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This paper presents the results of both experimental and numerical investigations on the overall structural performance of two-equal-span reinforced concrete perforated (castellated) beams subjected to external pre-stressing. First, the effects of providing castellated openings along with the application of external pre-stressing on both the ultimate capacity and the percentage of moment redistribution were investigated experimentally. Then, after validation of the numerical modelling, the effects of controlling the parameters on the percentage of moment redistribution were investigated numerically. Experimental results showed that providing castellated openings accelerated the appearance of both flexural and shear cracks, and decreased the ultimate capacity by about 24% compared to that of a solid beam. Moreover, application of external pre-stressing on the castellated beam compensated for the reduction in ultimate capacity and outperformed it by about 9% compared to that of a solid beam. Based on the numerical results, it appears to be better to increase the amount of main tensile steel and strand eccentricity at the hogging moment zone, as well as increase the effective pre-stressing force, to reduce the percentage of moment redistribution at both sagging and hogging moments.

Fibre-reinforced polymer bars are rapidly becoming an approved alternative to conventional reinforcing steel bars, especially for severely exposed structures such as bridges. This paper reports on an experimental study on the bond characteristics of both sand-coated and ribbed-surface glass-fibre-reinforced polymer bars embedded in high-strength concrete (HSC). A total of 145 pull-out tests were conducted to examine the effect of varying parameters on the bond characteristics, namely embedment length, bar diameter, surface treatment and concrete cover. In addition, 45 pull-out tests were conducted to investigate the effect of providing headed-end anchorage for the sand-coated bars. The experimental results showed that the sand-coated bars exhibited better bond strength than the ribbed-surface bars, which entailed lower development lengths. Thus, based on the experimental results, expressions for the development length of both sand-coated and ribbed-surface bars embedded in HSC were developed and compared against the results of formulae in available design standards. The comparison revealed that ACI 440-1R-06 produced lower conservative results than CAN/CSA S806-12.

This paper presents an experimental study on the bond characteristics of both sand-coated and ribbed-surface glass fiber reinforced polymer (GFRP) bars embedded in high-performance concrete (HPC). A total of 145 pullout tests were conducted in order to examine the effect of varying parameters on the bond characteristics, namely: embedment length, bar diameter, surface treatment, concrete cover and bond stress-slip relationships. The experimental results showed that the sand-coated bars exhibited better bond strength than that developed by the ribbed-surface GFRP bars, which entails lower development lengths. Besides, it was found that the increase in bar diameter was accompanied by a decrease in the bond strength. Furthermore, experimental results displayed a slight increase in the bond strength as the concrete cover increased from 40 to 60 mm. Finally, based on the material properties of the used GFRP bars and concrete patch, using HPC surrounding both sand-coated and ribbed surface GFRP bars resulted in unfavorable modes of failure. That is because in most cases GFRP bars failed by either shearing of the ribs of the ribbed-surface bars or peeling of the sand-coating layer out of the core diameter for the sand-coated bars.

In this work, an analysis for thermoelastic homogeneous isotropic nanobeams under damage mechanics consideration was built. Under easily supported boundary conditions with fixed side ratios, the Green-Naghdi model type-II, an extended thermoelasticity theory model, has been utilized. For the governing differential equations, the Laplace transforms technique was used on the time variable. The answers were found in the domain of the Laplace transform. Tzou’s approximation approach based on an iteration formula was used to calculate the Laplace transform inversions numerically. The numerical findings for a rectangular silicon nitride thermoelastic nanobeam have been obtained and validated. As a case study, we assumed that the beam is thermally loaded with ramp-type heat and that its two edges are simply supported. Figures representing different scenarios have been used to display the numerical results. Mechanical damage value, ramp-time heat parameter and beam thickness are all reported to have a substantial influence on all of the examined functions.

In this article, the improved chaotic electromagnetic field optimization (ICEFO) algorithm is adopted to generate the optimal values of unknown parameters of fuel cells (FCs). The mathematical model of polymer electrolyte membrane FC (PEMFC) considers nonlinear and complex optimization problems with different control variables. The sum of squared error between the measured and computed stack voltages is considered as the main objective function. The performance of the ICEFO algorithm is tested on three PEMFC stacks. Moreover, sensitivity and statistical measures are presented to confirm the reliability and accuracy of ICEFO. In addition, the effect of changing the cell temperature and reactants pressures is studied for more validation of ICEFO. Furthermore, the results obtained by ICEFO are competitive compared with other optimization methods. These results confirm the effectiveness of ICEFO in solving the optimization problem of PEMFC parameter estimation. Finally, based on the optimization results a Simulink model for PEMFC is developed to examine the dynamic performance of the PEMFCs.

