Engineering Research Journal (Shoubra), Dec 31, 2023
Rebars fabricated from Fiber-Reinforced Polymers (FRP) are innovative materials utilized as an al... more Rebars fabricated from Fiber-Reinforced Polymers (FRP) are innovative materials utilized as an alternative to traditional steel reinforcement rebars in reinforced concrete structures to overcome corrosion problems especially in harsh and aggressive environments. FRP rebars manufactured from glass or basalt fibers embedded in a polymer matrix have high tensile strength, stiffness and enhanced durability. Also, FRP rebars have moderate costs. This research investigates experimentally the flexural performance of FRP-reinforced concrete beams. In the experimental program, two concrete beams reinforced by glass and basalt FRP bars were tested under a four-point flexural test until failure. Both the failure load, the failure mechanism and the mid-span deflection of the tested beams are presented and discussed. The experimental investigation showed that the major failure mode of the tested beams reinforced by FRP bars is crushing of concrete at the top substrate. Additionally, theoretical analysis of the ultimate flexural capacity and the failure loads were computed using American design guidelines and were found to be in good agreement with the experimental results.
Engineering Research Journal (Shoubra), Sep 30, 2023
This paper presents an experimental program performed on a structural panel fabricated from glass... more This paper presents an experimental program performed on a structural panel fabricated from glass fiber reinforced polymer (GFRP) and a wooden frame. The tested panel consists of a timber frame with the dimensions of 1200 x 600 x 25 mm covered by GFRP layers which were manufactured by a hand-layup process. Tensile and flexure tests were conducted for the GFRP specimens and for GFRP-covered wood sections to evaluate the material properties. The results showed brittle failure under average maximum load of 9.28 kN, average maximum elongation of 7.7 mm and the modulus of elasticity for the GFRP was about 2400 MPa. The obtained bending stress for GFRP-covered wood sections ranged between 90-115 MPa. Additionally, full-scale panels were tested under distributed loads until failure to study their flexural behavior. The experimental results demonstrated good mechanical and physical properties for the presented GFRP-wood panels, which renders the use of such composite GFRP-wood panel promising in prefabricated structures.
Engineering Research Journal (Shoubra), Sep 30, 2023
Geopolymer concrete has developed as an environmentally sustainable construction material the gai... more Geopolymer concrete has developed as an environmentally sustainable construction material the gained importance due to its cement-free production process. This paper presents numerical modeling through nonlinear finite element analysis (NLFEA) of reinforced geopolymer concrete beams as well as an analytical study. The numerical modeling and nonlinear analysis are performed using commercial software ANSYS, made for previously tested geopolymer concrete (GC) beams with main reinforcement bars of steel and glass fiber reinforced polymers (GFRP), and contains two types of dispersed fibers: steel and polypropylene fibers. The numerical results are presented and compared with the published experimental findings. A reasonable correlation between numerical and experimental results is observed, thus validating the efficiency of the modeling methodology for analyzing and designing geopolymer concrete c elements .
Wooden beams have been traditionally used for centuries as the supporting elements for roofs. Lon... more Wooden beams have been traditionally used for centuries as the supporting elements for roofs. Long exposure to environmental conditions and aging cause deterioration and decay of the wooden beams in historical structures, whereby restoration or strengthening is often needed to preserve its historical and archaeological value. This research addresses wooden beams strengthened using Fiber-Reinforceded Polymers (FRP). Numerical modelling is carried out by Finite Element Method (FEM) using a commercial Simulia ABAQUS software ABAQUS, taking into account the anisotropic nature of wood materials and nonlinear behaviour. Validation of the numerical modelling procedure was made by conducting FEM analysis of previously tested two wooden beams: solid wooden beam and FRP-strengthened wooden beam. Description of the modelling procedures for the two beams are described. Agreement between the numerically obtained and the experimentally observed flexural behaviour and failure validates the numerical modelling and analysis approach for investigating and design of various configurations for strengthening wooden elements. A numerical study was conducted to investigate several fiber composites strengthening schemes for wood beam.
