The addition of 2,5-pyridinedicarboxylic acid(2,5-PDCA)to the Mg-Al LDH coating,which was prepared by one-step hydrothermal synthesis,had extremely enhanced the corrosion protection of AZ31 Mg alloy,although the 2,5-P...The addition of 2,5-pyridinedicarboxylic acid(2,5-PDCA)to the Mg-Al LDH coating,which was prepared by one-step hydrothermal synthesis,had extremely enhanced the corrosion protection of AZ31 Mg alloy,although the 2,5-PDCA could not be intercalated into the interlayer spacing.The corrosion current density of 0.05 mol L^(−1)2,5-PDCA LDH containing LDH coating is 3.18 nA cm^(−2),reduced by two orders of magnitude compared to the LDH coating without inhibitor,and the corrosion inhibition efficiency of the coating is 98.05%.The coating formed on the surface of AZ31 was peeled off from the substrate by using a mechanical method and SEM observation of the cross-section showed that the coating consisted of three different layers.The innermost layer is a thick layer that consists of Mg(OH)_(2)and the intermediate layer is LDH,which is vertical to the substrate and the outmost layer is a thin but very dense deposit layer of LDH agglomerates with complexes of 2,5-PDCA and Mg.This kind of sediment/LDH/Mg(OH)_(2)three-layer composite structure was accountable for the increase in the corrosion resistance of AZ31 Mg alloy.展开更多
Wuhan Tianxingzhou Changjiang (WTC) Bridge and Nanjing Dashengguan Changjiang (NDC) Bridge are two super high-speed railway 3-trusses composite bridges. This is the first time of using three trusses in such large brid...Wuhan Tianxingzhou Changjiang (WTC) Bridge and Nanjing Dashengguan Changjiang (NDC) Bridge are two super high-speed railway 3-trusses composite bridges. This is the first time of using three trusses in such large bridges in the world. These two types of railway floor systems of the two bridges have never been used in China before. The problem how to conform the deformations and stress levels of the railway floor system of WTC Bridge was studied. After finite element analysis and comparison,the plan of arranging one expansion stringer every two panels in railway floor system were proposed and good effect was obtained. Because of the application of three trusses,the allocation of the loads acted on the deck in three trusses is different and varies in different places of NDC Bridge. This problem was studied by model experiment and 3D finite element analysis. The results of 3D FEM analysis coincide with the model test results. The allocation rule of the loads acting on the deck in three trusses was presented. Because of the application of monolithic decks,the stiffness and structural integrity of NDC Bridge are high.展开更多
A full-scale composite floor plate was tested to investigate the flexural behavior and in-plane effects of the floor slab in a grillage of composite beams that reduces the tendency for longitudinal splitting of the co...A full-scale composite floor plate was tested to investigate the flexural behavior and in-plane effects of the floor slab in a grillage of composite beams that reduces the tendency for longitudinal splitting of the concrete slab along the line of the primary beams. This is important in cases where the steel decking is discontinuous when it is orientated parallel to the beams. In this case, it is important to demonstrate that the amount of transverse reinforcement required to transfer local forces from the shear connectors can be reduced relative to the requirements of Eurocode 4. The mechanism under study involved in-plane compression forces being developed in the slab due to the restraining action of the floor plate, which was held in position by the peripheral composite beams;while the secondary beams acted as transverse ties to resist the forces in the floor plate that would otherwise lead to splitting of the slab along the line of the primary beams. The tendency for cracking along the center line of the primary beam and at the peripheral beams was closely monitored. This is the first large floor plate test that has been carried out under laboratory conditions since the Cardington tests in the early 1990s, although those tests were not carried out to failure. This floor plate test was designed so that the longitudinal force transferred by the primary beams was relatively high (i.e., it was designed for full shear connection), but the transverse reinforcement was taken as the minimum of 0.2% of the concrete area. The test confirmed that the primary beams reached their plastic bending resistance despite the discontinuous decking and transverse reinforcement at the minimum percentage given in Eurocode 4. Based on this test, a reduction factor due to shear connectors at edge beams without U-bars is proposed.展开更多
A large-span steel–concrete composite beam with precast hollow core slabs(CBHCSs)is a relatively new floor structure that can be applied to various long-span structures.However,human-induced vibrations may present se...A large-span steel–concrete composite beam with precast hollow core slabs(CBHCSs)is a relatively new floor structure that can be applied to various long-span structures.However,human-induced vibrations may present serviceability issues in such structures.To alleviate vibrations,both the walking forces excited by humans and the associated floor responses must be elucidated.In this study,150 load–time histories of walking,excited by 25 test participants,are obtained using a force measuring plate.The dynamic loading factors and phase angles in the Fourier series functions for one-step walking are determined.Subsequently,walking tests are performed on seven CBHCS specimens to capture the essential dynamic properties of mode shapes,natural frequencies,damping ratios,and acceleration time histories.The CBHCS floor system generally exhibits a high frequency(>10 Hz)and low damping(damping ratio<2%).Sensitivity studies using the finite element method are conducted to investigate the vibration performance of the CBHCS floor system,where the floor thickness,steel beam type,contact time,and human weight are considered.Finally,analytical expressions derived for the fundamental frequency and peak acceleration agree well with the experimental results and are hence proposed for practical use.展开更多
