In this study, the blast performance of steel reinforced concrete(RC) beams was experimentally and analytically investigated. The experiment consists of a total of 10 one-half-scale beams subjected to different levels...In this study, the blast performance of steel reinforced concrete(RC) beams was experimentally and analytically investigated. The experiment consists of a total of 10 one-half-scale beams subjected to different levels of blast loading using live explosives. The reflected pressure-time histories were recorded and different damage levels and modes were observed. The blast resilience of the damaged beams was quantified by measuring the time-dependent displacements. Experiment results show that the damage in steel reinforced concrete beams with higher explosive mass is enhanced compared with that of the beams with smaller explosive mass at the same scaled distance. Based on the experiment data, an empirical expression is developed via dimensional analysis to correct the relationship between the midspan displacement and scaled distance. Besides, a complex single degree of freedom model(SDOF)incorporating complex features of the material behavior, high strain-rate effect and the column geometry was proposed and validated by test results.展开更多
The reinforced concrete(RC) structural component might suffer a great damage under close-in explosion.Different from distant explosions, blast loads generated by the close-in explosion are non-uniformly distributed on...The reinforced concrete(RC) structural component might suffer a great damage under close-in explosion.Different from distant explosions, blast loads generated by the close-in explosion are non-uniformly distributed on the structural component and may cause both local and structural failure. In this study,an experimental study was conducted to investigate the dynamic responses of RC beams under doubleend-initiated close-in explosions. The experimental results show that the distribution of blast loads generated by the double-end-initiated explosion is much more non-uniform than those generated by single-point detonation, which is caused by the self-Mach-reflection effects. A 3 D finite element model was developed and validated in LS-DYNA by employing the modified K&C model. Intensive numerical calculations were conducted to study the influences of the initiation way, scaled distance and longitudinal reinforcement ratio on the dynamic responses and failure modes of RC beams. Numerical results show that the RC beam suffers greater damage as the cylindrical explosive is detonated at its double ends than the scenario in which the cylindrical explosive is detonated at its central point. RC beams mainly suffer flexural failure and flexure-shear failure under the double-end close-in explosion, and the failure modes of RC beams change from the flexural damage to flexure-shear damage as the scaled distance or the longitudinal reinforcement ratio decreases. The direct shear failure mode is not usually observed in the double-end-initiated explosion, since the intense blast loads is basically concentrated in the midspan of RC beam, which is due to self-Mach-reflection enhancement.展开更多
This article presents an experimental study on the flexural performance of reinforced concrete(RC)beams with fiber reinforced cementitious composites(FRCC)and hybrid fiber reinforced cementitious composites(HFRCC)in t...This article presents an experimental study on the flexural performance of reinforced concrete(RC)beams with fiber reinforced cementitious composites(FRCC)and hybrid fiber reinforced cementitious composites(HFRCC)in the hinge portion.Beam specimens with moderate confinement were used in the study and tested under monotonic loading.Seven diverse types of FRCC including hybrid composites using fibers in different profiles and in different volumes are employed in this study.Companion specimens such as cylindrical specimens and prism specimens are also used to study the physical properties of composites employed.The moment?curvature,stiffness behavior,ductility,crack pattern and modified flexural damage ratio are the main factors considered in this study to observe the efficacy of the employed hybrid composites.The experimental outputs demonstrate the improved post yield behavior with less rate of stiffness degradation and better damage tolerance capacity than conventional technique.展开更多
This study presents experimental and numerical investigations of simply supported steel reinforced concrete(RC)beams under fire.The temperature field of cross sections,the vertical deflection at mid-span,and specifica...This study presents experimental and numerical investigations of simply supported steel reinforced concrete(RC)beams under fire.The temperature field of cross sections,the vertical deflection at mid-span,and specifically the axial expansion displacement at beam-ends were measured during the fire tests.A novel finite element(FE)model of a RC beam under fire was developed,in which the water loss in the heat transfer analysis and the concrete transient strain in the mechanical analysis were considered.Based on the validated FE model proposed in this study,parametric studies were conducted to investigate the effects of the beam type,the protective layer thickness,and the load ratio on the thermal and mechanical behavior of simply supported RC beams.It was found that greater fire resistance and fire performance of girder beams in comparison to secondary beams contributed to the non-structural reinforcements,which effectively compensated for the reduced tensile capacities of structural reinforcements because of the degradation of the material properties.In addition,the history of normal stress distributions of concrete under fire can be divided into three phases:expansion,stress redistribution and plateau phases.展开更多
