الفهرس 
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Abstract
Concrete filled tubes became an attractive solution for constructing ordinary and special structures. It can provide excellent structural properties, such as high ductility and large ultimate capacity. In addition to the enhancement in structural properties, a considerable amount of construction time can be reduced due to the elimination of permanent formwork. Coping with the trend of using integral bridges, the need of using flexible columns with high ultimate capacity, to minimize the restraining effect and sustain the expected high force levels, is increasing rapidly. For such bridges the high strength concrete filled tubes (HSCFT) offer a suitable solution for the substructure.
The implemented design codes, such as (EC4-1-1) are limited to concrete strength fck = 60 MPa, and hence not appropriate for the design of (HSCFT). This research work aimed to evaluate, experimentally and analytically, the Behaviour of (HSCFT) subjected to eccentric loading, with fixed – hinged boundary conditions. The chosen boundary condition is simulating the real condition of the columns when used as supporting elements for integral bridges.
In this content a total of thirteen (HSCFT) where tested under eccentric static loading till failure. Columns having diameter to wall thickness ratios between 33 < D/t < 50, length to tube diameter ratios of 24 < L/D < 28 and concrete cube compressive strength of fck = 90 and 120 MPa were tested. The test results showed an increased capacity, when compared to current design codes, due to the effect of concrete confinement.
The test results were used to calibrate a non-linear finite element model, which was developed using the (ABAQUS v.6.7) software package. The calibrated model was adapted to perform a parametric study in order to develop interaction curves for (HSCFT) with various properties. Based on the least square technique between the numerically developed interaction diagrams and the interaction diagrams developed using the (EC4-1-1) equations, new analytical equations for the design interaction diagram were developed. Finally, the result of this research work will be combined with any other available information to formulate the basics for the design recommendations and code limitations of such kind of structures.