Taher Abu-Lebdeh - Academia.edu (original) (raw)

Papers by Taher Abu-Lebdeh

American Journal of Applied Sciences, 2014

This study examines the seismic performance of four nonseismically designed reinforced concrete s... more This study examines the seismic performance of four nonseismically designed reinforced concrete structures with core walls and proposes proper rehabilitation methods. The structures were selected based on the height of the structures, occupancy levels and floor plans. The seismic assessment results were compared based on the performance of the structures before rehabilitation and after rehabilitation. The results indicate that most of the structures are unsatisfactory in terms of their failure to reach a level of life safety. Three types of rehabilitation methods, i.e., reinforcement walls, braces and columns, were applied to assess the seismic performance of the four case studies. The two-phase seismic assessments of the rehabilitated structures were conducted according to current provisions used in Korea.

American Journal of Engineering and Applied Sciences, 2014

The disposal of scrap tires is a challenging task and hence an innovative solution to meet these ... more The disposal of scrap tires is a challenging task and hence an innovative solution to meet these challenges is needed. Extensive work has been done on the utilization of waste tires in a variety of applications in asphalt pavements and concrete. However, previous investigations focus only on the mechanical properties of the rubberized materials, but few on the thermal performance. This is especially true for rubberized gypsum. Limited or no experimental data on the thermal performance of rubberized gypsum board are available. In this study, an experimental program is established to investigate the effect of amount and size of crumb rubber on the thermal properties of gypsum materials. Gypsum is replaced by four different percentage of crumb rubber: 10, 20, 30 and 40% by weight of gypsum and two sizes of crumb rubber (#30, #10_20) to make eight rubberized gypsum specimens. The prepared specimens were tested for thermal conductivity using an apparatus specially designed and constructed for this purpose. The experimental program was concluded by proposing an empirical equation to predict the thermal conductivity of rubberized gypsum board. Results indicated better thermal performance of the gypsum board due to the addition of crumb rubber. Thermal conductivity of the rubberized gypsum was 18-38% lower than the ordinary gypsum. It is concluded that thermal conductivity of rubberized gypsum decreases with the increase of crumb rubber regardless the size of the rubber and that thermal conductivity of mixtures contained 40% of rubber was about 38% lower than conventional mixture when crumb rubber #10_20 was added, while the thermal conductivity reduced by 22% when crumb rubber #30 was added. The study suggested for future work to investigate the effect of air voids size and ratio on the thermal conductivity of rubberized gypsum.

American Journal of Engineering and Applied Sciences, 2012

The purpose of this research was to experimentally characterize the flexural and tensile characte... more The purpose of this research was to experimentally characterize the flexural and tensile characteristics of fiber-reinforced Very High-Strength Concrete (VHSC) panels. The panels were made with a unique mix of cementitous materials achieving compressive strength of 26,000 psi (180 MPa) or greater. VHSC panels were reinforced with polypropylene fibers of 1 inch (25.4 mm) in length and Polyvinyl alcohol (PVA) micro-fibers of ½ inch length, incorporated at 1.5% by volume. For the flexural behavior, 17×2×¾ inch flat panels were tested under third-point loading tests, while the direct tension experiments were tested on 10×3×½ inch tension panels under a direct tensile load. Flexural tests were conducted on three panels of plain VHSC, three panels of VHSC reinforced with polypropylene fibers and three panels of VHSC reinforced with ½ inch micro-fibers. Similar testing program was used to conduct the direct tension tests. Also, compression test conducted on 2×2×2 inch cubes and compressive test conducted on 4 inch by 8 inch cylinders test were used to establish compressive strength and modulus of elasticity respectively. Results show that the compressive strength, tensile strength and fracture toughness of the VHSC panels were much greater than those normally obtained by typical concrete material. The presence of fibers increases the toughness of VHSC specimens between 80 and 190% and increases the tensile strength by 23 to 47%. The modulus of elasticity and Poisson's ratio recorded herein were determined according to ASTM C 469-02. Laboratory experiments on flexural and tensile properties of thin, very high-strength, fiber reinforced concrete panels, were used to study the material and characterize the panels' reaction to load. Parameters such as compressive strength, tensile strength, toughness, elastic modulus, Poisson's ratio and first-crack strength were determined and may be considered for potential use as design parameters in future material improvements.

American Journal of Engineering and Applied Sciences, 2014

A laboratory study was conducted to investigate the effects of Amine based modifier on rheologica... more A laboratory study was conducted to investigate the effects of Amine based modifier on rheological characteristics of particle filled viscous medium such as asphalt binder in presence of Recycled Asphalt Shingles (RAS). In this study, virgin asphalt binder (PG 64-22), three different percentages (20, 30 and 40%) of tear-off shingles and modifiers; Rediset, Evotherm and Bio-binder were used. The tear-off shingles acquired from local reroofing company in Greensboro, North Carolina; were finely grinded (85% passing of sieve # 200). The virgin binder and different percentages of RAS were then blended at 180°C using shearing speed of 400 rpm. Following that themixture was blended with 1.5% of Rediset, 0.5% of Evotherm and 5% of bio-binder. The properties of the blended binder were studied using the Rotational Viscometer (RV) equipped with two different spindle types:-One was Smooth Cylindrical spindle (SC4-27D) and the other one was Vane spindle (V 73). The analysis showed that the viscosity was increased with increasing the RAS percentage. Furthermore, the viscosity measured by vane spindle was continuously higher than the value measured by smooth spindle; however the difference between the two measurements reduced as the blending were improved using modifiers. Moreover, temperature found to be the main contributor to reduction of the viscosity in both spindles cases. In addition the coefficient of variation was significantly lower in the case of vane spindle, indicating that the vane spindle could be more appropriate in measuring viscosity of particle filled viscous medium such as RAS asphalt. Based on the experimental result an empirical index called blending index was introduced in this study to measure the blending behavior and status for modified mixtures. As expected it was found that the blending index increases as the temperature and rotational speed increases. In other word, higher temperature and shearing rate could enhance blending resulting in higher blending index. The blending index was further used as a laboratory measure to compare effectiveness of various additives in enhancing blending of RAS modified mixtures. It was shown that among three modifiers used in this study, the bio-binder was more effective to increase the blending index.