The time parameter for thermal relaxation is essential to change the nanobeam resonator’s energy damping and thermal quality. This paper has established a thermal analysis model to analyze the relaxation times and the effect of the static pre-stress on a nano-resonator made of silicone. In the fractional dual-phase heat-conducting model, the equations have been constructed. The thermal quality factor impacts were discussed of the fractional parameter, length-scale, static pre-stress, isothermal frequency, and thermal relaxation times. The model may expect a significant enhancement in thermal quality factors by tuning the static pre-stress and length scale. The isothermal frequency and fractional order parameter have significant effects on the thermal quality factor of a silicon nanobeam resonator.

There is a limited design guidance for practitioners regarding the shear design equations of circular-concrete members with fiber reinforced polymer (FRP) reinforcements, especially the case of incorporating FRP bars and spirals. The objective of this study is to enhance the methods used for estimating the shear capacity of reinforced concrete (RC) beams with FRP bars and spirals. A database of 44 circular concrete beams reinforced with FRP bars tested under shear were compiled from different experimental studies. Two proposed models based on approaches developed for rectangular sections, to predict the shear capacity of beams without and with stirrups, were compared with the selected available shear design equations. The shear strength estimated using the proposed models are slightly more accurate. The comparison indicates that the shear capacity of FRP-reinforced concrete members with circular cross sections may be determined with the V cf and Vsf approaches developed for rectangular sections provided that certain modifications are made to take into account the effective shear depth, equivalent breadth, the mechanical properties and geometry of GFRP spirals.

This paper presents an experimental study on the shear performance of reinforced concrete (RC) beams provided with pre-prepared steel trusses in the shear span zone. Those steel trusses were assembled using electrical welding for steel strips of 2 mm thickness. For comparison purpose, corresponding steel trusses were assembled from equivalent rounded steel bars and used to reinforce the shear span zone of corresponding reinforced concrete beams, and then the shear behavior of beams reinforced with either trussed strips or trussed bars was compared. Accordingly, an experimental program consisted of fifteen reinforced concrete beams included one control beam have been prepared where the shear span-to-depth ratio was the same for all beams (2.3). Experimental test results showed that the beams reinforced with trussed steel strips showed better shear performance from the viewpoint of both the ultimate capacity and the developed major shear crack width compared with those of the beams reinforced with equivalent trussed bars. That is because the internal trussed strips have higher surface area than that of the equivalent rounded bars, which enabled the reinforced beam to maintain the confinement of the concrete core inside the section thus decreased the major shear crack width and increased the ultimate strength of reinforced concrete beam. Consequently, the ultimate capacity for reinforced concrete beams reinforced with internal trussed strips was higher than the corresponding capacity of beams reinforced with equivalent trussed bars by an average value of about 16%. Besides, the internal steel strips hindered the appearance of shear cracks and decreased the major shear crack width compared to the case of using equivalent rounded bars. Moreover, the experimental findings showed comparable results against the available analytical models from the viewpoints of ultimate shear capacity and maximum shear crack width.

Two configurations of closure strips between precast reinforced concrete (RC) slab panels were fabricated and filled with either non-shrink grout or ultrahigh-performance strain-hardening cementitious composite (UHP-SHCC) material. The strips were then strengthened with externally bonded carbon-fibre-reinforced polymer (CFRP) sheets in order to compensate the drawback associated with decreasing the amount of connected steel reinforcing bars required to transfer the bending moment between panels. In total, 12 specimens divided into three groups were cast and tested under short-term non-reversed repeated patch loads simulating wheel load at the central joint. The test results showed that the UHP-SHCC filling material enabled the connected panels to exhibit more ductile behaviour compared with the panels whose closure strips were filled with non-shrink grout. On the other hand, the CFRP strengthening sheets for the first configuration of the closure strip failed to restore the ultimate capacity of the un-strengthened monolithic specimen. However, the second configuration, using UHP-SHCC filling material, enabled the connecting panels to restore lost capacity, with a performance improvement of about 14% compared with the un-strengthened monolithic specimen.

A mathematical model was created in this article, which consists of a thermoelastic, unified, and isotropic rigid sphere subjected to thermal diffusion. Thermal and chemical potential shocks of a diffusive substance have loaded the sphere's bounding structure. The governing equations were established in the form of a theory of generalized thermoelastic diffusion with mechanical damage taken into account. The temperature increment, concentration, pressure, displacement, stress, and chemical potential numerical effects have been expressed in figures with different values of the mechanical damage parameter, thermal relaxation time, and diffusional relaxation time. All the studied functions are significantly affected by the mechanical damage parameter, radial distance, time, thermal, and diffusional relaxation times. In the Lord-Shulman model, heat, diffusion, and mechanical waves spread at finite speeds on the thermoelastic solid sphere.

