Local Bearing Capacity of Concrete Under the Interaction of Headed Bars

Abstract

The application of reinforcement with headed bars is widely used in the construction industry. Moreover, when the net distance between headed bars is close, the concrete areas for distributing bearing under the headed bars will overlap with each other. The local bearing capacity of concrete will also be affected by the overlapping area. To evaluate the effect of the overlapping area on the local bearing capacity of concrete, the experimental study was conducted on 6 concrete pull-out specimens. Based on the pull-out test, the parameter that net distance between headed bars was researched. The failure modes of specimens can be divided into two types. The first failure mode was marked by the formation of the dovetail slot structure during the failure process, and the second failure mode was characterized by the formation of through cracks in the cross section of specimens. The pull-out test results show that the local bearing capacity of concrete decreases firstly with the increase of net distance and then increases with the increase of net distance. Therefore, the relationship between the ratio of net distance to the side length of headed bars and the percentage decrease value of the local bearing capacity were given for the two segments. In addition, the critical value of the two segments was also analyzed and the corresponding formulas were also proposed. In order to verify the accuracy of formulas for the two segments, the test data from the similar pull-out tests with two or three headed bars were collected. And the calculation was recalculated according to the method proposed in this paper. Based on the ratio of the test data to the calculated values, the average value, standard deviation, and coefficient of variation are 1.08, 0.12, and 0.11 for the descending segment, respectively. And the values are 1.21, 0.22, and 0.18 for the rising segment, respectively. It is proved that there is a high accuracy for the formulas and the calculation method for the local bearing capacity of concrete under the interaction of headed bars was established.