This paper investigates the explicit use of rock reinforcement in a discontinuous stress analysis model.A series of numerical experiments was undertaken to evaluate the performance of local and global reinforcement mo...This paper investigates the explicit use of rock reinforcement in a discontinuous stress analysis model.A series of numerical experiments was undertaken to evaluate the performance of local and global reinforcement models implemented in universal distinct element code(UDEC).This was made possible by calibrating the reinforcement models to the laboratory behavior of a fully-grouted rebar bolt tested under pure pull and pure shear loading conditions.The model calibration focuses on matching different loading stages of the force-displacement curve including the initial elastic response,the hardening behavior and the bolt rupture.The paper concludes with a discussion on the suitability of the different reinforcement models in UDEC including their advantages and limitations.Finally,it addresses the choice of input parameters required for a realistic simulation of fully-grouted rebar bolts.展开更多
The hot deformation behavior of a Nb microalloyed anti-seismic rebar was investigated at deformation temperatures of 950-1 100 ℃ and strain rates of 0. 01-0. 1 s- 1 on a Gleeble-3800 thermo-mechnical simulator. The f...The hot deformation behavior of a Nb microalloyed anti-seismic rebar was investigated at deformation temperatures of 950-1 100 ℃ and strain rates of 0. 01-0. 1 s- 1 on a Gleeble-3800 thermo-mechnical simulator. The flow stress-strain curves show the typical dynamic recrystallization with a peak,before reaching the steady state flow at higher deformation temperatures and lower strain rates. The constitutive equation governing the dynamic recrystallization( DRX) was obtained and the average activation energy of deformation was calculated as Q = 389. 5 kJ / mol by the regression analysis. The DRX grain size was also found to decrease with the increasing strain rate and the decreasing deformation temperature. The austenite grain size was refined from 118. 0 μm to 15. 07-40. 01 μm by DRX. The DRX grain size under diverse deformation conditions predicted by mathematical model agrees well with experimental results.展开更多
A method was proposed to improve the anti-rust property of hot rolled rebar, which uses oil–water emulsion cooling instead of water cooling after hot rolling. The experiments were carried out by two cooling methods, ...A method was proposed to improve the anti-rust property of hot rolled rebar, which uses oil–water emulsion cooling instead of water cooling after hot rolling. The experiments were carried out by two cooling methods, one cooled by water, the other cooled by oil–water emulsion. The results of wet/dry cyclic accelerated corrosion test showed that the anti-rust property of rebar cooled by oil–water emulsion was better than that by water obviously. The results of OM, SEM and EPMA analysis indicated that these two scales contained three layers: an outer Fe_3O_4 layer, an intermediate Fe O layer with island-shaped pro-eutectoid Fe_3O_4, an inner eutectoid Fe_3O_4 layer. For the water cooled rebar, all three layers of oxide scale were relatively thin. Moreover, the scale had plenty of defects such as porosity, and crack. However, for the oil–water emulsion cooled rebar, all three layers of oxide scale were relatively thick and compact, which played an important role in protecting the rebar from atmospheric rust.展开更多
The corrosion resistance of rebar in fly ash-Lime silicate concrete as well as its marco properties and pore distribution is investigated. The results show that the fly ash is activated, the compressrve strength of th...The corrosion resistance of rebar in fly ash-Lime silicate concrete as well as its marco properties and pore distribution is investigated. The results show that the fly ash is activated, the compressrve strength of the silicate concrete is strengthened and its pore structure is modified after fly ash and lime being hybrid ground. Also the corrosion resistance of rebar in the silicate concrete is improved.展开更多
The influence of alloying elements and coolingconditions after rolling on the microstructures andmechanical properties of a series of medium carbonSi-Mn-Mo-V high-strength precision-formedrebars were investigated.It i...The influence of alloying elements and coolingconditions after rolling on the microstructures andmechanical properties of a series of medium carbonSi-Mn-Mo-V high-strength precision-formedrebars were investigated.It is found that steel withcombined addition of Mo and V appears to be themost promising one than those containing V andNb or containing V alone under the same pro-cessing conditions.From CCT curve of the steeland the cooling curve of the bar determined by sim-ulating the cooling rate in mill practice,the reasonwhy 40Si2MnMoV bar has excellent combinationof strength and ductility is clarified.展开更多
