This paper presents a finite-element (FE) analysis of hybrid fiber-reinforced polymer (FRP)-concrete-steel double-skin tube (FSDT) in the form of columns. The FSDT columns that were examined consisted of a concrete wall sandwiched between... more
This paper presents a finite-element (FE) analysis of hybrid fiber-reinforced polymer (FRP)-concrete-steel double-skin tube (FSDT) in the form of columns. The FSDT columns that were examined consisted of a concrete wall sandwiched between an outer FRP tube and an inner steel tube. A FE software was used to develop a pushover analysis of three-dimensional FSDT models to simulate seismic loading. The FE models were validated against the experimental results gathered from seven FSDT columns tested under cyclic loading. The FE analysis results were in good agreement with the experimental backbone curves. The maximum error was 9% in predicting the bending strengths of the columns. Aparametric study evaluated the effect of axial load level, concrete wall thickness, concrete strength, diameter-to-thickness ratio (D=t) of the steel tube, and number of FRP layers on the FSDT columns’ behavior. This study revealed that the behavior of FSDT columns is quite complex. It also revealed that this behavior is controlled by the interactions that occur among the steel tube’s stiffness, the concrete wall’s stiffness, and the FRP hoop’s stiffness. Local buckling occurred in all of the specimens examined. This buckling caused the FSDT system to rupture. Two modes of failure were defined as follows: (1) steel/concrete compression failure, and (2) FRP rupture. Compression failure was relatively gradual whereas failure due to FRP rupture was quite abrupt. Finally, the bending strength increased as the applied axial load, concrete compressive strength, and number of FRP layers increased. The bending strength also increased as both the concrete wall’s thickness and the D=t decreased.
Confining concrete is an effective method to enhance the strength and ductility of reinforced concrete columns. Fibre reinforced polymer (FRP) composites are emerging as a suitable confining material to replace conventional materials... more
Confining concrete is an effective method to enhance the strength and ductility of reinforced concrete columns.
Fibre reinforced polymer (FRP) composites are emerging as a suitable confining material to replace conventional
materials such as steel and fibre-reinforced cement composites. Past research on the behaviour of FRP confined
concrete in compression is considerable; however, limited research has been reported on the behaviour of confined
concrete under sustained compressive loading. This paper reports the preliminary results of an experimental
investigation on the deformational behaviour of carbon FRP (CFRP) confined concrete columns under sustained
compressive stress levels, corresponding to 40% and 60% of the unconfined concrete compressive strength for up to
150 days. The results show that the creep of confined concrete columns is marginally influenced under moderate
sustained stress/strength ratios.
Hollow Concrete Columns (HCCs) are one of the preferred construction systems in civil infrastructures including bridge piers, ground piles, and utility poles to minimize the overall weight and costs. HCCs are also considered a solution to... more
Hollow Concrete Columns (HCCs) are one of the preferred construction systems in civil infrastructures including bridge piers, ground piles, and utility poles to minimize the overall weight and costs. HCCs are also considered a solution to increase the strength to mass ratio of structures. However, HCCs are subjected to brittle failure behaviour by concrete crushing means that the displacement capacity and the strength after steel yielding in HCCs are decreasing due to the unconfined concrete core. Absence of the concrete core changes the inner stress formation in HCCs from triaxial to biaxial causes lower strength. A new type of Hollow Composite Reinforcing System (HCRS) has recently been designed and developed to create voids in structural members. This reinforcing system has four external flanges to facilitate mechanical bonding and interaction with concrete. Therefore, providing the inner Hollow Composite Reinforced Sections (HCRS) can significantly increase strength by providing a higher reinforcement ratio and confining the inner concrete core triaxially. The corrosion of steel is also a notable factor in the case of steel reinforced HCCs which became more critical because their outer and inner surfaces exposing more concrete surface area. An alternative reinforcement is Glass Fibre Reinforced Polymer (GFRP) bars, can overcome the brittle behaviour of steel reinforced HCC. In previous studies, HCC shows high strength capacity, when appropriate reinforcement in the form of longitudinal GFRP bars, laterally using GFRP spirals and internally using newly developed HCRS which provide enough inner confinement. Therefore, this study aims to determine the effect of HCRS of different cross sections and also the effect of change in position of its flanges on the axial performance of HCC analytically using ANSYS software.
Many construction buildings and Structural barrier members that was built before 90s in USA, they weren't designed for Seismic resistance until Federal Emergency Management Agency FEMA started to do seismic evaluation and rehabilitation... more
Many construction buildings and Structural barrier members that was built before 90s in USA, they weren't designed for Seismic resistance until Federal Emergency Management Agency FEMA started to do seismic evaluation and rehabilitation and suggested reinforcement methods. In this article we evaluate FRP sheet reinforcement.
Experimental investigation of reinforced concrete composite columns behaviour was conducted. Eight rectangular reinforced concrete columns with different parameters were tested under axial loads and biaxial bending. Four columns were... more
Experimental investigation of reinforced concrete composite columns behaviour was conducted. Eight rectangular reinforced concrete columns with different parameters were tested under axial loads and biaxial bending. Four columns were internally reinforced with I-section structural steel and the other four were heavily reinforced with reinforcement bars with an equivalent area to the I-section. The variables considered in the study were: 1 the eccentricity of the applied force 2 the ratio of M x and M y. The main goal of this research was to compare the behaviour of the two groups. The results of the tests indicated that the experimental loads for internally reinforced columns were about 82% of that for the composite columns. A computer program was developed based on the ACI provisions to calculate the theoretical capacity of the tested columns. All the experimental failure loads were greater than the predicted theoretical values by an average value of 84%.