With consideration of the differences between concrete and steel,three solutions using genetic evolutionary structural optimization algorithm were presented to automatically develop optimal strut-and-tie model for dee...With consideration of the differences between concrete and steel,three solutions using genetic evolutionary structural optimization algorithm were presented to automatically develop optimal strut-and-tie model for deep beams.In the finite element analysis of the first method,the concrete and steel rebar are modeled by a plane element and a bar element,respectively.In the second method,the concrete and steel are assigned to two different plane elements,whereas in the third method only one kind of plane element is used with no consideration of the differences of the two materials.A simply supported beam under two point loads was presented as an example to verify the validity of the three proposed methods.The results indicates that all the three methods can generate optimal strut-and-tie models and the third algorithm has powerful capability in searching more optimal results with less computational effort.The effectiveness of the proposed algorithm III has also been demonstrated by other two examples.展开更多
Tests were carried out on 8 self-compacting reinforced concrete(SCC) beams and 4 normal reinforced concrete beams. The effects of mode of consolidation,load level,reinforcing ratio and structural type on long term beh...Tests were carried out on 8 self-compacting reinforced concrete(SCC) beams and 4 normal reinforced concrete beams. The effects of mode of consolidation,load level,reinforcing ratio and structural type on long term behavior of SCC were investigated. Under the same environmental conditions,the shrinkage-time curve of self-compacting concrete beam is very similar to that of normal concrete beam. For both self-compacting reinforced concrete beams and normal reinforced concrete beams,the rate of shrinkage at early stages is higher,the shrinkage strain at 2 months is about 60% of the maximum value at one year. The shrinkage strain of self-compacting reinforced concrete beam after one year is about 450×10-6. Creep deflection of self-compacting reinforced concrete beam decreases as the tensile reinforcing ratio increases. The deflection creep coefficient of self-compacting reinforced concrete beam after one and a half year is about 1.6,which is very close to that of normal reinforced concrete beams cast with vibration. Extra cautions considering shrinkage and creep behavior are not needed for the use of SCC in engineering practices.展开更多
The load-bearing capacity of reinforced concrete(RC) beams primarily relies on internal reinforced bars.However, limited research has been conducted on the dynamic response of these bars. To address this gap, this stu...The load-bearing capacity of reinforced concrete(RC) beams primarily relies on internal reinforced bars.However, limited research has been conducted on the dynamic response of these bars. To address this gap, this study has established an analytical model using dimensional analysis for calculating the deformation of reinforced bars within RC beams subjected to contact explosion. Comparison with experimental data reveals that the model has a relative error of 5.22%, effectively reflecting the deformation of reinforced bars. Additionally, based on this model, the study found that while concrete does influence the deformation of reinforced bars, this influence can be disregarded in comparison to the material properties of the bars themselves. The findings of this study have implications for calculating the residual load-bearing capacity of damaged RC beams, evaluating the extent of damage to RC beams after blast loading, and providing guidance for the blast-resistant design of RC structures.展开更多
In order to get the formulae for calculating the equivalent frame width coefficient of reinforced concrete hollow slab-column structures with edge beam,the finite element structural program was used in the elastic ana...In order to get the formulae for calculating the equivalent frame width coefficient of reinforced concrete hollow slab-column structures with edge beam,the finite element structural program was used in the elastic analysis of reinforced concrete hollow slab-column structure with different dimensions to study internal relationship between effective beam width and the frame dimensions.In addition,the formulas for calculating the increasing coefficient of edge beam were also obtained.展开更多
The special reinforced concrete composite beam consists of a steel fiber reinforced self-stressing concrete composite layer and a reinforced concrete T-beam, and constructional bars are set up at their bonding interfa...The special reinforced concrete composite beam consists of a steel fiber reinforced self-stressing concrete composite layer and a reinforced concrete T-beam, and constructional bars are set up at their bonding interface. Fatigue properties of the composite beam under the action of negative moment were experimentally studied. Through inverted loading mode the load-beating state of a composite beam was simulated under the action of negative moment. With the ratios of constructional bars being 0, 0.082% and 0.164% respectively as parameters, the effects of constructional bars on the properties of composite beam, such as fatigue life, crack propagation, rigidity loss as well as damage behavior of bonding interface, were studied. The mechanism of the constructional bars on the fatigue properties of the composite beams and the restriction mechanism of crack widths and rigidity loss were analyzed. The test results show that the constructional bars can enhance the shear resistance of the bonding interface between composite layer and old concrete beam and restrict expanding of steel fiber reinforced self-stressing concrete, which are beneficial to synergistic action of composite layer and old concrete beam, to reducing the stress amplitude of bars and the crack width of composite layer, and to increasing the durability and fatigue life of the composite beam.展开更多
