الفهرس 
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Abstract
The main objective of this thesis was to study the behavior of headed bars with lap splices in
tension zones in reinforced concrete slabs. The effect of several variables affecting the
behavior of flexural members with lap splice in tension was studied. The experimental
program was carried out at the Reinforced Concrete Laboratory, Faculty of Engineering,
Alexandria University. The experimental study consisted of nine simply supported reinforced
concrete one-way slabs. All tested slabs had the same dimensions (2400 mm x 1000 mm x
120 mm), the same longitudinal reinforcement ratio (μ= 0.413%). The thickness of clear
concrete cover from bottom, side cover, and relative head area were kept constant as 20 mm,
60 mm, and 6.91 respectively. All slabs were tested using four lines loading, until failure
occurred. The main studied variables were:
1- Lap splice length (15, 27, and 45 times the bar diameter, db).
2- Confinement in the lap splice zone; two kinds of confinement were used. These include transverse embedded beams with stirrups and circular spiral stirrups around the spliced bars, with a constant lap length of 15 times the bar diameter (db).
3- Effect of debonding the spliced bars in the lap splice zone.
4- Effect of applying repeated cyclic loading on the behavior and the integrity of lap joint of the slabs provided with different confinement schemes in the lap zone.
Test results were illustrated and discussed in details. Some of outcome conclusions may be summarized as follows for the dimensions and reinforcement used in the present study:
1- The behavior of ordinary slab without splice can be achieved in slabs with spliced tension reinforcement with 100% cut off ratio when the lap splice length equals to 45 db without headed bars, and without using any confinement at the splice zone. This behavior can be obtained when the lap length equals to 27 db with headed bars, and without using any confinement at the splice zone, or when the lap length equals to 15 db with headed bars, and confinement at splice zone was provided.
2- Spliced slabs with the lap length 15 db with headed bars, without using any confinement at the spliced zone, and with 100% cut off ratio, a reduction in ductility and ultimate load capacity occurred. The mode of failure changed from ductile flexural failure to brittle (bottom split).
3- In spliced slabs with the lap length 15 db, 100% cut off ratio, and provided with confinement in the spliced zone, the mode of failure changed from brittle (as occurred for slab without confinement) to ductile flexural failure.
4- Debonding of the lapped headed bars resulted in a fewer number of surface cracks but with larger width comparing with the similar bonded specimen. Also, debonding resulted in a loss of ductility and the overall capacity was also reduced due to the loss of bond contribution. Generally, this specimen showed less ductility than that of the unspliced specimen, and the failure was brittle.
5- Slabs subjected to repeated cyclic loading and had different confinement stirrups in the lap zone showed energy dissipation, exhibited good ductility, and also showed almost stable hysteric loops. The integrity of the lap joint was preserved during all the loading and unloading cycles.