A full-range nonlinear analysis method for fatigue damage in prestressed concrete beams is presented. New damage accumulation models are proposed to describe the fatigue damage evolution in concrete and reinforcement ...A full-range nonlinear analysis method for fatigue damage in prestressed concrete beams is presented. New damage accumulation models are proposed to describe the fatigue damage evolution in concrete and reinforcement respectively. Based on the stress analysis for cross section, the stress redistrbution in the fatigue damage process, due to the different damage mechanisms of concrete and reinforcement, is considered. The nonlinear damage analysis is achieved by means of piecewise linearity, and it is applicable on the condition of repeated loadings with variable amplitude. Fatigue damage modeling of a beam is implemented to illustrate that the proposed method can preferably fit the experimental results.展开更多
The flexural behaviors of continuous fully and partially prestressed steel fiber reinforced high strength concrete beams are studied by experiment and nonlinear finite element analysis. Three levels of partial prestre...The flexural behaviors of continuous fully and partially prestressed steel fiber reinforced high strength concrete beams are studied by experiment and nonlinear finite element analysis. Three levels of partial prestress ratio （PPR） are considered, and three pairs of two-span continuous beams with box sections varying in size are designed. The major parameters involved in the study include the PPR and the fiber location. It is concluded that the prestressed high strength concrete beam exhibits satisfactory ductility; the influences of steel fiber on the crack behaviors for partially prestressed beams are not as obvious as those for fully prestressed ones; steel fibers can improve the structural stiffness after cracking for fully prestressed high strength concrete beams; the moment redistribution from mid-span to intermediate support in the first stage should be mainly considered in practical design.展开更多
Analyses and computations of the natural frequencies of external prestressed concrete structures are the bases for studying the dynamic properties of such structures. We carded out dynamic tests on three types of exte...Analyses and computations of the natural frequencies of external prestressed concrete structures are the bases for studying the dynamic properties of such structures. We carded out dynamic tests on three types of external simply supported beams, pulling the beams gradually. Then vertical loads were applied to the beams while the frequencies and related coefficients were measured at every step. We calculated natural frequencies and the results indicate that natural frequencies increase as the prestressing force rises in the pre-crack stage, and decrease significantly during the post-crack stage. Substantial incoincidences exist between the calculated and experimental results for the frequency and its tendency to changel Based on the experimental results, we modified the stiffness and other parameters in the equations. The results calculated using the modified equations agree with experimental results well, so the modified eauations can be used nractically.展开更多
T he ductility of partially prestressed concrete structure can take the full advan tage of material's largest potential energy, and make people design structures all the better. An important consideration of duct...T he ductility of partially prestressed concrete structure can take the full advan tage of material's largest potential energy, and make people design structures all the better. An important consideration of ductility analysis is to find out the moment-curvature relationship of partially prestressed concrete member sect ion, which has been derived in this paper.展开更多
Time-dependant reliability is analyzed for the flexural cracking of prestressed concrete bridges under service limit state. The limit state function and random variables are derived from Chinese highway bridge design ...Time-dependant reliability is analyzed for the flexural cracking of prestressed concrete bridges under service limit state. The limit state function and random variables are derived from Chinese highway bridge design specifications. For deterioration of structural performances, chloride-induced reinforcement corrosion is emphasized. Through integrating first order reliability method （FORM） and time discretized approach, the time-variant reliability is evaluated. For illustrative propose, the reliability of a typical simply supported prestressed concrete beam is exemplified.展开更多
According to the experimental results of model beams, the curvature of a partially prestressed concrete beam is defined, then the influence of PPR(partial prestressing ratio), net reinforcement index, concrete streng...According to the experimental results of model beams, the curvature of a partially prestressed concrete beam is defined, then the influence of PPR(partial prestressing ratio), net reinforcement index, concrete strength and fatigue on ductility of partially prestressed concrete beam are discussed respectively.展开更多
The design scheme of long span and low depth composite steel concrete beams is introduced, and the methods of avoiding the cracking of concrete deck in the negative moment regions are proposed. Moreover, significa...The design scheme of long span and low depth composite steel concrete beams is introduced, and the methods of avoiding the cracking of concrete deck in the negative moment regions are proposed. Moreover, significant exploration for problems of the composite beams has been made, such as optimizing construction steps to regulate the stress, applying jacking technique to exert prestress on the concrete deck, investigating the uplifting force principle of the shear connectors by means of model test and non linear finite element analysis, and pointing out the countermeasure to reduce tension force of the shear connectors.展开更多
文摘A full-range nonlinear analysis method for fatigue damage in prestressed concrete beams is presented. New damage accumulation models are proposed to describe the fatigue damage evolution in concrete and reinforcement respectively. Based on the stress analysis for cross section, the stress redistrbution in the fatigue damage process, due to the different damage mechanisms of concrete and reinforcement, is considered. The nonlinear damage analysis is achieved by means of piecewise linearity, and it is applicable on the condition of repeated loadings with variable amplitude. Fatigue damage modeling of a beam is implemented to illustrate that the proposed method can preferably fit the experimental results.