American Journal of Engineering and Applied Sciences, 2011

In this research, four reduced End Plate Moment Connection (EPMC) specimens (T-stubs) are tested ... more In this research, four reduced End Plate Moment Connection (EPMC) specimens (T-stubs) are tested to verify the numerical and theoretical methods for preanalysis of the Low Cycle Fatigue (LCF) behavior of a four-bolt extended unstiffened EPMC. Approach: The T-stub specimens are bolted to a support frame and a monotonic load is applied to the stem plate. Yield line theory and the Kennedy method are used to analyze the strength of the end plates and bolts. The Finite Element Model (FEM) and experimental tests are used to verify the theoretical calculations. Results: The theoretical calculations, FEM results and experimental test results show reasonable relationships. Conclusion: The theoretical calculations could be used to predict LCF behavior of specimens.

American Journal of Engineering and Applied Sciences, 2011

Problem statement: The integrity of deck joints in highway bridges plays a major role to determin... more Problem statement: The integrity of deck joints in highway bridges plays a major role to determine overall performance of bridge system. As the bridge maintenance program, the defects in deck joints have historically been detected by conventional non-destructive testing and evaluation methods such as visual inspection, chain-dragging and by the detecting sounds under the traffic. Future bridge maintenance challenges will demand the development of techniques and procedures to detect and monitor such defects before they become apparent. Approach: Two non-destructive methods; namely Ground Penetration Radar (GPR) and Seismic Properties Analyzer (SPA) were employed to assess the integrity of deck joins installed in North Carolina bridges. Results: The results obtained with the GPR and SPA allows to quantify the subsurface defects in bridge deck joints. Conclusion: The practical application and limitations of each method are discussed in this study.

American Journal of Engineering and Applied Sciences, 2011

Problem statement: Recycled materials aggregate from the demolished concrete structures and fly a... more Problem statement: Recycled materials aggregate from the demolished concrete structures and fly ash from burning coal shows the possible application as structural and non structural components in concrete structures. This research aims to evaluate the feasibility of using concrete containing recycled concrete aggregate and fly ash in concrete pavement. Approach: Two water cement ratio (0.45 and 0.55) the compressive strength, modulus of electricity and flexural strength for concrete with recycled aggregate and fly ash with 0, 25% replacing cement in mass were considered. Results: The material properties of recycled aggregate concrete with fly ash indicate comparable results with that of concrete with natural aggregate and without fly ash. Conclusion/Recommendations: The recycled materials could be used in concrete pavement and it will promote the sustainability of concrete.

American Journal of Engineering and Applied Sciences, 2011

Problem statement: Crack sealing and filling is the most widely used maintenance activity for in-... more Problem statement: Crack sealing and filling is the most widely used maintenance activity for in-service pavements. If an appropriate sealant material is selected and properly installed at the appropriate time of the pavement life, it retards pavement deterioration and increases its service life at a relatively low cost. However, in some cases it is reported that sealants failed prematurely, mainly due to environmental factors and water exposure. While there have been several studies on environmental factors, water related factors has not received appropriate attention. Nevertheless, various sealants have different water resistance property; hence, they perform differently when exposed to large amount of rain and humidity. Approach: Currently, there is no standard test method to evaluate sealant water resistance. Therefore, there is a need for a standard test method to precisely predict sealant performance when exposed to water. Such a test method can help examine various sealants in terms of their water resistance. This study introduces water conditioning procedure and a test method to measure bond strength of sealant under dry and wet condition. The effect of water on the Interfacial Fracture Energy (IFE) of bituminous sealants was measured by means of a blister test. This test allows the calculations of two fundamental parameters: tensile modulus and the Interfacial Fracture Energy (IFE). Results: Experimental results showed water exposure caused a significant drop in adhesion strength. However, no significant difference was observed between adhesion strength of specimens conditioned for 8 and 12 h of conditioning. Conclusion/Recommendations: The proposed approach and testing method can be used by the sealant manufacturers to improve their sealants' adhesion properties at the presence of water. However, further research works are needed to examine how sealant adhesion strength varies with water exposure duration. Also, the effect of water pH on sealant adhesion strength can be studied.

American Journal of Engineering and Applied Sciences, 2014

This study presents an effective navigation architecture that combines 'go-to-goal', 'avoid-obsta... more This study presents an effective navigation architecture that combines 'go-to-goal', 'avoid-obstacle' and 'follow-wall' controllers into a full navigation system. A MATLAB robot simulator is used to implement this navigation control algorithm. The robot in the simulator moves to a goal in the presence of convex and non-convex obstacles. Experiments are carried out using a ground mobile robot, Dr Robot X80SV, in a typical office environment to verify successful implementation of the navigation architecture algorithm programmed in MATLAB. The research paper also demonstrates algorithms to achieve tasks such as 'move to a point', 'move to a pose', 'follow a line', 'move in a circle' and 'avoid obstacles'. These control algorithms are simulated using Simulink models.

American Journal of Engineering and Applied Sciences, 2014

The life expectancy of Asphalt Binder (AB) has been negatively impacted by the harsh bombardment ... more The life expectancy of Asphalt Binder (AB) has been negatively impacted by the harsh bombardment of UV rays. UV rays cause asphalt to oxidize faster, which results in deterioration of asphalt rheological characteristics that can lead to pavement distresses. This study investigates the impact of bio-char and nanoclay of asphalt rheological properties. Two nano scale materials were used for this study were nano-clay and bio-char. Nano-clay (Cloisite 30B) is a naturally occurring inorganic mineral. Bio-char is the waste product from bio-binder production. Bio-binder is produced from swine manure using a thermochemical conversion process. This process is then followed by a filtration procedure where the bio-char is produced. Chemical and physical properties of bio-char showed a significant presence of carbon which could in turn enhance asphalt flow properties and reduce the rate of asphalt oxidation. In this study several mixtures are designed and evaluated using Rotational Viscometer testing (RV) and X-Ray Diffraction (XRD). Nano-clay is blended at 2 and 4% by weight, with and without bio-binder (5% by weight of dry mass). Bio-char is grinded to nano scale and added to the virgin asphalt binder (PG 64-22) at 2, 5 and 10% by weight. The study results showed that introduction of nano-clay could be effective in reducing temperature susceptibility of asphalt binder.