Based on the theory of concrete structure, a new expression was derived for lagged strain of fiber-reinforced polymer （FLIP） laminates in reinforced concrete （RC） beams strengthened with FRP. The influence of diff...Based on the theory of concrete structure, a new expression was derived for lagged strain of fiber-reinforced polymer （FLIP） laminates in reinforced concrete （RC） beams strengthened with FRP. The influence of different preloaded states and nonlinear stress-strain relationship of compressed concrete were both taken into account in this approach. Then a simplified expression was given by ignoring tensile resistance of concrete. Comparison of analytical predictions with experimental results indicates satisfactory accuracy of the procedures. The errors are less than 8% and 10% respectively when the tensile resistance of concrete is or not considered. While the maximum error of existing procedures is up to 60%.展开更多
Reinforced concrete(RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthqu...Reinforced concrete(RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthquakes, but also more economical. The effect of progressive collapse caused by removal of load bearing elements, in various positions in plan and stories of the RC load bearing wall system was evaluated by nonlinear dynamic and static analyses. For this purpose, three-dimensional model of 10-story structure was selected. The analysis results indicated stability, strength and stiffness of the RC load-bearing wall system against progressive collapse. It was observed that the most critical condition for removal of load bearing walls was the instantaneous removal of the surrounding walls located at the corners of the building where the sections of the load bearing elements were changed. In this case, the maximum vertical displacement was limited to 6.3 mm and the structure failed after applying the load of 10 times the axial load bored by removed elements. Comparison between the results of the nonlinear dynamic and static analyses demonstrated that the "load factor" parameter was a reasonable criterion to evaluate the progressive collapse potential of the structure.展开更多
Rehabilitation of existing structures with fiber reinforced plastic(FRP)has been growing in popularity because they offer superior performance in terms of resistance to corrosion and high specific stiffness.The strain...Rehabilitation of existing structures with fiber reinforced plastic(FRP)has been growing in popularity because they offer superior performance in terms of resistance to corrosion and high specific stiffness.The strain coordination results of 34 reinforced concrete beams(four groups)strengthened with different methods were presented including external-bonded or near-surface mounted glass or carbon FRP or helical rib bar in order to study the strain coordination of the strengthening materials and steel rebar of RC beam.Because there is relative slipping between concrete and strengthening materials(SM),the strain of SM and steel rebar of RC beam satisfies the double linear strain distribution assumption,that is,the strain of longitudinal fiber parallel to the neutral axis of plated beam within the scope of effective height(h0)of the cross section is in direct proportion to the distance from the fiber to the neutral axis.The strain of SM and steel rebar satisfies the equation εGCH=βεsteel,where the value of β is equal to 1.1-1.3 according to the test results.展开更多
The objective of this work is to investigate the fatigue behavior of reinforced concrete(RC) beams strengthened with externally bonded carbon fiber reinforced polymer(CFRP) and steel plate. An experimental investigati...The objective of this work is to investigate the fatigue behavior of reinforced concrete(RC) beams strengthened with externally bonded carbon fiber reinforced polymer(CFRP) and steel plate. An experimental investigation and theoretical analysis were made on the law of deflection development and stiffness degradation, as well as the influence of fatigue load ranges. Test results indicate that the law of three-stage change under fatigue loading is followed by both midspan deflection and permanent deflection, which also have positive correlation with fatigue load amplitude. Fatigue stiffness of composite strengthened beams degrades gradually with the increasing of number of cycles. Based on the experimental results, a theoretical model by effective moment of inertia method is developed for calculating the sectional stiffness of such composite strengthened beams under fatigue loading, and the calculated results are in good agreement with the experimental results.展开更多
基金supported by The National Natural Science Foundation of China under Grant No.11390362 and No.11221202
文摘In this study, the blast performance of steel reinforced concrete(RC) beams was experimentally and analytically investigated. The experiment consists of a total of 10 one-half-scale beams subjected to different levels of blast loading using live explosives. The reflected pressure-time histories were recorded and different damage levels and modes were observed. The blast resilience of the damaged beams was quantified by measuring the time-dependent displacements. Experiment results show that the damage in steel reinforced concrete beams with higher explosive mass is enhanced compared with that of the beams with smaller explosive mass at the same scaled distance. Based on the experiment data, an empirical expression is developed via dimensional analysis to correct the relationship between the midspan displacement and scaled distance. Besides, a complex single degree of freedom model(SDOF)incorporating complex features of the material behavior, high strain-rate effect and the column geometry was proposed and validated by test results.