A new low-cost corrosion-resistant rebar(HRB400 R) was designed and fabricated by chromium micro-alloying. The effects of Cr on the passivation and corrosion behavior of this rebar in the simulated concrete pore solut...A new low-cost corrosion-resistant rebar(HRB400 R) was designed and fabricated by chromium micro-alloying. The effects of Cr on the passivation and corrosion behavior of this rebar in the simulated concrete pore solutions were studied systematically, and its improved corrosion resistance was revealed. In the Cl--free saturated Ca(OH)_2 solution, the HRB400 R rebar presented nearly the same passive film and similar passivation ability compared to the common carbon steel rebar. In the long-term immersion corrosion test in the Cl--contained Ca(OH)_2 solution, the HRB400 R rebar presented improved corrosion resistance and obvious longer passivation-maintaining period. Micro-alloying of Cr element in the rebar matrix enhanced its corrosion resistance against Cl--attack and retarded the corrosion initiation in the matrix. In the alkaline Na Cl salt spraying test, the HRB400 R rebar also presented obviously lower mass-loss rate. The enrichment of Cr element in the rust layer improved its retardant effect to the penetration of aggressive medium, and decreased the corrosion propagation rate of the rebar.展开更多
BACKGROUND Combined penetrating trauma involving the chest, pericardium, abdomen, and thigh is rare and lethal. It is difficult to quickly rescue patients with penetrating injuries from long steel bars.CASE SUMMARY A ...BACKGROUND Combined penetrating trauma involving the chest, pericardium, abdomen, and thigh is rare and lethal. It is difficult to quickly rescue patients with penetrating injuries from long steel bars.CASE SUMMARY A previously healthy 56-year-old male worker presented with a length of rebar that penetrated the chest-abdomen-pelvic cavity and was palpable on the anterior side of the neck and thigh. On radiological imaging, the left chest wall-left chest cavity-mediastinum-abdominal cavity-right groin area-right thigh demonstrated a strip-like density shadow, about 1.5 cm thick, with the heart, stomach wall, and part of the intestine involved. There was a left-sided pleural effusion, left lung compression of about 50%-60%, and a small amount of left pleural effusion/blood accumulation;possible perforation of hollow organs;and double multiple ribs fractures on the side. An emergency green channel was opened to provide a rescue process for smooth and timely diagnostic and treatment to save the patient's life. The patient was followed at 4 mo after discharge and showed good recovery.CONCLUSION For pre-hospital emergency treatment in locations that are not fully prepared for surgery, we do not recommend cutting the steel bars outside the body. We advocate pulling out foreign bodies intact to reduce secondary injuries.展开更多
Inhibitors are regularly used as one of the principal prevention and control techniques in reinforcement corrosion. Hence this study investigates the effect of calcium nitrate and sodium nitrite inhibitors on the reba...Inhibitors are regularly used as one of the principal prevention and control techniques in reinforcement corrosion. Hence this study investigates the effect of calcium nitrate and sodium nitrite inhibitors on the rebar corrosion of medium carbon steel in seawater and cassava fluid with a view to determining inhibitive potentials of the different inhibitors in the two media. Gravimetric and voltametric techniques were employed in this study and a total of forty-five corrosion coupons of different dimensions were produced. Forty coupons were used for gravimetric analysis and the remaining five for corrosion potentials measurements. Eight of the samples were used as control;while other eight samples each were admixed with calcium nitrate and sodium nitrite in concrete cubes. It was later immersed in seawater and cassava fluid for a total duration of 32 days and the measurements were taken at the interval of 4 days in order to determine the corrosion rates in mils per year (mmpy). Two controls and admixed samples each were later immersed in seawater and cassava fluid, respectively, for durations of 32 days to determine the corrosion potentials using a