纤维类型及取向对纤维-UHPC基体拔出性能影响研究

纤维与基体之间的粘结能力和机械锚固作用是基体将荷载传递给纤维的决定因素之一,不同类型的纤维和取向在拉拔时的受力形式和破坏形式决定试件承载能力。采用单根纤维拉拔试验探究了纤维类型、取向对超高性能混凝土(UHPC)界面拉伸性能的影响。结果表明:随着纤维取向的增加拔出荷载先增大后减小,在45°时拔出荷载达到最大值；随着纤维取向增加,纤维拔出时对基体破坏面积增大,纤维拔出时对于基体的破坏能力:波纹线>端勾型>直线型。由第一峰值荷载分析,波纹型钢纤维相比于直线型和端勾型钢纤维更容易脱黏。对纤维拔出时进行力学行为分析,波纹型钢纤维和端勾型钢纤维拔出过程中首先发生纤维屈服,随着荷载持续基体产生破坏,直线型钢纤维在拔出过程中最先发生纤维与基体脱黏。

Study of effects of fiber types and orientations on pull-out properties of fiber-UHPC matrix

The bonding ability and mechanical anchorage between fibers and matrix is one of the determinants of the load transfer from the matrix to the fibers, and the forms of force and damages for different fiber types and orientations during pull-out determine the load carrying capacity of specimens. In this study, the effects of fiber types and orientations on the tensile properties of ultra-high performance concrete (UHPC) interfaces were investigated using single fiber pull-out tests. Results show that with increasing fiber orientations,the pull-out load first increased and then decreased, and it reached the maximum value at 45°.With the increase in the fiber orientations, the damage area of the matrix increased when the fibers were pulled out, and the damage capacity of the matrix when the fibers were pulled out was: corrugated type>end-hook type>linear type.According to the first peak load analysis, corrugated steel fibers were more likely to debond compared with linear and end-hook steel fibers. The mechanical behaviors during fiber pull-out were analyzed.It was found that fiber yielding occurred first during the pull-out of corrugated and end-hooked steel fibers, and damage occurred to the matrix as the load continued;linear steel fibers were the first to debond from the matrix during pull-out.