Pub Date : 2021-07-01DOI: 10.12989/CAC.2021.28.1.001
Guangji Yin, X. Zuo, Xiao D. Wen, Yu-Juan Tang
The stress-strain curve of concrete under a uniaxial compression can reflect much information about its mechanical properties. This paper performs an experimental study and modeling on the stress-strain curve of concrete subjected to external sulfate attack (ESA). To shorten the experimental period, cement mortar specimen (CMS) with a small size is selected as research objected, and is immersed into purified water, 2.5% and 5.0% Na2SO4 solution. First, an economic test equipment is designed by adding rigid elements to ordinary hydraulic testing machine. Second, the evolution of stress-strain curve and mechanical properties of sulfate-corroded CMS with immersion time is obtained. Based on least-square method, the expressions of two chemical damage parameters are determined to respectively characterize the time-varying elastic modulus and compression strength of CMS caused by ESA. Then, a coupling chemo-mechanical damage constitutive model for sulfatecorroded CMS is established by introducing the chemical damage parameters. Finally, the numerical solution of the model is presented, and is validated by the above experimental data of stress-strain curve of CMS.
{"title":"Experimental study and modeling on stress-strain curve of sulfate-corroded concrete","authors":"Guangji Yin, X. Zuo, Xiao D. Wen, Yu-Juan Tang","doi":"10.12989/CAC.2021.28.1.001","DOIUrl":"https://doi.org/10.12989/CAC.2021.28.1.001","url":null,"abstract":"The stress-strain curve of concrete under a uniaxial compression can reflect much information about its mechanical properties. This paper performs an experimental study and modeling on the stress-strain curve of concrete subjected to external sulfate attack (ESA). To shorten the experimental period, cement mortar specimen (CMS) with a small size is selected as research objected, and is immersed into purified water, 2.5% and 5.0% Na2SO4 solution. First, an economic test equipment is designed by adding rigid elements to ordinary hydraulic testing machine. Second, the evolution of stress-strain curve and mechanical properties of sulfate-corroded CMS with immersion time is obtained. Based on least-square method, the expressions of two chemical damage parameters are determined to respectively characterize the time-varying elastic modulus and compression strength of CMS caused by ESA. Then, a coupling chemo-mechanical damage constitutive model for sulfatecorroded CMS is established by introducing the chemical damage parameters. Finally, the numerical solution of the model is presented, and is validated by the above experimental data of stress-strain curve of CMS.","PeriodicalId":50625,"journal":{"name":"Computers and Concrete","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88419712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-07-01DOI: 10.12989/CAC.2021.28.1.055
K. Yaswanth, J. Revathy, P. Gajalakshmi
Engineered Geopolymer Composites has proved to be an excellent eco-friendly strain hardening composite materials, as well as, it exhibits high tensile strain capacity. An intelligent computing tool based predictive model to anticipate the compressive strength of ductile geopolymer composites would help various researchers to analyse the material type and its contents; the dosage of fibers; producing tailor-made materials; less time consumption; cost-saving etc., which could suit for various infrastructural applications. This paper attempts to develop a suitable ANN based machine learning model in predicting the compressive strength of strain hardening geopolymer composites with greater accuracy. A simple ANN network with a various number of hidden neurons have been trained, tested and validated. The results revealed that with seventeen inputs and one output parameters respectively for mix design & compressive strength and thirteen hidden neurons in its layer have provided the notable prediction with R2 as 96% with the RMSE of 2.64. It is concluded that a simple ANN model would have the perspective of estimating the compressive strength properties of engineered geopolymer composite to an accuracy level of more than 90%. The sensitivity analysis of ANN model with 13-hidden neurons, also confirms the accuracy of prediction of compressive strength.