Engineering Research Journal (Shoubra), Dec 31, 2023
This paper investigates experimentally the efficiency of thermal insulation layers in preserving ... more This paper investigates experimentally the efficiency of thermal insulation layers in preserving the flexural capacity of fiber-reinforced polymer (FRP) reinforced concrete beams subjected to elevated temperature. FRP rebars are innovative alternatives to conventional steel reinforcement rebars in reinforced concrete structures. There is a need to identify the performance of those beams under fire scenario. Four concrete beams reinforced by different FRP rebars were investigated under elevated temperature exposure up to 800 o C for two hours. Two of those beams were thermally insulated by a 25 mm thick thermal insulation layer from perlite mortar. Experimental tests showed that the insulation layer enhanced the flexural performance of the concrete beams compared to the uninsulated beams. Moreover, the thermally insulated beams showed that the major failure mode is the crushing concrete at the top substrate of tested beams as recommended by the design guidelines. The thermal progression, failure load, failure mechanism and mid-span deflection of the tested beams are presented and discussed.
Интеллектуальные системы в производстве, Oct 8, 2019
Self-compacting concrete (SSC) is a concrete that flows and consolidates under its own weight wit... more Self-compacting concrete (SSC) is a concrete that flows and consolidates under its own weight without additional compaction; it has special mix design which provides high flow ability and high segregation resistance. This paper presents an experimental program that investigates the structural behavior of SCC beams with additives of Nano-silica (Nano-SiO 2) and Nano manganese ferrite (Nano-MnFe 3 O 4). Ten SCC mixes were prepared containing Nano-SiO 2 additives with three percentages 1%, 2% and 3% of cement weight, and Nano-MnFe 3 O 4 with percentages 0.3%, 0.5% and 0.7%. Laboratory tests were performed to determine the fresh properties (workability, passing ability and segregation resistance), mechanical properties (compressive strength, splitting tensile strength and flexural strength), and durability (water permeability and chloride penetration). The experimental results show that using Nano additives with 25% cement replacement by fly ash improved the mechanical and durability properties of SCC. Mixes with the optimum percentage were used to cast reinforced concrete beams which were tested in bending until failure in order to investigate the effect of Nano materials additives on the flexural performance.
This experimental research aims at investigating the possibility of utilizing local glass waste i... more This experimental research aims at investigating the possibility of utilizing local glass waste in the production of concrete for construction. Experimental program is conducted to study the effects of using glass powder (GP) obtained by crushing of local glass waste as partial replacement of cement on the fresh and hardened properties of concrete. Five percentages of GP were used: 0%, 10%, 15%, 20%, and 25% by weight of cement. For all concrete mixes, slump test was made for fresh concrete and tests were made for hardened concrete to evaluate compressive strength, splitting tensile strength and flexural strength. The experimental results show that workability increased by increasing GP content. Concrete compressive strength was reduced for all mixes with glass powder, but is improved by time. The positive effect of using GP as cement replacement extends to 20% on concrete tensile strength. The results showed that as the amount of GP increases the flexure strength. The use of 20 % g...
Engineering Research Journal - Faculty of Engineering (Shoubra)
There is a need to create a new generation of rehabilitation and design processes that integrate ... more There is a need to create a new generation of rehabilitation and design processes that integrate performance-based engineering principles. These include evaluating available capacities and structural strength then comparing them to deformation demands related to acceptable performance levels. This paper concerns with structural non-linear static analysis procedure (NSP) to investigate the performance of reinforced concrete (RC) buildings under seismic hazard. Two case studies of constructed high-rise buildings were analyzed using response spectrum analysis (RSA) and pushover analysis (POA) to evaluate the post-yield behavior, relative damage of the structure, story shears, roof displacement, story drifts, story moments, time period, plastic hinges formation, structure performance level and response modification factor (R). Based on the results of performance points for the two case studies, the buildings can sustain seismic base shear ranging from 85% to 65% of their ultimate capacity from POA in X-and Y-Directions. Furthermore, the calculated response modification factor differs from that prescribed by building codes.
