Based on the finite element method, a numerical investigation into the bonded repair efficiency of cracked plates under in plane biaxial loadings is presented. The main considerations are: reduction in stress intensi...Based on the finite element method, a numerical investigation into the bonded repair efficiency of cracked plates under in plane biaxial loadings is presented. The main considerations are: reduction in stress intensity factor (SIF) at the crack tip, the maximum tensile stress in the composite patch and the maximum shear stress in the adhesive bond between the patch and the plate. Without the patch, a tensile or compressive stress parallel to the crack has no effect on the SIF at the crack tip. While with a composite patch, there exists coupling effect between the normal stress parallel to the crack and the SIF, and the coupling effect depends significantly on ply orientation of the patch and the biaxial stress ratio of the plate.展开更多
Biaxial compression tests are performed on 100 mm × 100 mm × 100 mm cubic specimens of plain high-strength highperformance concrete (HSHPC) at seven kinds of stress ratios, σ2:σ3 =0 : - 1, -0.20 : - 1...Biaxial compression tests are performed on 100 mm × 100 mm × 100 mm cubic specimens of plain high-strength highperformance concrete (HSHPC) at seven kinds of stress ratios, σ2:σ3 =0 : - 1, -0.20 : - 1, -0.30 : - 1, -0.40 : - 1, -0.50 : -1, -0. 75 : - 1, and - 1.00 : - 1 after exposure to normal and high temperatures of 20, 200, 300, 400, 500 and 600 ℃, using a large static-dynamic true triaxial machine. Frictionreducing pads are three layers of plastic membranes with glycerine in-between for the compressive loading plane. Failure modes of the specimens are described. The two principally static compressive strengths are measured. The influences of the temperatures and stress ratios on the biaxial strengths of HSHPC after exposure to high temperatures are also analyzed. The experimental results show that the uniaxial compressive strength of plain HSHPC after exposure to high temperatures does not decrease completely with the increase in temperature; the ratios of the biaxial to its uniaxial compressive strengths depend on the stress ratios and brittleness-stiffness of HSHPC after exposure to different high temperatures. The formula of the Kupfer-Gerstle failure criterion modified with the temperature and stress ratio parameters for plain HSHPC is proposed.展开更多
Thirteen specimens were tested out of which nine were for creep of sealed concrete and four for shrinkage test,for a period of 700 d under controlled temperature condition.The experimental results for creep and shrink...Thirteen specimens were tested out of which nine were for creep of sealed concrete and four for shrinkage test,for a period of 700 d under controlled temperature condition.The experimental results for creep and shrinkage were compared with creep and shrinkage computation model B3 and distinct discrepancies between observed and calculated creep and shrinkage strains were observed.Based on regression analysis,modification on B3 model has been formulated which will be applicable at least for concrete of characteristics strength of C40 and C50 with additives.Besides,on the basis of observation on identical specimens with varied stress strength ratio,a function is generated which accounts effect of stress strength ratio on creep.Finally,Civil Engineering community is suggested not to follow the creep prediction models without correction at least for modern concrete,as they do not account the effect of additives on its compliance function.展开更多
This paper reports investigation conducted to study the fatigue performance of steel fibre reinforced concrete (SFRC) containing fibres of mixed aspect ratio. An extensive experimental program was conducted in which 9...This paper reports investigation conducted to study the fatigue performance of steel fibre reinforced concrete (SFRC) containing fibres of mixed aspect ratio. An extensive experimental program was conducted in which 90 flexural fatigue tests were carried out at different stress levels on size 500 mm×100 mm×100 mm SFRC specimens respectively containing 1.0%, 1.5% and 2.0% volume fraction of fibres. About 36 static flexural tests were also conducted to determine the static flexural strength prior to fatigue testing. Each volume fraction of fibres incorporated corrugated mixed steel fibres of size 0.6 mm×2.0 mm×25 mm and 0.6 mm×2.0 mm×50 mm in ratio 50:50 by weight. The results are presented both as S-N relationships, with the maximum fatigue stress expressed as a percentage of the strength under static loading, and as relationships between actually applied fatigue stress and number of loading cycles to failure. Two-million-cycle fatigue strengths of SFRC containing different volume fractions of mixed fibres were obtained and compared with plain concrete.展开更多