International journal of pavement research and technology, Nov 1, 2014

The life expectancy of Asphalt Binder is negatively impacted by the harsh bombardment of ultravio... more The life expectancy of Asphalt Binder is negatively impacted by the harsh bombardment of ultraviolet (UV) rays. UV rays cause asphalt to oxidize faster which results in deterioration of asphalt's rheological characteristics that can lead to pavement distresses. This paper investigates merits of application of combination of nano-clay and bio-char to increase effectiveness of nano-clay to reduce asphalt oxidative aging while enhancing nan-clay dispersion. The study was conducted using one control binder (PG 64-22), two nano-clay sources and one type of bio-char, as such several modified binder blends were prepared at varying concentrations of nano-clay;the specimens were then analyzed in terms of their rheological characteristics before and after laboratory oxidation aging. The modifiers used in this study wereorgano clays (Cloisite-11 and Cloisite-15) along with bio-char, which is derived from swine manure. Rolling Thin Film Oven (RTFO) was used to age all specimens; aged and un-aged samples were then tested using a Rotational Viscometer (RV) to evaluate the changes in their rheological behavior before and after aging. Four modified blends were formulated incorporating 3% and 6% of Cloisite-11 and Cloisite-15, in presence of 3% Bio-char. Bio-char was used to improve dispersion, flow and liquidity retention, while enhancing oxidation resistance.

American Journal of Engineering and Applied Sciences, 2013

The behavior of reinforced concrete beams at failure by shear is distinctly different from their ... more The behavior of reinforced concrete beams at failure by shear is distinctly different from their behavior by bending, which is considered to be unsafe mode of failure. The shear failure of beams is usually sudden without sufficient advanced warning and the diagonal cracks that develop due to excess shear forces are considerably wider than the flexural cracks. The cost and safety of shear reinforcement in reinforced concrete beams led to the study of other alternatives. Swimmer bar system is a new type of shear reinforcement. It is a small inclined bars, with its both ends bent horizontally for a short distance and welded to both top and bottom flexural steel reinforcement. Regardless of the number of swimmer bars used in each inclined plane, the swimmer bars form plane-crack interceptor system instead of bar-crack interceptor system when stirrups are used. Test results of several reinforced concrete beams will be presented. The effectiveness of the new swimmer bar system as related to the old stirrup system will be discussed. Beam deflection is also targeted experimentally in the lab. Several deflection measurements were taken to study the effect of using new swimmer bar system on deflection. Also the crack width of the tested reinforced concrete beams was monitored.

American Journal of Engineering and Applied Sciences, 2011

Problem statement: The newly developed Very High Strength Concrete (VHSC), having compressive str... more Problem statement: The newly developed Very High Strength Concrete (VHSC), having compressive strengths of 29 ksi and flexural strengths of 6 ksi, represents a breakthrough in concrete technology. Study to further enhance the properties of this new concrete is continuing. Approach: The objective of this study is to investigate the effect of exposing Very High Strength Concrete (VHSC) specimens to rapid freeze/thaw cycles. Twenty one specimens were tested according to the Standards of the American Society for Testing and Materials ASTM C215, ASTM C666 and ASTM C78. Results: One hundred freeze/thaw cycles were performed on the VHSC specimens. Change in specimen's dimensions and material's properties were recorded at zero, forty, seventy and one hundred cycles. Dimensions and properties considered were: dimension of cross section, length, weight, Dynamic Moduli, Poisson's Ratio, durability factor and Modulus of Rupture. Conclusion/Recommendations: The test results indicated that VHSC is good freeze-thaw resistance (durability factor > 85%) and can avoid freeze/thaw damage. Freeze-thaw cycling did not significantly affect VHSC specimens' cross sectional dimensions, length, or Poisson's Ratio. However, there was a decrease in the specimens' weight with the increase in number of freeze/thaw cycles, but the decrease was very slim indicating little or no deterioration has occur. Moreover, the fine voids exist in VHSC greatly lower the freezing point of any trapped water, making the material less susceptible to Freeze-Thaw damage.

American Journal of Engineering and Applied Sciences, 2015

The life expectancy of Asphalt Binder (AB) has been negatively impacted by the harsh bombardment ... more The life expectancy of Asphalt Binder (AB) has been negatively impacted by the harsh bombardment of Ultraviolet (UV) rays. UV rays cause asphalt to oxidize faster, which results in the deterioration of asphalt's rheological characteristics that can lead to pavement distresses. This paper investigates merits of bio-char to improve asphalt aging susceptibility by blending one control binder (PG 64-22) and two bio-modified binder at concentrations of 3 and 6% individually; the specimens were then analyzed in terms of their rheological characterization before and after aging. Rolling Thin Film Oven (RTFO) method was used to age all specimens, aged and un-aged samples were then tested using a Rotational Viscometer (RV) to evaluate the changes in their rheological behavior before and after aging as a result of aforementioned modifications. This paper also looks at the chemical composition and elemental analysis of bio-char along with biochars' ability to absorb chromium. A sorption procedure was used to determine whether or not bio-char can be used to absorb chromium. The highest chromium removal occurred at a pH value of 5.5. Bio-char was used to improve dispersion and liquid retention, while enhancing oxidation resistance.

American Journal of Engineering and Applied Sciences, 2015

This paper investigates the feasibility of using silica fume to enhance the rheological propertie... more This paper investigates the feasibility of using silica fume to enhance the rheological properties of asphalt binder. It has been widely reported that asphalt binder oxidation is one of the phenomena that reduces the service life of asphalt pavement by negatively impacting its rheological properties. This in turn can lead to a more brittle pavement which is more prone to cracks due to thermal stress and traffic loading. Prior research has shown that introduction of nano-silica to asphalt can reduce asphalt oxidation aging; however, the main challenge with use of nano-silica found to be agglomeration of nano-particles to form micro size clusters which can reduce nano-silica effectiveness while making asphalt binder more susceptible to shear. Therefore, this paper studies effectiveness of using silica fume to reduce asphalt oxidative aging while alleviating agglomeration issue. To do so, various percentages of silica fume was introduced to a base asphalt binders and the rheological properties and high temperature performance of each specimen was evaluated by measuring the rotational viscosity and complex shear modulus before and after oxidative aging. Analysis of the experimental results showed that silica fume reduced asphalt aging index significantly; in addition the temperature susceptibility of asphalt binder was reduced as the percentage of silica fume increased. The flow of modified mixtures increased and the loss of stability of samples decreased as the amount of silica fume increased. The positive effect of silica fume on base asphalt's rheological properties could be attributed to the high surface area and the low degree of agglomeration of the silica fume due to their high polarity. This in turn could improve silica fume's blending properties resulting in a uniformly distributed silica fume modified matrix with enhanced oxidative aging resistance.