Engineering Research Journal - Faculty of Engineering (Shoubra), Apr 1, 2022
Engineered Cementitious Composite (ECC) was recently developed and was reported to improve the st... more Engineered Cementitious Composite (ECC) was recently developed and was reported to improve the strength, damage tolerance, ductility, energy dissipation capacity, and durability of components when compared to conventional reinforced concrete. A polyvinyl alcohol fiber reinforced engineered cementitious composite (PVA-ECC) using local ingredientsnamely local sand instead of using microsilica sandwas developed, aiming for tensile strain capacity matching that of steel reinforcement for commonly used reinforced concrete structures while reducing the cost. The main objectives of this research are to develop and validate a procedure for numerical modeling and structural analysis of PVA-ECC beams using local sand. Also, the research aims to study the effects of several parameters on the flexural and shear behaviors of PVA-ECC beams. The results of numerical study indicated that the PVA-ECC beams have excellent shear capacity that helps in decreasing shear reinforcement congestion in structural elements. Consequently, PVA-ECC with local sand is very useful for structural elements to resist seismic loads. Furthermore, the peak load is increased with increasing of longitudinal reinforcement ratio (µ) and with increasing of yielding stress. On the other hand, the peak load is decreased with increase of shear span-to-depth ratio (S/d) and the mid-span deflection at peak load is increased with the increasing of S/d in all cases. The stiffness of PVA-ECC is decreased with increasing of S/d and is slightly increased with increasing of µ values. Also, there are minor differences in stiffness when yielding stress of steel reinforcement is changed.
This paper presents a finite element (FE) model for the thermo-mechanical analysis of insulated F... more This paper presents a finite element (FE) model for the thermo-mechanical analysis of insulated FRP-strengthened reinforced concrete (RC) beams exposed to fire. In the model, the effects of loading, thermal expansion of materials, and degradations in both the mechanical properties of materials and the bond behavior at FRP-to-concrete and steel-to-concrete interfaces due to elevated temperatures are all considered. The validity of the FE model is demonstrated through comparisons of FE predictions with results from existing standard fire tests on insulated FRP-strengthened RC beams.
Abstract This addresses the bond between masonry and near surface mounted steel bars through expe... more Abstract This addresses the bond between masonry and near surface mounted steel bars through experimental and numerical investigation. In the experimental program, 12 masonry prisms were prepared from commercial clay bricks and were strengthened using NSM steel bars fixed by cement mortar or epoxy; the prisms were subjected to pull-out testing and the failure loads and modes were studied. Numerical modeling and nonlinear analysis were made for the tested prisms using commercial software ANSYS.V.15. Comparison between experimental and numerical results showed good agreement regarding failure loads and failure modes which validates the efficiency of the adopted numerical modeling and nonlinear analysis approach. The numerical analysis showed that the widespread assumption of perfect bond between the strengthening bars and masonry gives misleading results, and therefore the behavior and resistance of the interface between steel bars and mortar/epoxy or between the mortar/epoxy and masonry should be adequately included in the modeling. Moreover, a numerical study was conducted to investigate the influence of several variables, namely the bar diameter and the embedment length, on the bond between NSM steel bars and masonry elements. The numerical study revealed that the failure load obviously increases with increase of embedment length and slightly with increasing the steel bar diameter.
Background:Unreinforced masonry towers are especially vulnerable to damage during earthquakes.A h... more Background:Unreinforced masonry towers are especially vulnerable to damage during earthquakes.A historic stone masonry minaret in Cairo (1468 A.D.) showed signs of damage and obvious inclination after occurrence of strong earthquakes in 1992 and 2015. Investigating the dynamic behavior of this historical tower is of primary importance to assure its structural safety and seismic vulnerability and enable conservation of thisheritagemonument. Materials and Methods: Numerical modeling and seismic analysis are performed for the minaret in its current condition using finite element commercial software in order to investigate its seismic behavior and to assess its structural efficiency. Several numerical models are made for the minaret to study the influence of openings and of the spiral stairs to the dynamic behavior. Results: The obtained numerical results regarding stresses and deformations are analyzed and correlatedto the observed damages and inclination. The results indicate overall ...
