DAMAGE ASSESSMENT FOR CONCRETE STRUCTURES UNDER EARTHQUAKE

A constitutive model with rate-sensitivity and special stress effect is presented to depict damage and failure for concrete under dynamic loading. The basic version of the model is a combination between visco-elasto-plastic model and the damage theory of continuum damage mechanics. This version of the model takes into account the basic traits of concrete under tension and compression with different response including intensity and the stiffness reduction with the increase of external loading and softening behavior. Then the damage failure criterions comprise tensive part and compressive part for their different behavior comprising the diversity of constitutive curve and development of damage and failure. And the model is further enhanced with rate sensitivity for concrete under dynamic loading, such as earthquake, blast and so on. The main advantages of this model are the employment of a failure criterion for the damage and rupture characteristic of concrete and the rate sensitivity.The model is implemented into a three-dimensional finite element program capable of treating static and general dynamic problems. The validation and performance of the proposed model is demonstrated by characteristic numerical examples including a concrete console and a spatial structure under earthquake. The original damage patterns of the structure are taken into account. Damage patterns are given to depict the damage fields in the structure and its express damage developments of the structure. Meanwhile the damage of the structure show the fracture zone and breakage position in the body. The applications show damage and progressive failure patterns for the structures under dynamic loading and the damage parameter is rather better than stress index on figuring progressive rupture procedure for concrete structures because of the latter swing under dynamic loading.