文摘The flexural behaviors of continuous fully and partially prestressed steel fiber reinforced high strength concrete beams are studied by experiment and nonlinear finite element analysis. Three levels of partial prestress ratio （PPR） are considered, and three pairs of two-span continuous beams with box sections varying in size are designed. The major parameters involved in the study include the PPR and the fiber location. It is concluded that the prestressed high strength concrete beam exhibits satisfactory ductility; the influences of steel fiber on the crack behaviors for partially prestressed beams are not as obvious as those for fully prestressed ones; steel fibers can improve the structural stiffness after cracking for fully prestressed high strength concrete beams; the moment redistribution from mid-span to intermediate support in the first stage should be mainly considered in practical design.
基金Funded by the National Science Foundation of China (No. 50808090)
文摘Analyses and computations of the natural frequencies of external prestressed concrete structures are the bases for studying the dynamic properties of such structures. We carded out dynamic tests on three types of external simply supported beams, pulling the beams gradually. Then vertical loads were applied to the beams while the frequencies and related coefficients were measured at every step. We calculated natural frequencies and the results indicate that natural frequencies increase as the prestressing force rises in the pre-crack stage, and decrease significantly during the post-crack stage. Substantial incoincidences exist between the calculated and experimental results for the frequency and its tendency to changel Based on the experimental results, we modified the stiffness and other parameters in the equations. The results calculated using the modified equations agree with experimental results well, so the modified eauations can be used nractically.
文摘T he ductility of partially prestressed concrete structure can take the full advan tage of material's largest potential energy, and make people design structures all the better. An important consideration of ductility analysis is to find out the moment-curvature relationship of partially prestressed concrete member sect ion, which has been derived in this paper.
文摘Time-dependant reliability is analyzed for the flexural cracking of prestressed concrete bridges under service limit state. The limit state function and random variables are derived from Chinese highway bridge design specifications. For deterioration of structural performances, chloride-induced reinforcement corrosion is emphasized. Through integrating first order reliability method （FORM） and time discretized approach, the time-variant reliability is evaluated. For illustrative propose, the reliability of a typical simply supported prestressed concrete beam is exemplified.
文摘According to the experimental results of model beams, the curvature of a partially prestressed concrete beam is defined, then the influence of PPR(partial prestressing ratio), net reinforcement index, concrete strength and fatigue on ductility of partially prestressed concrete beam are discussed respectively.
文摘The design scheme of long span and low depth composite steel concrete beams is introduced, and the methods of avoiding the cracking of concrete deck in the negative moment regions are proposed. Moreover, significant exploration for problems of the composite beams has been made, such as optimizing construction steps to regulate the stress, applying jacking technique to exert prestress on the concrete deck, investigating the uplifting force principle of the shear connectors by means of model test and non linear finite element analysis, and pointing out the countermeasure to reduce tension force of the shear connectors.
