الفهرس 
Reinforced Concrete ColumnsOnly 14 pages are availabe for public view
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Abstract
Because reinforced concrete columns are one of the most important structural parts
in any concrete structure, their failure leads to the failure of the entire system. Many
studies and researches have concentrated on the topic of concrete column
strengthening, rehabilitation, repair, and retrofitting.
The purpose of this thesis is to study the following topics:
• The effect of transverse reinforcement densification at the top and bottom
zones, as well as along the length of columns, on the capacity of short and long
reinforced concrete columns under static axial loads.
• Determination of failure modes and physical changes for short and long
columns with different stirrups densification ratios.
• Strains, deformations, and cracking of columns are compared to control
columns.
• The effect of different diameters of lateral reinforcement on the behavior of
R.C. columns under static axial load.
On 26 specimens, an experimental program was carried out. Four groups consisting of
26 specimens with different cross sections and different densifications of stirrups were
tested under static axial loads. Failure load and strain values at various loading stages,
as well as failure modes, were recorded for each tested specimen.
Tested specimens consist of 4 groups: A, B, C and D.
• group (A) consists of R.C. short square columns with a cross section of 200 x
200 mm and a height of 1200 mm, with main reinforcing longitudinal steel of
4Φ12 mm bars and stirrups of Ø6 mm, with a change in densification along the
height of the columns.
• group (B) consists of R.C. short square columns with a cross section of 200 x
200 mm and a height of 1200 mm, with main reinforcing longitudinal steel of
Chapter (7) Summary & Conclusion
7-2
4Φ12 mm bars and stirrups of Ø8 mm, with a change in densification along the
height of the columns.
• group (C) consists of R.C. circular short columns with a diameter of 200 mm
and a height of 1200 mm, with main reinforcing longitudinal steel of 6Φ10 mm
bars and stirrups of Ø8 mm, with a change in densification along the height of
the columns.
• group (D) consists of R.C. long square columns with a cross section of 150 x
150 mm and a height of 1600 mm, with main reinforcing longitudinal steel of
4Φ10 mm bars and stirrups of Ø8 mm, with a change in densification along the
height of the columns.
Finite element models have been produced for all specimens using ABAQUS
(6.14-2) to investigate the compatibility of behavior between numerical and
experimental research. As previously illustrated, many models were developed to
cover all of the studied parameters.
7.2. Conclusion
The following research results are summarized based on both experimental and
analytical studies.
• By increasing the percentage of stirrups’ densification height at the top and
bottom of the column to the total column height, the failure load increases.
• The influence of stirrup spacing is greater than the effect of stirrup bar
diameter.
• A smaller stirrup bar diameter at smaller spacing is more effective than a larger
stirrup bar diameter at greater spacing.
• Stirrups’ densification throughout the column’s length is more effective than
stirrups densification at the top and bottom.
• By increasing the percentage of stirrups’ densification height at the top and
bottom of the column to the total column height, the ductility increases.
Chapter (7) Summary & Conclusion
7-3
• Finite element models can determine the structural behavior of tested columns
and are a better alternative to damaging laboratory tests.
• The best performance of stirrups’ configuration distance in the densification
zone is not more than half the distance between the stirrups outside of the
densification zone.
• Increasing the percentage of stirrups’ densification height at the top and bottom
of the column leads to increasing the capacity of the column, and at the same
time, it is more economical than increasing the dimension of the column or
increasing the main reinforcement.
• Increasing slenderness ratio of column leads to decreasing the capacity of the
column.
7.3. Future study
1- The effect of stirrups’ densification on the behavior of rectangular and circular
columns subjected to both axial and lateral loads.
2- Use stirrups with a diameter of 10 mm instead of 6 mm and illustrate the
difference.
3- The effect of stirrup densification on the behavior of large -scale R.C. columns.