This paper presents the results of four partially prestressed ultra-high strength concrete beams in flexure. The test results are used to evaluate the effects of prestressing tendon depth and area on flexure behavior ...This paper presents the results of four partially prestressed ultra-high strength concrete beams in flexure. The test results are used to evaluate the effects of prestressing tendon depth and area on flexure behavior of specimen beams. The test results indicate that: the cracking load,yielding load,peak load and stiffness postcracking of specimen beams are enhanced by reducing prestressing tendon depth or increasing prestressing tendon area, and the flexural ductility is improved by increasing prestressing tendon depth or reducing prestressing tendon area. The effect of complex reinforcement index considering the strength of the equivalence principle and the reinforcement position on loading levels under serviceability limit state,flexural strength and displacement ductility factor are studied. The influence coefficient of prestressing tendon kpis introduced in the complex reinforcement index. As the complex reinforcement index increases, the loading levels under serviceability limit state and flexural strength increases linearly,and the displacement ductility factor decreases linearly. The test results also verify the conventional beam flexural theory based on the plane cross-section assumption for predicting ultimate flexural strength of partially prestressed ultra-high strength concrete beams is valid. After the introduction of the coefficient kp,the calculation method of cracks in code for design of concrete structure in china are appropriated for the specimen beams.展开更多
A study on fatigue behavior of unbonded partially prestressed concrete beams is presented. Model tests have been carried out in static loading and cyclic compressive loading on 15 beams with flexure. The ratios of the...A study on fatigue behavior of unbonded partially prestressed concrete beams is presented. Model tests have been carried out in static loading and cyclic compressive loading on 15 beams with flexure. The ratios of the lower limit to the upper limit of fatigue load are 0.5 and 0.3 respectively, and the frequencies of cyclic loading are 8 Hz and 4.5 Hz respectively. The experimental results of the strains of the concrete and steel bars, the deflection of test beams, and the crack width of normal section are analyzed. According to statistics and analysis of test results, the corresponding calculation models are developed and presented.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
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
基金Sponsored by the National Natural Science Foundation of China(Grant No.50878037,51078059,51178078)
文摘This paper presents the results of four partially prestressed ultra-high strength concrete beams in flexure. The test results are used to evaluate the effects of prestressing tendon depth and area on flexure behavior of specimen beams. The test results indicate that: the cracking load,yielding load,peak load and stiffness postcracking of specimen beams are enhanced by reducing prestressing tendon depth or increasing prestressing tendon area, and the flexural ductility is improved by increasing prestressing tendon depth or reducing prestressing tendon area. The effect of complex reinforcement index considering the strength of the equivalence principle and the reinforcement position on loading levels under serviceability limit state,flexural strength and displacement ductility factor are studied. The influence coefficient of prestressing tendon kpis introduced in the complex reinforcement index. As the complex reinforcement index increases, the loading levels under serviceability limit state and flexural strength increases linearly,and the displacement ductility factor decreases linearly. The test results also verify the conventional beam flexural theory based on the plane cross-section assumption for predicting ultimate flexural strength of partially prestressed ultra-high strength concrete beams is valid. After the introduction of the coefficient kp,the calculation method of cracks in code for design of concrete structure in china are appropriated for the specimen beams.
文摘A study on fatigue behavior of unbonded partially prestressed concrete beams is presented. Model tests have been carried out in static loading and cyclic compressive loading on 15 beams with flexure. The ratios of the lower limit to the upper limit of fatigue load are 0.5 and 0.3 respectively, and the frequencies of cyclic loading are 8 Hz and 4.5 Hz respectively. The experimental results of the strains of the concrete and steel bars, the deflection of test beams, and the crack width of normal section are analyzed. According to statistics and analysis of test results, the corresponding calculation models are developed and presented.
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.
