An experimental study is carried out on fatigue defect of layer steel fiber reinforced concrete (LSFRC). Based on experimental data,the various relation curves are given corresponding to different stress levels 0.9, 0...An experimental study is carried out on fatigue defect of layer steel fiber reinforced concrete (LSFRC). Based on experimental data,the various relation curves are given corresponding to different stress levels 0.9, 0.85, and 0.8. Furthermore, the fatigue defect degree is defined, and the strain cycle ratio equations and defect cycle ratio equations with the correlation coefficients very close to 1, are regressed in terms of the cubic polynomial,of which the fittings are preferable.In addition,the results show that the fatigue defect of LSFRC presents three phase development regularity too.And in comparison with the plain concrete,the third phase of the fatigue defect of LSFRC is longer, therefore the fatigue failure of LSFRC is more ductile.The mechanism of the fatigue defect is discussed too.展开更多
Based on the theory of continuum damage mechanics,a bi-variable damage mechanics model is developed,which,according to thermodynamics,is accessible to derivation of damage driving force,damage evolution equation and d...Based on the theory of continuum damage mechanics,a bi-variable damage mechanics model is developed,which,according to thermodynamics,is accessible to derivation of damage driving force,damage evolution equation and damage evolution criteria. Furthermore,damage evolution equations of time rate are established by the generalized Drucker＇s postulate. The damage evolution equation of cycle rate is obtained by integrating the time damage evolution equations,and the fatigue life prediction method for smooth specimens under repeated loading with constant strain amplitude is constructed. Likewise,for notched specimens under the repeated loading with constant strain amplitude,the fatigue life prediction method is obtained on the ground of the theory of conservative integral in damage mechanics. Thus,the material parameters in the damage evolution equation can be obtained by reference to the fatigue test results of standard specimens with stress concentration factor equal to 1,2 and 3.展开更多
Generally, the number of fatigue cycles, the range of the repeated stresses, and the type of the structural details are the key factors affecting fatigue in large-scale welded structures. Seven types of struc- ture ...Generally, the number of fatigue cycles, the range of the repeated stresses, and the type of the structural details are the key factors affecting fatigue in large-scale welded structures. Seven types of struc- ture details were tested using a 2000-kN hydraulic-pressure-servo fatigue machine to imitate fatigue behav- ior in modern steel-truss-structures fabricated using thicker welded steel plates and integral joint technology. The details included longitudinal edge welds, welded attachment affecting detail, integral joint, and weld re- pairs on plate edges. The fatigue damage locations show that the stress (normal or shear), the shape, and the location of the weld start and end points are three major factors reducing the fatigue strength. The test results can be used for similar large structures.展开更多
文摘An experimental study is carried out on fatigue defect of layer steel fiber reinforced concrete (LSFRC). Based on experimental data,the various relation curves are given corresponding to different stress levels 0.9, 0.85, and 0.8. Furthermore, the fatigue defect degree is defined, and the strain cycle ratio equations and defect cycle ratio equations with the correlation coefficients very close to 1, are regressed in terms of the cubic polynomial,of which the fittings are preferable.In addition,the results show that the fatigue defect of LSFRC presents three phase development regularity too.And in comparison with the plain concrete,the third phase of the fatigue defect of LSFRC is longer, therefore the fatigue failure of LSFRC is more ductile.The mechanism of the fatigue defect is discussed too.
文摘Based on the theory of continuum damage mechanics,a bi-variable damage mechanics model is developed,which,according to thermodynamics,is accessible to derivation of damage driving force,damage evolution equation and damage evolution criteria. Furthermore,damage evolution equations of time rate are established by the generalized Drucker＇s postulate. The damage evolution equation of cycle rate is obtained by integrating the time damage evolution equations,and the fatigue life prediction method for smooth specimens under repeated loading with constant strain amplitude is constructed. Likewise,for notched specimens under the repeated loading with constant strain amplitude,the fatigue life prediction method is obtained on the ground of the theory of conservative integral in damage mechanics. Thus,the material parameters in the damage evolution equation can be obtained by reference to the fatigue test results of standard specimens with stress concentration factor equal to 1,2 and 3.
基金Supported by the Science and Technology Development Project of the Ministry of Railways China (No. 96G35)
文摘Generally, the number of fatigue cycles, the range of the repeated stresses, and the type of the structural details are the key factors affecting fatigue in large-scale welded structures. Seven types of struc- ture details were tested using a 2000-kN hydraulic-pressure-servo fatigue machine to imitate fatigue behav- ior in modern steel-truss-structures fabricated using thicker welded steel plates and integral joint technology. The details included longitudinal edge welds, welded attachment affecting detail, integral joint, and weld re- pairs on plate edges. The fatigue damage locations show that the stress (normal or shear), the shape, and the location of the weld start and end points are three major factors reducing the fatigue strength. The test results can be used for similar large structures.
