Showing papers by "Mohamed A. ElGawady published in 2015"

Evaluation of sandwich panels with various polyurethane foam-cores and ribs

Abstract: The objective of this study was to evaluate three potential core alternatives for glass fiber reinforced polymer (GFRP) foam-core sandwich panels. The proposed system could reduce the initial production costs and the manufacturing difficulties while improving the system performance. Three different polyurethane foam configurations were considered for the inner core, and the most suitable system was recommended for further prototyping. These configurations consisted of high-density polyurethane foam (Type 1), a bidirectional gridwork of thin, interconnecting, GFRP webs that is in-filled with lowdensity polyurethane foam (Type 2), and trapezoidal-shaped, low-density polyurethane foam utilizing GFRP web layers (Type 3). The facings of the three cores consisted of three plies of bidirectional E-glass woven fabric within a compatible polyurethane resin. Several types of small-scale experimental investigations were conducted. The results from this study indicated that the Types 1 and 2 cores were very weak and flexible making their implementation in bridge deck panels less practical. The Type 3 core possessed a higher strength and stiffness than the other two types. Therefore, this type is recommended for the proposed sandwich system to serve as a candidate for further development. Additionally, a finite element model (FEM) was developed using software package ABAQUS for the Type 3 system to further investigate its structural behavior. This model was successfully compared to experimental data indicating its suitability for parametric analysis of panels and their design.

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

Abstract: 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. 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...

Concrete-Filled-Large Deformable FRP Tubular Columns under Axial Compressive Loading

Abstract: The behavior of concrete-filled fiber tubes (CFFT) polymers under axial compressive loading was investigated. Unlike the traditional fiber reinforced polymers (FRP) such as carbon, glass, aramid, etc., the FRP tubes in this study were designed using large rupture strains FRP which are made of recycled materials such as plastic bottles; hence, large rupture strain (LRS) FRP composites are environmentally friendly and can be used in the context of green construction. This study performed finite element (FE) analysis using LS-DYNA software to conduct an extensive parametric study on CFFT. The effects of the FRP confinement ratio, the unconfined concrete compressive strength ( ), column size, and column aspect ratio on the behavior of the CFFT under axial compressive loading were investigated during this study. A comparison between the behavior of the CFFTs with LRS-FRP and those with traditional FRP (carbon and glass) with a high range of confinement ratios was conducted as well. A new hybrid FRP system combined with traditional and LRS-FRP is proposed. Generally, the CFFTs with LRS-FRP showed remarkable behavior under axial loading in strength and ultimate strain. Equations to estimate the concrete dilation parameter and dilation angle of the CFFTs with LRS-FRP tubes and hybrid FRP tubes are suggested.

Strength and Seismic Performance Factors of Posttensioned Masonry Walls

Abstract: In this chapter, the behavior of PT-MWs is investigated using a database of tested walls. The accuracy of ignoring elongation of PT bars which is considered in the current masonry standard joint committee (MSJC in Building code requirements for masonry structures, ACI 530/ASCE 5, TMS 402, American Concrete Institute, Detroit, 2013) code in evaluating the strength of PT-MWs is studied using the available test results. Using the experimental results, the structural response parameters including ductility, response modification factor and displacement amplification factor are determined for different types of walls including fully grouted, partially grouted, ungrouted walls, walls with confinement plates, walls with supplemental mild steel and walls with an opening.

Hybrid Jacketing for Rapid Repair of Seismically Damaged Reinforced Concrete Columns

Abstract: This study proposes hybrid jacketing for rapid repair of seismically damaged concrete columns for bridge safety. The hybrid jacketing for a reinforced concrete (RC) column is composed of a thin cold-formed steel sheet wrapped around the column and its outside prestressing strands. Although the prestressing strands can prevent buckling of the confining steel sheet, the steel sheet can in turn prevent the prestressing strands from cutting into the concrete. The hybrid jacketing concept was validated with testing of a large-scale RC column with lap splice deficiency typical of pre-1970 bridge constructions in the Central United States. Results from the original and repaired columns were compared for hysteresis loops, strength, stiffness, ductility, and energy dissipation. The hybrid jacketing proved to be effective in restoring structural behavior of the damaged column to prevent bridge collapse. Such a cost-effective solution can be implemented at bridge sites in hours. Design equations to establish the lat...

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

Abstract: 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.

