Symbols and Terminology
This section presents a table of symbols and variables referenced by the ACI 318 design codes.
Symbol | Description |
---|---|
Ac | Area of concrete in compression (inside the Whitney compression-block) |
Ag | Gross area of section |
As | Reinforcing steel area |
Av | Shear Reinforcing steel area |
a | Depth of equivalent rectangular stress block as defined in ACI 10.2.7.1 |
b |
Total Section Width Length of critical section in compression |
C | Column section maximum compression capacity |
Cc | Compression force in concrete |
Cs | Compression force in reinforcement bar |
d | Distance from the top of compression surface to center of the flexure reinforcement perpendicular to that direction of the shear plane |
db | Nominal diameter of reinforcement bar |
Ec | Concrete modulus of elasticity |
Es | Reinforcement steel bar modulus of elasticity |
Fs | Individual reinforcement stress |
f'c | Concrete max permissible stress |
fct | Average splitting tensile strength of lightweight aggregate concrete (psi units) |
fy | Reinforcement stress capacity (psi units) |
h | Total section depth |
k | Effective length factor of column |
Lc | Distance from Neutral Axis (N.A.) to maximum concrete compression fiber |
Ls | Distance from Neutral Axis (N.A.) to center of reinforcement bar being considered |
lc | Length of compression member in a frame, measured from center to center of the joints in the frame |
ld | Reinforcement bar development length |
Ms | Moment capacity contribution of reinforcement bars to section capacity |
Mc | Moment capacity contribution of concrete to section capacity |
Mn | Nominal moment capacity of concrete section |
Mu | Factored ultimate moment on section |
Mθ | Moment about a given angle. Calculates as |
P | Section compression capacity for given neutral axis and compression side |
Pb | Balanced compression capacity |
Pn | Nominal axial capacity of concrete section |
Pu | Factored ultimate axial on section |
Tc | Torsional capacity of concrete section |
Ts | Tension force in reinforcement bar |
Tu | Factored ultimate torsion on section |
s | Reinforcement spacing |
Vu | Factored ultimate shear force on section |
Vs | Shear reinforcement capacity |
Vc | Concrete section shear capacity |
ϕc | Concrete compression capacity reduction factor
|
ϕb | Flexure capacity reduction factor of concrete (0.90 for ACI 318-99) |
ϕT | Torsional capacity reduction factor of concrete (0.85 for ACI 318-99, 0.75 for ACI 318-02) |
ϕs | Shear capacity reduction factor of concrete (0.85 for ACI 318-99, 0.75 for ACI 318-02) |
δc | Actual concrete density used |
ρ | Reinforcement ratio of section |
ρb | Balanced reinforcement ratio |
εc | Concrete max permissible strain |
Ψ | Ratio of ΣEI/lc of compression members to ΣEI/l of flexure members in a plane at one end of a compression member |