{"title":"Artificial intelligence for the compressive strength prediction of novel ductile geopolymer composites","authors":"K. Yaswanth, J. Revathy, P. Gajalakshmi","doi":"10.12989/CAC.2021.28.1.055","DOIUrl":"https://doi.org/10.12989/CAC.2021.28.1.055","url":null,"abstract":"Engineered Geopolymer Composites has proved to be an excellent eco-friendly strain hardening composite materials, as well as, it exhibits high tensile strain capacity. An intelligent computing tool based predictive model to anticipate the compressive strength of ductile geopolymer composites would help various researchers to analyse the material type and its contents; the dosage of fibers; producing tailor-made materials; less time consumption; cost-saving etc., which could suit for various infrastructural applications. This paper attempts to develop a suitable ANN based machine learning model in predicting the compressive strength of strain hardening geopolymer composites with greater accuracy. A simple ANN network with a various number of hidden neurons have been trained, tested and validated. The results revealed that with seventeen inputs and one output parameters respectively for mix design & compressive strength and thirteen hidden neurons in its layer have provided the notable prediction with R2 as 96% with the RMSE of 2.64. It is concluded that a simple ANN model would have the perspective of estimating the compressive strength properties of engineered geopolymer composite to an accuracy level of more than 90%. The sensitivity analysis of ANN model with 13-hidden neurons, also confirms the accuracy of prediction of compressive strength.","PeriodicalId":50625,"journal":{"name":"Computers and Concrete","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77144064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-01DOI: 10.12989/CAC.2021.27.6.513
A. Demir, Mehmet Mete Cengiz
Brick infill walls (BIW) have significant effects on reinforced concrete (RC) structures' seismic performances. However, mechanical effects on the structural performance of BIWs, which are regarded as only weight at the design stage, are not considered in many seismic codes. Therefore, seismic performances of new and existing RC structures could not be realistically obtained. This study aims to investigate the effects on the structural behavior of BIWs, stucco types, and soft story. RC structures with and without BIWs are modeled by using the SAP2000 program. BIW is modeled with the equivalent diagonal compression strut method, and mechanical properties of BIWs plastered with conventional and polypropylene fibrous stuccos are taken from literature. Seismic performances of all structures are investigated using the pushover analysis method, according to Turkish Seismic Code-2007 (TSC-2007) principles. Besides, natural periods, rigidities, ductilities and energy dissipation capacities of all structures are obtained. As a result of analyses, it is determined that BIWs have significant effects on structural performances in terms of rigidity and ductility, and fibrous stucco considerably increases RC structures' rigidity and ductility. These walls can even lead to the collapse of structures in severe earthquakes if design engineers don't regard BIWs or BIWs are placed as asymmetric or deficient on the structure.
{"title":"Effect of infill wall properties on seismic response of RC structures","authors":"A. Demir, Mehmet Mete Cengiz","doi":"10.12989/CAC.2021.27.6.513","DOIUrl":"https://doi.org/10.12989/CAC.2021.27.6.513","url":null,"abstract":"Brick infill walls (BIW) have significant effects on reinforced concrete (RC) structures' seismic performances. However, mechanical effects on the structural performance of BIWs, which are regarded as only weight at the design stage, are not considered in many seismic codes. Therefore, seismic performances of new and existing RC structures could not be realistically obtained. This study aims to investigate the effects on the structural behavior of BIWs, stucco types, and soft story. RC structures with and without BIWs are modeled by using the SAP2000 program. BIW is modeled with the equivalent diagonal compression strut method, and mechanical properties of BIWs plastered with conventional and polypropylene fibrous stuccos are taken from literature. Seismic performances of all structures are investigated using the pushover analysis method, \u0000according to Turkish Seismic Code-2007 (TSC-2007) principles. Besides, natural periods, rigidities, ductilities and energy dissipation capacities of all structures are obtained. As a result of analyses, it is determined that BIWs have significant effects on structural performances in terms of rigidity and ductility, and fibrous stucco considerably increases RC structures' rigidity and ductility. These walls can even lead to the collapse of structures in severe earthquakes if design engineers don't regard BIWs or BIWs are placed as asymmetric or deficient on the structure.","PeriodicalId":50625,"journal":{"name":"Computers and Concrete","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76119637","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-01DOI: 10.12989/CAC.2021.27.6.549
M. Mota, E. Fairbairn, F. Ribeiro, P. Rossi, J. Tailhan, H. C. C. Andrade, M. Rita
Concrete is globally the most used building material. This fact shows the need to make advances in the prediction of its mechanical behavior. Despite being considered homogenous in many cases for simplification purposes, this material naturally has a high degree of heterogeneity, which presents challenges in terms of fracture process modeling, due to phenomena such as scale effect and softening behavior. In this context, the objective of this work is to present a 3D probabilistic cracking model based on the finite element method, in which material discontinuities are explicitly represented by interface elements. The threedimensional modeling of cracks makes it possible to analyze the fracture process in a more realistic way. In order to estimate statistical parameters that define the material heterogeneity, an inverse analysis procedure was performed using general laws defined by experimental investigations. The model and the inverse analysis strategy were validated mainly by the verification of scale effect at a level similar to that experimentally observed, taking into account the tensile failure of plain concretes. Results also indicate that different softening levels can be obtained.
