Corrosion of reinforcement has a significant effect on the deformation of reinforced concrete beams by deteriorating the bond-slip characteristics, diminishing the cross-sectional area of reinforcement, and causing cr...Corrosion of reinforcement has a significant effect on the deformation of reinforced concrete beams by deteriorating the bond-slip characteristics, diminishing the cross-sectional area of reinforcement, and causing cracking. The traditional way of quantifying the load capacity and simulating deflection is the moment-curvature(M/χ) approach. The problem is that the M/χ approach is semi-empirical after cracking as it is strain-based and cannot allow for tension stiffening. This paper introduces the new displacement-based moment-rotation(M/θ) approach which directly simulates the development of cracks and hence allows for tension stiffening. This M/θ approach is then used to predict the load-deflection behavior of reinforced concrete beams with corrosion effect by incorporating the corrosion-affected bond-slip model. The bond-slip model only considers the corrosion effect but ignores the confinement effect. It is used here as an example to describe the procedure of how to quantify the corrosion effect on reinforced concrete beam behavior. The load-deflection curves obtained from the numerical simulation show a good agreement with test results. For reinforced concrete beams with confinement, the only difference is to replace the bond-slip model with the one which includes both corrosion and stirrup effects. Additionally, the paper shows how to use the M/θ approach with the bond-slip model to predict the real corrosion level of reinforcement in some tests in which only the theoretical corrosion levels are provided.展开更多
The study aims to incorporate cellulosic canola(Brassica napus L.)biopolymers with wood biomass to increase flexural strength more than wood fraction alone.A facile fabrication process-at ambient temperature-is employ...The study aims to incorporate cellulosic canola(Brassica napus L.)biopolymers with wood biomass to increase flexural strength more than wood fraction alone.A facile fabrication process-at ambient temperature-is employed for ease of producing two different sets of bio-composites utilizing unsaturated polyester resin:pristine composite structures of 100%wood and hybrid composite structures of a canola-wood blend.The curing process is accompanied by methyl ethyl ketone peroxide(MEKP).Besides the lightweight feature,the hybrid composite structures exhibit maximum flexural strength up to 59.6 and 89.58 MPa at 2.5 and 5%fibre polymer fraction,outperforming the pristine wood composites(49.25 MPa).Also,the bending behaviours of the composite structures are illustrated by the load-deflection curves and the associated SEM micrographs display their fractured and debonded surface at the cross-section.The novel canola fibre benefits from its inherent hollow architecture,facilitating an excellent strength to weight ratio for the thermoset composites.Interestingly,canola displays a fibre diameter and density of 79.80(±41.31)μm and 1.34(±0.0014)g/cc,contributing effectively towards the flexure performance and high packing density.The breaking tenacity(13.31±4.59 g-force/tex)and tensile strength(174.93±60.29)of canola fibres are comparable to other bast fibres.The synergy among fibre diameters,density and break-ing tenacity creates a good interphase to successfully transfer the external compressive load from the resin matrix to the fibres.Further,the two-parameter Weibull distribution model is applied for predicting the failure and reliability probability of composite specimens against a wide range of compressive loads.Finally,prioritized SWOT factors have been summa-rized associated with the prospects and key challenges of canola biopolymers-an attempt to strategize the planning and decision-making process for a potential business environment.The introduction of canola into the plastic industries would ultimately promote the application of sustainable biopolymers in diverse grounds including the interior panels for aerospace,automotive,and furniture industries.展开更多
Layered steel fiber reinforced rubber concrete （LSFRRC）, a new type of pavement concrete based on the requirements of national standard were experimentally researched. The different properties of flexural-tensile st...Layered steel fiber reinforced rubber concrete （LSFRRC）, a new type of pavement concrete based on the requirements of national standard were experimentally researched. The different properties of flexural-tensile strength from plain concrete （PC）, rubber concrete （RC）, layered steel fiber reinforced concrete （LSFRC） and LSFRRC were presented. Experimental results show that the tensile strength of LSFRRC is improved by 4.12% compared with PC, by 13.75% compared with RC. The load-deflection curve on flexural-tensile propertiesis put forward. The flexural-tensile toughness index I10 of LSFRRC is improved 10.32 times compared with PC.展开更多
