This study investigated how different rest times affect the strength development of fly-ashbased ... more This study investigated how different rest times affect the strength development of fly-ashbased alkali-activated mortar (AAM) over a period of 90 days. Two types of fly ash with varying calcium oxide contents of 37 and 21% were used. The rest times ranged from 2 to 36 h, and three curing methods (ambient, oven, and steam) were tested. The results showed that the rest time significantly influenced the compressive strength of the AAM. The optimal rest time was found to be between 12 and 30 h depending on the curing method and fly ash type. Beyond this range, there were only minor changes in strength. One type of fly ash (FA21) showed higher strength with longer rest times up to 30 h, while the other type (FA37) had the highest strength within a rest time range of from 12 to 24 h. Over the 90-day period, the specimens cured under ambient, oven, and steam conditions at 55 • C (131 • F) experienced increasing strength, but those steam-cured at 80 • C (176 • F) showed a decrease in strength. Analysis revealed the formation of hydration products in FA37, while FA21 showed a reduction in peaks for its main compounds. Additionally, XRD analysis revealed the formation of hydration products (CSH and CASH) in FA37, while FA21 displayed a reduction in peaks for its main compounds. EDS analysis indicated the presence of partially unreacted FA particles, highlighting the impact of curing methods on dissolving FA particles and the formation of geopolymer products (NASH and CNASH) responsible for compressive strength development.
Green construction has been a very important aspect in the concrete production field in the last ... more Green construction has been a very important aspect in the concrete production field in the last decade. One of the most problematic waste materials is scrap tires. The use of scrap tires in civil engineering is increasing. This article investigates the effect of the strain rate on the confined concrete mechanical properties. Self consolidating (SCC) control and rubberized concrete mixtures were designed and used during the course of this study to test the properties of concrete having 0%, 10%, and 20% volume replacement of sand with shredded rubber. The compressive strength of the concrete was reduced by the use of rubber. The confined compressive strength was also reduced for the FRP tubes by the use of rubber. The confinement of both conventional and rubberized concrete resulted in an increase in both the compressive strength and ductility. The increase in the strain rate by two and three orders of magnitude resulted in an increase in the compressive strength and ductility of the confined concrete in the FRP tubes.
Under an extreme ground motion, the flexural capacity of a well designed Reinforced Concrete (RC)... more Under an extreme ground motion, the flexural capacity of a well designed Reinforced Concrete (RC) column deteriorates due to crushing of core concrete and buckling of longitudinal bars. Hence, the need for developing new cross sections and systems for seismic applications is evident. This paper presents the shake-table test of a damage-resistant segmental double skin bridge column with post-tensioned unbounded strands with incorporated replaceable energy dissipaters. The column cross-section is a double skin section composed of an outside glass fiber reinforced polymer tube, an inside steel tube, and concrete cast in between the two. The energy dissipaters consist of mild steel fuses outside the cross-section. The column has the advantages of accelerated bridge construction, self centering due to rocking, energy dissipation, and ease of replacing the dissipaters. The column was subjected to a sequence of scaled near-fault pulse-like ground motions. A reference RC column was also tested for comparison
Many existing unreinforced masonry (URM) buildings are seismically vulnerable and need to be retr... more Many existing unreinforced masonry (URM) buildings are seismically vulnerable and need to be retrofitted. The main structural element that resist earthquakes in these buildings are the old URM walls which were designed to resist mainly gravity loads. This paper presents the experimental results of testing URM wall including a door opening. The wall was tested before and after retrofitting using glass fiber reinforced polymers (GFRP).The test results were compared to two different assessment guidelines namely FEMA 356 (2000) and Lang (2002).
ABSTRACT Hybrid FRP-concrete-steel double-skin tubular columns (hybrid DSTCs) are a new form of h... more ABSTRACT Hybrid FRP-concrete-steel double-skin tubular columns (hybrid DSTCs) are a new form of hybrid columns which consists of a layer of concrete sandwiched between an inner steel tube and an outer FRP tube. While a large amount of research has been conducted on the monotonic behavior of this novel form of columns, only a limited amount of work has been conducted on their behavior under cyclic loading. This paper presents the first ever study on the behavior of circular hybrid DSTCs under cyclic axial compression. Results from a series of stub column tests, where the hybrid DSTCs were subjected to cyclic axial compression, are first presented and discussed. The test results show that hybrid DSTCs are very ductile under cyclic axial compression, with the envelope axial load-strain curve being almost the same as the axial load-strain curve of a corresponding DSTC under monotonic compression. It is also shown that repeated unloading/reloading cycles have a cumulative effect on the permanent strain and the stress deterioration of the confined concrete in hybrid DSTCs. The experimental stress–strain curves of the confined concrete in hybrid DSTCs are then compared with predictions from two existing models: (1) a monotonic stress–strain model for the confined concrete in hybrid DSTCs; and (2) a cyclic stress–strain model for the concrete in FRP-confined solid columns. The comparison suggests that the combined use of the two models can give reasonably accurate predictions of the test results.