In the present investigation, we constructed a novel mathematical model of a one-dimensional thermoelastic semiconducting solid sphere based on the L-S model to study the photothermal interaction. ...

A reinforced concrete beam with a recess is an example of a non-prismatic beam, which develops stress concentrations at the corner of the recess owing to the abrupt change in its depth. This entail...

This paper deals with the photothermal interaction of an isotropic, homogenous, semiconducting, viscothermoelastic solid cylinder in the context of Lord-Shulman's of generalized thermoelasticity theory. The cylinder rotates around its axis with constant angular velocity. The bounding surface of the cylinder has been thermally shocked. The governing equations have been constructed in the Laplace transform domain and numerically calculated inversions of Laplace using the Tzou method. The numerical results for the carrier density increment, temperatures increment, strain, stress, and stress-strain energy have been represented graphically with various values mechanical relaxation time, angular velocity parameter, and lifetime parameter of a photogenerated carrier. The mechanical relaxation time and angular velocity of the rotation parameter have minimal effects on the carrier density function and temperature increment, while its effects on the strain, stress, and stress-strain energy are significant. The photogenerated carrier's lifespan parameter has essential implications on all functions studied.

In the present paper, the analysis has been constructed for thermoelastic homogeneous isotropic nanobeams. A generalized model of the viscothermoelasticity theory of one relaxation time with variable thermal conductivity has been used under simply supported conditions for fixed aspect ratios. Laplace transform has been applied for the governing differential equations. The inverse of the Laplace transform has been calculated by using the Tzou approximation method. The numerical results have been validated for a thermoelastic rectangular nanobeam of silicon nitride as a case when it is subjected to ramp-type heating and simply supported. The numerical results have been shown in figures to stand on the viscothermoelastic parameter's effects and the ramp-type heat parameter. The effect of the variability of thermal conductivity is a very significant consideration. The nanobeam thickness has a significant impact on all the studied state functions.

The environment and the physiological conditions play a vital role in the thermal processes in the human tissues, such as the multi-layered human-eye. In this work, a mathematical model of the human eye concerning the change in blood perfusion, porosity, evaporation rate, and ambient temperatures has been formulated based on non-Fourier heat conduction law with appropriate boundary and interface conditions. A direct method and MAPLE 17 software was used to get the numerical solution, and the results have been shown in figures. The temperature distribution based on various values of the relaxation times parameters has been discussed first to stand on its effect on the value of the temperature in each layer of the human eye. The impact of the blood perfusion, porosity, evaporation rate, time, and ambient temperatures have been discussed; they have significant effects on the thermal wave passing through the human eye layers. For validity, the results of this model have agreed with the results of some other works.

A numerical analysis investigation, using finite element model (FEM) and modified compression field theory (MCFT), was conducted to evaluate the shear capacity and behavior of circular concrete piles reinforced with steel and FRP bars by considering shear behavior, shear strength, and deflection shape. The FEM and MCFT models were verified against the experimental results of full-scale circular concrete speciemns previously tested by the authors. Load-deformation response curve, load-strain for the concrete and reinforced rebars were predicted using finite element analysis were compared to experimental results. The FEM outcomes showed that the model was able to capture the behavior of the specimens with good accuracy. While, the modified compression field theory using Response 2000 (R2K) software provided good predictions of the shear strength with an average value of Vexp/VResponse2000 for specimens is 1.17. Subsequently, a parameric study was performed to study the effect of member’s depth (300, 400, and 600 mm), longitudinal reinforcement ratio (1.5, 2.5, and 3.5%), and reinforcing bars material (Steel, Glass-FRP, Carbon-FRP) on the behaviour of circular concrete piles.

In the present paper, the analysis for thermoelastic homogeneous isotropic microbeams has been constructed. A generalized viscothermoelasticity theory of one relaxation time with variable thermal conductivity in the context of damage mechanics definition has been applied based on simply supported conditions for aspect ratios. Laplace transform has been applied for the governing differential equations, and its inverse has been carried out by using the Tzou method. Microbeam of silicon nitride has been considered when it is subjected to ramp-type heating and simply supported. The results have been illustrated in figures to stand on the impacts of the viscothermoelastic parameter, the thermal conductivity parameter, the value of the beam thickness, and the ramp-type heating parameter. The influences of the mentioned parameters are significant on all the studied functions, and the ramp-type heating parameter plays a vital role in thermodynamically damping of the energy which has been generated on the beam.