{"title":"A 3D probabilistic model for explicit cracking of concrete","authors":"M. Mota, E. Fairbairn, F. Ribeiro, P. Rossi, J. Tailhan, H. C. C. Andrade, M. Rita","doi":"10.12989/CAC.2021.27.6.549","DOIUrl":"https://doi.org/10.12989/CAC.2021.27.6.549","url":null,"abstract":"Concrete is globally the most used building material. This fact shows the need to make advances in the prediction of its mechanical behavior. Despite being considered homogenous in many cases for simplification purposes, this material naturally has a high degree of heterogeneity, which presents challenges in terms of fracture process modeling, due to phenomena such as scale effect and softening behavior. In this context, the objective of this work is to present a 3D probabilistic cracking model based on the finite element method, in which material discontinuities are explicitly represented by interface elements. The threedimensional modeling of cracks makes it possible to analyze the fracture process in a more realistic way. In order to estimate statistical parameters that define the material heterogeneity, an inverse analysis procedure was performed using general laws defined by experimental investigations. The model and the inverse analysis strategy were validated mainly by the verification of scale effect at a level similar to that experimentally observed, taking into account the tensile failure of plain concretes. Results also indicate that different softening levels can be obtained.","PeriodicalId":50625,"journal":{"name":"Computers and Concrete","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74033985","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-01DOI: 10.12989/CAC.2021.27.6.585
Omar R. Abuodeh, R. Hawileh, Jamal A. Abdalla
This study presents a nonlinear finite element (FE) model development of reinforced concrete (RC) beams externally strengthened with aluminum alloy (AA) plates. The aim of this numerical study was to elucidate the effects of different anchorage schemes on the capacity, ductility, and failure mode of AA plate strengthened beams reported in a published test. Three FE models were developed; namely, a reference RC beam, a beam externally bonded (EB) with an AA plate, and a beam EB with an AA plate with carbon fiber reinforced polymers (CFRP) U-wraps at the plate's end. Validation of the developed FE models was carried out by comparing their load-deflection plots, maximum attained loads, deflections at failure, and failure modes with those reported during the test. The results of each FE model yielded an absolute percentage error less than 5%. Moreover, premature failure modes like end-plate and intermediate crack debonding were simulated and closely agreed with those observed during the test. Finally, the validated models were used to employ a parametric study comprising of twelve beams varying in size of steel reinforcement, presence of AA plates, and end-anchorage. It was concluded that the developed FE models could serve as a design platform for assisting structural engineers during flexural retrofit applications using AA plates.