American Journal of Engineering and Applied Sciences, 2015

Neural networks have been frequently used in various areas. In the implementation of the networks... more Neural networks have been frequently used in various areas. In the implementation of the networks, time delays and uncertainty are present and known to lead to complex behaviors, which are hard to predict using classical analysis methods. In this study, stability and robust stability of neural networks considering time delays and parametric uncertainty is studied. For stability analysis, the rightmost eigenvalues (or dominant characteristic roots) are obtained by using an approach based on the Lambert W function. The Lambert W function has already been embedded in various commercial software packages (e.g., MATLAB, Maple and Mathematica). In a way similar to non-delayed systems, stability is determined from the positions of the characteristic roots in the complex plane. Conditions for oscillation and robust stability are also given. Numerical examples are provided and the results are compared to existing approaches (e.g., bifurcation method) and discussed.

Journal of Computer Science, 2012

Problem statement: Extended endplate connection is one of the most widely used beam-to column ste... more Problem statement: Extended endplate connection is one of the most widely used beam-to column steel connections because of its fabrication simplicity, good overall performance and cost effectiveness compared with other connection types. The objective of this research is to develop threedimensional finite element models to study the behavior of large capacity eight-bolt extended unstiffened wide endplate steel connections, using current-technology elements instead of legacy elements which were previously used by other researchers. Approach: A finite element software package (ANSYS, version 11.0) was used to create and analyze three finite element models. Two of the finite element models were compared with previously reported experimental results to validate the accuracy of the finite element models. The third model was based on a modification of the second finite element model to improve bolt force distribution. Eight-node brick solid elements were used to model the connection members. The bolt shank was modeled using one three-dimensional spar element that connected the bolt head and nut together. Pretension in bolts, contact algorithm and material nonlinearity were considered in the finite element models. Results: Results of the first and the second finite element models were compared with experimental data. The comparison was based on moment-beam rotation and moment-endplate separation of the finite element models and the corresponding tested specimens. The results of the finite element models were used to compare the behavior of the bolts in the tension region adjacent to the beam bottom flange. Conclusion: The comparison showed good correlations between the finite element models and the corresponding tested specimens which confirmed the validity of the proposed models. Thus, a modified connection was proposed to improve the connection response. A finite element model of the modified connection was modeled, analyzed and compared to the original finite element model prior to modification to show their correlation.

American Journal of Engineering and Applied Sciences, 2011

Problem statement: Manufactured homes are susceptible to hurricane damage. Each year, significant... more Problem statement: Manufactured homes are susceptible to hurricane damage. Each year, significant losses, in terms of fatalities and property damage, are reported. There is always a prevalent concern about lateral load resistance capacity of tie-down system of manufactured homes when subjected to windstorms. This study is performed to determine the effects of hurricane wind on manufactured homes' foundations. Approach: A 1:120th scale model of single wide manufactured home of size 14 ft by 80 ft was designed for the wind tunnel test. Proper instrumentations and simulations were considered to measure wind forces applied on the model. Sting balance and Pitot static tube were used to measure forces and air velocity during the wind tunnel test. Displacements of anchors were observed during the test. Results: The ultimate forces as well as the displacements of the anchors were determined at different angles of wind direction ranging from 30-180°. Wind speed inside the tunnel was increased at the rate of 5 miles h −1. Conclusion/Recommendations: Test result showed that auger anchors used to support lateral load are incapable to resist hurricane wind loads. It was found that anchors displaced 2 in. vertically and 4 in. horizontally at loads less than 4725lb. Tested manufactured homes anchors experienced maximum force of 4087 lb when 45 miles h −1 wind acted in transverse direction to the wall. The manufactured home anchors displaced more than 2 inches in vertical direction and 4 inches in horizontal direction due to this wind load. This research indicated that manufactured homes ground anchors can sustain wind velocity of 95 miles h −1 when the wind is acting at longitudinal direction.

American Journal of Engineering and Applied Sciences, 2011

Problem statement: There is a need to better understand the rate dependence behavior of reinforce... more Problem statement: There is a need to better understand the rate dependence behavior of reinforced concrete structures in order to improve their response to impact and blast loads. Analysis and design of reinforced concrete structures subjected to seismic loadings has been recommended in many FEMA guidelines. However, reevaluation of design becomes extremely important in cases where large deformations are expected such as blast and impact resistant. Approach: This study presents a numerical model to evaluate reinforced concrete columns submitted to high strain rates expected for seismic, impact and blast loadings. The model utilizes dynamic stress-strain response and considers the effect of strain rate on concrete strength; strain at peak stress; yield and ultimate strength of steel; and slope of the softening portion of the stress-strain curve. Results: Results are presented in the form of interaction diagrams and compared with the available analytical and experimental results. Comparison with available data shows that the proposed model can give consistent prediction of the dynamic behavior of reinforced concrete columns. Conclusion/Recommendations: The established interaction diagrams may be used to design columns to withstand high velocity impact loads. Also, knowledge gained can be used to improve dynamic behavioral models and computer-aided analysis and design of reinforced concrete columns subjected to severe blast loadings.

2007 37th annual frontiers in education conference - global engineering: knowledge without borders, opportunities without passports, 2007

Educators all agree that there are several key factors in a student's ability to succeed in the h... more Educators all agree that there are several key factors in a student's ability to succeed in the highly demanding Engineering curriculum. In an ongoing attempt to improve undergraduate education the Dean's office at North Carolina A&T State University organized a group of core topic engineering educators to meet regularly and discuss and share ideas on classroom topics. The importance of classroom management can never be understated. A successful experience for our students begins with preparation and as professors, the internet and online tools offers a means to encourage this preparation. Then we have shown more evidence that attendance is also crucial. Finally, the quality of good notes is noted for the most successful students. More importantly, attention to taking more complete notes can help the lower end students achieve greater success.

