الفهرس 
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Abstract
The main objective of this investigation was to investigate the behavior of statically determinate prestressed concrete beams subjected to fire. The various parameters included the concrete compressive strength, concrete cover,
prestressing Level (fully or partially or non prestressed), and presence of non prestressed steel. An experimental program was carried out to study the effect of fire. The experimental program consisted of twelve specimens; five of them
were partially prestressed, another five specimens were fully prestressed and two specimens were non-prestressed concrete beams. Modes of failure, ultimate carrying load, deflection and strain of steel reinforcement and concrete at critical
sections were examined. The beams had different reinforcement ratios at midspan.
All beams had the same dimensions and shear reinforcement. The beams had an overall width, depth and length of 160, 340 and 4400-mm respectively, and were simply supported with a clear span of 4000-mm. The Prestressing strand had a draped profile similar to the shape of the bending moment produced by the acting
loads. The main reinforcement of the specimens changed according to the Prestressing index. One strand with diameter 15.24-mm was used to prestress the fully prestressed beams, one strand with diameter 12-mm in addition to two 10-
mm diameter bars were used to reinforce the partially prestressed beams and six 10-mm diameter bars were used to reinforce the non- prestressed beams. The stirrups were 10-mm diameter bars every 200-mm at the middle part of the beams and every 100-mm at the edges to prevent the possibility of shear failure. Details of
shear reinforcement were kept the same for all the specimens. Additional horizontal stirrups were added at anchor zone to resist the splitting force. All specimens of the experimental program were tested in the laboratories of the Housing and
Building National Research Centre The cracking and service load behavior of prestressed and non prestressed concrete beams were presented. The analyses and comparison of the experimental test results including modes of failure, ultimate loads and ductility were also introduced.
Analytical investigation based on strain compatibility approach of tested specimens including prediction of the deformational behaviour of prestressed and non prestressed reinforced concrete beams. A comparison of the theoretical and experimental test results was carried out.
6-2 Conclusions
The experimental and theoretical investigation on behaviour of statically determinate prestressed concrete beams subjected to fire led to the following conclusions:
1) Exposure to fire for 3 hours duration at 600oC slightly decreased the load-carrying capacity of non prestressed, partially prestressed and
fully prestressed beams with concrete compressive strength equals to 40 MPa by about 3, 5 and 11 %, respectively. Higher decrease in the load-carrying capacity of partially and fully prestressed sections by 17% and 20%, respectively was observed for beams with concrete compressive strength equals to 80 MPa.
2) Exposure to fire for 3 hours duration at 600oC reduced the ductility of partially and non prestressed concrete beams by about 8.5 and
11%, respectively.
3) After exposure to fire for 3 hours duration at 600oC the reduction in ductility of the partially prestressed high strength concrete beams
was 11.5 % higher than that of partially prestressed normal strength concrete beam .
4) Exposure to fire for 3 hours duration at 600oC increased the mid span deflection and ductility for fully prestressed concrete beams. This is
attributed to the loss in the beam stiffness of the fully prestressed beam confirmed by the observed high crack width after fire exposure due to absence of non prestressed steel.
5) Exposure to fire for 3 hours duration at 600oC increased the deflection and compression strain at mid span at the same load level compared to the non-exposed beams. The difference in the thermal
expansion between concrete and steel caused non uniform hair cracks along the fired area.
6) Increasing the concrete cover had a negative effect on the flexural capacity of partially prestressed beams when exposed to fire. This is
mainly due to the separation of the concrete cover at the level of the non prestressed steel. However, increasing the concrete cover of fully prestressed beams helped in protecting the prestressed strand
from fire and therefore enhancement in the strength was achieved.
7) The ductility of the partially prestressed concrete beams with 25 mm concrete cover was 15% higher in comparison to that of the partially
prestressed concrete with 40 mm concrete cover. This decrease in ductility was due to the decrease in the load carrying capacity of beam with 40 mm concrete cover.
8) The partially and non prestressed concrete beams with concrete coverequal to 25 mm had higher resistance to the three hour fire duration at
600ºC than fully prestressed concrete beam in terms of ultimate capacity.
9) The behaviour of the control specimens (non-prestressed, partially and fully prestressed beams) was confirmed as per the well established in the literature in terms of deflection, ductility and
stiffness.
10) An analytical model using strain compatibility approach incorporating reduced material properties to simulate the effect of
fire was able to predict the behaviour of partially, fully prestressed and non prestressed concrete beams.
6-3 Recommendations for Future Research Work
The following recommendations are suggested for future research work:
1) Ductility and behavior of partially and fully prestressed concrete beams with ultra high strength concrete (comparison of prestressed concrete beams with fcu 100 and 150 Mpa).
2) Protection of prestressed concrete beams exposed to fire (comparison of prestressed concrete beams with and without protection).
3) Effect of exposure to fire at different temperature and duration on the behavior of flexural member. (Exposed to 300, 600 and 800 ºC for 1, 2 and 3 hours).
4) Ductility and behavior of partially and fully prestressed concrete beams with different cross section (comparison of prestressed concrete beams
with rectangular and T section).