Australian Journal of Structural Engineering, 2014
ABSTRACT This paper aims to evaluate the expressions in a range of international design codes for... more ABSTRACT This paper aims to evaluate the expressions in a range of international design codes for estimating the in-plane shear strength of partially grouted reinforced masonry (PGM) walls, by comparing them to available experimental results. The shear equations considered are taken from masonry design codes of practice of the United States (MSJC 2011), New Zealand (NZS4230 2004), Canada (CSA S304.1-04) and Australia (AS3700-2011). The experimental results were taken from a data base of 89 wall specimens that displayed shear failure collected from a range of published research. The ability of the code equations to predict shear strength is compared with the experimental results. In addition, a range of parameters that are influential on the shear strength, including masonry tensile strength, level of axial compressive stress, wall aspect ratio, and the amount and spacing of vertical and horizontal reinforcement are studied and compared with test results in detail. Both uni-variate and multivariate regression analysis have been employed to investigate the effect of each parameter. This study illustrates poor correlation between code predictions and test results, indicating that current codes are unable to predict the shear strength of PGM walls effectively. In some cases the code predictions were up to three times the actual shear strength determined from the test, indicating that modifications are needed as the current provisions are unconservative. An equation is therefore proposed which better estimates the strength of PGM walls.
ABSTRACT In recent years, a very important environmental issue all over the world is the disposal... more ABSTRACT In recent years, a very important environmental issue all over the world is the disposal of waste tyres. Rubber from waste tyres can be used to replace part of the natural aggregates in conventional concrete, resulting in a product called crumb rubber concrete (CRC). CRC can improve ductility, damping ratio, and energy dissipation, which are the most important parameters in concrete structures resisting earthquakes. However, CRC can have lower compressive strength when compared with conventional concrete. This paper presents an empirical model able to predict CRC compressive strength. The proposed model is verified using 148 different CRC mixes and compared to two previous models. The proposed model resulted in CRC strength predictions with only 10.7% mean error. The proposed model reduced the mean error in the predictions by 24.6% compared to the nearest predictions by previous models. This paper can aid structural designers who are considering using CRC as a promising alternative to conventional concrete in seismic zones.
International Journal of Impotence Research, Jul 9, 2015
The aim of the present study was to assess female sexual function in an obese group (250 women) a... more 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 (P40.05). The difference between both groups regarding the total (FSFI) score was insignificant (P40.05), 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.
The behavior of concrete-filled fiber tubes (CFFT) polymers under axial compressive loading was i... more 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.
Journal of Structural Engineering-asce, May 1, 2016
AbstractThis paper reports on an experimental study on four unbonded posttensioned masonry walls ... more AbstractThis paper reports on an experimental study on four unbonded posttensioned masonry walls (PT-MWs). All walls had identical thickness, height, and length of 190, 2,000, and 1,400 mm, respectively, and were constructed using concrete masonry units (CMUs) and mortar type N, and were fully grouted. Different horizontal spacing values of 400, 600, and 1,200 mm were used between the posttensioning bars in the walls. Only Wall W4 had horizontal bonded reinforcement, located in the fourth and seventh courses. Two different levels of posttensioning force corresponding to an average posttensioning compressive axial stress on the masonry of 1.35 and 2.7 MPa were applied to the walls. Different initial posttension stresses in the bars ranging from 0.32 to 0.63 of the yield stress of each bar were applied to the walls. The walls were subjected to incrementally increasing in-plane lateral displacement cyclic load applied to the top of each wall. The experimental results including damage pattern, force displacem...
