Omar I. Abdelkarim

Analytical and Finite-Element Modeling of FRP-Concrete-Steel Double-Skin Tubular Columns

AbstractThis 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. A parametric 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 co...

Behavior of Hollow-Core Steel-Concrete-Steel Columns Subjected to Torsion Loading

AbstractThe torsional behavior of hollow-core steel-concrete-steel (HC-SCS) columns is presented using finite-element (FE) and analytical approaches. The HC-SCS columns consist of a concrete shell sandwiched between two steel tubes. Software was used to develop a three-dimensional model of an HC-SCS column that was subjected to torsional loading. The FE results were validated against the experimental results collected from six HC-SCS columns tested under pure torsion. The average error from the FE analysis was 4.8%, compared with experimental results, when predicting the column’s torsion strength. The study revealed that the interaction between the steel tube’s stiffness and concrete shell’s thickness controls the behavior of the column. A parametric study was conducted to further analyze each parameter affecting the column’s torsion behavior. The parametric analysis concluded that the torsional behavior of the column mainly depends on the outer steel tube’s properties and the thickness of the concrete sh...

Seismic Performance of Innovative Hollow-Core FRP–Concrete–Steel Bridge Columns

Abstract This paper presents the seismic behavior of hollow-core fiber-reinforced polymer–concrete–steel (HC-FCS) columns. The typical HC-FCS column consists of a concrete wall sandwiched between an outer fiber-reinforced polymer (FRP) tube and an inner steel tube. The inner steel and outer FRP tubes provide continuous confinement for the concrete shell; hence, the concrete shell achieves significantly higher strain, strength, and ductility than unconfined concrete in conventional columns. Three large-scale HC-FCS columns were investigated in this study. Each column had an outer diameter of 610 mm (24 in.) and a height-to-diameter ratio of 4.0. The steel tube was embedded into a reinforced concrete footing with an embedded length of 1.6–1.8 times the steel tube diameter, whereas the FRP tube only confined the concrete wall thickness and truncated at the top of the footing level. In general, the columns exhibited high lateral drift, reaching to 11.6%, and failed gradually as a result of concrete crushing a...

Seismic Behavior of Hollow-Core FRP-Concrete-Steel Bridge Columns

This paper presents the behavior of precast hollow-core fiber reinforced polymer (FRP)-concrete-steel tubular columns (HC-FCS) under combined axial and lateral loading. The HC-FCS column consisted of a concrete wall sandwiched between an outer FRP tube and an inner steel tube. Two large scale columns, RC-column and HC-FCS column were investigated during this study. The steel tube of the HC-FCS column was embedded into the footing while the FRP tube was stopped at the top of the footing level, i.e., the FRP tube provided confinement only. The hollow steel tube is the only reinforcement for shear and flexure inside the HC-FCS column. The FRP in HC-FCS ruptured at lateral drift of 15.2% while the RC-column displayed 10.9% lateral drift at failure. The RC-column failed due to rebar rupture and the moment capacity suddenly dropped more than 20% after that. However, the HC-FCS suffered gradual failure due to concrete crushing, steel local buckling and yielding, followed by FRP rupture.

Design of Short Reinforced Concrete Bridge Columns Under Vehicle Collision

This paper presents the behavior of reinforced concrete bridge columns subjected to vehicle collision. An extensive parametric study consisting of 13 parameters was conducted, examining the peak dynamic force and the equivalent static force (ESF) of a vehicle collision with reinforced concrete bridge columns. The ESF was calculated by using the Eurocode approach and the approach of the peak of the 25-ms moving average of the dynamic impact force. The ESFs from these two approaches were compared with the AASHTO load and resistance factor design ESF of 2,670 kN (600 kips). This ESF was found to be nonconservative for some cases and too conservative for others. The AASHTO load and resistance factor design ESF was nonconservative when the vehicle’s velocity exceeded 120 km/h (75 mph) and when the vehicle’s mass exceeded 16 tons (30 kips). This paper presents the first equation that calculates a design impact force, which is a function of the vehicle’s mass and velocity. The equation covers a wide range of vehicle velocities, from 56 km/h (35 mph) to 160 km/h (100 mph), and a wide range of vehicle masses, from 2 tons (4.4 kips) to 40 tons (90 kips). This approach will allow departments of transportation to design different bridge columns for different highways depending on the anticipated truck loads and speeds collected from the survey of roadways. A simplified equation based on the Eurocode equation of the ESF is proposed. These equations do not require finite element analyses.