Hollow-core FRP-concrete-steel bridge columns under extreme loading.

Abstract: This report presents the behavior of hollow-core fiber reinforced polymer-concrete-steel columns (HC-FCS) under combined axial-flexural as well as vehicle collision loads. The HC-FCS column consists of a concrete wall sandwiched between an outer fiber reinforced polymer (FRP) tube and an inner steel tube. Four large-scale columns including a conventionally reinforced concrete (RC) column having solid cross section and three HC-FCS columns were investigated during this study. Each column had an outer diameter of 24 inch and a column’s height-to-diameter ratio of 4.0. The steel tube was embedded into reinforced concrete footing with an embedded length of 1.6 times the steel tube diameter. The FRP tube truncated at the top of the footing level; hence, it provided only confinement to the concrete. The hollow steel tube was the only reinforcement for shear and flexure inside the HC-FCS column. The HC-FCS column exhibited high lateral drift reaching 15.2% and failed gradually due to concrete crushing, steel tube local buckling, followed by FRP rupture. The reference RC-column failed at drift of 10.9% due to rebar rupture. Finite element models using LS-DYNA software were developed and validated against the experimental results of the investigated large-scale columns and experimental results of small-scale columns available in the literature. The proposed model was able to predict the behaviors of the investigated columns with good accuracy. Finite element modeling of vehicle collision with RC and HC-FCS bridge columns was also presented in this report. Evaluation of the peak dynamic force (PDF) and the equivalent static force (ESF) through an extensive parametric study were conducted. The American Association of State Highway and Transportation Officials (AASHTO)-Load and Resistance Factor Design (LRFD) design force was found to be non-conservative when the column was collided with heavy vehicles of a weight more than 35 kips or high-speed vehicle more than 70 mph. A new equation for estimating the ESF based on the vehicle’s mass and velocity was developed. This approach will allow Departments of Transportation (DOTs) to design different bridge columns to different impact force demands depending on the anticipated truckloads and velocities. In general, the PDF values of the HC-FCS columns were lower than those of the RC column when they were subjected to vehicle collision.

Effect of Dimensions on the Compressive Strength of Concrete Masonry Prisms

Abstract: This chapter investigates the accuracy of the height-to-thickness ratio (h/t) correction factors presented in the ASTM standard (ASTM C1314-03) and in other international standards using numerical finite element analysis. The FEM is calibrated with experimental results, and then a parametric study is performed to examine the effect of size on the strength of masonry prisms. Calibration of masonry material provided in this chapter is then used in developing finite element models of PT-MWs presented in Chap. 5.

Assessment of female sexual function in a group of uncircumcised obese Egyptian women

Abstract: The aim of the present study was to assess female sexual function in an obese group (250 women) and to compare it with a control group (100 women), among 25-35-year-old uncircumcised Egyptian women, using female sexual function index (FSFI) score. FSFI total score of ⩽ 26.55 was considered diagnostic of Female Sexual Dysfunction (FSD). The percentage of FSD in the obese group was 73.6% while it was 71% in the control group, which was statistically insignificant (P > 0.05). The difference between both groups regarding the total (FSFI) score was insignificant (P > 0.05), but arousal and satisfaction domains scores were significantly lower in the obese group. In the obese group, a strong negative correlation between body mass index and arousal, orgasm and the total FSFI score was found. Women with excessive obesity had the lowest total FSFI score. In the obese group, college graduates had the highest total scores and all domain scores of FSFI followed by high school graduates while the least educated women had the lowest scores and when these subgroups were compared, significant differences were found among them. We conclude that in uncircumcised 25-35-year-old Egyptian women, obesity is not a major detrimental factor for FSD, but it may affect some sexual domains such as arousal and satisfaction, although excessive obesity is associated with FSD. Also, educational and cultural factors may have an impact on perception of sex and pleasure.