American Journal of Applied Sciences, 2014

This study examines the seismic performance of four nonseismically designed reinforced concrete s... more This study examines the seismic performance of four nonseismically designed reinforced concrete structures with core walls and proposes proper rehabilitation methods. The structures were selected based on the height of the structures, occupancy levels and floor plans. The seismic assessment results were compared based on the performance of the structures before rehabilitation and after rehabilitation. The results indicate that most of the structures are unsatisfactory in terms of their failure to reach a level of life safety. Three types of rehabilitation methods, i.e., reinforcement walls, braces and columns, were applied to assess the seismic performance of the four case studies. The two-phase seismic assessments of the rehabilitated structures were conducted according to current provisions used in Korea.

American Journal of Engineering and Applied Sciences, 2014

The disposal of scrap tires is a challenging task and hence an innovative solution to meet these ... more The disposal of scrap tires is a challenging task and hence an innovative solution to meet these challenges is needed. Extensive work has been done on the utilization of waste tires in a variety of applications in asphalt pavements and concrete. However, previous investigations focus only on the mechanical properties of the rubberized materials, but few on the thermal performance. This is especially true for rubberized gypsum. Limited or no experimental data on the thermal performance of rubberized gypsum board are available. In this study, an experimental program is established to investigate the effect of amount and size of crumb rubber on the thermal properties of gypsum materials. Gypsum is replaced by four different percentage of crumb rubber: 10, 20, 30 and 40% by weight of gypsum and two sizes of crumb rubber (#30, #10_20) to make eight rubberized gypsum specimens. The prepared specimens were tested for thermal conductivity using an apparatus specially designed and constructed for this purpose. The experimental program was concluded by proposing an empirical equation to predict the thermal conductivity of rubberized gypsum board. Results indicated better thermal performance of the gypsum board due to the addition of crumb rubber. Thermal conductivity of the rubberized gypsum was 18-38% lower than the ordinary gypsum. It is concluded that thermal conductivity of rubberized gypsum decreases with the increase of crumb rubber regardless the size of the rubber and that thermal conductivity of mixtures contained 40% of rubber was about 38% lower than conventional mixture when crumb rubber #10_20 was added, while the thermal conductivity reduced by 22% when crumb rubber #30 was added. The study suggested for future work to investigate the effect of air voids size and ratio on the thermal conductivity of rubberized gypsum.

American Journal of Engineering and Applied Sciences, 2012

The purpose of this research was to experimentally characterize the flexural and tensile characte... more The purpose of this research was to experimentally characterize the flexural and tensile characteristics of fiber-reinforced Very High-Strength Concrete (VHSC) panels. The panels were made with a unique mix of cementitous materials achieving compressive strength of 26,000 psi (180 MPa) or greater. VHSC panels were reinforced with polypropylene fibers of 1 inch (25.4 mm) in length and Polyvinyl alcohol (PVA) micro-fibers of ½ inch length, incorporated at 1.5% by volume. For the flexural behavior, 17×2×¾ inch flat panels were tested under third-point loading tests, while the direct tension experiments were tested on 10×3×½ inch tension panels under a direct tensile load. Flexural tests were conducted on three panels of plain VHSC, three panels of VHSC reinforced with polypropylene fibers and three panels of VHSC reinforced with ½ inch micro-fibers. Similar testing program was used to conduct the direct tension tests. Also, compression test conducted on 2×2×2 inch cubes and compressive test conducted on 4 inch by 8 inch cylinders test were used to establish compressive strength and modulus of elasticity respectively. Results show that the compressive strength, tensile strength and fracture toughness of the VHSC panels were much greater than those normally obtained by typical concrete material. The presence of fibers increases the toughness of VHSC specimens between 80 and 190% and increases the tensile strength by 23 to 47%. The modulus of elasticity and Poisson's ratio recorded herein were determined according to ASTM C 469-02. Laboratory experiments on flexural and tensile properties of thin, very high-strength, fiber reinforced concrete panels, were used to study the material and characterize the panels' reaction to load. Parameters such as compressive strength, tensile strength, toughness, elastic modulus, Poisson's ratio and first-crack strength were determined and may be considered for potential use as design parameters in future material improvements.

American Journal of Engineering and Applied Sciences, 2014

A laboratory study was conducted to investigate the effects of Amine based modifier on rheologica... more A laboratory study was conducted to investigate the effects of Amine based modifier on rheological characteristics of particle filled viscous medium such as asphalt binder in presence of Recycled Asphalt Shingles (RAS). In this study, virgin asphalt binder (PG 64-22), three different percentages (20, 30 and 40%) of tear-off shingles and modifiers; Rediset, Evotherm and Bio-binder were used. The tear-off shingles acquired from local reroofing company in Greensboro, North Carolina; were finely grinded (85% passing of sieve # 200). The virgin binder and different percentages of RAS were then blended at 180°C using shearing speed of 400 rpm. Following that themixture was blended with 1.5% of Rediset, 0.5% of Evotherm and 5% of bio-binder. The properties of the blended binder were studied using the Rotational Viscometer (RV) equipped with two different spindle types:-One was Smooth Cylindrical spindle (SC4-27D) and the other one was Vane spindle (V 73). The analysis showed that the viscosity was increased with increasing the RAS percentage. Furthermore, the viscosity measured by vane spindle was continuously higher than the value measured by smooth spindle; however the difference between the two measurements reduced as the blending were improved using modifiers. Moreover, temperature found to be the main contributor to reduction of the viscosity in both spindles cases. In addition the coefficient of variation was significantly lower in the case of vane spindle, indicating that the vane spindle could be more appropriate in measuring viscosity of particle filled viscous medium such as RAS asphalt. Based on the experimental result an empirical index called blending index was introduced in this study to measure the blending behavior and status for modified mixtures. As expected it was found that the blending index increases as the temperature and rotational speed increases. In other word, higher temperature and shearing rate could enhance blending resulting in higher blending index. The blending index was further used as a laboratory measure to compare effectiveness of various additives in enhancing blending of RAS modified mixtures. It was shown that among three modifiers used in this study, the bio-binder was more effective to increase the blending index.