Precast segmental construction technique is an excellent candidate for economic rapid bridge cons... more Precast segmental construction technique is an excellent candidate for economic rapid bridge construction in highly congested urban environments and environmentally sensitive regions. This paper presents three dimensional nonlinear finite element models using ABAQUSnStandard for evaluating the behavior of segmental precast post-tensioned piers under lateral loads. The piers were constructed by stacking precast concrete filled fiber reinforced polymer tube segments one on top of the other and then connecting the assembly structurally with vertical post-tensioning tendons passing through ducts located in the precast segments. A stress-strain relationship for confined concrete was used to model the concrete. The post-tensioning tendons were modeled with beam elements. The model was able to predict the backbone curves for two piers subjected to cyclic loads. A parametric study indicated that increasing the applied post-tensioning force increases nominal strength. Finally, the model showed that the pier aspect ratio, cross sectional diameter size, pier size, and confinement have significant effects on the performance of the investigated piers.
Australasian Structural Engineering Conference 2012: The past, present and future of Structural Engineering, 2012
The objective of this paper is to compare the in-plane shear strength of partially grouted masonr... more The objective of this paper is to compare the in-plane shear strength of partially grouted masonry walls (PG-MW) in the Australian code (AS3700-2001) with other codes. This is of high importance because while most of the test experiments have been done recently - and have affected other codes, shear equations in the Australian masonry design code remained relatively unchanged since 1988 (AS3700-1988). Therefore it is important to find out the differences between Australian provisions and provisions in other codes such as MSJC-2011, NZS4230-2004 and S304.1-2004. These codes were selected as they were calibrated against comprehensive test results. In this paper the effectiveness of various parameters that influence the shear strength of PG-MWs is investigated and discussed. The differences between the selected design provisions are also highlighted. The comparison shows significant differences between AS3700-2001 and the other codes' design expressions.
In recent years, a very important environmental issue all over the world is the disposal of waste... more In recent years, a very important environmental issue all over the world is the disposal of waste tires. One possibility being explored is to use rubber from waste tires to replace part of the natural aggregates in conventional concrete, resulting in a product called crumb rubber concrete (CRC). Recent research on CRC is focusing on using it in structures subject to seismic loads, due to its higher ductility, damping ratio, and energy dissipation compared to conventional concrete. However CRC can have lower compressive strength (ƒ\u27CRC), tensile strength (ƒ\u27TRC), and modulus of elasticity (ERC) when compared with conventional concrete. This paper presents empirical models able to predict the CRC characteristics (ƒ\u27CRC, ƒ\u27TRC, and ERC). The proposed models are verified through the results of 148 CRC mixes as well as compared with two previous models. The proposed models resulted in predictions of the CRC characteristics with only 10.7%, 12.6%, and 11.3% errors in the predictions of ƒ\u27CRC, ƒ\u27TRC, and ERC, respectively. The proposed ƒ\u27CRC model reduced the mean, standard deviation and maximum error percentages by 24.6%, 5.8%, and 20.2%, respectively, compared with the nearest best predictions by previous models. The proposed models can aid structural engineers who are considering CRC as an environmentally-friendly alternative to conventional concrete in structural applications
To the Faculty of Washington State University: The members of the Committee appointed to examine ... more To the Faculty of Washington State University: The members of the Committee appointed to examine the thesis of ALAN BENJAMIN KUPER find it satisfactory and recommend that it be accepted.
An accidental collision with bridge structures can have catastrophic consequences. Such collision... more An accidental collision with bridge structures can have catastrophic consequences. Such collisions have resulted in human casualties and partial or full collapse of bridge structures. In the U.S., 15% of bridge failures were due to a vehicle collision. Increasing traffic volume resulted in an increase of collision events, especially with over-height trucks on highways. Innovative impact protection systems have become a point of interest to protect both structures and human lives. Metamaterial systems that have the ability to exhibit unusual properties such as negative stiffness behavior can dissipate high levels of energy. Such systems became a point of interest in base isolation, impact protection, and shock absorption applications. Bistable elements such as pre-buckled beams can be designed to exhibit negative stiffness behavior under transverse loading. Recent studies have shown that such systems can dissipate up to 70% of the input energy by transferring from one mode of buckling to another. The snap-through behavior of such elements remains in the elastic region of the material, which allows the system to recover the initial configuration after unloading. Finite element modeling (FEM) of bi-stable elements was carried out to address the bi-stability behavior and predict the force threshold as well as the amount of energy dissipated through such elements. FEM results were validated with experimental results. Key parameters that affect the behavior of bi-stable elements were investigated to study the different force thresholds and energy dissipation levels. The developed FEM can be used to predict the behavior of bi-stable elements and hence, design them in accordance with force thresholds and energy dissipation requirements.
