Axially loaded member (pure tension)

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26 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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Example:

The concrete beam shown below is subjected to a tensile load of
60

kN. Determine the
elongation of the member when the temperature increases 2
0
˚C.
Note that the beam is symmetrically
loaded and reinforced.


Given
I
nformation:

Concrete
































Steel
R
einforcement
































Solution:

Calculated Properties:













(

)













An a
lternate equation to determine tangential modulus of elasticity of concrete:
























Note:
tangential modulus

is used since the concrete is subjected to
a
small load
and hence small
deformation. It is understood that u
nder small deformations

(i.e. prior to cracking)

the
tangential modulus is more accurate than the secant modulus.





























Note: concrete tensile stress is determined from
direct tensile test
.


































(

)
(

)


(

)













(

)







EQUILIBRIUM:



















Assume concrete does
not crack



Assume reinforcement does not yield






















COMPATIBILITY:

















Assum
e

perfect bond
ing

(reasonable)

N

N

200

200

4
No. 15M

3000 mm








































(No shrinkage or
creep)

























(

)
(





)








































(

)
(





)










SUBSTITUTION:



























(



)
(










)


(



)
(











)




























(







)
(

)








CHECK ASSUMPTIONS:









Concrete does not crack









































































Steel reinforcement does not yield












































































Note:
Thermal effects should not be included in strain checks since they do not produce any
internal stress
es
. They would
only be considered

if the member is restrained from movement
(fixed).

CHECK INITIAL LOAD:



























(












)


(











)








(



)


(



)