الفهرس 
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Abstract
The strength and serviceability of reinforced concrete (RC) and prestressed concrete (PC)
elements are generally affected after fire exposure. The main objective of this investigation
is to study the behavior of the prestressed beams under two levels of elevated temperature
statically determinate prestressed concrete beams subjected to elevated temperature. The
tested specimens consisted of simply supported unbounded post tension and conventional
beams with and without carbon nano-tube (CNT) additions. The overall dimensions of
the specimens were 150 x 300 x 1250 mm. All prestressing specimens were cast using
unbonded prestressing strands. The strands were stressed after the concrete had reached an
age of 28 days.
The experimental program was divided into three groups. In the first group, the objective
was studying the flexural behavior of conventional simply supported beams with and
without of carbon nano tube (CNT) after exposed to elevated temperature at levels lab
temperature, and 400ºC, for 120 minutes durations respectively were studied .
In the second group, the objective was studying flexural behavior of post tensioned
simply supported beams with and without of carbon nano tube (CNT) after exposed to
elevated temperature at levels lab temperature, and 400ºC, for120 minutes durations
respectively were studied .
In the third group the objective was studying the flexural behavior of post tensioned simply
supported beams with steel reinforcement additions after exposed to elevated temperature
at levels lab temperature, and 400ºC, for120 minutes durations respectively were studied.
All specimens of the experimental program were tested under static vertical load in the
laboratories of the National Research Center. Physical, and mechanical characteristics of
the used materials were evaluated. Details of the specimen geometry, materials, casting
and testing methodology are described. Test setup, control system and measurement
devices which were used in the experiments are also reported.
The following data was recorded :
The crack pattern for all beams.
The load at each increment and failure load for beams.
The deflection corresponding to load at the mid – span and quarter – span for each
tested beams.
The surface concrete strains at compression and tension concrete zones at critical
section for each tested beams by using strain gauges.
Commulative deformation at compression and tension concrete zones at critical sections
for each tested beams by using ( LVDT ).
As the numerical study will be considered in this thesis, The modeling steps with ANSYS
(12). ANSYS was applied, as a Finite Element Model FEM, to a plain the flexural behavior
of the prestressed beams loaded at mid-span of beams. The model specimens consisted of
simply supported unbounded post tension and conventional beams. This thesis includes a
comparison between the theoretical study according to ECP 203, ACI 318m-11 codes and
experimental test results.
The results showed that decreasing the crack number due to presence of carbon nano-tube
(CNT) for conventional, prestressed concrete beams . the presence of carbon nano-tube
(CNT) had improved the mechanical performance of prestressed beams after exposed to
elevated temperatures with carbon nano-tube (CNT). While the steel reinforcement
additions beams had more significant than (CNT) addition beams. The decrease in
mechanical performance of prestressed beams after exposed to elevated temperature. The
results obtained by FEA and theoretical study according to ECP 203, ACI 318m-11 codes
indicated good agreement with the experimental program.