{"title":"Finite element modelling of aluminum alloy plated reinforced concrete beams","authors":"Omar R. Abuodeh, R. Hawileh, Jamal A. Abdalla","doi":"10.12989/CAC.2021.27.6.585","DOIUrl":"https://doi.org/10.12989/CAC.2021.27.6.585","url":null,"abstract":"This study presents a nonlinear finite element (FE) model development of reinforced concrete (RC) beams externally strengthened with aluminum alloy (AA) plates. The aim of this numerical study was to elucidate the effects of different anchorage schemes on the capacity, ductility, and failure mode of AA plate strengthened beams reported in a published test. Three FE models were developed; namely, a reference RC beam, a beam externally bonded (EB) with an AA plate, and a beam EB with an AA plate with carbon fiber reinforced polymers (CFRP) U-wraps at the plate's end. Validation of the developed FE models was carried out by comparing their load-deflection plots, maximum attained loads, deflections at failure, and failure modes with those reported during the test. The results of each FE model yielded an absolute percentage error less than 5%. Moreover, premature failure modes like end-plate and intermediate crack debonding were simulated and closely agreed with those observed during the test. Finally, the validated models were used to employ a parametric study comprising of twelve beams varying in size of steel reinforcement, presence of AA plates, and end-anchorage. It was concluded that the developed FE models could serve as a design platform for assisting structural engineers during flexural retrofit applications using AA plates.","PeriodicalId":50625,"journal":{"name":"Computers and Concrete","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72367191","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-01DOI: 10.12989/CAC.2021.27.6.563
Hamed Arjomandi, Ali Foroghi Asl
In this study, the effect of SiO2 nanoparticles on the bonding behavior of steel and glass fiber reinforced polymer (GFRP) bar embedded in contained Light-weight Self-Consolidating Concrete (LWSCC) has been studied experimentally and numerically. The measurement of the mechanical properties of LWSCC modified with SiO2 nanoparticles, including compressive and tensile strength, elastic modulus and density were also carried out. Studies are conducted on 7, and 28-day aged LWSCC samples containing 0, 2 and 5% SiO2 nanoparticles with 12 mm and 16 mm diameter GFRP and steel bars. The results show that LWSCC modified with SiO2 nanoparticles increases the bonding strength between concrete and bar. In LWSCC with 2 and 5 wt.% SiO2, the maximum pull-out force of 16 mm diameter steel bar is increased by 48.5% and 54.7%, respectively, compared to the LWSCC without nanoparticle addition. Also, bonding improvement between GFRP bars with a diameter of 16mm and LWSCC having 2 and 5 wt.% SiO2 is 32.3% and 40%, respectively.
{"title":"Pull-out strength between Nano-SiO2 contained light-weightself-consolidating concrete and GFRP and steel bars","authors":"Hamed Arjomandi, Ali Foroghi Asl","doi":"10.12989/CAC.2021.27.6.563","DOIUrl":"https://doi.org/10.12989/CAC.2021.27.6.563","url":null,"abstract":"In this study, the effect of SiO2 nanoparticles on the bonding behavior of steel and glass fiber reinforced polymer (GFRP) bar embedded in contained Light-weight Self-Consolidating Concrete (LWSCC) has been studied experimentally and numerically. The measurement of the mechanical properties of LWSCC modified with SiO2 nanoparticles, including compressive and tensile strength, elastic modulus and density were also carried out. Studies are conducted on 7, and 28-day aged LWSCC samples containing 0, 2 and 5% SiO2 nanoparticles with 12 mm and 16 mm diameter GFRP and steel bars. The results show that LWSCC modified with SiO2 nanoparticles increases the bonding strength between concrete and bar. In LWSCC with 2 and 5 wt.% SiO2, the maximum pull-out force of 16 mm diameter steel bar is increased by 48.5% and 54.7%, respectively, compared to the LWSCC without nanoparticle addition. Also, bonding improvement between GFRP bars with a diameter of 16mm and LWSCC having 2 and 5 wt.% SiO2 is 32.3% and 40%, respectively.","PeriodicalId":50625,"journal":{"name":"Computers and Concrete","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85257657","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-01DOI: 10.12989/CAC.2021.27.6.575
Zouaoui R. Harrat, S. Amziane, B. Krour, M. B. Bouiadjra
The present study investigates the static behavior of concrete beams impregnated with silicon dioxide (SiO2) nanoparticles. Nanosilica, by virtue of its small particle size, can affect the microstructure of concretes and enhance their properties. Voigt's model is used to take account of the agglomeration effect and obtain the equivalent nano-composite properties. Furthermore, the reinforced concrete beam is simulated mathematically with higher-order shear deformation theory because of its simplicity and accuracy. The soil medium is simulated with Pasternak elastic foundation, including a shear layer, and Winkler spring. The equilibrium equations are derived using the principle of virtual work, and using Hamilton's principle, the energy equations are obtained. Also, analytical methods are employed to obtain the closed-form solutions of simply supported beams. Numerical results are presented, considering the effect of different parameters such as the volume percent of SiO2 nanoparticles, mechanical loads, geometrical parameters, and soil medium, on the static behavior of the beam. The majority of findings from this work indicate that the use of SiO2 nanoparticles in concretes increases their mechanical resistance, and that the deflections and stresses decrease. In addition, the elastic foundation has a significant impact on the bending of concrete beams.