This paper addresses the efficiency of thermal insulation layers applied to protect structural el... more This paper addresses the efficiency of thermal insulation layers applied to protect structural elements strengthened by fiber-reinforced polymers (FRP) in the case of fire event. The paper presents numerical modeling and nonlinear analysis of reinforced concrete (RC) columns externally strengthened by FRP and protected by thermal insulation layers when subjected to elevated temperature specified by standard fire tests, in order to predict their residual capacity and fire endurance. The adopted numerical approach uses commercial software includes heat transfer, variation of thermal and mechanical properties of concrete, steel reinforcement, FRP and insulation material with elevated temperature. The numerical results show good agreement with published results of full-scale fire tests. A parametric study was conducted to investigate the influence of several variables on the structural response and residual capacity of insulated FRP-confined columns loaded by service loads when exposed ...
The present research addresses an issue which is a major concern about the use of fiber reinforce... more The present research addresses an issue which is a major concern about the use of fiber reinforced polymers (FRP) in retrofit and strengthening applications. This paper presents an experimental investigation of the effectiveness of different fire protection materials and techniques on the efficiency of concrete axial members strengthened by FRP and subjected to high temperatures such as in the case of fire. Three locally available and economic materials are investigated: ordinary Portland cement mortar, Perlite and Vermiculite. These were applied with different thicknesses over FRP wrapped concrete specimens and subjected to elevated temperature in a closed furnace. For each case, variation of the temperature on the underlying concrete surface and the ultimate load carrying capacity were studied in order to explore and compare the effectiveness of these protection layers. Protective layers were applied over concrete cylinders strengthened using glass or carbon FRP wraps and subjecte...
Abstract This paper presents a novel application of artificial neural networks (ANNs) for predict... more Abstract This paper presents a novel application of artificial neural networks (ANNs) for predicting complete temperature profiles with varying time for circular reinforced concrete (RC) columns exposed to fire. The application is valid for un-strengthened columns or columns strengthened with fibre reinforced polymers (FRP) and isolated with different types and thicknesses of insulation materials under varying fire exposure condition. In addition, prediction of the temperature variation with time for constituent materials of the column such as concrete, reinforcement steel and FRP sheets is conducted. To reach this end, extensive nonlinear finite element analysis was conducted using ANSYS software to build database of 1200 training samples with different column diameters, concrete cover thicknesses, thermal conductivity curves, specific heat curves, insulation types and thicknesses. The prediction results of ANN model is validated against published full-scale experimental studies which reveal good agreement between experimental and predicted results. The novelty of this technique is the ability of ANN model to predict rapidly and efficiently the temperature–time for any part of continent materials of reinforced concrete column many in case scenarios of parameters; this is especially useful in avoiding the time-consuming and costly full-scale experimental fire tests. Moreover, this study encourages designers to use FRP in design applications in spite of the threat of fire conditions, by utilizing ANN as backend calculation provider for software design tool with graphical user interface presented in this paper.
Самоуплотняющийся бетон – это бетон, который течет и уплотняется под собственным весом без дополн... more Самоуплотняющийся бетон – это бетон, который течет и уплотняется под собственным весом без дополнительного воздействия; он имеет особый состав смеси, который обеспечивает высокую текучесть и устойчивость к расслоению. В данной статье представлены результаты исследования, направленного на изучение структурного поведения балок из самоуплотняющегося бетона с добавками нанокремнезема (Nano-SiO2) и наномарганцевого феррита (Nano-MnFe3O4). Было приготовлено десять типов смесей, содержащих добавки нано-SiO2 с тремя концентрациями: 1, 2 и 3 % от массы цемента и нано-MnFe3O4 с концентрациями 0,3, 0,5 и 0,7 %.Лабораторные испытания проводились для определения свойств свежеприготовленной смеси (пластичности, проходимости и устойчивость к расслоению), механических свойств (прочности на сжатие, прочности на раскалывание и прочности на изгиб) и долговечности (водопроницаемости и проникновения хлоридов). Результаты эксперимента показывают, что использование нанодобавок и замена 25 % цемента летуче...