voltmeter and a Copper-Copper Sulphate Electrode (Cu/CuSO4). The pH of each medium was measured throughout the period of exposure. The results obtained expressed that all the samples except the control samples, displayed some degree of inhibition. The inhibition levels for the admixed samples in seawater were higher compared with those in cassava fluid. Inhibition efficiencies for various inhibitors followed different trends in different environment. The inhibition efficiencies for calcium nitrate in cassava fluid and seawater were 26.81% and 64.85% respectively. The study concluded that inorganic inhibitors were effective in inhibiting corrosion in cyanide and chloride contaminated concrete cubes.展开更多
Chemical mitigation is regularly used as one of the principal prevention and control techniques in reinforcement corrosion. Hence this study presents the effect of toluene and dioctylphthalate on the rebar corrosion o...Chemical mitigation is regularly used as one of the principal prevention and control techniques in reinforcement corrosion. Hence this study presents the effect of toluene and dioctylphthalate on the rebar corrosion of medium carbon steel in seawater and cassava fluid with a view to determining inhibitive potentials of the different inhibitors in the two media. Gravimetric and voltametric techniques were employed in this study and a total of forty-five corrosion coupons of different dimensions were produced. Forty coupons were used for gravimetry and the remaining five for corrosion potentials measurements. Eight of the samples were used as control;while other eight samples were admixed with dioctylphthalate and toluene in concrete cubes. It was later immersed in seawater and cassava fluid for a total duration of 32 days and the measurements were taken at interval of 4 days in order to determine the corrosion rates in mils per year (mmpy). Two controls and admixed samples were later immersed in seawater and cassava fluid, respectively, for durations of thirty-two days to determine the corrosion potentials using a voltmeter and a Copper-Copper Sulphate Electrode (Cu/CuSO4). The pH of each medium was also measured throughout the period of exposure. The results obtained showed that all the samples except the control samples, displayed some degree of inhibition. The inhibition levels for the admixed samples in seawater were on the higher side compared with those in cassava fluid. The inhibition efficiencies for different inhibitors followed different trends in different environment. The inhibition efficiencies for toluene in cassava fluid and seawater were 21.64% and 45.78% respectively. The study concluded that organic inhibitors were effective in inhibiting corrosion in cyanide and chloride contaminated concrete cubes.展开更多
Thoracic traumas have an important place among all injuries as they can cause significant mortality and morbidity. The thoracic injuries are the large part of trauma with head and extremity injuries. Thoracic traumas ...Thoracic traumas have an important place among all injuries as they can cause significant mortality and morbidity. The thoracic injuries are the large part of trauma with head and extremity injuries. Thoracic traumas are divided into two groups, including penetrating and blunt. The primary causes for penetrating traumas are wounds caused by gunshot and sharp objects. The lungs are the most injured organ in penetrating thoracic traumas with many organ injuries accompanied. This case report is about a rebar impalement into bilateral hemitoraces and pericardium after falling down in spite of any injury is not occurred in heart, lung and great vessels. The fact that an injury to such an extent does not cause any intrathoracic catastrophic event is something that has not been reported in the past.展开更多
In this paper,a 3D finite element(FE) program ADINA was applied to analyzing a tunnel with 9 segment rings. The loads acting on these segment rings included the squeezing action of tail brush of shield machine under a...In this paper,a 3D finite element(FE) program ADINA was applied to analyzing a tunnel with 9 segment rings. The loads acting on these segment rings included the squeezing action of tail brush of shield machine under attitude deflection,the jacking forces,the grouting pressure and the soil pressure. The analyses focused on the rebar stress in two statuses:(1) normal construction status without shield machine squeezing;(2) squeezing action induced by shield machine under attitude deflection. The analyses indicated that the rebar stress was evidently affected by the construction loads. In different construction status,the rebar stress ranges from -80 MPa to 50 MPa,and the rebar is in elastic status. Even some cracks appear on segments,the stress of segment rebar is still at a low level. It is helpful to incorporate a certain quantity of steel fiber to improve the anti-crack and shock resistance performance.展开更多