Impact Analysis of Vehicle Collision with Reinforced Concrete Bridge Columns

Abstract: This paper presents a detailed description of the finite element modeling of the vehicle collision with concrete bridge columns. Also, it evaluates the peak dynamic force (PDF) and the equivalent static force (ESF) of the impact loading through an extensive parametric study. LS- DYNA software was used to simulate the collision of Chevrolet pickup trucks and Ford single unit trucks (SUTs) with reinforced concrete (RC) bridge columns. A verification of the finite element modeling of a vehicle’s collision was conducted with a pervious study. The parametric study included the maximum unconfined compressive stress (f'c, percentage of longitudinal reinforcement, hoop reinforcement, column span-to-depth ratio, vehicle velocity, and vehicle mass. Three methods were considered during the course of this research to investigate the ESF. In the first method, ESF(SB), the ESF was defined as the force needed to produce the same maximum displacement by a collision event at the point of impact. In the second method, ESF(EC), the ESF was calculated by Eurocode. In the third method, PTMSA, the ESF was defined as the peak of the 25 millisecond moving average. In general, the ESF(EC) was the lower limit however the ESF(SB) was the upper limit among the ESFs. The ESF of American Association of State Highway and Transportation Officials- Load and Resistance Factor Design (AASHTO-LRFD; 600 kips) is nonconservative when the column was collided with heavy vehicles of a weight more than 35 kips (16 ton).

Seismic Behavior of Ultra High Performance Segmental Bridge Columns

Abstract: Under an extreme ground motion excitation, the flexural capacity of a well-designed reinforced concrete (RC) column deteriorates due to significant damage to the plastic hinge. Plastic hinge damage includes spalling of concrete cover, buckling and rupture of longitudinal bars, and concrete core crushing. Thus, it is important to prevent damage at the plastic hinge region for developing "seismic resistant" columns. This paper presents a bilateral cyclic loading experimental investigation of bridge columns having plastic hinges consisted of ultra-high performance steel fibre concrete (UFC). Two columns having different plastic hinges details were investigated using bilateral cyclic loading; one column had reinforced concrete core encased in UFC jacket and the other column had UFC hollow-core plastic hinge combined with post-tensioning. Both columns were designed to have approximately the same nominal strength. The columns were constructed and tested at Tokyo institute of Technology in Japan using orbital bilateral cyclic loading customized to impose flexural deformations along with investigating the possibility of twisting of the columns. The column having solid concrete core was able to carry the applied axial load until a drift of 6% whereas the post-tensioned column was able to carry the applied axial load until a drift of 3.5%. The seismic performance of the column with concrete core is clarified based on a hybrid loading experiment.

Analysis of Innovative Hollow-Core FRP-Concrete-Steel Columns

Abstract: This paper presents a finite element analysis of hybrid fiber reinforced polymer (FRP)-concrete- steel double-skin tubular columns (FSDTs). This FSDT consists of a concrete wall sandwiched between an outer FRP tube and an inner steel tube. LS-DYNA was used to develop a pushover analysis of three-dimensional FSDT models to simulate seismic loading. Finite element (FE) models were validated against the experimental results gathered from seven FSDT columns tested under cyclic loading. The FE results were in good agreement with the experimental backbone curves. The maximum error was 9% in predicting the bending strengths of the columns. This study revealed that the behavior of FSDTs is quite complex. It also revealed that this behavior is controlled by the interactions that occur between 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: steel/concrete compression failure and FRP rupture. Compression failure was relatively gradual while failure due to FRP rupture was quite abrupt. However, the bending strength could be simply calculated with a good accuracy, more than 80%, using sectional analysis based on Navier-Bernoulli’s assumptions and strain compatibility concepts.

Vehicle Collision with Reinforced Concrete Bridge Columns

Abstract: This paper evaluates the peak dynamic force (PDF) and the equivalent static force (ESF) of the vehicle collision with reinforced concrete bridge columns through an extensive finite element (FE) analyses. An extensive parametric study of thirteen parameters was conducted. Three approaches were considered during the course of this research to investigate the ESF. In the first approach, stiffness based, the ESF was defined as the static force producing the same maximum displacement which is produced by a vehicle collision at the point of impact. In the second approach, the ESF was calculated following the Eurocode. In the third approach, PTMSA, the ESF was defined as the peak of the 25 millisecond moving average. The different ESFs were compared to the ESF of American Association of State Highway and Transportation Officials-Load and Resistance Factor Design (AASHTO-LRFD; 2,670 kN (600 kips)). In general, the ESF calculated following the Eurocode presented the lower bound while those from the stiffness based approach presented the upper bound. The recommended ESF of the AASHTO-LRFD was found to be non-conservative for some cases and too conservative for others. This research proposed an equation to calculate a design impact force which is function of the vehicle’s mass and velocity. This paper proposed a simplified equation based on the Eurocode equation of the ESF. However, the proposed equations do not need cumbersome FE analyses