cover to the center of the bars depth of bottom reinforcement (h cover) depth of top reinforcement (h cover)

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1 Interaction (ACI318) Checker today Input Column dimensions Reinforcement Materials (steel, concrete, bolts) Output Moment capacity Column interaction diagram RC Column Capacity - Axial Force - Bending Moment Interaction (ACI 318) Axial force bending moment interaction ultimate limit state Column dimensions h = 10 in b = 18 in A g = h * b = 180 in 2 RC Element Area Reinforcement cover d = d 2.44 in 7.56 in 2.44 in cover to the center of the bars depth of bottom reinforcement (h cover) depth of top reinforcement (h cover) Tension side reinforcement # 9 n = 3 A s = 3.00 in 2 tens.reinf = 1.67 % Compression side reinforcement # 9 n = 3 A s.b = 3.00 in 2 comp.reinf = 1.67 % bar size no of bars area of tension reinforcement percentage of tension reinforcement bar size no of bars area of compression reinforcement percentage of compression reinforcement A s.t = A s + A s.b = 6.00 in 2 total area of reinforcement = 3.33 % element total percentage of reinforcement per ACI 318 Section Confinement reinforcement (tied or spiral) tied Reinf percentage should be between 0.01Ag and 0.08Ag Materials Concrete f c ' = 4 ksi Reinforcement type A 615 Grade 60 f y = 60 ksi concrete characteristic cylinder strength reinforcement yield strength see reinforcement types here

2 Reinforcement modulus of elasticity per ACI 318 E s = ksi Section f y / E s = Modulus of elasticity of reinforcement The relationship between concrete compressive stress and concrete strain is satisfied by an equivalent rectangular concrete stress distribution defined by a 0.85*f c ' uniform stress over an equivalent compression zone bounded by edges of the cross section and a straight line located parallel to the neutral axis at a distance a = 1 *c from the fiber of maximum compressive strain. Sections and = For tension controlled sections Compression controlled section with spiral reinforcement Compression controlled section other reinforced members Section Values of strength reduction factor Maximum usable strain at extreme concrete compression fiber is Section Maximum usable strain at extreme concrete compression fiber shall be assumed equal to ; The relation between concrete compressive stress and concrete strain is assumed rectangular Section f c ' value uniformly distributed over an equivalent compression zone bounded by edges of the cross section and a straigth line located parale to the neutral axis at a distance a = 1 *c from the fiber of max. compression strain 1 = 0.85 a = 1 * c factor relating depth of equivalent rectangular compressive to neutral axis depth depth of equivalent rectangular Section between 2500 and 4000 psi b1 = 0.85, above will be reduced lineary at a rate of 0.05 per 1000 psi but not lower than 0.65 Section Section stress in reinforcement below f y shall be taken as E s times steel strain. For strains greater than that corresponding to fy, stress in reinforcement shall be considered independent of strain and equal to f y.

3 Point 1 Pure compression P n,max = 0.80 [0.85f c '(A g A st )+f y A st ] P n,max = Point 2 f s = kips The neutral axis is located in the center of the bottom reinforcement d = 7.56 in *(c d c )/c= per ACI 318 eq and 10 2 Maximum allowable value of the nominal axial strength of cross section multiplied by the strength reduction factor compressive shortening strain and f s = 0 Neutral axis location in this case in the center of the bottom reinforcement a = 1 * 6.43 in depth of equivalent rectangular * [ 0.85* f c ' * a * b *Es* A s.b ] kips * [(0.85* f c ' * a * b) * (h/2 a/2) + ( 0.002*Es* A s.b ) * (h/2 d c )] ft kips Point 3 f s = 0.5 * f y Bottom reinforcement strain (tension): t = ( 0.5 * f y ) / E s = 5.62 in compressive shortening strain and f s = 0.5 * f y *(c d c )/ a = 1 * 4.78 in * [ 0.85* f c ' * a * b + depth of equivalent rectangular *Es* A s.b t * E s * A s ] kips * [(0.85* f c ' * a * b) * (h/2 a/2) + ( *Es* A s.b ) * (h/2 d c ) + t * E s * A s * (d h/2)] ft kips

4 Point 4 f s = f y (Balanced point) Bottom reinforcement strain (tension): t = f y / E s = Section compressive shortening strain and tension reinforcement reaches the strain corresponding to f y (f s = f y ) 4.47 in *(c d c )/ a = 1 * 3.80 in depth of equivalent rectangular * [ 0.85* f c ' * a * b *Es* A s.b f y * A s ] kips ft kips * [(0.85* f c ' * a * b) * (h/2 a/2) + ( *Es* A s.b ) * (h/2 d c ) + f y * A s * (d h/2)] Point 4b f s = f y Transition from Compression controlled section to Tension Controlled Section Bottom reinforcement strain (tension): t = f y / E s = 0 For sections in which the net tensile strain at nominal strength t is between the limits for compression controlled ans tension controlled sections f will be linearly increased from that for compression controlled to in *(c d c )/ = 0.73 transition from compression controlled to tension controlled section a = 1 * 3.19 in depth of equivalent rectangular * [ 0.85* f c ' * a * b *Es* A s.b f y * A s ] kips ft kips * [(0.85* f c ' * a * b) * (h/2 a/2) + ( 0.001*Es* A s.b ) * (h/2 d c ) + f y * A s * (d h/2)]

5 Point 4c f s = f y Transition from Compression controlled section to Tension Controlled Section Bottom reinforcement strain (tension): t = f y / E s = compressive shortening strain and tension reinforcement is in transition from tension controlled to tensin controlled 3.23 in *(c d c )/ = 0.82 transition from compression controlled to tension controlled section a = 1 * 2.74 in depth of equivalent rectangular * [ 0.85* f c ' * a * b *Es* A s.b f y * A s ] kips ft kips * [(0.85* f c ' * a * b) * (h/2 a/2) + ( *Es* A s.b ) * (h/2 d c ) + f y * A s * (d h/2)] Point 5 t = tension controlled section Bottom reinforcement strain (tension): t = compressive shortening strain and et has reached corresponding to = 0.9 (tension controlled section) 2.84 in *(c d c )/ = 0.90 tension controlled section a = 1 * 2.41 in * [ 0.85* f c ' * a * b + depth of equivalent rectangular *Es* A s.b f y * A s ] 3.46 kips ft kips * [(0.85* f c ' * a * b) * (h/2 a/2) + ( *Es* A s.b ) * (h/2 d c ) + f y * A s * (d h/2)]

6 Point 6 Pure Bending compressive shortening strain and et has reached Bottom reinforcement strain (tension): t = corresponding to = 0.9 (tension controlled section) 2.67 in *(c d c )/ = 0.90 tension controlled section a = 1 * 2.27 in depth of equivalent rectangular * [ 0.85* f c ' * a * b *Es* A s.b f y * A s ] kips ft kips * [(0.85* f c ' * a * b) * (h/2 a/2) + ( *Es* A s.b ) * (h/2 d c ) + f y * A s * (d h/2)] Point 7 Maximum tension = 0.90 tension controlled section = * f y * [A s.b + A s ] kips 0.00 ft kips Data for the M N interaction graph: N cap M cap Point Point Point Point Point 4b Point 4c Point Point Point N (kip) N eff M eff CO CO CO M (kip ft)