This article deals with a new model of photothermoelastic and semiconducting two-dimensional solid cylinder in the context of Lord–Shulman's theory of thermoelasticity. The surface of the cylinder ...

Thermal and mechanical relaxation times play essential roles in the thermal quality factor Q - f a c t o r of the micro-resonators, where controls the energy damping through the coupling of thermal and mechanical behavior. In this work, we developed an analytical mathematical model that assumed a pre-stress in a two-temperature micro-viscothermoelastic resonator of silicon to modify the thermal and mechanical relaxation times and thus increase the thermal quality factor. The impacts of length-scale and pre-stress on the thermal quality factor have been discussed. The present model predicts that significant enhancement in terms of thermal quality factors is enabled by tuning the static-pre-stress, the thermal and mechanical relaxation times parameters. The isothermal value of frequency and the two-temperature parameter have impact effects on the thermal quality factor of the micro-resonators.

Geopolymer cementitious system represents an eco-friendly innovative construction material made without cement as a binder. Hence, the current study is devoted to investigate geopolymer’s characterization as repairing material for reinforced cementitious concrete elements in comparison with commercial high-strength grout. The adhesion performance of the geopolymer mortar using bonding agents based on styrene butadiene rubber (SBR) and epoxy resin were evaluated using slant shear test and pull-off test. In addition, the pull-out test was performed in order to evaluate the bond strength between steel reinforcing bars and different surrounding thicknesses of geopolymer mortar (GPM), namely; 3, 5, 11, 7.5, and 11.5 mm. Besides, the flexural performance of polypropylene fiber reinforced geopolymer mortar (FRGPM) was also evaluated. Moreover, the accelerated corrosion and half-cell potential tests were performed in order to investigate the effect of GPM thickness around steel reinforcing bars (2, 5, and 8.5 mm) as a corrosion protective layer. Test results showed that GPM had good bond strength to the cementitious concrete. In addition, epoxy resin-based bonding agent enabled the geopolymer repair mortar to achieve higher bond strength than that developed by SBR-based bonding agent. The results of rebar pull-out tests showed that using GPM mortar for anchorage of steel reinforcing bars should be implemented with minimum thickness of 5 mm in order to have sufficient bond strength. Moreover, the application of FRGPM as a tension layer enabled the repaired beam to outperform its flexural performance from the viewpoints of ultimate capacity, toughness and crack control. Furthermore, it was found that using GPM as corrosion protective layer of 2 mm thickness or more had the ability and efficiency to delay and control the chloride ions diffusivity.

In the present paper, we constructed a new mathematical model of a thermoelastic semiconducting solid sphere based on the L-S model to study the photothermal interaction. Among this work, we considered the fractional-order strain, which has been introduced by Youssef. The bounding surface of the sphere has been thermally loaded by a thermal shock. Laplace transform has been applied, and its inversions have been obtained numerically. For silicon (Si) material, the numerical results of the temperature increment, carrier density increment, strain, displacement, stress, and stress-strain energy have been represented in figures with various values of the fractional-order parameter, relaxation time parameter, and reference temperature. The relaxation time parameter and reference temperature have significant effects on all the studied functions. The fractional-order parameter has limited effects on the temperature increment and carrier density increment, while it has significant effects on the strain, displacement, stress, and stress-strain energy.

The present paper is dealing with a new mathematical model of a thermoelastic semiconducting solid sphere based on the Green-Naghdi theories to study the photothermal interaction. We applied two co...

We establish a mathematical model of thermally conducting an isotropic, homogeneous, and circular microplate in the context of Kirchhoff’s Love plate theory. We define the governing equations in the context of the generalized dual-phase-lagging model and coupled viscothermoelastic plate. We illustrate the scaled viscothermoelasticity for the case of a circular plate for an aspect ratio for clamped boundary conditions. The bounding plane of the plate has been thermally shocked by ramp heating. We apply the Laplace transform and numerically calculate its inversions. The results are obtained for a ceramic plate. The effects of the damage variables and the thickness of the resonator on the temperature increment distribution are found to be minimal, whereas the effect of the ramp heat parameter on the temperature increment is significant. The damage variables and the thickness of the resonator have significant effects. We determine that the ramp heat parameter can be used as a controller to tune the energy damping.