This paper is concerned with a special steel-concrete composite beam in which the resisting system is a truss structure whose bottom chord is made of a steel plate supporting the precast floor system. This system work...This paper is concerned with a special steel-concrete composite beam in which the resisting system is a truss structure whose bottom chord is made of a steel plate supporting the precast floor system. This system works in two distinct phases with two different resisting mechanisms: during the construction phase, the truss structure bears the precast floor system and the resisting system is that of a simply supported steel truss;once the concrete has hardened, the truss structure becomes the reinforcing element of a steel-concrete composite beam, where it is also in a pre-stressed condition due to the loads carried before the hardening of concrete. Within this framework, the effects of the diagonal bars on the bending stiffness of this composite beam are investigated. First, a closed-form solution for the evaluation of the equivalent bending stiffness is derived. Subsequently, the influence of geometrical and mechanical characteristics of shear reinforcement is studied. Finally, results obtained from parametric and numerical analyses are discussed.展开更多
The present study explores the influence of electromagnetic effects on the flow of a nanofluid in a saturated permeable medium,confined between a clear viscous fluid in an inclined channel.The nanofluid consists of co...The present study explores the influence of electromagnetic effects on the flow of a nanofluid in a saturated permeable medium,confined between a clear viscous fluid in an inclined channel.The nanofluid consists of cobalt ferrite nanoparticles dispersed in ethylene glycol.The governing equations are derived considering Darcy's law for the permeable medium and Tiwari's model for fluids containing nano-sized particles.Additionally,radiation and dissipation effects are incorporated into the energy equation.The equations are transformed into dimensionless form and solved analytically using the perturbation technique.The results are analyzed through graphs and tables for different material parameters.The findings reveal that higher electric and magnetic strengths have a significant impact on the fluid velocity at the interface of the two fluids,resulting in reduced shear both at the clear fluid surface and the interface between them.This highlights the crucial role played by electric and magnetic strengths in modifying flow phenomena.Consequently,combining electric and magnetic strengths with nanofluids can be utilized to achieve desired qualities in multi-fluid flow and enhance heat transfer characteristics.展开更多
文摘The addition of 2,5-pyridinedicarboxylic acid(2,5-PDCA)to the Mg-Al LDH coating,which was prepared by one-step hydrothermal synthesis,had extremely enhanced the corrosion protection of AZ31 Mg alloy,although the 2,5-PDCA could not be intercalated into the interlayer spacing.The corrosion current density of 0.05 mol L^(−1)2,5-PDCA LDH containing LDH coating is 3.18 nA cm^(−2),reduced by two orders of magnitude compared to the LDH coating without inhibitor,and the corrosion inhibition efficiency of the coating is 98.05%.The coating formed on the surface of AZ31 was peeled off from the substrate by using a mechanical method and SEM observation of the cross-section showed that the coating consisted of three different layers.The innermost layer is a thick layer that consists of Mg(OH)_(2)and the intermediate layer is LDH,which is vertical to the substrate and the outmost layer is a thin but very dense deposit layer of LDH agglomerates with complexes of 2,5-PDCA and Mg.This kind of sediment/LDH/Mg(OH)_(2)three-layer composite structure was accountable for the increase in the corrosion resistance of AZ31 Mg alloy.
基金Projects(2004G028, 2004G016) supported by the Science and Technology Development Program of Railways Department, China
文摘Wuhan Tianxingzhou Changjiang (WTC) Bridge and Nanjing Dashengguan Changjiang (NDC) Bridge are two super high-speed railway 3-trusses composite bridges. This is the first time of using three trusses in such large bridges in the world. These two types of railway floor systems of the two bridges have never been used in China before. The problem how to conform the deformations and stress levels of the railway floor system of WTC Bridge was studied. After finite element analysis and comparison,the plan of arranging one expansion stringer every two panels in railway floor system were proposed and good effect was obtained. Because of the application of three trusses,the allocation of the loads acted on the deck in three trusses is different and varies in different places of NDC Bridge. This problem was studied by model experiment and 3D finite element analysis. The results of 3D FEM analysis coincide with the model test results. The allocation rule of the loads acting on the deck in three trusses was presented. Because of the application of monolithic decks,the stiffness and structural integrity of NDC Bridge are high.