Engineering Research Journal (Shoubra), Dec 31, 2023
Rebars fabricated from Fiber-Reinforced Polymers (FRP) are innovative materials utilized as an al... more Rebars fabricated from Fiber-Reinforced Polymers (FRP) are innovative materials utilized as an alternative to traditional steel reinforcement rebars in reinforced concrete structures to overcome corrosion problems especially in harsh and aggressive environments. FRP rebars manufactured from glass or basalt fibers embedded in a polymer matrix have high tensile strength, stiffness and enhanced durability. Also, FRP rebars have moderate costs. This research investigates experimentally the flexural performance of FRP-reinforced concrete beams. In the experimental program, two concrete beams reinforced by glass and basalt FRP bars were tested under a four-point flexural test until failure. Both the failure load, the failure mechanism and the mid-span deflection of the tested beams are presented and discussed. The experimental investigation showed that the major failure mode of the tested beams reinforced by FRP bars is crushing of concrete at the top substrate. Additionally, theoretical analysis of the ultimate flexural capacity and the failure loads were computed using American design guidelines and were found to be in good agreement with the experimental results.
Engineering Research Journal (Shoubra), Sep 30, 2023
This paper presents an experimental program performed on a structural panel fabricated from glass... more This paper presents an experimental program performed on a structural panel fabricated from glass fiber reinforced polymer (GFRP) and a wooden frame. The tested panel consists of a timber frame with the dimensions of 1200 x 600 x 25 mm covered by GFRP layers which were manufactured by a hand-layup process. Tensile and flexure tests were conducted for the GFRP specimens and for GFRP-covered wood sections to evaluate the material properties. The results showed brittle failure under average maximum load of 9.28 kN, average maximum elongation of 7.7 mm and the modulus of elasticity for the GFRP was about 2400 MPa. The obtained bending stress for GFRP-covered wood sections ranged between 90-115 MPa. Additionally, full-scale panels were tested under distributed loads until failure to study their flexural behavior. The experimental results demonstrated good mechanical and physical properties for the presented GFRP-wood panels, which renders the use of such composite GFRP-wood panel promising in prefabricated structures.
Engineering Research Journal (Shoubra), Sep 30, 2023
Geopolymer concrete has developed as an environmentally sustainable construction material the gai... more Geopolymer concrete has developed as an environmentally sustainable construction material the gained importance due to its cement-free production process. This paper presents numerical modeling through nonlinear finite element analysis (NLFEA) of reinforced geopolymer concrete beams as well as an analytical study. The numerical modeling and nonlinear analysis are performed using commercial software ANSYS, made for previously tested geopolymer concrete (GC) beams with main reinforcement bars of steel and glass fiber reinforced polymers (GFRP), and contains two types of dispersed fibers: steel and polypropylene fibers. The numerical results are presented and compared with the published experimental findings. A reasonable correlation between numerical and experimental results is observed, thus validating the efficiency of the modeling methodology for analyzing and designing geopolymer concrete c elements .
Wooden beams have been traditionally used for centuries as the supporting elements for roofs. Lon... more Wooden beams have been traditionally used for centuries as the supporting elements for roofs. Long exposure to environmental conditions and aging cause deterioration and decay of the wooden beams in historical structures, whereby restoration or strengthening is often needed to preserve its historical and archaeological value. This research addresses wooden beams strengthened using Fiber-Reinforceded Polymers (FRP). Numerical modelling is carried out by Finite Element Method (FEM) using a commercial Simulia ABAQUS software ABAQUS, taking into account the anisotropic nature of wood materials and nonlinear behaviour. Validation of the numerical modelling procedure was made by conducting FEM analysis of previously tested two wooden beams: solid wooden beam and FRP-strengthened wooden beam. Description of the modelling procedures for the two beams are described. Agreement between the numerically obtained and the experimentally observed flexural behaviour and failure validates the numerical modelling and analysis approach for investigating and design of various configurations for strengthening wooden elements. A numerical study was conducted to investigate several fiber composites strengthening schemes for wood beam.