Behavior of Hybrid FRP-Concrete-Steel Double-Skin Tubes Subjected to Cyclic Axial Compression

This paper presents the results of an experimental study that was conducted to investigate the effects of key parameters on the compressive behavior of fiber-reinforced polymer (FRP)-concrete-steel double-skin tubular columns (FSDT). Hybrid FSDT columns have been introduced as a new form of hybrid columns. They consist of an outer tube made of FRP and inner tub made of steel, with sandwiched concrete between them. This paper investigated the effect of fiber angle and the ratio of steel tube diameter to its thickness (Di/ts) on the compressive behavior of FSDT columns. Six FSDT cylinders with different (Di/ts), in addition to two concrete filled-fiber tuber (CFFT) cylinders, were manufactured and tested under axial cyclic compression. The results of the experimental study indicate that the overall behavior of FSDT and CFFT is similar and the main difference is in the capacity load. The cylinders with high D/t ratio achieve lower capacity than the normal capacity due to the local buckling of the steel tubes. Using the saturated fiber tube increases the axial ductility but does not give high confinement. These results are presented together with a discussion on the influence of the studied parameters on the compressive behavior of FSDTs.

Dynamic and Static Behavior of Hollow-Core FRP-Concrete-Steel and Reinforced Concrete Bridge Columns under Vehicle Collision

This paper presents the difference in behavior between hollow-core fiber reinforced polymer-concrete-steel (HC-FCS) columns and conventional reinforced concrete (RC) columns under vehicle collision in terms of dynamic and static forces. The HC-FCS column consisted of an outer FRP tube, an inner steel tube, and a concrete shell sandwiched between the two tubes. The steel tube was hollow inside and embedded into the concrete footing with a length of 1.5 times the tube diameter while the FRP tube stopped at the top of footing. The RC column had a solid cross-section. The study was conducted through extensive finite element impact analyses using LS-DYNA software. Nine parameters were studied including the concrete material model, unconfined concrete compressive strength, material strain rate, column height-to-diameter ratio, column diameter, column top boundary condition, axial load level, vehicle velocity, and vehicle mass. Generally, the HC-FCS columns had lower dynamic forces and higher static forces than the RC columns when changing the values of the different parameters. During vehicle collision with either the RC or the HC-FCS columns, the imposed dynamic forces and their equivalent static forces were affected mainly by the vehicle velocity and vehicle mass.

Behavior of Hollow-Core FRP-Concrete-Steel Columns under Static Cyclic Flexural Loading

AbstractThis paper presents the seismic behavior of hollow-core fiber-reinforced polymer (FRP)-concrete-steel (HC-FCS) columns comparable with the conventional RC column. The typical HC-FCS column ...

Embedded FSS sensing for structural health monitoring of bridge columns

Structural health monitoring (SHM) is important to the infrastructure and transportation industries. SHM is often performed nondestructively, and a number of testing modalities including microwave nondestructive testing (NDT) have been successfully used to accomplish this goal. Within the realm of microwave NDT, sensors based on frequency selective surface (FSS) principles have found application for SHM, including detection of normal and shear strain, as well as delamination and disbond detection in layered structures. This work focuses on the design and implementation of an embedded FSS sensor for detection of strain and buckling during displacement load testing of a novel steel-tube reinforced concrete column.