Awad Ali Saqier

alligatorsavoryUrban and Civil

Nov 26, 2013 (3 years and 11 months ago)

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Republic of Iraq

Ministry of Higher Education

And Scientific Research

Babylon University

College of Engineering

Civil Engineering Department



A Thesis

Submitted to the College of Engineering of
the

University of Babylon in Fulfillment

Of Partial Requirement for

The Degree of Master

Of Science in Civil

Engineering



By

Awad Ali Saqier

M.Sc

Supervised by

Assist. Prof .Dr.
Mahdi S. Essa

Assist. Prof.
Samir A. Al Mashhedi

E
ffect
of Fire Flame Exposure on Flexural Behavior
and Shear Strength of Reinforced NSC and HPC
Beams


200
8
October


142
9
Shawwal




With the increasing use of high


performance concrete in
buildings construction, the risk of exposing it to high temperatures
during fires has increased significantly. The exposure of reinforced
concrete beams to fire flame causes changes in their str
uctural
behavior.


This research aims to study the flexural behavior and shear
strength of reinforced concrete beams made of

normal strength
concrete (NSC) and high performance concrete (HPC) with
compressive strength (30,78) MPa respectively at (28)

days

age, and
assessing the residual flexural and shear strengths after exposure to
fire flame.


Twenty reinforced concrete shallow beam specimens having the
dimensions (100*100*1000)mm and reinforced with both tension
and web reinforcement to yield fle
xural failure with steel ratio of
(0.0126).


Twenty reinforced concrete deep beam specimens having the
dimensions (100*150*600)mm and reinforced with tension steel
only (no web reinforcement) to present shear failure, and having
steel ratio of (0.004).


The concrete specimens were subjected to fire flame at
temperature levels of (400

º
C
) and (700

º
C
) at two periods of
exposure (1, 1.5) hour then cooled either by air and water. Firing and
testing the beam specimens were conducted at age of (60) days.

Abstract




Residual flexural and shear strengths, load
-

deflection curves and
crack pattern, for the two types HPC and NSC after exposure to fire
flame were all recorded and discussed.


Results indicate remarkable reduction in flexural and shear
strengths after

exposure to fire flame. The residual flexural strength
is (84
-

88%), (70
-

72%)

for HPC, and (86
-

91%), (84
-

88%) for
NSC with (1.0) and (1.5) hour exposure periods respectively at fire
temperature (400

º
C
), while the residual at fire temperature (700

º
C
)
is (50
-
58%), (37
-
38%)

for HPC, and (53
-
60%), (26
-
41%)

for NSC
with (1.0) and (1.5) hour exposure periods respectively. The residual
shear strength is (90
-
98%), (78
-
93%)

for HPC, and (78
-

93%), (75
-

77%)

for NSC with (1.0) and (1.5) hour exposure periods
r
espectively at fire temperature (400

º
C
), while the residual at fire
temperature (700

º
C
) is (50
-
55%), (40
-
45%)

for HPC, and (54
-
57%),
(38
-
46%)

for NSC with (1.0) and (1.5) hour exposure periods
respectively.


Load


deflection curves indicate changing response with the fire
exposure, but the behavior of the HPC beams remain superior in
spite of their sensitivity to high temperatures.

It is found that the

ACI 318/ 2005
-
code equations are safe to predict
bend
ing moment capacity and shear strength for fire temperature
(400

º
C
)
, but become unable to predict them at fire temperature (700

º
C
)
.

The shear strength prediction of reinforced concrete beams without
web reinforcement by the three codes ( ACI, Canadian, N
ew
Zealand), Zsutty equation and Rebeiz equation, it is found that the
equations are unconserative to predict shear strength after exposure
to fire flame except the

New Zealand code equation which was
found able to predict shear strength after exposure to
fire flame
temperature for the two types of concrete HPC and NSC.

The results of this research show that the residual bending moment
capacity for HPC is more sensitive to fire flame temperature than
NSC, while the residual shear strength for NSC is more s
ensitive

to
fire flame temperature than HPC.


Flexural failure was characterized by widening of the vertical
cracks and subsequent crushing of the top fiber concrete, while shear
failure occurred by sudden excessive

opening wide diagonal cracks
and
characterized as true shear failure that occurres in beams with
a/d


1.