EAS 209-Fall 2010
Instructors: Christine Human
9/17/2010
1
Lecture 15- Bending in Composite
Lecture 15
Bending in Composite Members
Beams subjected to bending can be made of two or
more materials to form a composite section.
One example is a reinforced concrete beam which
is often used in buildings to support floors.
•
Concrete has good compressive strength, but is
weak in tension
•
Steel reinforcing bars (rebar) are embedded in the
concrete to help resist tensile forces.
Today’s Objective:
•
Calculate bending stresses in composite
members using transformed sections
Today’s Homework:
rebar
Reinforced concrete beam
with distributed load, q is in
positive bending:
•
compressive stresses on
the top surface
•
tensile stresses on the
bottom surface
q
EAS 209-Fall 2010
Instructors: Christine Human
9/17/2010
2
Lecture 15- Bending in Composite
For a homogeneous beam, the maximum stress is
given by
I
Mc
m
=
σ
From last lecture the curvature of the beam,
κ
EI
M
=
=
ρ
κ
1
Therefore
Ec
I
Mc
m
κ
σ
=
=
However, for a composite beam each material will
have a different modulus E, in which case the
above equations does not apply.

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