This study investigated retrofitting measures for improving the seismic performance of rectangula... more This study investigated retrofitting measures for improving the seismic performance of rectangular columns in existing bridges. Experimental tests were conducted on 0.4-scale column specimens which incorporated details that were selected to represent deficiencies present in older bridges in Washington State. Two unretrofitted specimens were tested to examine the performance of the as-built columns incorporating lap splices at the base of the columns and deficient transverse reinforcement. Five columns were retrofitted with carbon fiber reinforced polymer (CFRP) composite wrapping and one specimen was retrofitted with a steel jacket. The specimens were subjected to increasing levels of cycled lateral displacements under constant axial load. Specimen performance was evaluated based on failure mode, displacement ductility capacity and hysteretic behavior. For retrofitting of rectangular columns, it is recommended that oval-shaped jackets be used whenever possible. Column specimens with oval-shaped jackets of steel and CFRP composite material performed similarly, both producing ductile column performance. Failure in these specimens was due to flexural hinging in the gap region between the footing and retrofit jacket, leading to eventual low-cycle fatigue fracture of the longitudinal reinforcement. Details and procedures for the design of ovalshaped steel jackets are provided in FHWA Seismic Retrofitting Manual for Highway Bridges (2006). Design guidelines for ovalshaped CFRP jackets are given in ACTT-95/08 (Seible et al., 1995). Oval-shaped jackets designed according to these recommendations can be expected to prevent slippage of lapped bars within the retrofitted region. Design guidelines for rectangular-shaped retrofitting using CFRP composite materials are proposed for application to columns with cross-section aspect ratios of 2 or less. While no slippage of the lap splice was observed, it is conservatively recommended that rectangular-shaped CFRP wrapping be used only for the situation where controlled debonding of the lap splice is acceptable.
This paper presents the behavior of reinforced concrete bridge columns subjected to vehicle colli... more 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.
This study investigated how different rest times affect the strength development of fly-ashbased ... more This study investigated how different rest times affect the strength development of fly-ashbased alkali-activated mortar (AAM) over a period of 90 days. Two types of fly ash with varying calcium oxide contents of 37 and 21% were used. The rest times ranged from 2 to 36 h, and three curing methods (ambient, oven, and steam) were tested. The results showed that the rest time significantly influenced the compressive strength of the AAM. The optimal rest time was found to be between 12 and 30 h depending on the curing method and fly ash type. Beyond this range, there were only minor changes in strength. One type of fly ash (FA21) showed higher strength with longer rest times up to 30 h, while the other type (FA37) had the highest strength within a rest time range of from 12 to 24 h. Over the 90-day period, the specimens cured under ambient, oven, and steam conditions at 55 • C (131 • F) experienced increasing strength, but those steam-cured at 80 • C (176 • F) showed a decrease in strength. Analysis revealed the formation of hydration products in FA37, while FA21 showed a reduction in peaks for its main compounds. Additionally, XRD analysis revealed the formation of hydration products (CSH and CASH) in FA37, while FA21 displayed a reduction in peaks for its main compounds. EDS analysis indicated the presence of partially unreacted FA particles, highlighting the impact of curing methods on dissolving FA particles and the formation of geopolymer products (NASH and CNASH) responsible for compressive strength development.
Green construction has been a very important aspect in the concrete production field in the last ... more Green construction has been a very important aspect in the concrete production field in the last decade. One of the most problematic waste materials is scrap tires. The use of scrap tires in civil engineering is increasing. This article investigates the effect of the strain rate on the confined concrete mechanical properties. Self consolidating (SCC) control and rubberized concrete mixtures were designed and used during the course of this study to test the properties of concrete having 0%, 10%, and 20% volume replacement of sand with shredded rubber. The compressive strength of the concrete was reduced by the use of rubber. The confined compressive strength was also reduced for the FRP tubes by the use of rubber. The confinement of both conventional and rubberized concrete resulted in an increase in both the compressive strength and ductility. The increase in the strain rate by two and three orders of magnitude resulted in an increase in the compressive strength and ductility of the confined concrete in the FRP tubes.
