钢纤维补强能够极大提升混凝土结构物的耐久性能,非常适用于长寿命,高耐久性,并且供用环境腐蚀条件苛刻,磨耗严重的都市深层排水隧道衬砌混凝土。依据有关钢纤维补强混凝土结构的国际混凝土结构联合会制订的模型代码:fib model code 20...钢纤维补强能够极大提升混凝土结构物的耐久性能,非常适用于长寿命,高耐久性,并且供用环境腐蚀条件苛刻,磨耗严重的都市深层排水隧道衬砌混凝土。依据有关钢纤维补强混凝土结构的国际混凝土结构联合会制订的模型代码:fib model code 2010,以及欧洲的相关技术规范,结合伦敦的深层排水隧道:Lee Tunnel的具体工程实例,对如何应用钢纤维补强技术在盾构隧道衬砌混凝土管片,以及现场浇筑二次衬砌自密实混凝土进行了探讨。同时通过钢纤维补强混凝土缺口梁试件的抗折强度试验,大型梁试件的弯曲加载试验,以及试验结果的非线性有限元逆向解析,确认了钢纤维取代钢筋的结构补强性能,控制裂缝效果,以及应变硬化性能,能够满足Lee tunnel工程项目的砌筑混凝土性能要求,适用于深层排水隧道:Lee tunnel衬砌混凝土补强。展开更多
The impact properties of normal concrete (NC) and reinforced concrete (RC) specimens,steel fibre reinforced concrete (SFRC) specimens and RC+SFRC specimens with different steel fibre dosages were investigated with the...The impact properties of normal concrete (NC) and reinforced concrete (RC) specimens,steel fibre reinforced concrete (SFRC) specimens and RC+SFRC specimens with different steel fibre dosages were investigated with the drop-weight impact test recommended by ACI Committee 544.The results indicate that the number of blows to final failure is greatly increased by addition of steel fibres.Moreover,the combination of steel fibres and steel rebars demonstrates a significant positive composite effect on the impact resistance,which results in the improvement in impact toughness of concrete specimens.In the view of variation of impact test results,the two-parameter Weibull distribution was adopted to analyze the experimental data.It is proved that the probabilistic distributions of the blows to first crack and to final failure of six types of samples approximately follow two-parameter Weibull distribution.展开更多
A hydrogen permeation barrier was manufactured by the in situ reaction of zirconium hydride with oxygen. A reduction in the hydrogen permeation of the oxide films was detected by measuring the mass difference of the z...A hydrogen permeation barrier was manufactured by the in situ reaction of zirconium hydride with oxygen. A reduction in the hydrogen permeation of the oxide films was detected by measuring the mass difference of the zirconium hydride samples after the dehydrogenation experiment. The reaction of zirconium hydride with oxygen occurs only under the condition that the temperature is higher than 673 K in the oxygen partial pressure of 0.1 MPa. The oxide film is composed of two layers, a permeable oxide layer and a dense oxide layer, and the main phase of the oxide film is ZrO2 with baddeleyite structure. The XPS analysis shows that O-H bonds exist in the oxide film, which are helpful for resisting hydrogen diffusion through the oxide film.展开更多
The tensile and shear strength of intrinsic bolting support systems has always been a major concern of designers. A comprehensive laboratory testing program was designed to evaluate the tensile and shear strength of i...The tensile and shear strength of intrinsic bolting support systems has always been a major concern of designers. A comprehensive laboratory testing program was designed to evaluate the tensile and shear strength of individual wires and completely wound PC-strand cables. PC-strand cables with smooth wires and the recent anchorage enhancement innovation of indentation were evaluated and compared. The testing protocol detailed in ISO Standard 15630 utilizes a mandrel system that was investigated at 3different diameters which alters the wire to mandrel ratio from 2:1 to 9:1. The results demonstrate that the difference between smooth and indented wires is statistically insignificant when larger diameter mandrels are used,and that indentation does not adversely affect strand properties and performance.Insight into the shearing mechanism and evaluation techniques are discussed with the introduction of triaxial loading to describe the PC-strand tensile and shearing mechanisms. Another important result indicates that the shear strength of PC-strand cable bolting systems has a greater shear strength value than traditional steel bar bolting systems.展开更多
基金Project(50578026) supported by the National Natural Science Foundation of ChinaProject supported by FCT (SFRH/BPD/22680/2005)and Research Center of Mathematics of the University of Minho through the FCT Pluriannual Funding Program
文摘The impact properties of normal concrete (NC) and reinforced concrete (RC) specimens,steel fibre reinforced concrete (SFRC) specimens and RC+SFRC specimens with different steel fibre dosages were investigated with the drop-weight impact test recommended by ACI Committee 544.The results indicate that the number of blows to final failure is greatly increased by addition of steel fibres.Moreover,the combination of steel fibres and steel rebars demonstrates a significant positive composite effect on the impact resistance,which results in the improvement in impact toughness of concrete specimens.In the view of variation of impact test results,the two-parameter Weibull distribution was adopted to analyze the experimental data.It is proved that the probabilistic distributions of the blows to first crack and to final failure of six types of samples approximately follow two-parameter Weibull distribution.
基金the National Natural Science Foundation of China (No. 50674015)
文摘A hydrogen permeation barrier was manufactured by the in situ reaction of zirconium hydride with oxygen. A reduction in the hydrogen permeation of the oxide films was detected by measuring the mass difference of the zirconium hydride samples after the dehydrogenation experiment. The reaction of zirconium hydride with oxygen occurs only under the condition that the temperature is higher than 673 K in the oxygen partial pressure of 0.1 MPa. The oxide film is composed of two layers, a permeable oxide layer and a dense oxide layer, and the main phase of the oxide film is ZrO2 with baddeleyite structure. The XPS analysis shows that O-H bonds exist in the oxide film, which are helpful for resisting hydrogen diffusion through the oxide film.
文摘The tensile and shear strength of intrinsic bolting support systems has always been a major concern of designers. A comprehensive laboratory testing program was designed to evaluate the tensile and shear strength of individual wires and completely wound PC-strand cables. PC-strand cables with smooth wires and the recent anchorage enhancement innovation of indentation were evaluated and compared. The testing protocol detailed in ISO Standard 15630 utilizes a mandrel system that was investigated at 3different diameters which alters the wire to mandrel ratio from 2:1 to 9:1. The results demonstrate that the difference between smooth and indented wires is statistically insignificant when larger diameter mandrels are used,and that indentation does not adversely affect strand properties and performance.Insight into the shearing mechanism and evaluation techniques are discussed with the introduction of triaxial loading to describe the PC-strand tensile and shearing mechanisms. Another important result indicates that the shear strength of PC-strand cable bolting systems has a greater shear strength value than traditional steel bar bolting systems.
