الفهرس 
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Abstract
The objective of this experimental study of bridge columns is to investigate the influence of axial loading
and eccentric loads with different eccentricities (small and large) on three types of columns: concrete-filled
steel tube (CFST) short columns, concrete-filled double steel tube (CFDST) short columns, and prefabricated
concrete-filled double steel tube (PCFDST) short columns (post-tensioned precast segmental CFDST). The
study is divided into two main sections. Part I: Investigation and Comparison of CFST Columns and CFDST
Columns (emulative system) with the same outer tube diameter and concrete grade. CFDST columns had
approximately 0.49 of the concrete area replaced with an inner steel tube. This part included two groups: Group
I consisted of CFST columns, and group III consisted of CFDST columns. Each group had three columns that
were subjected to different loading conditions. These conditions included a column with concentric loading, a
column with an eccentricity ratio (e/D) of 0.48, and a column with an eccentricity ratio (e/D) of 0.96. we
concluded that the failure mode of CFST Columns and CFDST Columns is identical. the CFDST columns
exhibited higher strength, stiffness, and moment capacity than CFST columns when subjected to eccentric
loading. This is attributed to the additional confinement effect provided by the inner steel tube in CFDST
columns, which enhances the column’s resistance to lateral bending and improves its load-carrying capacity,
and improves the overall performance of the columns under eccentric loading. Part II: The performance
evaluation of post-tensioned precast segmental CFDST columns (non-emulative system) focuses on group III,
group IV, group V, and group VI. The evaluation is conducted under eccentric loading conditions and
considers two main aspects: accelerated construction techniques (Rocking and Embedded-rocking
mechanisms) and resistance mechanisms. A total of nine PCFDST columns were fabricated and subjected to
testing until failure. Each group consists of two columns, one with an eccentricity ratio (e/D) of 0.48 and
another with an eccentricity ratio of 0.96, except for group III, which consisted of three columns, the third
column in group III was tested under axial loading. These tests aimed to evaluate the response of the columns
under different loading conditions and investigate the effect of the number of segments in Groups III, IV, V,
and VI. Additionally, the study examined the types of connections, rocking, and embedded rocking
mechanisms. We concluded that the failure mode differed with an increase in the number of segments. The
increasing number of segments supports the occurrence of stress distribution in the overall column compared
to single-segment columns. Increasing the number of segments helped mitigate the reduction in strength under
eccentric loading compared to the emulative system. The multi-segment system achieved a larger moment
capacity than the emulative system under small eccentricity and the highest stiffness. However, the selfcentering
system of PCFDST columns requires additional components to achieve the maximum capacity of
emulative columns. The embedded rocking system was found to be the best system in terms of strength and
moment capacity compared to the rocking system.