This paper presents the experimental findings for different strengthening techniques applied on defected reinforced-concrete cantilever slabs to restore lost flexural capacities owing to insufficient bond length of the main tensile steel. The restoration technique was based on compensation of the main tensile steel by near-surface mounted steel bars, externally bonded steel plates or externally bonded carbon fibre-reinforced polymer sheets. In addition, new hybrid techniques are presented, which merge the traditional techniques with a 20 mm thick ultra-high-performance strain-hardening cementitious composites (UHP-SHCC) layer. It was found that the strengthening technique based on the embedded steel bars on the UHP-SHCC overlay enabled the strengthened slab to restore its lost capacity and outperformed it by about 5% compared to that of the properly detailed slab. Nevertheless, this restoration was at the expense of the exhibited ductility. Conversely, the strengthening technique based on the application of externally bonded steel plates on a transition layer of the UHP-SHCC material enabled the strengthened slab to restore the lost capacity by about 96% as well as to outperform its ductility by more than 29% compared to those of the properly detailed slab.

For a segmental pre-stressed beam, the joints between segments will open at the tension side under the effect of bending moment. Accordingly, the concrete will be crushed at the compression side and/or additional tensile force will be developed at the pre-stressed tendons. In addition, the open joint provides easy passage way for environment attack on pre-stressing tendons leading to durability problems. Thus, the overall performance of the segmental beam can be adversely affected. In the current paper, in order to tackle these issues, strengthening techniques were proposed to restrain the joints between segments at tension and/or upgrading the compressive strength at compression side. Thus, five pre-cast concrete segmental T-beams having dry joints pre-stressed by un-bonded tendons in addition to two monolithic control beams (one of them was pre-stressed) were prepared and tested under the effect of an incremental four-point loading scheme. The compression side was upgraded by the replacement of the upper top half of flange thickness by cast-in-situ high-performance concrete (HPC) layer. While the tension side was strengthened by either providing a steel assembly to restrain the open joints by connecting reinforcing steel bars across the joints or splicing the extended longitudinal bars between the segments and then encapsulating them by strain-hardening cementitious composite (SHCC) material. Test results showed that the ultimate capacity of the pre-stressed segmental beams can reach up to 96% of the ultimate capacity of monolithic pre-stressed beam when the segmental beams were strengthened at both tension and compression sides. However, this comes on the expenses of the developed ductility. Using the proposed steel assembly enabled the strengthened segmental beam to develop more ductile response than that obtained when spliced encapsulated bars were implemented. Finally, the recommended un-bonded post-tensioned tendon stress at ultimate stage stipulated by AASHTO, ECP 203-2018 and ACI 318-14 codes were compared against the experimental results. The comparison showed that all considered codes predicted well the un-bonded tendon stress; however, AASHTO equations yielded the least conservative predictions.

Impact loading could impair the entire structure or a part of it, thus making the human life at stake. In this study, to improve the impact resistance of reinforced concrete slabs under drop-weight loading, a thin layer of strain-hardening cementitious composites was added at either tension or compression side of the slab. The main parameter of this study was the three contact surface conditions, namely grinding, grinding plus steel dowels, and grinding plus epoxy adhesive, between the substrate slab and the strain-hardening cementitious composites layer. Therefore, 63 reinforced concrete slabs were prepared and tested under the effect of drop-weight falling from three different heights: 1, 1.5, and 2 m. In addition, for comparison purposes, additional seven slabs were tested under central incremental static loading until failure is presented. It was found that the strain-hardening cementitious composites–strengthening layer enhanced the impact and static response of the strengthened slabs when added at either tension or compression side. Besides, to achieve the outermost impact resistance showing ductile performance, it is better to provide a thin layer of the strain-hardening cementitious composites at the tension side of the slab connected to the substrate slab by epoxy resin applied on pre-prepared grinded surface.

This study investigates the photothermal interaction of an isotropic, homogeneous, semiconducting, viscothermoelastic solid cylinder in the context of Lord and Shulman's generalized thermoelasticity theory. The cylinder rotates with a constant angular velocity around its axis. The cylinder's outside surface has been thermally shocked. The governing equations were built in the Laplace transform domain and numerical inversions of Laplace were computed using the Tzou technique. The numerical findings for the carrier density increment, temperature increment, strain, stress, and stress-strain energy of a photogenerated carrier have been visually depicted with various values of mechanical relaxation time, angular velocity parameter, and lifespan parameter. The mechanical relaxation time and angular velocity of the rotation parameter have little influence on the carrier density function and temperature increment, but they have a substantial effect on the strain, stress, and stress-strain energy. The lifetime parameter of the photogenerated carrier has critical consequences for all functionalities investigated.