{"title":"On the static behavior of nano Si02 based concrete beamsresting on an elastic foundation","authors":"Zouaoui R. Harrat, S. Amziane, B. Krour, M. B. Bouiadjra","doi":"10.12989/CAC.2021.27.6.575","DOIUrl":"https://doi.org/10.12989/CAC.2021.27.6.575","url":null,"abstract":"The present study investigates the static behavior of concrete beams impregnated with silicon dioxide (SiO2) \u0000nanoparticles. Nanosilica, by virtue of its small particle size, can affect the microstructure of concretes and enhance their properties. Voigt's model is used to take account of the agglomeration effect and obtain the equivalent nano-composite properties. Furthermore, the reinforced concrete beam is simulated mathematically with higher-order shear deformation theory because of its simplicity and accuracy. The soil medium is simulated with Pasternak elastic foundation, including a shear layer, \u0000and Winkler spring. The equilibrium equations are derived using the principle of virtual work, and using Hamilton's principle, the energy equations are obtained. Also, analytical methods are employed to obtain the closed-form solutions of simply supported beams. Numerical results are presented, considering the effect of different parameters such as the volume percent of SiO2 nanoparticles, mechanical loads, geometrical parameters, and soil medium, on the static behavior of the beam. The majority of findings from this work indicate that the use of SiO2 nanoparticles in concretes increases their mechanical resistance, and that the deflections and stresses decrease. In addition, the elastic foundation has a significant impact on the bending of concrete beams.","PeriodicalId":50625,"journal":{"name":"Computers and Concrete","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91169893","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-01DOI: 10.12989/CAC.2021.27.5.417
M. Nematzadeh, R. Mousavi
The optimal distribution of steel fibers over different layers of concrete can be considered as an appropriate method in improving the structural performance and reducing the cost of fiber-reinforced concrete members. In addition, the use of waste tire rubber in concrete mixes, as one of the practical ways to address environmental problems, is highly significant. Thus, this study aimed to evaluate the flexural behavior of functionally graded steel fiber-reinforced concrete containing recycled tire crumb rubber, as a volume replacement of sand, after exposure to elevated temperatures. Little information is available in the literature regarding this subject. To achieve this goal, a set of 54 one-, two-, and three-layer concrete beam specimens with different fiber volume fractions (0, 0.25, 0.5, 1, and 1.25%), but the same overall fiber content, and different volume percentages of the waste tire rubber (0, 5, and 10%) were exposed to different temperatures (23, 300, and 600oC). Afterward, the parameters affecting the post-heating flexural performance of concrete, including flexural strength and stiffness, toughness, fracture energy, and load-deflection diagrams, along with the compressive strength and weight loss of concrete specimens, were evaluated. The results indicated that the flexural strength and stiffness of the three-layer concrete beams respectively increased by 10 and 7%, compared to the one-layer beam specimens with the same fiber content. However, the flexural performance of the two-layer beams was reduced relative to those with one layer and equal fiber content. Besides, the flexural strength, toughness, fracture energy, and stiffness were reduced by approximately 10% when a 10% of natural sand was replaced with tire rubber in the threelayer specimens compared to the corresponding beams without crumb rubber. Although the flexural properties of concrete specimens increased with increasing the temperature up to 300oC, these properties degraded significantly with elevating the temperature up to 600oC, leading to a sharp increase in the deflection at peak load.