Traditional methods focus on the ultimate bending moment of glulam beams and the fracture failure of materials with defects,which usually depends on empirical parameters.There is no systematic theoretical method to pr...Traditional methods focus on the ultimate bending moment of glulam beams and the fracture failure of materials with defects,which usually depends on empirical parameters.There is no systematic theoretical method to predict the stiffness and shear distribution of glulam beams in elastic-plastic stage,and consequently,the failure of such glulam beams cannot be predicted effectively.To address these issues,an analytical method considering material nonlinearity was proposed for glulam beams,and the calculating equations of deflection and shear stress distribution for different failure modes were established.The proposed method was verified by experiments and numerical models under the corresponding conditions.Results showed that the theoretical calculations were in good agreement with experimental and numerical results,indicating that the equations proposed in this paper were reliable and accurate for such glulam beams with wood material in the elastic-plastic stage ignoring the influence of mechanic properties in radial and tangential directions of wood.Furthermore,the experimental results reported by the previous studies indicated that the method was applicable and could be used as a theoretical reference for predicting the failure of glulam beams.展开更多
Nonlinear solution of reinforced concrete structures, particularly complete load-deflection response, requires tracing of the equilibrium path and proper treatment of the limit and bifurcation points. In this regard, ...Nonlinear solution of reinforced concrete structures, particularly complete load-deflection response, requires tracing of the equilibrium path and proper treatment of the limit and bifurcation points. In this regard, ordinary solution techniques lead to instability near the limit points and also have problems in case of snap-through and snap-back. Thus they fail to predict the complete load-displacement response. The arc-length method serves the purpose well in principle, received wide acceptance in finite element analysis, and has been used extensively. However modifications to the basic idea are vital to meet the particular needs of the analysis. This paper reviews some of the recent developments of the method in the last two decades, with particular emphasis on nonlinear finite element analysis of reinforced concrete structures.展开更多
Aluminum alloys are typical nonlinear materials, and consequently bending members made of this material exhibit a nonlinear behavior. Most design codes do not pay much attention to such deformations and adopt a simple...Aluminum alloys are typical nonlinear materials, and consequently bending members made of this material exhibit a nonlinear behavior. Most design codes do not pay much attention to such deformations and adopt a simple linear analysis for the calculation of deflections. This paper presents an investigation of the nonlinear deformation of aluminum bending members using the finite-element analysis （FEA）. The plastic adaptation coefficient, which can be used to limit the residual deflection, is introduced, and the influence of residual deflection is investigated. A method for evaluating the plastic adoption coefficient is proposed. This paper also shows the load-deflection curve of aluminum bending members and the influence of several parameters. A semi-empirical formula is derived, and some numerical examples are given by FEA. The coefficients of the semi-empirical formula are modified by the FEA results using the nonlinear fitting method. Based on these results, two improved design methods for strength and deformation of aluminum bending members are proposed. Through the comparison with test data, these methods are proved to be suitable for structural design.展开更多
基金Project supported by the National Natural Science Foundation of China(No.51478422)。
文摘Corrosion of reinforcement has a significant effect on the deformation of reinforced concrete beams by deteriorating the bond-slip characteristics, diminishing the cross-sectional area of reinforcement, and causing cracking. The traditional way of quantifying the load capacity and simulating deflection is the moment-curvature(M/χ) approach. The problem is that the M/χ approach is semi-empirical after cracking as it is strain-based and cannot allow for tension stiffening. This paper introduces the new displacement-based moment-rotation(M/θ) approach which directly simulates the development of cracks and hence allows for tension stiffening. This M/θ approach is then used to predict the load-deflection behavior of reinforced concrete beams with corrosion effect by incorporating the corrosion-affected bond-slip model. The bond-slip model only considers the corrosion effect but ignores the confinement effect. It is used here as an example to describe the procedure of how to quantify the corrosion effect on reinforced concrete beam behavior. The load-deflection curves obtained from the numerical simulation show a good agreement with test results. For reinforced concrete beams with confinement, the only difference is to replace the bond-slip model with the one which includes both corrosion and stirrup effects. Additionally, the paper shows how to use the M/θ approach with the bond-slip model to predict the real corrosion level of reinforcement in some tests in which only the theoretical corrosion levels are provided.
基金supported by MITACS Canada,Composites Innovation Centre(CIC Engineering,Canada)the University of Manitoba Graduate Fellowship.
