Design of Fastenings for Use in Concrete
Selected chapters from the German concrete yearbook are now being published in the new English 'Beton-Kalender Series' for the benefit of an international audience.
Since it was founded in 1906, the Ernst & Sohn 'Beton-Kalender' has been supporting developments in reinforced and prestressed concrete. The aim was to publish a yearbook to reflect progress in 'ferro-concrete' structures until - as the book's first editor, Fritz von Emperger (1862-1942), expressed it - the 'tempestuous development' in this form of construction came to an end. However, the 'Beton-Kalender' quickly became the chosen work of reference for civil and structural engineers, and apart from the years 1945-1950 has been published annually ever since.
Rolf Eligehausen, Prof. Dr.-Ing., studied structural engineering at the Technical University Braunschweig and gained his doctorate from the University Stuttgart. Following two years of research at the University of California Berkeley, he became professor for fastenings technology at the University Stuttgart in 1984. Professor Eligehausen is a member of numerous national and international expert commissions in the fields of steel-reinforced concrete and fastening technology and the author of a large number of articles and books on these topics.
Rainer Mallée, Dr.-Ing., studied structural engineering at the Technical University Braunschweig and gained his doctorate from the University Stuttgart. Between 1980 and 1987 he was head of Professor Rehm's engineering bureau in Munich, before becoming head of development in fastening elements at fischer in Waldachtal, Germany. Between 1996 and 2010 he was head of research at the fischer group of companies. Prior to his retirement in 2010 he was a member of numerous national and international expert commissions in the fields of fastening technology and the author of a large number of articles on these topics.
Werner Fuchs, Dr.-Ing., studied structural engineering at the Technical University Karlsruhe and gained his doctorate from the University Stuttgart. Between 1991 and 1997 he assumed a senior position at Hilti's R&D center in Kaufering, Germany. In 1997 Dr. Fuchs returned to the University of Stuttgart, where he manages research and coordination of projects in different fields pertaining to fastenings in concrete and masonry. Since 2003 he is also lecturer for fastening technology at the University Karlsruhe. He is a member of numerous national and international expert commissions in the fields of steel-reinforced concrete and fastening technology. He has published a large number of articles related to these topics.
Design of Fastenings for Use in Concrete
Fields of Application
CEN/TS covers the design of post-installed fastenings (fasteners) and cast in situ fasteners (headed fasteners and anchor channels) in concrete components. The following types of fasteners are considered:
- expansion fasteners, undercut fasteners, concrete screws, bonded fasteners, bonded expansion fasteners and bonded undercut fasteners - headed bolts as well as anchor channels with stiff connection of anchorage element and channel.
In Figure 2.1 the different types of post-installed fasteners are shown schematically, Figures 2.2 and 2.3 show typical headed fasteners and anchor channels.
Fig. 2.1 Types of post-installed fasteners
(a1) torque-controlled fastener (sleeve type)
(a2) torque-controlled fastener (bolt type, also named or wedge type)
(b) deformation-controlled fastener (drop-in fastener)
(c1) undercut fastener (undercut in the direction to the bottom of the borehole enlarged)
(c2) undercut fastener (undercut in the direction to the concrete surface enlarged)
(d) concrete screw
(e1) bonded fastener
(e2) bonded expansion fastener
Fig. 2.2 Typical headed fasteners
Fig. 2.3 Typical anchor channel
Torque-controlled post-installed expansion fasteners are subdivided into sleeve type and bolt (wedge) type expansion fasteners. Post-installed fasteners of the sleeve type ( Figure 2.1a1 ) consist of a screw or a threaded rod with nut, washer, distance sleeve, a part to prevent spinning of the fastener in the borehole as well as an expansion cone. Post-installed fasteners of the bolt type ( Figure 2.1a2 ) consist of a bolt, the end of which is formed to one or two cones and shows at the other end a thread, expansion segments nested in the conical area of the bolt, as well as of a nut and a washer. The fasteners are anchored by applying a defined torque. During torqueing a prestressing force is generated in the bolt or in the screw, the cone or the cones at the end of the fastener is pulled into the expansion sleeve or segments. These are pressed against the borehole wall. The frictional forces caused thereby, fix the fasteners in the bore hole. The load-transfer mechanism employed by expansion anchors is called 'friction'.
Displacement-controlled post-installed fasteners ( Figure 2.1b ) consist of an expansion sleeve and a conical expansion plug. The internally threaded steel sleeve allows to screw in a screw or a threaded rod. They are set via the expansion of the sleeve as controlled by the axial displacement of the expansion plug within the sleeve. This is achieved by driving the expansion plug into the sleeve with a setting tool and a hammer. Like torque-controlled expansion fasteners, displacement-controlled expansion fasteners transfer external tension loads into the base material via friction and, in the zone of the localised deformation to some degree via mechanical interlock.
Undercut fasteners develop a mechanical interlock between anchor and base material (working principle 'mechanical interlock'). For this a cylindrically drilled hole is modified to create a notch, or undercut, of a specific dimension at a defined location either by means of a special drilling tool or by the undercutting action of the fastener itself (self-undercutting fastener). The Figures 2.1c1 and c2 show two typical undercut fasteners which differ for example in the direction of the undercut: Undercut that widens towards the bottom of the borehole ( Figure 2.1c1 ) or towards the concrete surface ( Figure 2.1c2 ). Undercut fasteners according to Figure 2.1c1 consist of a threaded stud with a conical end, expansion sleeve, nut, and washer. Internally threaded versions (not illust