American Journal of Engineering and Applied Sciences, 2011

In this research, four reduced End Plate Moment Connection (EPMC) specimens (T-stubs) are tested ... more In this research, four reduced End Plate Moment Connection (EPMC) specimens (T-stubs) are tested to verify the numerical and theoretical methods for preanalysis of the Low Cycle Fatigue (LCF) behavior of a four-bolt extended unstiffened EPMC. Approach: The T-stub specimens are bolted to a support frame and a monotonic load is applied to the stem plate. Yield line theory and the Kennedy method are used to analyze the strength of the end plates and bolts. The Finite Element Model (FEM) and experimental tests are used to verify the theoretical calculations. Results: The theoretical calculations, FEM results and experimental test results show reasonable relationships. Conclusion: The theoretical calculations could be used to predict LCF behavior of specimens.

American Journal of Engineering and Applied Sciences, 2011

Problem statement: The integrity of deck joints in highway bridges plays a major role to determin... more Problem statement: The integrity of deck joints in highway bridges plays a major role to determine overall performance of bridge system. As the bridge maintenance program, the defects in deck joints have historically been detected by conventional non-destructive testing and evaluation methods such as visual inspection, chain-dragging and by the detecting sounds under the traffic. Future bridge maintenance challenges will demand the development of techniques and procedures to detect and monitor such defects before they become apparent. Approach: Two non-destructive methods; namely Ground Penetration Radar (GPR) and Seismic Properties Analyzer (SPA) were employed to assess the integrity of deck joins installed in North Carolina bridges. Results: The results obtained with the GPR and SPA allows to quantify the subsurface defects in bridge deck joints. Conclusion: The practical application and limitations of each method are discussed in this study.

American Journal of Engineering and Applied Sciences, 2011

Problem statement: Recycled materials aggregate from the demolished concrete structures and fly a... more Problem statement: Recycled materials aggregate from the demolished concrete structures and fly ash from burning coal shows the possible application as structural and non structural components in concrete structures. This research aims to evaluate the feasibility of using concrete containing recycled concrete aggregate and fly ash in concrete pavement. Approach: Two water cement ratio (0.45 and 0.55) the compressive strength, modulus of electricity and flexural strength for concrete with recycled aggregate and fly ash with 0, 25% replacing cement in mass were considered. Results: The material properties of recycled aggregate concrete with fly ash indicate comparable results with that of concrete with natural aggregate and without fly ash. Conclusion/Recommendations: The recycled materials could be used in concrete pavement and it will promote the sustainability of concrete.

American Journal of Engineering and Applied Sciences, 2011

Problem statement: Crack sealing and filling is the most widely used maintenance activity for in-... more Problem statement: Crack sealing and filling is the most widely used maintenance activity for in-service pavements. If an appropriate sealant material is selected and properly installed at the appropriate time of the pavement life, it retards pavement deterioration and increases its service life at a relatively low cost. However, in some cases it is reported that sealants failed prematurely, mainly due to environmental factors and water exposure. While there have been several studies on environmental factors, water related factors has not received appropriate attention. Nevertheless, various sealants have different water resistance property; hence, they perform differently when exposed to large amount of rain and humidity. Approach: Currently, there is no standard test method to evaluate sealant water resistance. Therefore, there is a need for a standard test method to precisely predict sealant performance when exposed to water. Such a test method can help examine various sealants in terms of their water resistance. This study introduces water conditioning procedure and a test method to measure bond strength of sealant under dry and wet condition. The effect of water on the Interfacial Fracture Energy (IFE) of bituminous sealants was measured by means of a blister test. This test allows the calculations of two fundamental parameters: tensile modulus and the Interfacial Fracture Energy (IFE). Results: Experimental results showed water exposure caused a significant drop in adhesion strength. However, no significant difference was observed between adhesion strength of specimens conditioned for 8 and 12 h of conditioning. Conclusion/Recommendations: The proposed approach and testing method can be used by the sealant manufacturers to improve their sealants' adhesion properties at the presence of water. However, further research works are needed to examine how sealant adhesion strength varies with water exposure duration. Also, the effect of water pH on sealant adhesion strength can be studied.

American Journal of Engineering and Applied Sciences, 2014

This study presents an effective navigation architecture that combines 'go-to-goal', 'avoid-obsta... more This study presents an effective navigation architecture that combines 'go-to-goal', 'avoid-obstacle' and 'follow-wall' controllers into a full navigation system. A MATLAB robot simulator is used to implement this navigation control algorithm. The robot in the simulator moves to a goal in the presence of convex and non-convex obstacles. Experiments are carried out using a ground mobile robot, Dr Robot X80SV, in a typical office environment to verify successful implementation of the navigation architecture algorithm programmed in MATLAB. The research paper also demonstrates algorithms to achieve tasks such as 'move to a point', 'move to a pose', 'follow a line', 'move in a circle' and 'avoid obstacles'. These control algorithms are simulated using Simulink models.

American Journal of Engineering and Applied Sciences, 2014

The life expectancy of Asphalt Binder (AB) has been negatively impacted by the harsh bombardment ... more The life expectancy of Asphalt Binder (AB) has been negatively impacted by the harsh bombardment of UV rays. UV rays cause asphalt to oxidize faster, which results in deterioration of asphalt rheological characteristics that can lead to pavement distresses. This study investigates the impact of bio-char and nanoclay of asphalt rheological properties. Two nano scale materials were used for this study were nano-clay and bio-char. Nano-clay (Cloisite 30B) is a naturally occurring inorganic mineral. Bio-char is the waste product from bio-binder production. Bio-binder is produced from swine manure using a thermochemical conversion process. This process is then followed by a filtration procedure where the bio-char is produced. Chemical and physical properties of bio-char showed a significant presence of carbon which could in turn enhance asphalt flow properties and reduce the rate of asphalt oxidation. In this study several mixtures are designed and evaluated using Rotational Viscometer testing (RV) and X-Ray Diffraction (XRD). Nano-clay is blended at 2 and 4% by weight, with and without bio-binder (5% by weight of dry mass). Bio-char is grinded to nano scale and added to the virgin asphalt binder (PG 64-22) at 2, 5 and 10% by weight. The study results showed that introduction of nano-clay could be effective in reducing temperature susceptibility of asphalt binder.

