混凝土软化本构曲线形状对双K断裂参数的影响

INFLUENCES OF SOFTENING CONSTITUTIVE-CURVE SHAPE OF CONCRETE ON DOUBLE-K FRACTURE PARAMETERS

双K断裂准则能够定量描述混凝土结构裂缝的起裂、稳定扩展和失稳断裂。通过简便的试验和基于裂缝扩展粘聚力的解析方法 ,可计算双K断裂参数KiniIc和KunIc。反映粘聚力变化规律的软化本构曲线形状影响起裂韧度KiniIc的确定。对于简单实用的双线性软化本构曲线而言 ,取ws=CTODc,并引入一个直接影响混凝土软化本构曲线形状的参量λ ,结合本课题组新近所做的三点弯曲切口梁试验 ,调整参数λ ,得到了与实测结果相符的双线性软化本构曲线形状 ,用于确定双K断裂参数。

The fracture process in a concrete structure can be described quantitatively by the double-K fracture criterion.Whole fracture process is distinguished into three stages.These are the crack initiation,stable crack propagation,and unstable fracture.The double-K fracture parameters can be determined by using a simple test with an analytical method based on the cohesive force.The initial fracture toughness depends on the softening constitutive-curve shape.It reflects the cohesive force acted on the fictitious crack zone during crack propagation.With regard to the bilinear softening constitutive-curve,a new parameter λ is introduced.Parameter λ is effected directly on the softening constitutive-curve shape under the condition of ws being equal to CTOD c.According to the test of three-point bending notched beams,a softening constitutive-curve shape corresponding to the test results is obtained through adjusting the parameter λ . Then the double-K fracture parameters are calculated.