-Based on the experimental data, a stress variation model of the bond stress-slip relationship between steel bar and concrete is established. The characteristic of the model is that the boundary conditions are satisfi...-Based on the experimental data, a stress variation model of the bond stress-slip relationship between steel bar and concrete is established. The characteristic of the model is that the boundary conditions are satisfied very well; the effects of the material properties, the concrete cover, the crack spacing and the distance from the cracked cross section are considered. Good agreement between measured and calculated bond stress-slip relationship is found. This model is useful for the study of the stiffness, deformation and crack width of reinforced concrete members, and for the nonlinear analysis of reinforced concrete structures by the finite element method.展开更多
This study investigates the bond between seawater scoria aggregate concrete(SSAC)and stainless reinforcement(SR)through a series of pull-out tests.A total of 39 specimens,considering five experimental parameters—con-...This study investigates the bond between seawater scoria aggregate concrete(SSAC)and stainless reinforcement(SR)through a series of pull-out tests.A total of 39 specimens,considering five experimental parameters—con-crete type(SSAC,ordinary concrete(OC)and seawater coral aggregate concrete(SCAC)),reinforcement type(SR,ordinary reinforcement(OR)),bond length(3,5 and 8 times bar diameter),concrete strength(C25 and C30)and concrete cover thickness(42 and 67 mm)—were prepared.The typical bond properties(failure pattern,bond strength,bond-slip curves and bond stress distribution,etc.)of seawater scoria aggregate concrete-stainless rein-forcement(SSAC-SR)specimen were systematically studied.Generally,the failure pattern changed with the con-crete type used,and the failure surface of SSAC specimen was different from that of OC specimen.SSAC enhanced the bond strength of specimen,while its effect on the deformation of SSAC-SR was negative.On aver-age,the peak slip of SSAC specimens was 20%lower while the bond strength was 6.7%higher compared to OC specimens under the similar conditions.The effects of variables on the bond strength of SSAC–SR in increasing order are concrete type,bond length,concrete strength and cover thickness.The bond-slip curve of SSAC-SR specimen consisted of micro-slipping,slipping and declining stages.It can be obtained that SSAC reduced the curve curvature of bond-slip,and the decline of curve became steep after adopting SR.The typical distribution of bond stress along bond length changed with the types of concrete and reinforcement used.Finally,a specific expression of the bond stress-slip curve considering the effects of various variables was established,which could provide a basis for the practical application of reinforced SSAC.展开更多
The electronic product has gravitated towards component miniaturization and integration, employment of lead-free materials, and low-temperature soldering processes. Noble-metal aerogels have drawn increasing attention...The electronic product has gravitated towards component miniaturization and integration, employment of lead-free materials, and low-temperature soldering processes. Noble-metal aerogels have drawn increasing attention for high conduction and low density. However,the noble metal aerogels with outstanding solderability were rarely studied. This work has successfully synthesized an aerogel derived from silver nanowires(AgNWs) using a liquid phase reduction method. It is found that the noble metal aerogels can be made into diverse aerogel preformed soldering sheets. The influence of bonding temperature(150-300 ℃), time(2-20 min), and pressure(5-20 MPa) on the joint strength of the AgNWs aerogel affixed to electroless nickel/silver copper plates were investigated. Additionally, the AgNWs aerogel displays almost the same shear strength for substrates of various sizes. In a word, this study presents a flux-free, high-strength, and adaptable soldering structural material.展开更多
The shear bond of interface between concrete and basalt fiber reinforced polymer(BFRP)bars during freeze–thaw(F–T)cycles is crucial for the application of BFRP bar-reinforced concrete structures in cold regions.In t...The shear bond of interface between concrete and basalt fiber reinforced polymer(BFRP)bars during freeze–thaw(F–T)cycles is crucial for the application of BFRP bar-reinforced concrete structures in cold regions.In this study,48 groups of pull-out specimens were designed to test the shear bond of the BFRP-concrete interface subjected to F–T cycles.The effects of concrete strength,diameter,and embedment length of BFRP rebar were investigated under numerous F–T cycles.Test results showed that a larger diameter or longer embedment length of BFRP rebar resulted in lower interfacial shear bond behavior,such as interfacial bond strength,initial stiffness,and energy absorption,after the interface goes through F–T cycles.However,higher concrete strength and fewer F–T cycles were beneficial for enhancing the interfacial bond behavior.Subsequently,a three-dimensional(3D)interfacial model based on the finite element method was developed,and the interfacial bond behavior of the specimens was analyzed in-depth.Finally,a degradation bond strength subjected to F–T cycles was predicted by a proposed mechanical model.The predictions were fully consistent with the tested results.The model demonstrated accuracy in describing the shear bond behavior of the interface under numerous F–T cycles.展开更多
文摘-Based on the experimental data, a stress variation model of the bond stress-slip relationship between steel bar and concrete is established. The characteristic of the model is that the boundary conditions are satisfied very well; the effects of the material properties, the concrete cover, the crack spacing and the distance from the cracked cross section are considered. Good agreement between measured and calculated bond stress-slip relationship is found. This model is useful for the study of the stiffness, deformation and crack width of reinforced concrete members, and for the nonlinear analysis of reinforced concrete structures by the finite element method.