The aim of this research is to determine the effect of bridging liquid surface tension and specific surface area on strength factor of coal agglomerates. The production of coal agglomerates of the range 15-27.51 mm wa...The aim of this research is to determine the effect of bridging liquid surface tension and specific surface area on strength factor of coal agglomerates. The production of coal agglomerates of the range 15-27.51 mm was achieved. The crushing strength of the agglomerates was determined for good handling of fine (coal-liquid mixture) to improve fugitive dust control, decrease in transportation losses, reduce risk of coal freezing, lower risk of spontaneous combustion, etc. in iron and steel industries, railway corporations and coal corporations. Kerosene (paraffin oil) was used as a binder and the agglomerated coal oil mixture was pelletized using balling technique (disc). Mechanical and physical tests like compressive strength test, etc. were carried out. The relationship between the bridging liquid surface tension and specific surface area on strength factor of coal agglomerates showed that there is considerable variation in these parameters in the coal powder systems.展开更多
Objective: The aim of our study was to demonstrate the CT features of solid pseudopapillary tumor of the pancreas (SPTP) so as to improve the imaging diagnostic abilities. Methods: The CT materials of 10 cases with su...Objective: The aim of our study was to demonstrate the CT features of solid pseudopapillary tumor of the pancreas (SPTP) so as to improve the imaging diagnostic abilities. Methods: The CT materials of 10 cases with surgery and pathology proved SPTP were retrospectively analyzed, including 8 females and 2 males, their age ranged from 12 to 54 years (average being 27.2 years). All of the 10 cases underwent spiral CT scan and also with contrast enhancement before surgery. Results: All of the 10 cases were isolated mass. They were located at the head (n = 5), tail (n = 4), and body (n = 1) of the pancreas. Their shapes were round (n = 3), oval (n = 4), and irregular (n = 3). The long-axis diameter ranged from 2.1-8.6 cm (mean 6.5 cm). All of neoplasms consisted of solid and cystic components. Mostly solid components in 5 cases, nearly the same proportion of solid and cystic part in 3 cases, and mostly cystic components in 2 cases. After dynamic contrast-enhanced, the solid parts of the lesion showed progressive enhancement and the cystic parts of the lesion showed no enhancement. Calcification was noted in 5 cases, such as the spot, line-like, small nodules or patchy calcification. Fluid-debris level and "floating cloud" sign were noted in one case. In one case of mostly cystic components, patchy area of high attenuation were shown on CT imaging which then was proved as old hemorrhage by pathologic evaluation. Seven cases were completely encapsulated and made more remarkable on post-contrast images. Three cases had incomplete capsules, and adhesion to the surrounding tissues could be seen during operation, including one case in which invasion to the adjacent adipose tissues near the inferior vena cava and walls of the duodenum could be seen under the microscope. Pancreatic duct broadening or hepatic duct dilatation was caused by tumor each in 1 case. All of the 10 cases had no enlargement of the intra-abdominal lymph nodes or distant organ metastasis. Conclusion: SPTP occurs mainly in young women and has comparatively characteristic CT imaging features: a large solid and cystic tumor of pancreas, sharp edges, the solid parts of the lesion showed progressive enhancement, a few with hemorrhage and calcification.展开更多
文摘Based on the finite element method, a numerical investigation into the bonded repair efficiency of cracked plates under in plane biaxial loadings is presented. The main considerations are: reduction in stress intensity factor (SIF) at the crack tip, the maximum tensile stress in the composite patch and the maximum shear stress in the adhesive bond between the patch and the plate. Without the patch, a tensile or compressive stress parallel to the crack has no effect on the SIF at the crack tip. While with a composite patch, there exists coupling effect between the normal stress parallel to the crack and the SIF, and the coupling effect depends significantly on ply orientation of the patch and the biaxial stress ratio of the plate.
文摘Biaxial compression tests are performed on 100 mm × 100 mm × 100 mm cubic specimens of plain high-strength highperformance concrete (HSHPC) at seven kinds of stress ratios, σ2:σ3 =0 : - 1, -0.20 : - 1, -0.30 : - 1, -0.40 : - 1, -0.50 : -1, -0. 75 : - 1, and - 1.00 : - 1 after exposure to normal and high temperatures of 20, 200, 300, 400, 500 and 600 ℃, using a large static-dynamic true triaxial machine. Frictionreducing pads are three layers of plastic membranes with glycerine in-between for the compressive loading plane. Failure modes of the specimens are described. The two principally static compressive strengths are measured. The influences of the temperatures and stress ratios on the biaxial strengths of HSHPC after exposure to high temperatures are also analyzed. The experimental results show that the uniaxial compressive strength of plain HSHPC after exposure to high temperatures does not decrease completely with the increase in temperature; the ratios of the biaxial to its uniaxial compressive strengths depend on the stress ratios and brittleness-stiffness of HSHPC after exposure to different high temperatures. The formula of the Kupfer-Gerstle failure criterion modified with the temperature and stress ratio parameters for plain HSHPC is proposed.