文摘The study aims to incorporate cellulosic canola(Brassica napus L.)biopolymers with wood biomass to increase flexural strength more than wood fraction alone.A facile fabrication process-at ambient temperature-is employed for ease of producing two different sets of bio-composites utilizing unsaturated polyester resin:pristine composite structures of 100%wood and hybrid composite structures of a canola-wood blend.The curing process is accompanied by methyl ethyl ketone peroxide(MEKP).Besides the lightweight feature,the hybrid composite structures exhibit maximum flexural strength up to 59.6 and 89.58 MPa at 2.5 and 5%fibre polymer fraction,outperforming the pristine wood composites(49.25 MPa).Also,the bending behaviours of the composite structures are illustrated by the load-deflection curves and the associated SEM micrographs display their fractured and debonded surface at the cross-section.The novel canola fibre benefits from its inherent hollow architecture,facilitating an excellent strength to weight ratio for the thermoset composites.Interestingly,canola displays a fibre diameter and density of 79.80(±41.31)μm and 1.34(±0.0014)g/cc,contributing effectively towards the flexure performance and high packing density.The breaking tenacity(13.31±4.59 g-force/tex)and tensile strength(174.93±60.29)of canola fibres are comparable to other bast fibres.The synergy among fibre diameters,density and break-ing tenacity creates a good interphase to successfully transfer the external compressive load from the resin matrix to the fibres.Further,the two-parameter Weibull distribution model is applied for predicting the failure and reliability probability of composite specimens against a wide range of compressive loads.Finally,prioritized SWOT factors have been summa-rized associated with the prospects and key challenges of canola biopolymers-an attempt to strategize the planning and decision-making process for a potential business environment.The introduction of canola into the plastic industries would ultimately promote the application of sustainable biopolymers in diverse grounds including the interior panels for aerospace,automotive,and furniture industries.
文摘Layered steel fiber reinforced rubber concrete （LSFRRC）, a new type of pavement concrete based on the requirements of national standard were experimentally researched. The different properties of flexural-tensile strength from plain concrete （PC）, rubber concrete （RC）, layered steel fiber reinforced concrete （LSFRC） and LSFRRC were presented. Experimental results show that the tensile strength of LSFRRC is improved by 4.12% compared with PC, by 13.75% compared with RC. The load-deflection curve on flexural-tensile propertiesis put forward. The flexural-tensile toughness index I10 of LSFRRC is improved 10.32 times compared with PC.
基金support from High-Level Natural ScienceFoundation of Hainan Province of China (Grant No. 2019RC055)National Natural Science Foundation ofChina (Grant No. 51808176) and the Project Funded by the National First-Class Disciplines (PNFD).
文摘Traditional methods focus on the ultimate bending moment of glulam beams and the fracture failure of materials with defects,which usually depends on empirical parameters.There is no systematic theoretical method to predict the stiffness and shear distribution of glulam beams in elastic-plastic stage,and consequently,the failure of such glulam beams cannot be predicted effectively.To address these issues,an analytical method considering material nonlinearity was proposed for glulam beams,and the calculating equations of deflection and shear stress distribution for different failure modes were established.The proposed method was verified by experiments and numerical models under the corresponding conditions.Results showed that the theoretical calculations were in good agreement with experimental and numerical results,indicating that the equations proposed in this paper were reliable and accurate for such glulam beams with wood material in the elastic-plastic stage ignoring the influence of mechanic properties in radial and tangential directions of wood.Furthermore,the experimental results reported by the previous studies indicated that the method was applicable and could be used as a theoretical reference for predicting the failure of glulam beams.
文摘Nonlinear solution of reinforced concrete structures, particularly complete load-deflection response, requires tracing of the equilibrium path and proper treatment of the limit and bifurcation points. In this regard, ordinary solution techniques lead to instability near the limit points and also have problems in case of snap-through and snap-back. Thus they fail to predict the complete load-displacement response. The arc-length method serves the purpose well in principle, received wide acceptance in finite element analysis, and has been used extensively. However modifications to the basic idea are vital to meet the particular needs of the analysis. This paper reviews some of the recent developments of the method in the last two decades, with particular emphasis on nonlinear finite element analysis of reinforced concrete structures.
文摘Aluminum alloys are typical nonlinear materials, and consequently bending members made of this material exhibit a nonlinear behavior. Most design codes do not pay much attention to such deformations and adopt a simple linear analysis for the calculation of deflections. This paper presents an investigation of the nonlinear deformation of aluminum bending members using the finite-element analysis （FEA）. The plastic adaptation coefficient, which can be used to limit the residual deflection, is introduced, and the influence of residual deflection is investigated. A method for evaluating the plastic adoption coefficient is proposed. This paper also shows the load-deflection curve of aluminum bending members and the influence of several parameters. A semi-empirical formula is derived, and some numerical examples are given by FEA. The coefficients of the semi-empirical formula are modified by the FEA results using the nonlinear fitting method. Based on these results, two improved design methods for strength and deformation of aluminum bending members are proposed. Through the comparison with test data, these methods are proved to be suitable for structural design.