基金funded by the National Natural Science Foundation of China(Nos.51408346,51978389)the Systematic Project of Guangxi Key Laboratory of Disaster Prevention and Structural Safety(2019ZDK035)the Opening Foundation of Shandong Key Laboratory of Civil Engineering Disaster Prevention and Mitigation(No.CDPM2019KF12).
文摘This study investigates the bond between seawater scoria aggregate concrete(SSAC)and stainless reinforcement(SR)through a series of pull-out tests.A total of 39 specimens,considering five experimental parameters—con-crete type(SSAC,ordinary concrete(OC)and seawater coral aggregate concrete(SCAC)),reinforcement type(SR,ordinary reinforcement(OR)),bond length(3,5 and 8 times bar diameter),concrete strength(C25 and C30)and concrete cover thickness(42 and 67 mm)—were prepared.The typical bond properties(failure pattern,bond strength,bond-slip curves and bond stress distribution,etc.)of seawater scoria aggregate concrete-stainless rein-forcement(SSAC-SR)specimen were systematically studied.Generally,the failure pattern changed with the con-crete type used,and the failure surface of SSAC specimen was different from that of OC specimen.SSAC enhanced the bond strength of specimen,while its effect on the deformation of SSAC-SR was negative.On aver-age,the peak slip of SSAC specimens was 20%lower while the bond strength was 6.7%higher compared to OC specimens under the similar conditions.The effects of variables on the bond strength of SSAC–SR in increasing order are concrete type,bond length,concrete strength and cover thickness.The bond-slip curve of SSAC-SR specimen consisted of micro-slipping,slipping and declining stages.It can be obtained that SSAC reduced the curve curvature of bond-slip,and the decline of curve became steep after adopting SR.The typical distribution of bond stress along bond length changed with the types of concrete and reinforcement used.Finally,a specific expression of the bond stress-slip curve considering the effects of various variables was established,which could provide a basis for the practical application of reinforced SSAC.
基金the National Natural Science Foundation of China(Grant No.52075125,No.52105331)the Shenzhen Science and Technology Innovation Committee(Grant No.JCYJ20210324124203009,No.JSGG20201102154600003,No.GXWD20220818163456002)+1 种基金Special Fund for Science and Technology Innovation Strategy of Guangdong Province(Grant No.pdjh2022b0570)Sustainedly Supported Fundation by National Key Laboratory of Science and Technology on Space Microwave under Grant HTKJ2022KL504011,and NIO University Programme(NIO UP).
文摘The electronic product has gravitated towards component miniaturization and integration, employment of lead-free materials, and low-temperature soldering processes. Noble-metal aerogels have drawn increasing attention for high conduction and low density. However,the noble metal aerogels with outstanding solderability were rarely studied. This work has successfully synthesized an aerogel derived from silver nanowires(AgNWs) using a liquid phase reduction method. It is found that the noble metal aerogels can be made into diverse aerogel preformed soldering sheets. The influence of bonding temperature(150-300 ℃), time(2-20 min), and pressure(5-20 MPa) on the joint strength of the AgNWs aerogel affixed to electroless nickel/silver copper plates were investigated. Additionally, the AgNWs aerogel displays almost the same shear strength for substrates of various sizes. In a word, this study presents a flux-free, high-strength, and adaptable soldering structural material.
基金The authors acknowledge the financial support from the Key Laboratory of Performance Evolution and Control for Engineering Structures of the Ministry of Education of China(No.2019KF-4)the National Key Research Program of China(No.2021YFC1909901).
文摘The shear bond of interface between concrete and basalt fiber reinforced polymer(BFRP)bars during freeze–thaw(F–T)cycles is crucial for the application of BFRP bar-reinforced concrete structures in cold regions.In this study,48 groups of pull-out specimens were designed to test the shear bond of the BFRP-concrete interface subjected to F–T cycles.The effects of concrete strength,diameter,and embedment length of BFRP rebar were investigated under numerous F–T cycles.Test results showed that a larger diameter or longer embedment length of BFRP rebar resulted in lower interfacial shear bond behavior,such as interfacial bond strength,initial stiffness,and energy absorption,after the interface goes through F–T cycles.However,higher concrete strength and fewer F–T cycles were beneficial for enhancing the interfacial bond behavior.Subsequently,a three-dimensional(3D)interfacial model based on the finite element method was developed,and the interfacial bond behavior of the specimens was analyzed in-depth.Finally,a degradation bond strength subjected to F–T cycles was predicted by a proposed mechanical model.The predictions were fully consistent with the tested results.The model demonstrated accuracy in describing the shear bond behavior of the interface under numerous F–T cycles.