Thermal processes in human tissues, such as the multi-layered human eye, are influenced by the environment and physiological factors. Based on a non-Fourier heat conduction rule with proper boundary and interface conditions, a mathematical model of the human eye concerns changes in blood perfusion, porosity, evaporation rate, and ambient temperatures has been formulated in this study. The numerical solution was obtained using a direct technique and MAPLE 17 software, and the results are presented in figures. The temperature distribution based on various values of the relaxation times factors was first examined to determine its impact on the temperature value in each layer of the human eye. The effects of blood perfusion, porosity, evaporation rate, time, and ambient temperatures on the thermal wave passing through the human eye layers have been discussed; they have considerable influence on the thermal wave travelling through the human eye layers. The results of this model have agreed with the results of other studies in terms of validity.

High-performance concrete (HPC) is one of such new material that has a major improvement over conventional concrete; however, its behavior has to be fully understood. This paper presents experimental and numerical investigations in order to study the shear behavior of high-performance reinforced concrete beams. Four RC-HPC beams were tested experimentally in order to study the effect of the existence of web reinforcement and bar diameter of the web reinforcement as well as the amount of the tensile longitudinal steel bars on the shear behavior. Test results showed higher values of shear strength, stiffness, ductility and controlled the concrete cracking behavior due to the presence of stirrups. The ultimate load for beam having shear reinforcement of 6 mm diameter increased by about 16% compared to that of control beam BI-1 without shear reinforcement, while, that increase reached up to 34% for beam having 8 mm diameter web reinforcement. Besides, the numerical modeling enabled to capture satisfactory the behavior of HPC beam so that it can be used to study the effect of more parameters on the behavior of HPC beams.

This paper deals with the thermoelastic damping (Q-factor) of a gold nano-beam resonator and is based on twotemperature thermoelasticity models. An explicit formula of the Q-factor has been derived when Young’s modulus is variable as a function of the room temperature. The length of the beam and Young’s modulus has been studied with comparison being made between the Biot model and the Lord-Shulman model (L-S). The numerical results show that the values of beam length, the relaxation time parameter, and the two-temperature parameter have a strong influence on the thermoelastic damping quality factor.

In this research, a mixture of three agriculture waste fibres, for the first time, was used as biomodifier after alkali treatment, for enhancing the performance of asphalt binder as 3, 5, 7, and 10...

Prestressed concrete girders and piles with steel strands are used in construction of bridges in North America, due to their economy of design, fabrication, and installation. However, they are often exposed to harsh environments, which results in rapid degradation. Therefore, carbon fiber reinforced polymer (CFRP) tendons have successfully been introduced as prestressing reinforcement for pile applications. This paper presents a study on the physical characterization, microstructural analysis, and durability performance of unstressed and stressed carbon-fiber composite cables (CFCCs) for prestressing applications. This is achieved through testing 120 CFCC specimens, subjected to stress levels of about 40% and 65% of their guaranteed strength, and 51 specimens without sustained load under tension. Moreover, prediction models were introduced to assess the long-term performance and retentions of CFCC strands. The models included Arrhenius model, Fick's law, Fib Bulletin (40) model, and a developed approach that incorporates the effects of temperature, design life, and relative humidity of exposure into the environmental reduction factor. Based on the predication model, the tensile strength retention (CE) for CFCC strands, is predicted to retain over 0.95 and 0.84 of ultimate tensile strength for a relative humidity (RH)

This paper presents a study to investigate serviceability, strength, and deformability of normal- and high-strength concrete beams reinforced with deformed glass-fiber-reinforced-polymer (GFRP) bars under flexural loading. Understanding the flexural behavior of concrete beams reinforced with deformed GFRP bars with normal- and high-strength concrete would contribute to the existing literature and would provide information critical to the further use of deformed GFRP bars as internal reinforcement for concrete structures. Eight beams with a cross-sectional width and height of 200 mm and 300 mm, respectively, and a clear span of 2700 mm were tested under two-point flexural loading until failure. Four beams were made with 35 MPa normal-strength concrete (NSC); the other four with 65 MPa high-strength concrete (HSC). The bottom/tensile reinforcement of each beam consisted of two GFRP bars. Four different GFRP bar sizes (12 mm, 16 mm, 20 mm, and 25 mm in diameter) were used with reinforcement ratios ranging from 0.38% to 1.63%. Seven beams failed in concrete compression and the eighth beam failed in tension when the FRP ruptured. The test results showed that increasing the FRP reinforcement ratio had a greater effect on the service moment than the resistance moment. The effects of bar spacing on the behavior of wide beams were also investigated, revealing that the service moment increased when the bar spacing decreased, while the resistance moment increased when the concrete strength increased. In addition, the deformability concept produced significantly higher ductility indices than the energy-based concept. Neither method evidenced a clear trend in the ductility indices of the tested beams. A new approach was proposed to determine the ductility index of concrete beams with FRP bars based on beam curvature. This approach demonstrated a clear trend with the tested beams: the high-strength concrete beams had higher ductility indices than the normal-strength concrete beams.

