Fatigue tests were conducted on tapered plain concrete prism specimens under tri axial constant-amplitude tension-compression cyclic loading. The low stress of the cyclic loading was taken as 0.2f c and the upper st...Fatigue tests were conducted on tapered plain concrete prism specimens under tri axial constant-amplitude tension-compression cyclic loading. The low stress of the cyclic loading was taken as 0.2f c and the upper stress ranged from 0. 20f t to 0.65f t. Three constant lateral pressures were 0.1f c, 0.2f c and 0.3f c respec tively. Based on the results, the th ree-stage evolution rule of the fatigue stiffness, maximum(minimum) longitudina l strain and damage were analyzed, and a unified S-N curve to calculate fati gue strength factors was worked out. The results show that the fatigue strength and fa tigue life under triaxial constant-amplitude tension-compression cyclic loadin g are smaller than those under uniaxial fatigue condition. Moreover, the secondary strain creep rate is related to the fatigue life, a formula for describing thei r relation was derived. The investigation of this paper can provide information for the fatigue design of concrete structures.展开更多
Experiments were made on plain concrete subjected to triaxial static loading and constant amplitude compressive fatigue loading with a constant lateral pressure in two directions. The initial confining pressure was 0...Experiments were made on plain concrete subjected to triaxial static loading and constant amplitude compressive fatigue loading with a constant lateral pressure in two directions. The initial confining pressure was 0, 0.1 f c , 0.25 f c and 0.4 f c , respectively, for the static test, and 0.1 f c and 0.25 f c for the fatigue test. Based on the triaxial compressive constitutive behavior of concrete, the inflexion of confining pressure evolution was chosen to be the fatigue damage criterion during the test. The rule of evolution of longitudinal maximum and minimum strains, longitudinal cyclic modulus and damage were recorded and analyzed. According to the Fardis Chen criterion model and the concept of equivalent fatigue life and equivalent stress level, a unified S N curve for multi axial compressive fatigue loading was proposed. Thus, the fatigue strength factors for different fatigue loading cases can be obtained. The present investigation provides information for the fatigue design of concrete structures.展开更多
Lightweight aggregate concrete cube specimens (100 mm×100 mm×100 mm) and plate specimens (100 mm×100 mm×50 mm) were tested under biaxial compression-compression (CC) and compression-tension (CT) lo...Lightweight aggregate concrete cube specimens (100 mm×100 mm×100 mm) and plate specimens (100 mm×100 mm×50 mm) were tested under biaxial compression-compression (CC) and compression-tension (CT) load combinations. For comparison, normal concrete plate specimens (100 mm×100 mm×50 mm) were tested under the same load combinations. Based on the test results, a two-level strength criterion of lightweight aggregate concrete in both octahedral stress coordinate and principal stress coordinate was suggested. The lightweight aggregate concrete cube specimens (100 mm×100 mm×100 mm) were then tested under triaxial compression-compression-compression (CCC) load combination with corresponding tests on normal concrete cube specimens (100 mm×100 mm×100 mm). The effect of intermediate principal stress on triaxial compressive strength is further examined. A "plastic flow plateau" area was apparent in principal compressive stress-strain relationships of lightweight aggregate concrete but not in normal concrete. A quadratic formula was suggested for the expression of strength criterion under triaxial compression.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.50078010)
文摘Fatigue tests were conducted on tapered plain concrete prism specimens under tri axial constant-amplitude tension-compression cyclic loading. The low stress of the cyclic loading was taken as 0.2f c and the upper stress ranged from 0. 20f t to 0.65f t. Three constant lateral pressures were 0.1f c, 0.2f c and 0.3f c respec tively. Based on the results, the th ree-stage evolution rule of the fatigue stiffness, maximum(minimum) longitudina l strain and damage were analyzed, and a unified S-N curve to calculate fati gue strength factors was worked out. The results show that the fatigue strength and fa tigue life under triaxial constant-amplitude tension-compression cyclic loadin g are smaller than those under uniaxial fatigue condition. Moreover, the secondary strain creep rate is related to the fatigue life, a formula for describing thei r relation was derived. The investigation of this paper can provide information for the fatigue design of concrete structures.
文摘Experiments were made on plain concrete subjected to triaxial static loading and constant amplitude compressive fatigue loading with a constant lateral pressure in two directions. The initial confining pressure was 0, 0.1 f c , 0.25 f c and 0.4 f c , respectively, for the static test, and 0.1 f c and 0.25 f c for the fatigue test. Based on the triaxial compressive constitutive behavior of concrete, the inflexion of confining pressure evolution was chosen to be the fatigue damage criterion during the test. The rule of evolution of longitudinal maximum and minimum strains, longitudinal cyclic modulus and damage were recorded and analyzed. According to the Fardis Chen criterion model and the concept of equivalent fatigue life and equivalent stress level, a unified S N curve for multi axial compressive fatigue loading was proposed. Thus, the fatigue strength factors for different fatigue loading cases can be obtained. The present investigation provides information for the fatigue design of concrete structures.
基金Project (No. 50679007) supported by the National Natural Science Foundation of China
文摘Lightweight aggregate concrete cube specimens (100 mm×100 mm×100 mm) and plate specimens (100 mm×100 mm×50 mm) were tested under biaxial compression-compression (CC) and compression-tension (CT) load combinations. For comparison, normal concrete plate specimens (100 mm×100 mm×50 mm) were tested under the same load combinations. Based on the test results, a two-level strength criterion of lightweight aggregate concrete in both octahedral stress coordinate and principal stress coordinate was suggested. The lightweight aggregate concrete cube specimens (100 mm×100 mm×100 mm) were then tested under triaxial compression-compression-compression (CCC) load combination with corresponding tests on normal concrete cube specimens (100 mm×100 mm×100 mm). The effect of intermediate principal stress on triaxial compressive strength is further examined. A "plastic flow plateau" area was apparent in principal compressive stress-strain relationships of lightweight aggregate concrete but not in normal concrete. A quadratic formula was suggested for the expression of strength criterion under triaxial compression.