Based on the Canadian Standards Association (CSA) criteria,105 pullout specimens were tested to investigate the effect of different rib geometries on bond strength of glass fiber reinforced polymer (GFRP) rebars embed...Based on the Canadian Standards Association (CSA) criteria,105 pullout specimens were tested to investigate the effect of different rib geometries on bond strength of glass fiber reinforced polymer (GFRP) rebars embedded in concrete. Two kinds of conventional reinforcing rebars were also studied for comparison. Each rebar was embedded in a 150 mm concrete cube,with the embedded length being four times the rebar diameter. The experimental parameters were the rebar type,rebar component,rebar diameter,rebar surface texture,rib height,rib spacing and rib width. Theoretical analysis was also carried out to explain the experimental phenomena and results. The experimental and theoretical results indicated that the bond strength of GFRP rebars was about 13%～35% lower than that of steel rebars. The bond strength and bond-slip behavior of the specially machined rebars varied with the rebar type,rebar diameter,rebar surface texture,rib height,rib spacing and rib width. Using the results,design recom-mendations were made concerning optimum rib geometries of GFRP ribbed rebars with superior bond-slip characteristics,which concluded that the optimal rib spacing of ribbed rebars is the same as the rebar diameter,and that the optimal rib height is 6% of the rebar diameter.展开更多
The corrosion of rebar in reinforced concrete in marine environments causes significant damage to structures built in ocean environments. Studies on the process and mechanism of corrosion of rebar in the presence of m...The corrosion of rebar in reinforced concrete in marine environments causes significant damage to structures built in ocean environments. Studies on the process and mechanism of corrosion of rebar in the presence of multiple ions may help to control damage and predict the service life of reinforced concrete structures in such environments. The effect of interactions between sulfate and chloride ions and calcium hydroxide on the electrochemical behavior of rebar are also important for evaluation of structure durability. In this work, electrochemical impedance spectroscopy(EIS) plots of rebar in Ca(OH)_2 solution and cement grout, including NaCl and Na_2SO_4 as aggressive salts, were measured for different immersion times. The results show that corrosion of rebar was controlled by the rate of charge transfer as the rebar was exposed to chloride solution. In the presence of high concentrations of sulfate ions in the electrolyte, generation and dissolution of the passive film proceeded simultaneously and corrosion was mainly controlled by the diffusion rate. When Na_2SO_4 and NaCl were added to Ca(OH)_2 solution, the instantaneous corrosion rate decreased by a factor of 10 to 20 as a result of the higher p H of the corroding solution.展开更多
The electrochemical behavior of metallic passive film on rebar in concrete is characterized by its semiconductive nature. The charge distribution at the interface between a semiconductor and an electrolyte is often de...The electrochemical behavior of metallic passive film on rebar in concrete is characterized by its semiconductive nature. The charge distribution at the interface between a semiconductor and an electrolyte is often determined by measuring the capacitance of the space-charge layer (CSC) as a function of the electrode potential (E). When the space charge-layer serves as the depletion layer, the relation of CS?C2 vs E resembles a Mott-Schottky plot (M-S plot). The semiconductive properties of the passive film on rebar in concrete were analyzed with M-S plots to study the effect of chloride ions and mineral admixtures on rebar passive films. Some rebar electrodes were immersed in simulated concrete pore solutions, while others were embedded in concrete with/without mineral admixtures. In saturated Ca(OH)2 solutions, the relation of CS ?C2 -E of rebar electrodes shows linear Mott- Schottky relationship indicating that the passive film on rebar is a highly disordered n-type semiconductor, with donor density (ND) in the order of 1026 m?3. After adding chloride ions (Cl? wt%<0.2%) in system solutions, the M-S plot slopes significantly de-creased and ND increased, suggesting that chloride ion will cause passive film corrosion and breakdown. The M-S plots of the passive film on rebar electrodes embedded in concrete were similar to those immersed in simulated system solution. However, ND of those in concrete with mineral admixtures tended to be a little smaller, indicating that introducing proper quantity admixtures into concrete could make the rebar passive film have a thicker space-charge layer and therefore a thicker passive film layer.展开更多