基金supported by the National Natural Science Foundations of China(Nos. 51622812, and 51427807)National Basic Research Program of China(No. 2015CB058003)China Postdoctoral Science Foundation(No. 2017M613379)
文摘The reinforced concrete(RC) structural component might suffer a great damage under close-in explosion.Different from distant explosions, blast loads generated by the close-in explosion are non-uniformly distributed on the structural component and may cause both local and structural failure. In this study,an experimental study was conducted to investigate the dynamic responses of RC beams under doubleend-initiated close-in explosions. The experimental results show that the distribution of blast loads generated by the double-end-initiated explosion is much more non-uniform than those generated by single-point detonation, which is caused by the self-Mach-reflection effects. A 3 D finite element model was developed and validated in LS-DYNA by employing the modified K&C model. Intensive numerical calculations were conducted to study the influences of the initiation way, scaled distance and longitudinal reinforcement ratio on the dynamic responses and failure modes of RC beams. Numerical results show that the RC beam suffers greater damage as the cylindrical explosive is detonated at its double ends than the scenario in which the cylindrical explosive is detonated at its central point. RC beams mainly suffer flexural failure and flexure-shear failure under the double-end close-in explosion, and the failure modes of RC beams change from the flexural damage to flexure-shear damage as the scaled distance or the longitudinal reinforcement ratio decreases. The direct shear failure mode is not usually observed in the double-end-initiated explosion, since the intense blast loads is basically concentrated in the midspan of RC beam, which is due to self-Mach-reflection enhancement.
基金support of Reliance Industries and Bakaert Industries, India for providing fiber for the experimental work
文摘This article presents an experimental study on the flexural performance of reinforced concrete(RC)beams with fiber reinforced cementitious composites(FRCC)and hybrid fiber reinforced cementitious composites(HFRCC)in the hinge portion.Beam specimens with moderate confinement were used in the study and tested under monotonic loading.Seven diverse types of FRCC including hybrid composites using fibers in different profiles and in different volumes are employed in this study.Companion specimens such as cylindrical specimens and prism specimens are also used to study the physical properties of composites employed.The moment?curvature,stiffness behavior,ductility,crack pattern and modified flexural damage ratio are the main factors considered in this study to observe the efficacy of the employed hybrid composites.The experimental outputs demonstrate the improved post yield behavior with less rate of stiffness degradation and better damage tolerance capacity than conventional technique.
基金Project(51578548)supported by the National Natural Science Foundation of ChinaProject(2018JJ3202)supported by the Natural Science Foundation of Hunan Province,ChinaProject(17C0681)supported by the Educational Departmental Science Research of Hunan Province,China
文摘This study presents experimental and numerical investigations of simply supported steel reinforced concrete(RC)beams under fire.The temperature field of cross sections,the vertical deflection at mid-span,and specifically the axial expansion displacement at beam-ends were measured during the fire tests.A novel finite element(FE)model of a RC beam under fire was developed,in which the water loss in the heat transfer analysis and the concrete transient strain in the mechanical analysis were considered.Based on the validated FE model proposed in this study,parametric studies were conducted to investigate the effects of the beam type,the protective layer thickness,and the load ratio on the thermal and mechanical behavior of simply supported RC beams.It was found that greater fire resistance and fire performance of girder beams in comparison to secondary beams contributed to the non-structural reinforcements,which effectively compensated for the reduced tensile capacities of structural reinforcements because of the degradation of the material properties.In addition,the history of normal stress distributions of concrete under fire can be divided into three phases:expansion,stress redistribution and plateau phases.
基金Project(50908082) supported by the National Natural Science Foundation of ChinaProject(2009ZK3111) supported by the Science and Technology Department of Hunan Province,China
文摘With consideration of the differences between concrete and steel,three solutions using genetic evolutionary structural optimization algorithm were presented to automatically develop optimal strut-and-tie model for deep beams.In the finite element analysis of the first method,the concrete and steel rebar are modeled by a plane element and a bar element,respectively.In the second method,the concrete and steel are assigned to two different plane elements,whereas in the third method only one kind of plane element is used with no consideration of the differences of the two materials.A simply supported beam under two point loads was presented as an example to verify the validity of the three proposed methods.The results indicates that all the three methods can generate optimal strut-and-tie models and the third algorithm has powerful capability in searching more optimal results with less computational effort.The effectiveness of the proposed algorithm III has also been demonstrated by other two examples.
