacity check
Nominal vertical load; Vn = Vu / = 493.33 kN
Nominal vertical load capacity; Vn_cap = min(0.2  f’c  b  d, 5.5 MPa  b  d) = 742.50 kN
PASS - Nominal vertical load is less than the nominal vertical load capacity
Find shear friction reinforcement
Minimum horizontal force acting on corbel; Nuc_min = 0.2  Vu = 74.00 kN
Horizontal force acting on corbel; Nuc_act = max(Nuc, Nuc_min) = 75.00 kN
For balanced condition; j = 0.85
Area for shear friction reinforcement; Avf = Vn / (fy ) = 849 mm2
Af = [(Vu  a) + (Nuc_act  (h –d))] / (  fy  j  d) = 342 mm2
Nominal area required; An = Nuc_act / ( fy) = 241 mm2

2. DAR GROUP
Project
The Pearl
Job Ref.
Q09079
Section
PA
Sheet no./rev.
2
Calc. by
Eng.MS
Date
09-July-06
Chk'd by
Eng.AE
Date App'd by Date
Main tension reinforcement check
Minimum area of tension reinforcement; Asc_min = 0.04  f’c  b  d / fy = 455 mm2
Area of tension reinforcement required; Asc = max([(2  Avf) / 3] + An, Af + An) = 807 mm2
Asc_req = max(Asc, Asc_min) = 807 mm2
Main tension reinforcement; 3 No.6 bars
Diameter of tension bars; Dtension = 19 mm
Number of tension bars; Ntension = 3
Area of tension reinforcement provided; Asc_prov = Ntension    Dtension
2
/ 4 = 851 mm2
PASS - Tension reinforcement is adequate
Horizontal reinforcement check
Minimum area of horizontal reinforcement; Ah_min = 0.5  (Asc_req - An) = 283 mm2
Area of horizontal reinforcement required; Ah = max(Avf / 3, Af / 2) = 283 mm2
Ah_req = max(Ah, Ah_min) = 283 mm2
Horizontal reinforcement; 3 No.3 bars
Diameter of horizontal bars; Dhorizontal = 9 mm
Number of horizontal bars; Nhorizontal = 3
Area of horizontal reinforcement provided; Ah_prov = 2  Nhorizontal    Dhorizontal
2
/ 4 = 382 mm2
PASS - Horizontal reinforcement is adequate
Maximum spacing of horizontal bars; Sh_max = 2  d / (3  Nhorizontal) = 100 mm
Actual spacing of horizontal bars; Sh = 100 mm
PASS - Horizontal bar spacing is adequate
Design Summary
Single corbel 300 mm wide by 500 mm deep with 35 MPa concrete and 415 MPa steel
Provide main tension reinforcement as 3 No. 6 bars
Provide horizontal reinforcement as 3 No. 3 link bars at maximum 100 mm centres