基金supported by the Natural Science and Engineering Council of Canada
文摘This paper investigates the explicit use of rock reinforcement in a discontinuous stress analysis model.A series of numerical experiments was undertaken to evaluate the performance of local and global reinforcement models implemented in universal distinct element code(UDEC).This was made possible by calibrating the reinforcement models to the laboratory behavior of a fully-grouted rebar bolt tested under pure pull and pure shear loading conditions.The model calibration focuses on matching different loading stages of the force-displacement curve including the initial elastic response,the hardening behavior and the bolt rupture.The paper concludes with a discussion on the suitability of the different reinforcement models in UDEC including their advantages and limitations.Finally,it addresses the choice of input parameters required for a realistic simulation of fully-grouted rebar bolts.
基金National Natural Science Foundation of China(No.51261009)
文摘The hot deformation behavior of a Nb microalloyed anti-seismic rebar was investigated at deformation temperatures of 950-1 100 ℃ and strain rates of 0. 01-0. 1 s- 1 on a Gleeble-3800 thermo-mechnical simulator. The flow stress-strain curves show the typical dynamic recrystallization with a peak,before reaching the steady state flow at higher deformation temperatures and lower strain rates. The constitutive equation governing the dynamic recrystallization( DRX) was obtained and the average activation energy of deformation was calculated as Q = 389. 5 kJ / mol by the regression analysis. The DRX grain size was also found to decrease with the increasing strain rate and the decreasing deformation temperature. The austenite grain size was refined from 118. 0 μm to 15. 07-40. 01 μm by DRX. The DRX grain size under diverse deformation conditions predicted by mathematical model agrees well with experimental results.
基金Project(51374069) supported by the National Natural Science Foundation of China
文摘A method was proposed to improve the anti-rust property of hot rolled rebar, which uses oil–water emulsion cooling instead of water cooling after hot rolling. The experiments were carried out by two cooling methods, one cooled by water, the other cooled by oil–water emulsion. The results of wet/dry cyclic accelerated corrosion test showed that the anti-rust property of rebar cooled by oil–water emulsion was better than that by water obviously. The results of OM, SEM and EPMA analysis indicated that these two scales contained three layers: an outer Fe_3O_4 layer, an intermediate Fe O layer with island-shaped pro-eutectoid Fe_3O_4, an inner eutectoid Fe_3O_4 layer. For the water cooled rebar, all three layers of oxide scale were relatively thin. Moreover, the scale had plenty of defects such as porosity, and crack. However, for the oil–water emulsion cooled rebar, all three layers of oxide scale were relatively thick and compact, which played an important role in protecting the rebar from atmospheric rust.
文摘The corrosion resistance of rebar in fly ash-Lime silicate concrete as well as its marco properties and pore distribution is investigated. The results show that the fly ash is activated, the compressrve strength of the silicate concrete is strengthened and its pore structure is modified after fly ash and lime being hybrid ground. Also the corrosion resistance of rebar in the silicate concrete is improved.
文摘The influence of alloying elements and coolingconditions after rolling on the microstructures andmechanical properties of a series of medium carbonSi-Mn-Mo-V high-strength precision-formedrebars were investigated.It is found that steel withcombined addition of Mo and V appears to be themost promising one than those containing V andNb or containing V alone under the same pro-cessing conditions.From CCT curve of the steeland the cooling curve of the bar determined by sim-ulating the cooling rate in mill practice,the reasonwhy 40Si2MnMoV bar has excellent combinationof strength and ductility is clarified.