Under an extreme ground motion, the flexural capacity of a well designed Reinforced Concrete (RC)... more Under an extreme ground motion, the flexural capacity of a well designed Reinforced Concrete (RC) column deteriorates due to crushing of core concrete and buckling of longitudinal bars. Hence, the need for developing new cross sections and systems for seismic applications is evident. This paper presents the shake-table test of a damage-resistant segmental double skin bridge column with post-tensioned unbounded strands with incorporated replaceable energy dissipaters. The column cross-section is a double skin section composed of an outside glass fiber reinforced polymer tube, an inside steel tube, and concrete cast in between the two. The energy dissipaters consist of mild steel fuses outside the cross-section. The column has the advantages of accelerated bridge construction, self centering due to rocking, energy dissipation, and ease of replacing the dissipaters. The column was subjected to a sequence of scaled near-fault pulse-like ground motions. A reference RC column was also tested for comparison
Many existing unreinforced masonry (URM) buildings are seismically vulnerable and need to be retr... more Many existing unreinforced masonry (URM) buildings are seismically vulnerable and need to be retrofitted. The main structural element that resist earthquakes in these buildings are the old URM walls which were designed to resist mainly gravity loads. This paper presents the experimental results of testing URM wall including a door opening. The wall was tested before and after retrofitting using glass fiber reinforced polymers (GFRP).The test results were compared to two different assessment guidelines namely FEMA 356 (2000) and Lang (2002).
ABSTRACT Hybrid FRP-concrete-steel double-skin tubular columns (hybrid DSTCs) are a new form of h... more ABSTRACT Hybrid FRP-concrete-steel double-skin tubular columns (hybrid DSTCs) are a new form of hybrid columns which consists of a layer of concrete sandwiched between an inner steel tube and an outer FRP tube. While a large amount of research has been conducted on the monotonic behavior of this novel form of columns, only a limited amount of work has been conducted on their behavior under cyclic loading. This paper presents the first ever study on the behavior of circular hybrid DSTCs under cyclic axial compression. Results from a series of stub column tests, where the hybrid DSTCs were subjected to cyclic axial compression, are first presented and discussed. The test results show that hybrid DSTCs are very ductile under cyclic axial compression, with the envelope axial load-strain curve being almost the same as the axial load-strain curve of a corresponding DSTC under monotonic compression. It is also shown that repeated unloading/reloading cycles have a cumulative effect on the permanent strain and the stress deterioration of the confined concrete in hybrid DSTCs. The experimental stress–strain curves of the confined concrete in hybrid DSTCs are then compared with predictions from two existing models: (1) a monotonic stress–strain model for the confined concrete in hybrid DSTCs; and (2) a cyclic stress–strain model for the concrete in FRP-confined solid columns. The comparison suggests that the combined use of the two models can give reasonably accurate predictions of the test results.
Australian Journal of Structural Engineering, 2014
ABSTRACT This paper aims to evaluate the expressions in a range of international design codes for... more ABSTRACT This paper aims to evaluate the expressions in a range of international design codes for estimating the in-plane shear strength of partially grouted reinforced masonry (PGM) walls, by comparing them to available experimental results. The shear equations considered are taken from masonry design codes of practice of the United States (MSJC 2011), New Zealand (NZS4230 2004), Canada (CSA S304.1-04) and Australia (AS3700-2011). The experimental results were taken from a data base of 89 wall specimens that displayed shear failure collected from a range of published research. The ability of the code equations to predict shear strength is compared with the experimental results. In addition, a range of parameters that are influential on the shear strength, including masonry tensile strength, level of axial compressive stress, wall aspect ratio, and the amount and spacing of vertical and horizontal reinforcement are studied and compared with test results in detail. Both uni-variate and multivariate regression analysis have been employed to investigate the effect of each parameter. This study illustrates poor correlation between code predictions and test results, indicating that current codes are unable to predict the shear strength of PGM walls effectively. In some cases the code predictions were up to three times the actual shear strength determined from the test, indicating that modifications are needed as the current provisions are unconservative. An equation is therefore proposed which better estimates the strength of PGM walls.
