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ACI 318-08 - Chapter 10

Engr:

FLEXURE AND AXIAL LOADS

Date: 10-19-12

Proj. No.:

Variables:

Φ 0.9 :

=> factor for bending (9.3.2.1)

w.c 145 :

(10.2.3)

β1 0.85 :

=> for fc < OR = 4 ksi (10.2.7.3)

ε.c 0.003 :

fy 60 ksi * :

=> steel yield strength (ksi)

fc 4000 psi * :

=> concrete strength (psi)

E.c w.c 1.5^33 * fc psi * sqrt * :

(8.5.1)

b 12 in * :

=> width of section (in)

h 30 in * :

=> total depth of section (in)

E.c ksi 3644.147

bardia 1 in * :

=> diameter of tension reinf. bar (in)

E 29000 ksi * :

(AISC 360-10)

stirrup 1 in * :

=> diameter of shear stirrups (in)

clr 2 in * :

=> clearance for tension reinf (in)

Mu 37.2 kip * ft * :

=> factored moment on section

d h clr - stirrup - bardia 2 / - :

d in 26.5

= depth to center of tension reinf (in)

Determine moment capacity using:

As 0.42 in 2^* :

#6 @ 12" =>

ρ As b d * / :

ρ 0.001

a As fy * β1 fc * b * / :

a in 0.618

(10.2.7.1)

ΦMn Φ As * fy * d a 2 / - (* :

c a β1 / :

c in 0.727

Mu ΦMn / 0.751

ΦMn kip ft * 49.501

ε.t ε.c d c - c / (* :

ε.t 0.106407

ε.t 0.002 < check1 Compression Controlled : (Φ 0.65 : (& ε.t 0.005 > check1 Tension Controlled : (Φ 0.90 : (& check1 Transition : (Φ 0.65 ε.t 0.002 - (2503 / (* (+ : (& if if

Tension kip #

Compression kip #

check1 Tension Controlled

Φ 0.9

Determine area of steel REQUIRED to carry bending moment:

ω 1 1.18 / 11 2.36 Mu Φ / * b d 2^* fc * / - sqrt - (* :

ω 0.015

ρ ω fc fy / * :

ρ 9.896 104 -^*

reinforcement ratio

As.r ρ b * d * :

As.r in 2^0.315

=> Required

a As.r fy * β1 fc * b * / :

a in 0.463

Determine min and max area of steel for section:

ρ1 200 psi * fy / :

ρ2 3 fc psi * (sqrt fy / * :

ρ ρ2 ρ1 > ρ2 ρ1 if :

ρ 0.003

As.min ρ b * d * :

As.min in 2^1.06

=> Minimum required by (10.5.1)

Asb 0.85 β1 * fc * b * d * fy / 87 ksi * 87 ksi * fy + / (* :

Asb in 2^9.065

<= balanced area of steel

As.max 0.75 Asb * :

As.max in 2^6.799

=> MAX area of steel reinf. for section

(10.5.3) - If As provided is 1/3 larger than As required

then the requirement of 10.5.1 and 10.5.2 need not be followed

43 / (As.r * in 2^0.42

Shrinkage and Tempature Reinforcment:

As.shrink 0.0018 h * b * :

As.shrink in 2^0.648

(7.12.2.1)

Spacing:

fs 23 / fy * :

c.c 3 in * :

s 1540000 psi * fs / (* in * 2.5 c.c * - :

(10.6.4) Eq.(10-4)

s in 7.5

3 h * 18 in * ≥ s.max 18 in * : s.max 3 h * : if

(10.5.4) Maximumum spacing shall not exceed three time the thinckness,

s.max in 18

nor 18in for slabs and footings

ΦM.nbal kip ft * #