基金Funded by the National Basic Research Program of China(973 Program,2015CB655100)the Natural Science Foundation of China(Nos.51308111 and 51278098)+5 种基金the Industry-UniversityResearch Cooperative Innovation Fund of Jiangsu Province(No.BY2013091)the Research Project of Science and Technology Development of China Railway Corporation(No.2014G004-F)the“Six Talent Peak”Project of Jiangsu Province(No.2014-XCL-023 and 2016-XCL-196)the China Postdoctoral Science Foundation(No.2013M531249)the Postdoctoral Science Foundation of Jiangsu Province of China(1202008C)the Applied Research Foundation of Nantong City(No.BK2013001)
文摘A new low-cost corrosion-resistant rebar(HRB400 R) was designed and fabricated by chromium micro-alloying. The effects of Cr on the passivation and corrosion behavior of this rebar in the simulated concrete pore solutions were studied systematically, and its improved corrosion resistance was revealed. In the Cl--free saturated Ca(OH)_2 solution, the HRB400 R rebar presented nearly the same passive film and similar passivation ability compared to the common carbon steel rebar. In the long-term immersion corrosion test in the Cl--contained Ca(OH)_2 solution, the HRB400 R rebar presented improved corrosion resistance and obvious longer passivation-maintaining period. Micro-alloying of Cr element in the rebar matrix enhanced its corrosion resistance against Cl--attack and retarded the corrosion initiation in the matrix. In the alkaline Na Cl salt spraying test, the HRB400 R rebar also presented obviously lower mass-loss rate. The enrichment of Cr element in the rust layer improved its retardant effect to the penetration of aggressive medium, and decreased the corrosion propagation rate of the rebar.
基金the Science and Technology Program of Sichuan Science and Technology Department,Nos.2019YFS0029and 2019YFS0529the National Natural Science Foundation of China,No.81770566。
文摘BACKGROUND Combined penetrating trauma involving the chest, pericardium, abdomen, and thigh is rare and lethal. It is difficult to quickly rescue patients with penetrating injuries from long steel bars.CASE SUMMARY A previously healthy 56-year-old male worker presented with a length of rebar that penetrated the chest-abdomen-pelvic cavity and was palpable on the anterior side of the neck and thigh. On radiological imaging, the left chest wall-left chest cavity-mediastinum-abdominal cavity-right groin area-right thigh demonstrated a strip-like density shadow, about 1.5 cm thick, with the heart, stomach wall, and part of the intestine involved. There was a left-sided pleural effusion, left lung compression of about 50%-60%, and a small amount of left pleural effusion/blood accumulation;possible perforation of hollow organs;and double multiple ribs fractures on the side. An emergency green channel was opened to provide a rescue process for smooth and timely diagnostic and treatment to save the patient's life. The patient was followed at 4 mo after discharge and showed good recovery.CONCLUSION For pre-hospital emergency treatment in locations that are not fully prepared for surgery, we do not recommend cutting the steel bars outside the body. We advocate pulling out foreign bodies intact to reduce secondary injuries.