基金part of a collaborative project between the Steel Construction Institute, the University of Stuttgart, the University of Luxembourg, Arcelor Mittal S.A., and the University of Bradford funded by the European Community’s Research Fund for Coal and Steel (RFSR-CT-2012-00030)
文摘A full-scale composite floor plate was tested to investigate the flexural behavior and in-plane effects of the floor slab in a grillage of composite beams that reduces the tendency for longitudinal splitting of the concrete slab along the line of the primary beams. This is important in cases where the steel decking is discontinuous when it is orientated parallel to the beams. In this case, it is important to demonstrate that the amount of transverse reinforcement required to transfer local forces from the shear connectors can be reduced relative to the requirements of Eurocode 4. The mechanism under study involved in-plane compression forces being developed in the slab due to the restraining action of the floor plate, which was held in position by the peripheral composite beams;while the secondary beams acted as transverse ties to resist the forces in the floor plate that would otherwise lead to splitting of the slab along the line of the primary beams. The tendency for cracking along the center line of the primary beam and at the peripheral beams was closely monitored. This is the first large floor plate test that has been carried out under laboratory conditions since the Cardington tests in the early 1990s, although those tests were not carried out to failure. This floor plate test was designed so that the longitudinal force transferred by the primary beams was relatively high (i.e., it was designed for full shear connection), but the transverse reinforcement was taken as the minimum of 0.2% of the concrete area. The test confirmed that the primary beams reached their plastic bending resistance despite the discontinuous decking and transverse reinforcement at the minimum percentage given in Eurocode 4. Based on this test, a reduction factor due to shear connectors at edge beams without U-bars is proposed.
基金The authors acknowledge the financial support provided by the National Natural Science Foundation of China(51890902 and 51708058).
文摘A large-span steel–concrete composite beam with precast hollow core slabs(CBHCSs)is a relatively new floor structure that can be applied to various long-span structures.However,human-induced vibrations may present serviceability issues in such structures.To alleviate vibrations,both the walking forces excited by humans and the associated floor responses must be elucidated.In this study,150 load–time histories of walking,excited by 25 test participants,are obtained using a force measuring plate.The dynamic loading factors and phase angles in the Fourier series functions for one-step walking are determined.Subsequently,walking tests are performed on seven CBHCS specimens to capture the essential dynamic properties of mode shapes,natural frequencies,damping ratios,and acceleration time histories.The CBHCS floor system generally exhibits a high frequency(>10 Hz)and low damping(damping ratio<2%).Sensitivity studies using the finite element method are conducted to investigate the vibration performance of the CBHCS floor system,where the floor thickness,steel beam type,contact time,and human weight are considered.Finally,analytical expressions derived for the fundamental frequency and peak acceleration agree well with the experimental results and are hence proposed for practical use.
文摘This paper is concerned with a special steel-concrete composite beam in which the resisting system is a truss structure whose bottom chord is made of a steel plate supporting the precast floor system. This system works in two distinct phases with two different resisting mechanisms: during the construction phase, the truss structure bears the precast floor system and the resisting system is that of a simply supported steel truss;once the concrete has hardened, the truss structure becomes the reinforcing element of a steel-concrete composite beam, where it is also in a pre-stressed condition due to the loads carried before the hardening of concrete. Within this framework, the effects of the diagonal bars on the bending stiffness of this composite beam are investigated. First, a closed-form solution for the evaluation of the equivalent bending stiffness is derived. Subsequently, the influence of geometrical and mechanical characteristics of shear reinforcement is studied. Finally, results obtained from parametric and numerical analyses are discussed.
基金This work was supported by the research seed grant Ref no:RU:EST:MT:2022/4 funded by REVA University and also this work was supported by the research fund of Hanyang University(HY-202300000000544).
文摘The present study explores the influence of electromagnetic effects on the flow of a nanofluid in a saturated permeable medium,confined between a clear viscous fluid in an inclined channel.The nanofluid consists of cobalt ferrite nanoparticles dispersed in ethylene glycol.The governing equations are derived considering Darcy's law for the permeable medium and Tiwari's model for fluids containing nano-sized particles.Additionally,radiation and dissipation effects are incorporated into the energy equation.The equations are transformed into dimensionless form and solved analytically using the perturbation technique.The results are analyzed through graphs and tables for different material parameters.The findings reveal that higher electric and magnetic strengths have a significant impact on the fluid velocity at the interface of the two fluids,resulting in reduced shear both at the clear fluid surface and the interface between them.This highlights the crucial role played by electric and magnetic strengths in modifying flow phenomena.Consequently,combining electric and magnetic strengths with nanofluids can be utilized to achieve desired qualities in multi-fluid flow and enhance heat transfer characteristics.