The work is dealing with the studying the effect of the moving heat source with constant velocity on the biological skin tissue. The heat conduction equation has been considered to be a two-temperature high-order thermal lagging model. A limited length of skin tissue has been constructed to be initially at rest and the first end subjected to constant heat flux while the second end has zero heat flux. Laplace transform has been applied and the inversion has been calculated numerically. The results show that the two-temperature parameter and the value of the heat source velocity have significant effects on the conductive and dynamical temperatures increment.

In recent decades, high-strength concrete (HSC) has been widely used in bridge elements, tunnels, and precast-concrete members. Only a limited number of studies, however, have investigated the structural behavior of HSC columns reinforced with glass-fiber-reinforced-polymer (GFRP) bars. Moreover, most concrete codes do not explicitly cover concrete with strengths above 55 MPa. This paper investigates the structural behavior of HSC columns reinforced with GFRP bars and ties when subjected to eccentrically axial loads. Eight full-scale concrete columns with a 400 × 400 mm cross section and 2000 mm in height were tested under axial monotonic loading. The test variables were the eccentricity-to-width ratio, concrete strength, and reinforcement type using steel and GFRP bars and ties. The test results indicate that the failure of the test specimens under different levels of eccentricity was not triggered by rupture of the GFRP bars on the tension side, up to attaining the maximum section capacity governed by concrete-strain limitation. The load–axial displacement, load–lateral displacement, failure mode, and reinforcement strain responses of all the GFRP-reinforced HSC columns are presented and compared to that of the steel-reinforced HSC columns. The structural behavior of HSC columns reinforced with GFRP bars and ties subjected to eccentric axial loads were evaluated by drawing axial force–flexural moment interaction diagrams and comparing them to that for the steel-reinforced columns. An analytical method (layer-by-layer approach) was applied to predict the axial- and flexural-load capacity of the GFRP-reinforced HSC columns. A parametric study was used to examine the effect of increasing the reinforcement ratio and concrete strength and to investigate the strength contribution of GFRP compression bars.

This paper presents experimental data and theoretical studies on the effect of distributed glass fiber-reinforced-polymer (GFRP) bars in circular concrete members. Th experimental program reports the test results of eight full-scale circular reinforced-concrete (RC) specimens with a total length of 3020 mm and a diameter of 508 mm were constructed and tested under shear load up to failure. The test specimens comprised three specimens reinforced with GFRP bars and spirals, three specimens with only longitudinal GFRP bars, and two reference specimens reinforced with conventional steel bars, with and without steel spirals. The various experimental parameters included the longitudinal reinforcement ratio, the type of reinforcement (GFRP versus steel), and presence of shear reinforcement. The shear strengths of GFRP circular concrete specimens, obtained from the experimental results, were compared to current codes and design guidelines as well as to the recently available shear design equations on circular concrete members in the literature. The test results indicate that the use of more GFRP bars distributed uniformly in the cross section, of the specimens with and without spirals, reduces the loss of flexural stiffness after cracking and increase the shear strength. The comparison indicates that some of the available design methods provide reasonable predictions.

Using the lasers and heat transfer through biological skin tissue is essential for the processes of the medical treatment. Thus, two-temperature bio-heat transfer equations were introduced and used to discuss the variation of temperature in a laser-irradiated biological tissue. As a result, the Laplace and Fourier transform techniques have been applied, and the solutions of the conductive temperature have been represented in figures. The two-temperature parameter, the penetration depth parameter, the dimensions of the rectangular laser pulse, and the power density of laser irradiation parameter have significant effects on the thermal waves through the skin tissue.