International journal of pavement research and technology, Nov 1, 2014

The life expectancy of Asphalt Binder is negatively impacted by the harsh bombardment of ultravio... more The life expectancy of Asphalt Binder is negatively impacted by the harsh bombardment of ultraviolet (UV) rays. UV rays cause asphalt to oxidize faster which results in deterioration of asphalt's rheological characteristics that can lead to pavement distresses. This paper investigates merits of application of combination of nano-clay and bio-char to increase effectiveness of nano-clay to reduce asphalt oxidative aging while enhancing nan-clay dispersion. The study was conducted using one control binder (PG 64-22), two nano-clay sources and one type of bio-char, as such several modified binder blends were prepared at varying concentrations of nano-clay;the specimens were then analyzed in terms of their rheological characteristics before and after laboratory oxidation aging. The modifiers used in this study wereorgano clays (Cloisite-11 and Cloisite-15) along with bio-char, which is derived from swine manure. Rolling Thin Film Oven (RTFO) was used to age all specimens; aged and un-aged samples were then tested using a Rotational Viscometer (RV) to evaluate the changes in their rheological behavior before and after aging. Four modified blends were formulated incorporating 3% and 6% of Cloisite-11 and Cloisite-15, in presence of 3% Bio-char. Bio-char was used to improve dispersion, flow and liquidity retention, while enhancing oxidation resistance.

American Journal of Engineering and Applied Sciences, 2013

The behavior of reinforced concrete beams at failure by shear is distinctly different from their ... more The behavior of reinforced concrete beams at failure by shear is distinctly different from their behavior by bending, which is considered to be unsafe mode of failure. The shear failure of beams is usually sudden without sufficient advanced warning and the diagonal cracks that develop due to excess shear forces are considerably wider than the flexural cracks. The cost and safety of shear reinforcement in reinforced concrete beams led to the study of other alternatives. Swimmer bar system is a new type of shear reinforcement. It is a small inclined bars, with its both ends bent horizontally for a short distance and welded to both top and bottom flexural steel reinforcement. Regardless of the number of swimmer bars used in each inclined plane, the swimmer bars form plane-crack interceptor system instead of bar-crack interceptor system when stirrups are used. Test results of several reinforced concrete beams will be presented. The effectiveness of the new swimmer bar system as related to the old stirrup system will be discussed. Beam deflection is also targeted experimentally in the lab. Several deflection measurements were taken to study the effect of using new swimmer bar system on deflection. Also the crack width of the tested reinforced concrete beams was monitored.

American Journal of Engineering and Applied Sciences, 2011

Problem statement: The newly developed Very High Strength Concrete (VHSC), having compressive str... more Problem statement: The newly developed Very High Strength Concrete (VHSC), having compressive strengths of 29 ksi and flexural strengths of 6 ksi, represents a breakthrough in concrete technology. Study to further enhance the properties of this new concrete is continuing. Approach: The objective of this study is to investigate the effect of exposing Very High Strength Concrete (VHSC) specimens to rapid freeze/thaw cycles. Twenty one specimens were tested according to the Standards of the American Society for Testing and Materials ASTM C215, ASTM C666 and ASTM C78. Results: One hundred freeze/thaw cycles were performed on the VHSC specimens. Change in specimen's dimensions and material's properties were recorded at zero, forty, seventy and one hundred cycles. Dimensions and properties considered were: dimension of cross section, length, weight, Dynamic Moduli, Poisson's Ratio, durability factor and Modulus of Rupture. Conclusion/Recommendations: The test results indicated that VHSC is good freeze-thaw resistance (durability factor > 85%) and can avoid freeze/thaw damage. Freeze-thaw cycling did not significantly affect VHSC specimens' cross sectional dimensions, length, or Poisson's Ratio. However, there was a decrease in the specimens' weight with the increase in number of freeze/thaw cycles, but the decrease was very slim indicating little or no deterioration has occur. Moreover, the fine voids exist in VHSC greatly lower the freezing point of any trapped water, making the material less susceptible to Freeze-Thaw damage.

American Journal of Engineering and Applied Sciences, 2015

The life expectancy of Asphalt Binder (AB) has been negatively impacted by the harsh bombardment ... more The life expectancy of Asphalt Binder (AB) has been negatively impacted by the harsh bombardment of Ultraviolet (UV) rays. UV rays cause asphalt to oxidize faster, which results in the deterioration of asphalt's rheological characteristics that can lead to pavement distresses. This paper investigates merits of bio-char to improve asphalt aging susceptibility by blending one control binder (PG 64-22) and two bio-modified binder at concentrations of 3 and 6% individually; the specimens were then analyzed in terms of their rheological characterization before and after aging. Rolling Thin Film Oven (RTFO) method was used to age all specimens, aged and un-aged samples were then tested using a Rotational Viscometer (RV) to evaluate the changes in their rheological behavior before and after aging as a result of aforementioned modifications. This paper also looks at the chemical composition and elemental analysis of bio-char along with biochars' ability to absorb chromium. A sorption procedure was used to determine whether or not bio-char can be used to absorb chromium. The highest chromium removal occurred at a pH value of 5.5. Bio-char was used to improve dispersion and liquid retention, while enhancing oxidation resistance.

American Journal of Engineering and Applied Sciences, 2015

This paper investigates the feasibility of using silica fume to enhance the rheological propertie... more This paper investigates the feasibility of using silica fume to enhance the rheological properties of asphalt binder. It has been widely reported that asphalt binder oxidation is one of the phenomena that reduces the service life of asphalt pavement by negatively impacting its rheological properties. This in turn can lead to a more brittle pavement which is more prone to cracks due to thermal stress and traffic loading. Prior research has shown that introduction of nano-silica to asphalt can reduce asphalt oxidation aging; however, the main challenge with use of nano-silica found to be agglomeration of nano-particles to form micro size clusters which can reduce nano-silica effectiveness while making asphalt binder more susceptible to shear. Therefore, this paper studies effectiveness of using silica fume to reduce asphalt oxidative aging while alleviating agglomeration issue. To do so, various percentages of silica fume was introduced to a base asphalt binders and the rheological properties and high temperature performance of each specimen was evaluated by measuring the rotational viscosity and complex shear modulus before and after oxidative aging. Analysis of the experimental results showed that silica fume reduced asphalt aging index significantly; in addition the temperature susceptibility of asphalt binder was reduced as the percentage of silica fume increased. The flow of modified mixtures increased and the loss of stability of samples decreased as the amount of silica fume increased. The positive effect of silica fume on base asphalt's rheological properties could be attributed to the high surface area and the low degree of agglomeration of the silica fume due to their high polarity. This in turn could improve silica fume's blending properties resulting in a uniformly distributed silica fume modified matrix with enhanced oxidative aging resistance.