ABSTRACT In recent years, a very important environmental issue all over the world is the disposal... more ABSTRACT In recent years, a very important environmental issue all over the world is the disposal of waste tyres. Rubber from waste tyres can be used to replace part of the natural aggregates in conventional concrete, resulting in a product called crumb rubber concrete (CRC). CRC can improve ductility, damping ratio, and energy dissipation, which are the most important parameters in concrete structures resisting earthquakes. However, CRC can have lower compressive strength when compared with conventional concrete. This paper presents an empirical model able to predict CRC compressive strength. The proposed model is verified using 148 different CRC mixes and compared to two previous models. The proposed model resulted in CRC strength predictions with only 10.7% mean error. The proposed model reduced the mean error in the predictions by 24.6% compared to the nearest predictions by previous models. This paper can aid structural designers who are considering using CRC as a promising alternative to conventional concrete in seismic zones.
International Journal of Impotence Research, Jul 9, 2015
The aim of the present study was to assess female sexual function in an obese group (250 women) a... more 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 (P40.05). The difference between both groups regarding the total (FSFI) score was insignificant (P40.05), 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.
The behavior of concrete-filled fiber tubes (CFFT) polymers under axial compressive loading was i... more 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.
Journal of Structural Engineering-asce, May 1, 2016
AbstractThis paper reports on an experimental study on four unbonded posttensioned masonry walls ... more AbstractThis paper reports on an experimental study on four unbonded posttensioned masonry walls (PT-MWs). All walls had identical thickness, height, and length of 190, 2,000, and 1,400 mm, respectively, and were constructed using concrete masonry units (CMUs) and mortar type N, and were fully grouted. Different horizontal spacing values of 400, 600, and 1,200 mm were used between the posttensioning bars in the walls. Only Wall W4 had horizontal bonded reinforcement, located in the fourth and seventh courses. Two different levels of posttensioning force corresponding to an average posttensioning compressive axial stress on the masonry of 1.35 and 2.7 MPa were applied to the walls. Different initial posttension stresses in the bars ranging from 0.32 to 0.63 of the yield stress of each bar were applied to the walls. The walls were subjected to incrementally increasing in-plane lateral displacement cyclic load applied to the top of each wall. The experimental results including damage pattern, force displacem...
Precast segmental construction technique is an excellent candidate for economic rapid bridge cons... more Precast segmental construction technique is an excellent candidate for economic rapid bridge construction in highly congested urban environments and environmentally sensitive regions. This paper presents three dimensional nonlinear finite element models using ABAQUSnStandard for evaluating the behavior of segmental precast post-tensioned piers under lateral loads. The piers were constructed by stacking precast concrete filled fiber reinforced polymer tube segments one on top of the other and then connecting the assembly structurally with vertical post-tensioning tendons passing through ducts located in the precast segments. A stress-strain relationship for confined concrete was used to model the concrete. The post-tensioning tendons were modeled with beam elements. The model was able to predict the backbone curves for two piers subjected to cyclic loads. A parametric study indicated that increasing the applied post-tensioning force increases nominal strength. Finally, the model showed that the pier aspect ratio, cross sectional diameter size, pier size, and confinement have significant effects on the performance of the investigated piers.
Australasian Structural Engineering Conference 2012: The past, present and future of Structural Engineering, 2012
The objective of this paper is to compare the in-plane shear strength of partially grouted masonr... more The objective of this paper is to compare the in-plane shear strength of partially grouted masonry walls (PG-MW) in the Australian code (AS3700-2001) with other codes. This is of high importance because while most of the test experiments have been done recently - and have affected other codes, shear equations in the Australian masonry design code remained relatively unchanged since 1988 (AS3700-1988). Therefore it is important to find out the differences between Australian provisions and provisions in other codes such as MSJC-2011, NZS4230-2004 and S304.1-2004. These codes were selected as they were calibrated against comprehensive test results. In this paper the effectiveness of various parameters that influence the shear strength of PG-MWs is investigated and discussed. The differences between the selected design provisions are also highlighted. The comparison shows significant differences between AS3700-2001 and the other codes' design expressions.