Engineering Research Journal (Shoubra), Dec 31, 2023
This paper investigates experimentally the efficiency of thermal insulation layers in preserving ... more This paper investigates experimentally the efficiency of thermal insulation layers in preserving the flexural capacity of fiber-reinforced polymer (FRP) reinforced concrete beams subjected to elevated temperature. FRP rebars are innovative alternatives to conventional steel reinforcement rebars in reinforced concrete structures. There is a need to identify the performance of those beams under fire scenario. Four concrete beams reinforced by different FRP rebars were investigated under elevated temperature exposure up to 800 o C for two hours. Two of those beams were thermally insulated by a 25 mm thick thermal insulation layer from perlite mortar. Experimental tests showed that the insulation layer enhanced the flexural performance of the concrete beams compared to the uninsulated beams. Moreover, the thermally insulated beams showed that the major failure mode is the crushing concrete at the top substrate of tested beams as recommended by the design guidelines. The thermal progression, failure load, failure mechanism and mid-span deflection of the tested beams are presented and discussed.
Интеллектуальные системы в производстве, Oct 8, 2019
Self-compacting concrete (SSC) is a concrete that flows and consolidates under its own weight wit... more Self-compacting concrete (SSC) is a concrete that flows and consolidates under its own weight without additional compaction; it has special mix design which provides high flow ability and high segregation resistance. This paper presents an experimental program that investigates the structural behavior of SCC beams with additives of Nano-silica (Nano-SiO 2) and Nano manganese ferrite (Nano-MnFe 3 O 4). Ten SCC mixes were prepared containing Nano-SiO 2 additives with three percentages 1%, 2% and 3% of cement weight, and Nano-MnFe 3 O 4 with percentages 0.3%, 0.5% and 0.7%. Laboratory tests were performed to determine the fresh properties (workability, passing ability and segregation resistance), mechanical properties (compressive strength, splitting tensile strength and flexural strength), and durability (water permeability and chloride penetration). The experimental results show that using Nano additives with 25% cement replacement by fly ash improved the mechanical and durability properties of SCC. Mixes with the optimum percentage were used to cast reinforced concrete beams which were tested in bending until failure in order to investigate the effect of Nano materials additives on the flexural performance.
This experimental research aims at investigating the possibility of utilizing local glass waste i... more This experimental research aims at investigating the possibility of utilizing local glass waste in the production of concrete for construction. Experimental program is conducted to study the effects of using glass powder (GP) obtained by crushing of local glass waste as partial replacement of cement on the fresh and hardened properties of concrete. Five percentages of GP were used: 0%, 10%, 15%, 20%, and 25% by weight of cement. For all concrete mixes, slump test was made for fresh concrete and tests were made for hardened concrete to evaluate compressive strength, splitting tensile strength and flexural strength. The experimental results show that workability increased by increasing GP content. Concrete compressive strength was reduced for all mixes with glass powder, but is improved by time. The positive effect of using GP as cement replacement extends to 20% on concrete tensile strength. The results showed that as the amount of GP increases the flexure strength. The use of 20 % g...
Engineering Research Journal - Faculty of Engineering (Shoubra)
There is a need to create a new generation of rehabilitation and design processes that integrate ... more There is a need to create a new generation of rehabilitation and design processes that integrate performance-based engineering principles. These include evaluating available capacities and structural strength then comparing them to deformation demands related to acceptable performance levels. This paper concerns with structural non-linear static analysis procedure (NSP) to investigate the performance of reinforced concrete (RC) buildings under seismic hazard. Two case studies of constructed high-rise buildings were analyzed using response spectrum analysis (RSA) and pushover analysis (POA) to evaluate the post-yield behavior, relative damage of the structure, story shears, roof displacement, story drifts, story moments, time period, plastic hinges formation, structure performance level and response modification factor (R). Based on the results of performance points for the two case studies, the buildings can sustain seismic base shear ranging from 85% to 65% of their ultimate capacity from POA in X-and Y-Directions. Furthermore, the calculated response modification factor differs from that prescribed by building codes.