基金Project(50278097) supported by the National Natural Science Foundation of China
文摘Tests were carried out on 8 self-compacting reinforced concrete(SCC) beams and 4 normal reinforced concrete beams. The effects of mode of consolidation,load level,reinforcing ratio and structural type on long term behavior of SCC were investigated. Under the same environmental conditions,the shrinkage-time curve of self-compacting concrete beam is very similar to that of normal concrete beam. For both self-compacting reinforced concrete beams and normal reinforced concrete beams,the rate of shrinkage at early stages is higher,the shrinkage strain at 2 months is about 60% of the maximum value at one year. The shrinkage strain of self-compacting reinforced concrete beam after one year is about 450×10-6. Creep deflection of self-compacting reinforced concrete beam decreases as the tensile reinforcing ratio increases. The deflection creep coefficient of self-compacting reinforced concrete beam after one and a half year is about 1.6,which is very close to that of normal reinforced concrete beams cast with vibration. Extra cautions considering shrinkage and creep behavior are not needed for the use of SCC in engineering practices.
文摘The load-bearing capacity of reinforced concrete(RC) beams primarily relies on internal reinforced bars.However, limited research has been conducted on the dynamic response of these bars. To address this gap, this study has established an analytical model using dimensional analysis for calculating the deformation of reinforced bars within RC beams subjected to contact explosion. Comparison with experimental data reveals that the model has a relative error of 5.22%, effectively reflecting the deformation of reinforced bars. Additionally, based on this model, the study found that while concrete does influence the deformation of reinforced bars, this influence can be disregarded in comparison to the material properties of the bars themselves. The findings of this study have implications for calculating the residual load-bearing capacity of damaged RC beams, evaluating the extent of damage to RC beams after blast loading, and providing guidance for the blast-resistant design of RC structures.
文摘In order to get the formulae for calculating the equivalent frame width coefficient of reinforced concrete hollow slab-column structures with edge beam,the finite element structural program was used in the elastic analysis of reinforced concrete hollow slab-column structure with different dimensions to study internal relationship between effective beam width and the frame dimensions.In addition,the formulas for calculating the increasing coefficient of edge beam were also obtained.
基金Project(50578027) supported by the National Natural Science Foundation of China
文摘The special reinforced concrete composite beam consists of a steel fiber reinforced self-stressing concrete composite layer and a reinforced concrete T-beam, and constructional bars are set up at their bonding interface. Fatigue properties of the composite beam under the action of negative moment were experimentally studied. Through inverted loading mode the load-beating state of a composite beam was simulated under the action of negative moment. With the ratios of constructional bars being 0, 0.082% and 0.164% respectively as parameters, the effects of constructional bars on the properties of composite beam, such as fatigue life, crack propagation, rigidity loss as well as damage behavior of bonding interface, were studied. The mechanism of the constructional bars on the fatigue properties of the composite beams and the restriction mechanism of crack widths and rigidity loss were analyzed. The test results show that the constructional bars can enhance the shear resistance of the bonding interface between composite layer and old concrete beam and restrict expanding of steel fiber reinforced self-stressing concrete, which are beneficial to synergistic action of composite layer and old concrete beam, to reducing the stress amplitude of bars and the crack width of composite layer, and to increasing the durability and fatigue life of the composite beam.
基金Project(2002G043) supported by the Science & Technology Research Program of Chinese Railway MinistryProject (05JJ30101)supported by the Natural Science Foundation of Hunan Province, China
文摘Based on the theory of concrete structure, a new expression was derived for lagged strain of fiber-reinforced polymer （FLIP） laminates in reinforced concrete （RC） beams strengthened with FRP. The influence of different preloaded states and nonlinear stress-strain relationship of compressed concrete were both taken into account in this approach. Then a simplified expression was given by ignoring tensile resistance of concrete. Comparison of analytical predictions with experimental results indicates satisfactory accuracy of the procedures. The errors are less than 8% and 10% respectively when the tensile resistance of concrete is or not considered. While the maximum error of existing procedures is up to 60%.