This study investigates the loading impact of iron oxide (IO) and silane treated iron oxide (SIO) nanoparticles on thermal, mechanical and morphological behavior of epoxy matrix. Both IO and SIO nanoparticles were loaded with 1, 3 and 5 wt% from the total weight of epoxy matrix. The morphology of IO, and SIO epoxy nanocomposites are investigated by TEM. FTIR spectra are successfully able to confirm the good chemical interaction between SIO nanoparticles and epoxy matrix. Thermal resistance of epoxy IO, and SIO nanocomposites is studied by TGA. The mechanical properties of prepared nanocomposites including storage modulus, tan δ, stress-strain curves and toughness are studied using DMA at temperature range 25 °C–100 °C. The results approved that loading 3 wt% of SIO nanoparticles improved the morphological, thermal resistance and mechanical characteristics of epoxy matrix. Keywords: Iron oxide nanoparicles, Epoxy nanocomposites, Modulus, Toughness, Thermal stability

The main target of this article is to find out the most applicable strengthening technique to change the brittle punching shear failure of slab–column connection to a ductile one. The considered strengthening technique uses the combined effect of the internal single-leg stirrups and a thin layer of ultra-high-performance strain hardening cementitious composite material provided in either tension or compression side. Thus, 12 slab specimens divided into four groups were prepared and configured. It was found that the slab provided with properly anchored single-leg stirrups with a cross-shaped thin layer of ultra-high-performance strain hardening cementitious composite material at the compression side proved the most efficient technique among all the considered configurations. This technique enabled the slab to sustain a punching load of about 2.38 times that of the control unstrengthened slab. In addition, it exhibited ductile failure showing strain hardening and softening plateaus. Finally, the experimental shear resistances of all the strengthened slabs were compared against the design resistances stipulated by different design standards such as the ECP 203-2007, ACI 318-14, DIN 1045-1, and EC2-2004 codes. It can be concluded that the failure characteristics stipulated by the DIN 1045-1 code showed the most rational results compared with those of the experimental findings.

Basalt-fiber-reinforced polymer (BFRP) bars are expected to provide benefits that are comparable or superior to other types of FRP while being significantly cost-effective. However, extensive investigations are needed to evaluate the long-term characteristics and durability performance of these bars. This article presents an experimental study that investigated the physical, mechanical, microstructural, and durability characteristics of newly developed basalt-fiber-reinforced polymer (BFRP) bars. The physical, mechanical properties and microstructural characteristics were evaluated first on the unconditioned BFRP bars. The durability performance of the BFRP bars was then assessed by conducting the mechanical tests, such as transverse-shear test, flexural test, and interlaminar-shear test, on the specimens after different exposure periods (1000; 3000; and 5000 h) at 60 °C. Thereafter, the BFRP bar properties were assessed and compared with the values obtained on the unconditioned specimens. The test parameter was conditioning time (1000; 3000; and 5000 h). The test results revealed that the unconditioned BFRP bars had the best physical properties. On the other hand, the long-term durability performance revealed that the transverse shear-strength, flexural-strength, and interlaminar shear-strength retention were decreased by 12%, 19%, and 21%, respectively.

In this paper, two techniques are used to experimentally improve the solar cells efficiency by coating the outer surface of the panels with oil and chlorophyll. Coating the outer glass of solar cell with small layer of oil improves the value of sunlight absorbed by panel and accordingly the efficiency of the panels dramatically increases due to high transmissivity of some types of oils, especially vacuum oils. In this experiment, four types of oils are examined such as vacuum oil, engine oil, abro oil used as a mineral oils and sunflower oil examined as a natural oil. During the experiment, it has been observed the efficiency of the solar cell panels that have been coated with vacuum oil (labovac oil) increased by 11.28% compared to the efficiency of the same panel before coating. Similarly, coating the outer surface of solar panel with 1.5 mm layer of chlorophyll improves the efficiency by 4.17% as chlorophyll absorb a wide range of sunlight falling on surface of the photovoltaic panel and thus increase its efficiency.

Purpose: The physiological conditions and environment have vital roles in the heat transfer in the human tissues, such as the multilayered human-eye. In this paper, a mathematical model of the human eye subjected to an exponential laser beam concerning the change in blood perfusion, porosity, evaporation rate, and ambient temperatures has been constructed based on non-Fourier heat conduction law. Methods: The human eye has been divided into six layers. Appropriate boundary and interface conditions have been considered. A separable function has been assumed, and the twelve equations have been formulated in matrix form. The solutions have been calculated by using maple 17 software. Results: The results have been shown in figures with different cases. The absolute temperature distribution based on various values of the power density of laser irradiation and relaxation times parameters have been discussed first. The effect of the blood perfusion, porosity, evaporation rate, time, and ambient temperatures have also been discussed. Conclusions: The power density of laser irradiation, blood perfusion, porosity, evaporation rate, time, and ambient temperatures significantly affects the value of the temperature passing through the human eye layers.