文摘Inhibitors are regularly used as one of the principal prevention and control techniques in reinforcement corrosion. Hence this study investigates the effect of calcium nitrate and sodium nitrite inhibitors on the rebar corrosion of medium carbon steel in seawater and cassava fluid with a view to determining inhibitive potentials of the different inhibitors in the two media. Gravimetric and voltametric techniques were employed in this study and a total of forty-five corrosion coupons of different dimensions were produced. Forty coupons were used for gravimetric analysis and the remaining five for corrosion potentials measurements. Eight of the samples were used as control;while other eight samples each were admixed with calcium nitrate and sodium nitrite in concrete cubes. It was later immersed in seawater and cassava fluid for a total duration of 32 days and the measurements were taken at the interval of 4 days in order to determine the corrosion rates in mils per year (mmpy). Two controls and admixed samples each were later immersed in seawater and cassava fluid, respectively, for durations of 32 days to determine the corrosion potentials using a voltmeter and a Copper-Copper Sulphate Electrode (Cu/CuSO4). The pH of each medium was measured throughout the period of exposure. The results obtained expressed that all the samples except the control samples, displayed some degree of inhibition. The inhibition levels for the admixed samples in seawater were higher compared with those in cassava fluid. Inhibition efficiencies for various inhibitors followed different trends in different environment. The inhibition efficiencies for calcium nitrate in cassava fluid and seawater were 26.81% and 64.85% respectively. The study concluded that inorganic inhibitors were effective in inhibiting corrosion in cyanide and chloride contaminated concrete cubes.
文摘Chemical mitigation is regularly used as one of the principal prevention and control techniques in reinforcement corrosion. Hence this study presents the effect of toluene and dioctylphthalate on the rebar corrosion of medium carbon steel in seawater and cassava fluid with a view to determining inhibitive potentials of the different inhibitors in the two media. Gravimetric and voltametric techniques were employed in this study and a total of forty-five corrosion coupons of different dimensions were produced. Forty coupons were used for gravimetry and the remaining five for corrosion potentials measurements. Eight of the samples were used as control;while other eight samples were admixed with dioctylphthalate and toluene in concrete cubes. It was later immersed in seawater and cassava fluid for a total duration of 32 days and the measurements were taken at interval of 4 days in order to determine the corrosion rates in mils per year (mmpy). Two controls and admixed samples were later immersed in seawater and cassava fluid, respectively, for durations of thirty-two days to determine the corrosion potentials using a voltmeter and a Copper-Copper Sulphate Electrode (Cu/CuSO4). The pH of each medium was also measured throughout the period of exposure. The results obtained showed that all the samples except the control samples, displayed some degree of inhibition. The inhibition levels for the admixed samples in seawater were on the higher side compared with those in cassava fluid. The inhibition efficiencies for different inhibitors followed different trends in different environment. The inhibition efficiencies for toluene in cassava fluid and seawater were 21.64% and 45.78% respectively. The study concluded that organic inhibitors were effective in inhibiting corrosion in cyanide and chloride contaminated concrete cubes.
文摘Thoracic traumas have an important place among all injuries as they can cause significant mortality and morbidity. The thoracic injuries are the large part of trauma with head and extremity injuries. Thoracic traumas are divided into two groups, including penetrating and blunt. The primary causes for penetrating traumas are wounds caused by gunshot and sharp objects. The lungs are the most injured organ in penetrating thoracic traumas with many organ injuries accompanied. This case report is about a rebar impalement into bilateral hemitoraces and pericardium after falling down in spite of any injury is not occurred in heart, lung and great vessels. The fact that an injury to such an extent does not cause any intrathoracic catastrophic event is something that has not been reported in the past.
文摘In this paper,a 3D finite element(FE) program ADINA was applied to analyzing a tunnel with 9 segment rings. The loads acting on these segment rings included the squeezing action of tail brush of shield machine under attitude deflection,the jacking forces,the grouting pressure and the soil pressure. The analyses focused on the rebar stress in two statuses:(1) normal construction status without shield machine squeezing;(2) squeezing action induced by shield machine under attitude deflection. The analyses indicated that the rebar stress was evidently affected by the construction loads. In different construction status,the rebar stress ranges from -80 MPa to 50 MPa,and the rebar is in elastic status. Even some cracks appear on segments,the stress of segment rebar is still at a low level. It is helpful to incorporate a certain quantity of steel fiber to improve the anti-crack and shock resistance performance.