文摘Reinforced concrete(RC) load bearing wall is widely used in high-rise and mid-rise buildings. Due to the number of walls in plan and reduction in lateral force portion, this system is not only stronger against earthquakes, but also more economical. The effect of progressive collapse caused by removal of load bearing elements, in various positions in plan and stories of the RC load bearing wall system was evaluated by nonlinear dynamic and static analyses. For this purpose, three-dimensional model of 10-story structure was selected. The analysis results indicated stability, strength and stiffness of the RC load-bearing wall system against progressive collapse. It was observed that the most critical condition for removal of load bearing walls was the instantaneous removal of the surrounding walls located at the corners of the building where the sections of the load bearing elements were changed. In this case, the maximum vertical displacement was limited to 6.3 mm and the structure failed after applying the load of 10 times the axial load bored by removed elements. Comparison between the results of the nonlinear dynamic and static analyses demonstrated that the "load factor" parameter was a reasonable criterion to evaluate the progressive collapse potential of the structure.
基金Project(11B033)supported by the Foundation for Excellent Young Scholars of Hunan Scientific Committee,ChinaProject(116001)supported by the Consultative Program of the Chinese Academy of Engineering+1 种基金Project(11JJ6040)supported by the National Natural Science Foundation of Hunan Province,ChinaProject(2010GK3198)supported by the Science and Research Program of Hunan Province,China
文摘Rehabilitation of existing structures with fiber reinforced plastic(FRP)has been growing in popularity because they offer superior performance in terms of resistance to corrosion and high specific stiffness.The strain coordination results of 34 reinforced concrete beams(four groups)strengthened with different methods were presented including external-bonded or near-surface mounted glass or carbon FRP or helical rib bar in order to study the strain coordination of the strengthening materials and steel rebar of RC beam.Because there is relative slipping between concrete and strengthening materials(SM),the strain of SM and steel rebar of RC beam satisfies the double linear strain distribution assumption,that is,the strain of longitudinal fiber parallel to the neutral axis of plated beam within the scope of effective height(h0)of the cross section is in direct proportion to the distance from the fiber to the neutral axis.The strain of SM and steel rebar satisfies the equation εGCH=βεsteel,where the value of β is equal to 1.1-1.3 according to the test results.
文摘为探究钢筋混凝土(reinforced concrete,RC)梁在侧向近爆荷载下的动力响应和破坏形态,基于通用显式有限元分析软件LS-DYNA建立RC梁数值模型展开数值分析,并与竖向近爆荷载作用时RC梁进行对比,分析比例距离、惯性矩、荷载作用面积及不对称配筋对RC梁动力响应和破坏形态的影响。通过改进等效单自由度法进一步分析RC梁承受侧向近爆荷载时的动力响应发现:随着比例距离的减小,RC梁的动力响应逐渐增大;由于惯性矩和荷载作用面积的影响,侧向起爆时的峰值位移是竖向起爆时的4~5倍;侧向起爆时RC梁不对称配筋对位移影响较小;改进的等效单自由度(single degree of freedom,SDOF)法可用于侧向近爆荷载作用下RC梁的动力响应计算,结果可靠且计算效率高;竖向起爆时,随着比例距离的减小,RC梁的破坏形态由弯曲破坏逐渐转变为弯剪破坏,随着比例距离的减小剪力影响越来越大;侧向起爆时,随着比例距离的减小,RC梁的破坏形态由弯曲破坏逐渐转变为局部破坏,配筋率高的侧面可以更好地抑制混凝土裂缝的产生和发展;竖向起爆时RC梁具有更强的抗爆性能,RC梁承受侧向爆炸荷载时会发生更严重的破坏,对结构的影响更大,因此需重视侧向爆炸荷载下RC梁的工程防护研究。
基金Project(51108355)supported by the National Natural Science Foundation of ChinaProject(2011CDB269)supported by the Natural Science Foundation of Hubei Province,China
文摘The objective of this work is to investigate the fatigue behavior of reinforced concrete(RC) beams strengthened with externally bonded carbon fiber reinforced polymer(CFRP) and steel plate. An experimental investigation and theoretical analysis were made on the law of deflection development and stiffness degradation, as well as the influence of fatigue load ranges. Test results indicate that the law of three-stage change under fatigue loading is followed by both midspan deflection and permanent deflection, which also have positive correlation with fatigue load amplitude. Fatigue stiffness of composite strengthened beams degrades gradually with the increasing of number of cycles. Based on the experimental results, a theoretical model by effective moment of inertia method is developed for calculating the sectional stiffness of such composite strengthened beams under fatigue loading, and the calculated results are in good agreement with the experimental results.