{"title":"Post-fire flexural behavior of functionally graded fiber-reinforced concrete containing rubber","authors":"M. Nematzadeh, R. Mousavi","doi":"10.12989/CAC.2021.27.5.417","DOIUrl":"https://doi.org/10.12989/CAC.2021.27.5.417","url":null,"abstract":"The optimal distribution of steel fibers over different layers of concrete can be considered as an appropriate method in improving the structural performance and reducing the cost of fiber-reinforced concrete members. In addition, the use of waste tire rubber in concrete mixes, as one of the practical ways to address environmental problems, is highly significant. Thus, this study aimed to evaluate the flexural behavior of functionally graded steel fiber-reinforced concrete containing recycled tire crumb rubber, as a volume replacement of sand, after exposure to elevated temperatures. Little information is available in the literature regarding this subject. To achieve this goal, a set of 54 one-, two-, and three-layer concrete beam specimens with different fiber volume fractions (0, 0.25, 0.5, 1, and 1.25%), but the same overall fiber content, and different volume percentages of the waste tire rubber (0, 5, and 10%) were exposed to different temperatures (23, 300, and 600oC). Afterward, the parameters affecting the post-heating flexural performance of concrete, including flexural strength and stiffness, toughness, fracture energy, and load-deflection diagrams, along with the compressive strength and weight loss of concrete specimens, were evaluated. The results indicated that the flexural strength and stiffness of the three-layer concrete beams respectively increased by 10 and 7%, compared to the one-layer beam specimens with the same fiber content. However, the flexural performance of the two-layer beams was reduced relative to those with one layer and equal fiber content. Besides, the flexural strength, toughness, fracture energy, and stiffness were reduced by approximately 10% when a 10% of natural sand was replaced with tire rubber in the threelayer specimens compared to the corresponding beams without crumb rubber. Although the flexural properties of concrete specimens increased with increasing the temperature up to 300oC, these properties degraded significantly with elevating the temperature up to 600oC, leading to a sharp increase in the deflection at peak load.","PeriodicalId":50625,"journal":{"name":"Computers and Concrete","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2021-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79548481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-01DOI: 10.12989/CAC.2021.27.5.437
M. Gurunandan, T. Raghavendra
Retrofitting of structures has gained importance over the recent years. Particularly, Reinforced Cement Concrete (RCC) column strengthening has become a challenge to the structural engineers, owing to the risks and complexities involved in it. There are several methods of RCC column strengthening viz. RCC jacketing, steel jacketing and Fiber Reinforced Polymer (FRP) wrapping etc., FRP wrapping is the most promising alternative when compared to the others. The large research database shows FRP wrapping, through lateral confinement, improves the axial load carrying capacity of the columns under concentric loading. However, its confining efficiency reduces under eccentric loading. Hence a relative newer technique called Near Surface Mounting (NSM), in which Carbon FRP (CFRP) strips are epoxy grouted to the precut grooves in the cover concrete of the columns, has been thrust domain of research. NSM technique strengthens the column nominally under concentric load case while significantly under eccentric case. A novel configuration of NSM in which the vertical NSM (VNSM) strips are being connected by horizontal NSM (HNSM) strips was numerically investigated under both concentric and eccentric loading. It was found that the configuration with 6 HNSM strips performed better under eccentric loading than under concentric loading, while the configuration with 3 HNSM strips performed better under concentric loading than under eccentric loading. Hence an optimum of 4 HNSM strips is recommended as strengthening measure for the given column specifications. It was also found that Aluminum alloy cannot be used instead of CFRP in NSM applications owing to its lower mechanical properties.
