不同尺寸混凝土三点弯曲梁试件断裂过程试验研究

Experimental study on fracture process of various size specimens of three-point bending concrete beam

为探讨不同尺寸混凝土三点弯曲梁试件断裂过程的差异性及其尺寸效应,设计了高度为0.25 m、0.30 m、0.40 m、0.50 m的4组16根不同尺寸混凝土三点弯曲梁试件,对其进行全过程断裂试验,并分析了荷载~张口位移曲线、起裂和失稳荷载、起裂和失稳韧度等断裂参数的变化。结合双K断裂韧度计算方法,得到不同尺寸混凝土三点弯曲梁试件的起裂韧度和失稳韧度。结果表明：不同尺寸混凝土试件断裂过程具有差异性;起裂韧度不随试件高度的增加而变化,失稳断裂韧度随试件高度的增加而增大。试件高度从0.25 m增加到0.50 m时,失稳韧度增加了0.40 MPa·m1/2。

In order to study the discrepancies and their size effects of the fracture processes of various three-point bending concrete beams,4 group and 16 pieces of various three-point bending concrete beams with the heights of 0. 25 m,0. 30 m,0. 40 m and 0. 50 m respectively are designed,and then the whole process fracture experiments are made for them,while the changes of the fracture parameters,such as load-opening displacement curve,cracking and destabilizing loads,cracking and destabilizing toughnesses,etc. are analyzed as well. In accordance with the calculation method for the double-K fracture toughness,both the cracking toughness and the destabilizing toughness of various three-point bending concrete beams are obtained. The result shows that discrepancies are there among the fracture processes of various three-point bending concrete beams; i. e. the cracking toughness is not changed along with the increase of the height of the specimen,while the destabilizing fracture toughness is increased along with the height of the specimen. When the height of the specimen is increased from 0. 25 m to 0. 50 m,the destabilizing toughness is increased by 0. 40 MPa·m1 /2.