Transcribed Image Text: neutral axis of cracked section measured from top of beam, x =,

Transcribed Image Text: neutral axis of cracked section measured from top of beam, x =,
in
Ier =
in
(e) Compute the flexural stresses. Compressive stress of concrete at the top of the beam and
tensile stresses at the centroid of the top and bottom layers of steel bars.
Bending stress of concrete in extreme compression f. =
psi
Bending stress of top layer steel bars in tension f: =
psi
Bending stress of bottom layer steel bars in tension f: =
psi Transcribed Image Text: Transformed Area Method (Concrete Cracked – Elastic Stresses Stage)
Problem 2) Modified Problem 2.13 (page 55, McCormac and Brown, 10th Ed.)
Change f’c to 5 ksi and cross-sectional properties See figures below.
30 kip
W = 2 kip/ft
A
10 ft.
20 ft.
30 ft.
f’. = 5000 psi
30 in.
36 in.
8 #9 bars
3 in.
3 in.
16 in.
(a) Find the reactions at A and B. RA =
kip, RB =
kip
ft*kip
(b) Determine the maximum applied moment. Mmax =
(c) Calculate the cracking moment of the beam and verify that the beam has cracked under the
applied loads. Mer =
ft*kip
in3
Moment of inertia of gross section, Ig =
Modulus of Rupture f, =
(d) Calculate the cracked moment of inertia. Note that you will need to first calculate the concrete
psi
modulus of elasticity and modular ratio. Do not use the textbook modular ratio of n=8.
Ec =
psi (use the simplified equation for normal weight concrete)
Modular ratio, n =

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