基金Project (No. 200431882021) supported by the Western Communi-cation Construction and Science & Technological Project,China
文摘Based on the Canadian Standards Association (CSA) criteria,105 pullout specimens were tested to investigate the effect of different rib geometries on bond strength of glass fiber reinforced polymer (GFRP) rebars embedded in concrete. Two kinds of conventional reinforcing rebars were also studied for comparison. Each rebar was embedded in a 150 mm concrete cube,with the embedded length being four times the rebar diameter. The experimental parameters were the rebar type,rebar component,rebar diameter,rebar surface texture,rib height,rib spacing and rib width. Theoretical analysis was also carried out to explain the experimental phenomena and results. The experimental and theoretical results indicated that the bond strength of GFRP rebars was about 13%～35% lower than that of steel rebars. The bond strength and bond-slip behavior of the specially machined rebars varied with the rebar type,rebar diameter,rebar surface texture,rib height,rib spacing and rib width. Using the results,design recom-mendations were made concerning optimum rib geometries of GFRP ribbed rebars with superior bond-slip characteristics,which concluded that the optimal rib spacing of ribbed rebars is the same as the rebar diameter,and that the optimal rib height is 6% of the rebar diameter.
基金Supported by the National Natural Science Foundation of China(Nos.51178230,51378269,5142010501)the National Basic Research Program of China(973 Program)(No.2015CB655100)the Qingdao Science and Technological Foundation(Nos.13-1-4-176-jch,13-1-4-115-jch)
文摘The corrosion of rebar in reinforced concrete in marine environments causes significant damage to structures built in ocean environments. Studies on the process and mechanism of corrosion of rebar in the presence of multiple ions may help to control damage and predict the service life of reinforced concrete structures in such environments. The effect of interactions between sulfate and chloride ions and calcium hydroxide on the electrochemical behavior of rebar are also important for evaluation of structure durability. In this work, electrochemical impedance spectroscopy(EIS) plots of rebar in Ca(OH)_2 solution and cement grout, including NaCl and Na_2SO_4 as aggressive salts, were measured for different immersion times. The results show that corrosion of rebar was controlled by the rate of charge transfer as the rebar was exposed to chloride solution. In the presence of high concentrations of sulfate ions in the electrolyte, generation and dissolution of the passive film proceeded simultaneously and corrosion was mainly controlled by the diffusion rate. When Na_2SO_4 and NaCl were added to Ca(OH)_2 solution, the instantaneous corrosion rate decreased by a factor of 10 to 20 as a result of the higher p H of the corroding solution.
基金Project (No. 502019) supported by the Natural Science Foundationof Zhejiang Province, China
文摘The electrochemical behavior of metallic passive film on rebar in concrete is characterized by its semiconductive nature. The charge distribution at the interface between a semiconductor and an electrolyte is often determined by measuring the capacitance of the space-charge layer (CSC) as a function of the electrode potential (E). When the space charge-layer serves as the depletion layer, the relation of CS?C2 vs E resembles a Mott-Schottky plot (M-S plot). The semiconductive properties of the passive film on rebar in concrete were analyzed with M-S plots to study the effect of chloride ions and mineral admixtures on rebar passive films. Some rebar electrodes were immersed in simulated concrete pore solutions, while others were embedded in concrete with/without mineral admixtures. In saturated Ca(OH)2 solutions, the relation of CS ?C2 -E of rebar electrodes shows linear Mott- Schottky relationship indicating that the passive film on rebar is a highly disordered n-type semiconductor, with donor density (ND) in the order of 1026 m?3. After adding chloride ions (Cl? wt%<0.2%) in system solutions, the M-S plot slopes significantly de-creased and ND increased, suggesting that chloride ion will cause passive film corrosion and breakdown. The M-S plots of the passive film on rebar electrodes embedded in concrete were similar to those immersed in simulated system solution. However, ND of those in concrete with mineral admixtures tended to be a little smaller, indicating that introducing proper quantity admixtures into concrete could make the rebar passive film have a thicker space-charge layer and therefore a thicker passive film layer.