Engineering Research Journal - Faculty of Engineering (Shoubra), Apr 1, 2022
Engineered Cementitious Composite (ECC) was recently developed and was reported to improve the st... more Engineered Cementitious Composite (ECC) was recently developed and was reported to improve the strength, damage tolerance, ductility, energy dissipation capacity, and durability of components when compared to conventional reinforced concrete. A polyvinyl alcohol fiber reinforced engineered cementitious composite (PVA-ECC) using local ingredientsnamely local sand instead of using microsilica sandwas developed, aiming for tensile strain capacity matching that of steel reinforcement for commonly used reinforced concrete structures while reducing the cost. The main objectives of this research are to develop and validate a procedure for numerical modeling and structural analysis of PVA-ECC beams using local sand. Also, the research aims to study the effects of several parameters on the flexural and shear behaviors of PVA-ECC beams. The results of numerical study indicated that the PVA-ECC beams have excellent shear capacity that helps in decreasing shear reinforcement congestion in structural elements. Consequently, PVA-ECC with local sand is very useful for structural elements to resist seismic loads. Furthermore, the peak load is increased with increasing of longitudinal reinforcement ratio (µ) and with increasing of yielding stress. On the other hand, the peak load is decreased with increase of shear span-to-depth ratio (S/d) and the mid-span deflection at peak load is increased with the increasing of S/d in all cases. The stiffness of PVA-ECC is decreased with increasing of S/d and is slightly increased with increasing of µ values. Also, there are minor differences in stiffness when yielding stress of steel reinforcement is changed.
This paper presents a finite element (FE) model for the thermo-mechanical analysis of insulated F... more This paper presents a finite element (FE) model for the thermo-mechanical analysis of insulated FRP-strengthened reinforced concrete (RC) beams exposed to fire. In the model, the effects of loading, thermal expansion of materials, and degradations in both the mechanical properties of materials and the bond behavior at FRP-to-concrete and steel-to-concrete interfaces due to elevated temperatures are all considered. The validity of the FE model is demonstrated through comparisons of FE predictions with results from existing standard fire tests on insulated FRP-strengthened RC beams.
Abstract This addresses the bond between masonry and near surface mounted steel bars through expe... more Abstract This addresses the bond between masonry and near surface mounted steel bars through experimental and numerical investigation. In the experimental program, 12 masonry prisms were prepared from commercial clay bricks and were strengthened using NSM steel bars fixed by cement mortar or epoxy; the prisms were subjected to pull-out testing and the failure loads and modes were studied. Numerical modeling and nonlinear analysis were made for the tested prisms using commercial software ANSYS.V.15. Comparison between experimental and numerical results showed good agreement regarding failure loads and failure modes which validates the efficiency of the adopted numerical modeling and nonlinear analysis approach. The numerical analysis showed that the widespread assumption of perfect bond between the strengthening bars and masonry gives misleading results, and therefore the behavior and resistance of the interface between steel bars and mortar/epoxy or between the mortar/epoxy and masonry should be adequately included in the modeling. Moreover, a numerical study was conducted to investigate the influence of several variables, namely the bar diameter and the embedment length, on the bond between NSM steel bars and masonry elements. The numerical study revealed that the failure load obviously increases with increase of embedment length and slightly with increasing the steel bar diameter.
Background:Unreinforced masonry towers are especially vulnerable to damage during earthquakes.A h... more Background:Unreinforced masonry towers are especially vulnerable to damage during earthquakes.A historic stone masonry minaret in Cairo (1468 A.D.) showed signs of damage and obvious inclination after occurrence of strong earthquakes in 1992 and 2015. Investigating the dynamic behavior of this historical tower is of primary importance to assure its structural safety and seismic vulnerability and enable conservation of thisheritagemonument. Materials and Methods: Numerical modeling and seismic analysis are performed for the minaret in its current condition using finite element commercial software in order to investigate its seismic behavior and to assess its structural efficiency. Several numerical models are made for the minaret to study the influence of openings and of the spiral stairs to the dynamic behavior. Results: The obtained numerical results regarding stresses and deformations are analyzed and correlatedto the observed damages and inclination. The results indicate overall ...
