Degradation Feature And Failure Modes Of Concrete Under Uniaxial Compression

Degradation feature of concrete after peak stress under uniaxial compression is animportant way to understand catastrophic failure of concrete structure, but to get itscomplete curves of stress-strain is very difficult in the experiment. As a result, degradationfeature and failure modes of concrete is the key to understand and prevent failure ofconcrete structure.The paper makes use of the loading way of displacement by means of a large numberof specimens and obtains the complete curves of stress-strain in the experiment. Two typesof typical failure modes are observed in the experiment: gradual failure and catastrophicfailure. The evolution characteristic of different stages of curve of stress-strain areanalysed.Based on experiment observation, points of inflexion of which area that catastrophicfailure change from happen to unhappen are analysed in the degradation. The relation ofelastic modulus and peak stress of concrete are researched in the experiment, andstatistical law of peak stress and strain is obtained.Results shows that if strength of specimens raises, dispersed degree of peak stressand strain will increase accordingly; catastrophic failure will not appear if there isinflection in the degradation of curve of stress-strain, inflection will appear when peakstrain increases about1/3of itself, and it has superior dispersed degree; the more strengthof specimens, the more dispersed degree of elastic modulus, and catastrophic failure willhappen easier; elastic modulus and peak stress increase nearly on linearity; there aredifferent macroscopical failure modes in gradual failure and catastrophic failure of samebatch under same model of loading, even many different macroscopical failure modes areexisted in gradual failure.Based on numerical simulation, the process of initiation extension transfixion andfailure of micro-damage is analysed. Results shows that under uniaxial compressionloading, damage begins to appear in the specimen when the stress achieves about80%ofpeak stress. Initiation of new damage and extension of primary damage are induced further by local tensile stress around the primary damage unit element, and lead tomacroscopical failure ultimately.