Numerical analysis is carried out to study the sectional properties of the fiber-reinforced polymer（FRP）-confined reinforced concrete（RC）circular columns. The axial load ratio, the FRP confinement ratio and the lo...Numerical analysis is carried out to study the sectional properties of the fiber-reinforced polymer（FRP）-confined reinforced concrete（RC）circular columns. The axial load ratio, the FRP confinement ratio and the longitudinal reinforcement characteristic value are the three main parameters that can influence the neutral axis depth when concrete compression strain reaches an ultimate value. The formula for computing the central angle θ, corresponding to the compression zone, is established according to the data regression of the numerical analysis results. The numerical analysis results demonstrate that the concrete stress enhancement from transverse confinement and strain hardening of the longitudinal reinforcement can cause a much greater flexural strength than that defined by the design code. Based on the analytical studies and the test results of 36 large scale columns, the formula to calculate the flexural strength when columns fail under seismic loading is proposed, and the calculated results agree well with the test results. Finally, parametric studies are conducted on a typical column with different axial load ratios, longitudinal reinforcement characteristic value and FRP confinement ratios. Analysis of the results shows that the calculated flexural strength can be increased by 50% compared to that of unconfined columns defined by the code.展开更多
本文通过实验的方法,研究了氩气射频空心阴极放电(radio frequency hollow cathode discharge,RF-HCD)中发光条纹形成的影响因素。研究结果表明,在RF-HCD中,在一定的放电条件下,能清晰地观察到负辉区、法拉第暗区和正柱区。在RF-HCD中,...本文通过实验的方法,研究了氩气射频空心阴极放电(radio frequency hollow cathode discharge,RF-HCD)中发光条纹形成的影响因素。研究结果表明,在RF-HCD中,在一定的放电条件下,能清晰地观察到负辉区、法拉第暗区和正柱区。在RF-HCD中,功率、电极间距、气体流量和电极间有无介质管等均影响着发光条纹的形成。而背后更深层次的原因是电子密度、放电通道中是否存在正柱区、气压、以及介质管上的表面电荷等影响着RF-HCD中发光条纹的形成。如果放电时空心阴极孔外的电子密度达不到形成条纹的临界电子密度,则发光条纹无法形成;如果放电通道中不存在正柱区,即使密度足够大,条纹也无法在RF-HCD中形成;较高的流量和介质管上表面电荷的积累有利于条纹在RF-HCD中形成。展开更多
基金The National Basic Research Program of China (973 Program)(No.2007CB714200)the National Natural Science Foundationof China (No.50608015,50908102)
文摘Numerical analysis is carried out to study the sectional properties of the fiber-reinforced polymer（FRP）-confined reinforced concrete（RC）circular columns. The axial load ratio, the FRP confinement ratio and the longitudinal reinforcement characteristic value are the three main parameters that can influence the neutral axis depth when concrete compression strain reaches an ultimate value. The formula for computing the central angle θ, corresponding to the compression zone, is established according to the data regression of the numerical analysis results. The numerical analysis results demonstrate that the concrete stress enhancement from transverse confinement and strain hardening of the longitudinal reinforcement can cause a much greater flexural strength than that defined by the design code. Based on the analytical studies and the test results of 36 large scale columns, the formula to calculate the flexural strength when columns fail under seismic loading is proposed, and the calculated results agree well with the test results. Finally, parametric studies are conducted on a typical column with different axial load ratios, longitudinal reinforcement characteristic value and FRP confinement ratios. Analysis of the results shows that the calculated flexural strength can be increased by 50% compared to that of unconfined columns defined by the code.
文摘本文通过实验的方法,研究了氩气射频空心阴极放电(radio frequency hollow cathode discharge,RF-HCD)中发光条纹形成的影响因素。研究结果表明,在RF-HCD中,在一定的放电条件下,能清晰地观察到负辉区、法拉第暗区和正柱区。在RF-HCD中,功率、电极间距、气体流量和电极间有无介质管等均影响着发光条纹的形成。而背后更深层次的原因是电子密度、放电通道中是否存在正柱区、气压、以及介质管上的表面电荷等影响着RF-HCD中发光条纹的形成。如果放电时空心阴极孔外的电子密度达不到形成条纹的临界电子密度,则发光条纹无法形成;如果放电通道中不存在正柱区,即使密度足够大,条纹也无法在RF-HCD中形成;较高的流量和介质管上表面电荷的积累有利于条纹在RF-HCD中形成。