American Journal of Engineering and Applied Sciences, 2015

Neural networks have been frequently used in various areas. In the implementation of the networks... more Neural networks have been frequently used in various areas. In the implementation of the networks, time delays and uncertainty are present and known to lead to complex behaviors, which are hard to predict using classical analysis methods. In this study, stability and robust stability of neural networks considering time delays and parametric uncertainty is studied. For stability analysis, the rightmost eigenvalues (or dominant characteristic roots) are obtained by using an approach based on the Lambert W function. The Lambert W function has already been embedded in various commercial software packages (e.g., MATLAB, Maple and Mathematica). In a way similar to non-delayed systems, stability is determined from the positions of the characteristic roots in the complex plane. Conditions for oscillation and robust stability are also given. Numerical examples are provided and the results are compared to existing approaches (e.g., bifurcation method) and discussed.

Journal of Computer Science, 2012

Problem statement: Extended endplate connection is one of the most widely used beam-to column ste... more Problem statement: Extended endplate connection is one of the most widely used beam-to column steel connections because of its fabrication simplicity, good overall performance and cost effectiveness compared with other connection types. The objective of this research is to develop threedimensional finite element models to study the behavior of large capacity eight-bolt extended unstiffened wide endplate steel connections, using current-technology elements instead of legacy elements which were previously used by other researchers. Approach: A finite element software package (ANSYS, version 11.0) was used to create and analyze three finite element models. Two of the finite element models were compared with previously reported experimental results to validate the accuracy of the finite element models. The third model was based on a modification of the second finite element model to improve bolt force distribution. Eight-node brick solid elements were used to model the connection members. The bolt shank was modeled using one three-dimensional spar element that connected the bolt head and nut together. Pretension in bolts, contact algorithm and material nonlinearity were considered in the finite element models. Results: Results of the first and the second finite element models were compared with experimental data. The comparison was based on moment-beam rotation and moment-endplate separation of the finite element models and the corresponding tested specimens. The results of the finite element models were used to compare the behavior of the bolts in the tension region adjacent to the beam bottom flange. Conclusion: The comparison showed good correlations between the finite element models and the corresponding tested specimens which confirmed the validity of the proposed models. Thus, a modified connection was proposed to improve the connection response. A finite element model of the modified connection was modeled, analyzed and compared to the original finite element model prior to modification to show their correlation.

American Journal of Engineering and Applied Sciences, 2011

Problem statement: Manufactured homes are susceptible to hurricane damage. Each year, significant... more Problem statement: Manufactured homes are susceptible to hurricane damage. Each year, significant losses, in terms of fatalities and property damage, are reported. There is always a prevalent concern about lateral load resistance capacity of tie-down system of manufactured homes when subjected to windstorms. This study is performed to determine the effects of hurricane wind on manufactured homes' foundations. Approach: A 1:120th scale model of single wide manufactured home of size 14 ft by 80 ft was designed for the wind tunnel test. Proper instrumentations and simulations were considered to measure wind forces applied on the model. Sting balance and Pitot static tube were used to measure forces and air velocity during the wind tunnel test. Displacements of anchors were observed during the test. Results: The ultimate forces as well as the displacements of the anchors were determined at different angles of wind direction ranging from 30-180°. Wind speed inside the tunnel was increased at the rate of 5 miles h −1. Conclusion/Recommendations: Test result showed that auger anchors used to support lateral load are incapable to resist hurricane wind loads. It was found that anchors displaced 2 in. vertically and 4 in. horizontally at loads less than 4725lb. Tested manufactured homes anchors experienced maximum force of 4087 lb when 45 miles h −1 wind acted in transverse direction to the wall. The manufactured home anchors displaced more than 2 inches in vertical direction and 4 inches in horizontal direction due to this wind load. This research indicated that manufactured homes ground anchors can sustain wind velocity of 95 miles h −1 when the wind is acting at longitudinal direction.

American Journal of Engineering and Applied Sciences, 2011

Problem statement: There is a need to better understand the rate dependence behavior of reinforce... more Problem statement: There is a need to better understand the rate dependence behavior of reinforced concrete structures in order to improve their response to impact and blast loads. Analysis and design of reinforced concrete structures subjected to seismic loadings has been recommended in many FEMA guidelines. However, reevaluation of design becomes extremely important in cases where large deformations are expected such as blast and impact resistant. Approach: This study presents a numerical model to evaluate reinforced concrete columns submitted to high strain rates expected for seismic, impact and blast loadings. The model utilizes dynamic stress-strain response and considers the effect of strain rate on concrete strength; strain at peak stress; yield and ultimate strength of steel; and slope of the softening portion of the stress-strain curve. Results: Results are presented in the form of interaction diagrams and compared with the available analytical and experimental results. Comparison with available data shows that the proposed model can give consistent prediction of the dynamic behavior of reinforced concrete columns. Conclusion/Recommendations: The established interaction diagrams may be used to design columns to withstand high velocity impact loads. Also, knowledge gained can be used to improve dynamic behavioral models and computer-aided analysis and design of reinforced concrete columns subjected to severe blast loadings.

2007 37th annual frontiers in education conference - global engineering: knowledge without borders, opportunities without passports, 2007

Educators all agree that there are several key factors in a student's ability to succeed in the h... more Educators all agree that there are several key factors in a student's ability to succeed in the highly demanding Engineering curriculum. In an ongoing attempt to improve undergraduate education the Dean's office at North Carolina A&T State University organized a group of core topic engineering educators to meet regularly and discuss and share ideas on classroom topics. The importance of classroom management can never be understated. A successful experience for our students begins with preparation and as professors, the internet and online tools offers a means to encourage this preparation. Then we have shown more evidence that attendance is also crucial. Finally, the quality of good notes is noted for the most successful students. More importantly, attention to taking more complete notes can help the lower end students achieve greater success.