This paper addresses the efficiency of thermal insulation layers applied to protect structural el... more This paper addresses the efficiency of thermal insulation layers applied to protect structural elements strengthened by fiber-reinforced polymers (FRP) in the case of fire event. The paper presents numerical modeling and nonlinear analysis of reinforced concrete (RC) columns externally strengthened by FRP and protected by thermal insulation layers when subjected to elevated temperature specified by standard fire tests, in order to predict their residual capacity and fire endurance. The adopted numerical approach uses commercial software includes heat transfer, variation of thermal and mechanical properties of concrete, steel reinforcement, FRP and insulation material with elevated temperature. The numerical results show good agreement with published results of full-scale fire tests. A parametric study was conducted to investigate the influence of several variables on the structural response and residual capacity of insulated FRP-confined columns loaded by service loads when exposed ...
The present research addresses an issue which is a major concern about the use of fiber reinforce... more The present research addresses an issue which is a major concern about the use of fiber reinforced polymers (FRP) in retrofit and strengthening applications. This paper presents an experimental investigation of the effectiveness of different fire protection materials and techniques on the efficiency of concrete axial members strengthened by FRP and subjected to high temperatures such as in the case of fire. Three locally available and economic materials are investigated: ordinary Portland cement mortar, Perlite and Vermiculite. These were applied with different thicknesses over FRP wrapped concrete specimens and subjected to elevated temperature in a closed furnace. For each case, variation of the temperature on the underlying concrete surface and the ultimate load carrying capacity were studied in order to explore and compare the effectiveness of these protection layers. Protective layers were applied over concrete cylinders strengthened using glass or carbon FRP wraps and subjecte...
Abstract This paper presents a novel application of artificial neural networks (ANNs) for predict... more Abstract This paper presents a novel application of artificial neural networks (ANNs) for predicting complete temperature profiles with varying time for circular reinforced concrete (RC) columns exposed to fire. The application is valid for un-strengthened columns or columns strengthened with fibre reinforced polymers (FRP) and isolated with different types and thicknesses of insulation materials under varying fire exposure condition. In addition, prediction of the temperature variation with time for constituent materials of the column such as concrete, reinforcement steel and FRP sheets is conducted. To reach this end, extensive nonlinear finite element analysis was conducted using ANSYS software to build database of 1200 training samples with different column diameters, concrete cover thicknesses, thermal conductivity curves, specific heat curves, insulation types and thicknesses. The prediction results of ANN model is validated against published full-scale experimental studies which reveal good agreement between experimental and predicted results. The novelty of this technique is the ability of ANN model to predict rapidly and efficiently the temperature–time for any part of continent materials of reinforced concrete column many in case scenarios of parameters; this is especially useful in avoiding the time-consuming and costly full-scale experimental fire tests. Moreover, this study encourages designers to use FRP in design applications in spite of the threat of fire conditions, by utilizing ANN as backend calculation provider for software design tool with graphical user interface presented in this paper.
Самоуплотняющийся бетон – это бетон, который течет и уплотняется под собственным весом без дополн... more Самоуплотняющийся бетон – это бетон, который течет и уплотняется под собственным весом без дополнительного воздействия; он имеет особый состав смеси, который обеспечивает высокую текучесть и устойчивость к расслоению. В данной статье представлены результаты исследования, направленного на изучение структурного поведения балок из самоуплотняющегося бетона с добавками нанокремнезема (Nano-SiO2) и наномарганцевого феррита (Nano-MnFe3O4). Было приготовлено десять типов смесей, содержащих добавки нано-SiO2 с тремя концентрациями: 1, 2 и 3 % от массы цемента и нано-MnFe3O4 с концентрациями 0,3, 0,5 и 0,7 %.Лабораторные испытания проводились для определения свойств свежеприготовленной смеси (пластичности, проходимости и устойчивость к расслоению), механических свойств (прочности на сжатие, прочности на раскалывание и прочности на изгиб) и долговечности (водопроницаемости и проникновения хлоридов). Результаты эксперимента показывают, что использование нанодобавок и замена 25 % цемента летуче...
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Papers by Gehan Hamdy