Abstract
The form and the perpendicularity of boreholes influence the ultimate behaviour of post-installed fasteners and are restricted with regard to the concrete surface to 5° in Europe and to 6° in the United States in various regulations (e.g., EAD 330232-00-0601 resp. ACI 355.2-19). It is assumed that the deviation of the borehole from the vertical axis has an effect on the load transfer behaviour of an anchorage. This article investigates on the perpendicularity of vertically downward drilled boreholes using different drilling tools considering hammer drilling, hollow drilling and diamond core drilling. It can be shown that the requirements of e.g., EAD 330232-00-0601 of a maximum deviation to the concrete surface of 5° can be fulfilled for approximately 95% of the determined values for different drilling methods. This is based on a considerable number of measurements (generated from drilled boreholes) in different concrete types. As a result, a detailed statistical evaluation is provided to describe the borehole perpendicularity by means of statistical methods.
Highlights
In all relevant technical specifications for post-installed fasteners, there are recommendations for the perpendicularity of the drill holes
Different drilling methods as hammer drilling with different drill bit types [6], hollow drilling and diamond drilling with different drilling tools are used for drilling the boreholes into concrete to place post-installed anchorages
On a various number of different experimental data, this study shows on the one hand whether the required limits are met and on the other hand the statistical distribution of the aberration of drilled boreholes in different concrete specimens in a vertical downward direction
Summary
In all relevant technical specifications for post-installed fasteners, there are recommendations for the perpendicularity of the drill holes. EAD 330499-00-0601 [2] a maximum aberration of ± 5◦ to the surface of the concrete member is recommended, whereas in the United States ACI 355.2-19 [3] allows a maximum variance of ±6◦ for drilled boreholes. On a various number of different experimental data, this study shows on the one hand whether the required limits are met and on the other hand the statistical distribution of the aberration of drilled boreholes in different concrete specimens in a vertical downward direction. For the first time the following article a statistical characterisation is made when the deviation of drilling holes to the perpendicular axis is made, resulting in a general probability distribution function which can be determined for this variable.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