文摘Thirteen specimens were tested out of which nine were for creep of sealed concrete and four for shrinkage test,for a period of 700 d under controlled temperature condition.The experimental results for creep and shrinkage were compared with creep and shrinkage computation model B3 and distinct discrepancies between observed and calculated creep and shrinkage strains were observed.Based on regression analysis,modification on B3 model has been formulated which will be applicable at least for concrete of characteristics strength of C40 and C50 with additives.Besides,on the basis of observation on identical specimens with varied stress strength ratio,a function is generated which accounts effect of stress strength ratio on creep.Finally,Civil Engineering community is suggested not to follow the creep prediction models without correction at least for modern concrete,as they do not account the effect of additives on its compliance function.
基金Project supported by the Indian Council for Cultural Relations,India
文摘This paper reports investigation conducted to study the fatigue performance of steel fibre reinforced concrete (SFRC) containing fibres of mixed aspect ratio. An extensive experimental program was conducted in which 90 flexural fatigue tests were carried out at different stress levels on size 500 mm×100 mm×100 mm SFRC specimens respectively containing 1.0%, 1.5% and 2.0% volume fraction of fibres. About 36 static flexural tests were also conducted to determine the static flexural strength prior to fatigue testing. Each volume fraction of fibres incorporated corrugated mixed steel fibres of size 0.6 mm×2.0 mm×25 mm and 0.6 mm×2.0 mm×50 mm in ratio 50:50 by weight. The results are presented both as S-N relationships, with the maximum fatigue stress expressed as a percentage of the strength under static loading, and as relationships between actually applied fatigue stress and number of loading cycles to failure. Two-million-cycle fatigue strengths of SFRC containing different volume fractions of mixed fibres were obtained and compared with plain concrete.
文摘The aim of this research is to determine the effect of bridging liquid surface tension and specific surface area on strength factor of coal agglomerates. The production of coal agglomerates of the range 15-27.51 mm was achieved. The crushing strength of the agglomerates was determined for good handling of fine (coal-liquid mixture) to improve fugitive dust control, decrease in transportation losses, reduce risk of coal freezing, lower risk of spontaneous combustion, etc. in iron and steel industries, railway corporations and coal corporations. Kerosene (paraffin oil) was used as a binder and the agglomerated coal oil mixture was pelletized using balling technique (disc). Mechanical and physical tests like compressive strength test, etc. were carried out. The relationship between the bridging liquid surface tension and specific surface area on strength factor of coal agglomerates showed that there is considerable variation in these parameters in the coal powder systems.
文摘Objective: The aim of our study was to demonstrate the CT features of solid pseudopapillary tumor of the pancreas (SPTP) so as to improve the imaging diagnostic abilities. Methods: The CT materials of 10 cases with surgery and pathology proved SPTP were retrospectively analyzed, including 8 females and 2 males, their age ranged from 12 to 54 years (average being 27.2 years). All of the 10 cases underwent spiral CT scan and also with contrast enhancement before surgery. Results: All of the 10 cases were isolated mass. They were located at the head (n = 5), tail (n = 4), and body (n = 1) of the pancreas. Their shapes were round (n = 3), oval (n = 4), and irregular (n = 3). The long-axis diameter ranged from 2.1-8.6 cm (mean 6.5 cm). All of neoplasms consisted of solid and cystic components. Mostly solid components in 5 cases, nearly the same proportion of solid and cystic part in 3 cases, and mostly cystic components in 2 cases. After dynamic contrast-enhanced, the solid parts of the lesion showed progressive enhancement and the cystic parts of the lesion showed no enhancement. Calcification was noted in 5 cases, such as the spot, line-like, small nodules or patchy calcification. Fluid-debris level and "floating cloud" sign were noted in one case. In one case of mostly cystic components, patchy area of high attenuation were shown on CT imaging which then was proved as old hemorrhage by pathologic evaluation. Seven cases were completely encapsulated and made more remarkable on post-contrast images. Three cases had incomplete capsules, and adhesion to the surrounding tissues could be seen during operation, including one case in which invasion to the adjacent adipose tissues near the inferior vena cava and walls of the duodenum could be seen under the microscope. Pancreatic duct broadening or hepatic duct dilatation was caused by tumor each in 1 case. All of the 10 cases had no enlargement of the intra-abdominal lymph nodes or distant organ metastasis. Conclusion: SPTP occurs mainly in young women and has comparatively characteristic CT imaging features: a large solid and cystic tumor of pancreas, sharp edges, the solid parts of the lesion showed progressive enhancement, a few with hemorrhage and calcification.