In recent years, a very important environmental issue all over the world is the disposal of waste... more In recent years, a very important environmental issue all over the world is the disposal of waste tires. One possibility being explored is to use rubber from waste tires to replace part of the natural aggregates in conventional concrete, resulting in a product called crumb rubber concrete (CRC). Recent research on CRC is focusing on using it in structures subject to seismic loads, due to its higher ductility, damping ratio, and energy dissipation compared to conventional concrete. However CRC can have lower compressive strength (ƒ\u27CRC), tensile strength (ƒ\u27TRC), and modulus of elasticity (ERC) when compared with conventional concrete. This paper presents empirical models able to predict the CRC characteristics (ƒ\u27CRC, ƒ\u27TRC, and ERC). The proposed models are verified through the results of 148 CRC mixes as well as compared with two previous models. The proposed models resulted in predictions of the CRC characteristics with only 10.7%, 12.6%, and 11.3% errors in the predictions of ƒ\u27CRC, ƒ\u27TRC, and ERC, respectively. The proposed ƒ\u27CRC model reduced the mean, standard deviation and maximum error percentages by 24.6%, 5.8%, and 20.2%, respectively, compared with the nearest best predictions by previous models. The proposed models can aid structural engineers who are considering CRC as an environmentally-friendly alternative to conventional concrete in structural applications
To the Faculty of Washington State University: The members of the Committee appointed to examine ... more To the Faculty of Washington State University: The members of the Committee appointed to examine the thesis of ALAN BENJAMIN KUPER find it satisfactory and recommend that it be accepted.
An accidental collision with bridge structures can have catastrophic consequences. Such collision... more An accidental collision with bridge structures can have catastrophic consequences. Such collisions have resulted in human casualties and partial or full collapse of bridge structures. In the U.S., 15% of bridge failures were due to a vehicle collision. Increasing traffic volume resulted in an increase of collision events, especially with over-height trucks on highways. Innovative impact protection systems have become a point of interest to protect both structures and human lives. Metamaterial systems that have the ability to exhibit unusual properties such as negative stiffness behavior can dissipate high levels of energy. Such systems became a point of interest in base isolation, impact protection, and shock absorption applications. Bistable elements such as pre-buckled beams can be designed to exhibit negative stiffness behavior under transverse loading. Recent studies have shown that such systems can dissipate up to 70% of the input energy by transferring from one mode of buckling to another. The snap-through behavior of such elements remains in the elastic region of the material, which allows the system to recover the initial configuration after unloading. Finite element modeling (FEM) of bi-stable elements was carried out to address the bi-stability behavior and predict the force threshold as well as the amount of energy dissipated through such elements. FEM results were validated with experimental results. Key parameters that affect the behavior of bi-stable elements were investigated to study the different force thresholds and energy dissipation levels. The developed FEM can be used to predict the behavior of bi-stable elements and hence, design them in accordance with force thresholds and energy dissipation requirements.
This study investigated retrofitting measures for improving the seismic performance of rectangula... more This study investigated retrofitting measures for improving the seismic performance of rectangular columns in existing bridges. Experimental tests were conducted on 0.4-scale column specimens which incorporated details that were selected to represent deficiencies present in older bridges in Washington State. Two unretrofitted specimens were tested to examine the performance of the as-built columns incorporating lap splices at the base of the columns and deficient transverse reinforcement. Five columns were retrofitted with carbon fiber reinforced polymer (CFRP) composite wrapping and one specimen was retrofitted with a steel jacket. The specimens were subjected to increasing levels of cycled lateral displacements under constant axial load. Specimen performance was evaluated based on failure mode, displacement ductility capacity and hysteretic behavior. For retrofitting of rectangular columns, it is recommended that oval-shaped jackets be used whenever possible. Column specimens with oval-shaped jackets of steel and CFRP composite material performed similarly, both producing ductile column performance. Failure in these specimens was due to flexural hinging in the gap region between the footing and retrofit jacket, leading to eventual low-cycle fatigue fracture of the longitudinal reinforcement. Details and procedures for the design of ovalshaped steel jackets are provided in FHWA Seismic Retrofitting Manual for Highway Bridges (2006). Design guidelines for ovalshaped CFRP jackets are given in ACTT-95/08 (Seible et al., 1995). Oval-shaped jackets designed according to these recommendations can be expected to prevent slippage of lapped bars within the retrofitted region. Design guidelines for rectangular-shaped retrofitting using CFRP composite materials are proposed for application to columns with cross-section aspect ratios of 2 or less. While no slippage of the lap splice was observed, it is conservatively recommended that rectangular-shaped CFRP wrapping be used only for the situation where controlled debonding of the lap splice is acceptable.
This paper presents the behavior of reinforced concrete bridge columns subjected to vehicle colli... more 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.
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Papers by Mohamed ElGawady