{"title":"Novel NSM configuration for RC column strengthening-A numerical study","authors":"M. Gurunandan, T. Raghavendra","doi":"10.12989/CAC.2021.27.5.437","DOIUrl":"https://doi.org/10.12989/CAC.2021.27.5.437","url":null,"abstract":"Retrofitting of structures has gained importance over the recent years. Particularly, Reinforced Cement Concrete (RCC) column strengthening has become a challenge to the structural engineers, owing to the risks and complexities involved in it. There are several methods of RCC column strengthening viz. RCC jacketing, steel jacketing and Fiber Reinforced Polymer (FRP) wrapping etc., FRP wrapping is the most promising alternative when compared to the others. The large research database shows FRP wrapping, through lateral confinement, improves the axial load carrying capacity of the columns under concentric loading. However, its confining efficiency reduces under eccentric loading. Hence a relative newer technique called Near Surface Mounting (NSM), in which Carbon FRP (CFRP) strips are epoxy grouted to the precut grooves in the cover concrete of the columns, has been thrust domain of research. NSM technique strengthens the column nominally under concentric load case while significantly under eccentric case. A novel configuration of NSM in which the vertical NSM (VNSM) strips are being connected by horizontal NSM (HNSM) strips was numerically investigated under both concentric and eccentric loading. It was found that the configuration with 6 HNSM strips performed better under eccentric loading than under concentric loading, while the configuration with 3 HNSM strips performed better under concentric loading than under eccentric loading. Hence an optimum of 4 HNSM strips is recommended as strengthening measure for the given column specifications. It was also found that Aluminum alloy cannot be used instead of CFRP in NSM applications owing to its lower mechanical properties.","PeriodicalId":50625,"journal":{"name":"Computers and Concrete","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2021-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79066541","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-05-01DOI: 10.12989/CAC.2021.27.5.395
P. Jongvivatsakul, Phattarakan Laopaitoon, Yen Thi Hai Nguyen, Phuoc T. Nguyen, L. Bui
This study experimentally and analytically investigates the shear behavior of corroded reinforced concrete (RC) beams repaired using steel fiber-reinforced concrete (SFRC) in the flexural zone. The experimental parameters are the corrosion degree (0%, 12%, and 17%) and the steel fiber volume in the SFRC (1.0%, 1.5%, and 2.0%). The test results reveal that corrosion degree significantly affects the shear resistance of the beams. The shear capacity of the beam with the corrosion degree of 17% was higher than that of the uncorroded beam, whereas the shear capacity of the beam with the corrosion degree of 12% was lower than that of the uncorroded beam. The shear efficiency of damaged beams can be recovered by repairing them using SFRC that contains a reasonable amount of steel fibers. In addition, two methods to estimate the shear capacity of the repaired beams are developed using the modified truss analogy and strut-and-tie models. The estimated shear capacity of the beam using the modified truss analogy model agrees well with the experimental data.
{"title":"Assessment of shear resistance of corroded beams repaired using SFRC in the tension zone","authors":"P. Jongvivatsakul, Phattarakan Laopaitoon, Yen Thi Hai Nguyen, Phuoc T. Nguyen, L. Bui","doi":"10.12989/CAC.2021.27.5.395","DOIUrl":"https://doi.org/10.12989/CAC.2021.27.5.395","url":null,"abstract":"This study experimentally and analytically investigates the shear behavior of corroded reinforced concrete (RC) beams repaired using steel fiber-reinforced concrete (SFRC) in the flexural zone. The experimental parameters are the corrosion degree (0%, 12%, and 17%) and the steel fiber volume in the SFRC (1.0%, 1.5%, and 2.0%). The test results reveal that corrosion degree significantly affects the shear resistance of the beams. The shear capacity of the beam with the corrosion degree of 17% was higher than that of the uncorroded beam, whereas the shear capacity of the beam with the corrosion degree of 12% was lower than that of the uncorroded beam. The shear efficiency of damaged beams can be recovered by repairing them using SFRC that contains a reasonable amount of steel fibers. In addition, two methods to estimate the shear capacity of the repaired beams are developed using the modified truss analogy and strut-and-tie models. The estimated shear capacity of the beam using the modified truss analogy model agrees well with the experimental data.","PeriodicalId":50625,"journal":{"name":"Computers and Concrete","volume":null,"pages":null},"PeriodicalIF":4.1,"publicationDate":"2021-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80514305","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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