This preview shows pages 1–2. Sign up to view the full content.
Name: _ _SOLUTION _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
CE 441 Reinforced Concrete Design – Assignment 8
Due Thursday November 5, 2009
Notes: The modulus of elasticity of normal weight concrete is given by E
c
=57,000
'
c
f
(psi) according to
ACI 8.5.1. The modulus of rupture
f
r
=7.5
'
c
f
(psi) as specified by ACI 9.5.2.3.
The effective moment of
inertia of a beam is given by ACI 9.5.2.3 as
cr
a
cr
g
a
cr
e
I
M
M
I
M
M
I

+
=
3
3
1
. The cracking moment is
M
cr
=
f
r
I
g
/
y
t
where
y
t
is the distance from centroid of the gross section to the location of maximum tension in
concrete. The center deflection of a simply supported beam of span length
L
under uniformly distributed load
w
is
Δ
max
=5
wL
4
/(384
EI
).
1.
A concrete beam is used for a 25ft simple span. It has a rectangular section of width
b
=15 in. and has only
tension reinforcement with an effective depth
d
=20 in., total depth
h
=23 in.,
f
c
'=3,500 psi,
f
y
=60,000 psi,
A
s
=3 no. 10 bars in one row. Determine the location of the neutral axis
kd
for the cracked section (stresses
linear). Calculate the gross section moment of inertia
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview. Sign up
to
access the rest of the document.
This document was uploaded on 03/03/2010.
 Spring '09

Click to edit the document details