Anchor Fastening Element

Abstract

Anchor fastening element for fastening an object to a wall having a drilled hole, which comprises a threaded bolt having a threaded portion at one end and an anchor portion at the other end and also having a shank portion in between. The threaded portion and the anchor portion have a low ductility and the shank portion has a higher ductility.

Claims

1. An anchor fastening element for fastening an object in a drilled hole of a concrete part as an anchoring base, which is to absorb impact loads such as those occurring during earthquakes in an energy dissipating manner, comprising: a threaded bolt having a threaded portion at a first end, an anchor portion at the other, second end, and a shank portion between the threaded portion and the anchor portion; and a nut to be screwed on the threaded portion; wherein the threaded portion and the anchor portion on the one hand and the shank portion on the other exhibit a different ductility behavior, the threaded portion and the anchor portion having a lower ductility with less plastic deformation capacity, and the shank portion having a higher ductility with higher plastic deformation capacity, and wherein the shank portion finds a radial clearance within the drilled hole near the threaded portion, which is sufficiently large to allow for a plastic deformation corresponding to a global ductility of greater than 1.5 based on a stretching ductility and a bending ductility of the shank portion when the latter is clamped in the drilled hole due to the anchor portion.

2. The anchor fastening element as claimed in claim 1, wherein the shank portion has a reduced cross section as compared to that of the threaded portion.

3. The anchor fastening element as claimed in claim 1, wherein the global ductility ranges from 2 to 4.

4. The anchor fastening element as claimed in claim 1, wherein the global ductility is greater than 4.

5. The anchor fastening element as claimed in claim 1, which is formed as an adhesive anchor, wherein the anchor portion can be fastened adhesively in the drilled hole.

6. The anchor fastening element as claimed in claim 1, wherein a cylindrical anchor sleeve is provided, which has a round cross section and spreading segments at the end of the anchor sleeve adjacent the anchor portion, to complete the anchor fastening element into a spreading anchor.

7. The anchor fastening element as claimed in claim 6, wherein the anchor sleeve has a thickened wall in the region of the spreading segments, which at least partially engages the anchor portion, in order to obtain a spreading of the spreading segments during installation of the spreading anchor by a relative axial displacement between the anchor sleeve and the anchor portion.

8. The anchor fastening element as claimed in claim 1, wherein the threaded bolt is made of wrought iron steel which remains unhardened in the region of the shank portion.

9. The anchor fastening element as claimed in claim 1, wherein the threaded bolt is made of a copper alloy which has been hardened in the region of the threaded portion and the anchor portion.

10. The anchor fastening element as claimed in claim 1, wherein the anchor portion is cone-shaped and has a shoulder towards the shank portion, which comprises a material harder than that of the shank portion.

11. An anchor fastening element for fastening an object in a drilled hole of a concrete part as an anchoring base, which is to absorb impact loads such as those occurring during earthquakes in an energy dissipating manner, comprising: a threaded bolt having a threaded portion at a first end, an anchor portion at the other, second end, and a shank portion between the threaded portion and the anchor portion; and a nut to be screwed on the threaded portion; wherein the threaded portion and the anchor portion on the one hand and the shank portion on the other exhibit a different ductility behavior, the threaded portion and the anchor portion having a lower ductility with less plastic deformation capacity, and the shank portion having a higher ductility with higher plastic deformation capacity, and wherein the anchor portion is an anchor body separate from the threaded bolt, which cooperates with a screw thread on the second end of the threaded bolt.

12. A building wall anchor fastening element for absorbing impact overloads, wherein the fastening element comprises: a threaded bolt having a threaded portion at a first end, an anchor portion at a second end, and a shank portion between the threaded portion and the anchor portion, wherein shank and threaded portions are of monolithic construction, and the threaded portion and the anchor portion are harder than the shank portion.

13. The building wall anchor fastening element as claimed in claim 12, wherein the threaded bolt is made of wrought iron steel or a copper alloy.

14. The building wall anchor fastening element as claimed in claim 12, wherein the anchor portion is cone-shaped and has a shoulder towards the shank portion.

15. The building wall anchor fastening element as claimed in claim 12, wherein threaded bolt is of monolithic construction.

16. The building wall anchor fastening element as claimed in claim 12, wherein the anchor portion is an anchor body separate from the threaded bolt, which cooperates with a screw thread on the second end of the threaded bolt.

Description

DESCRIPTION OF THE DRAWINGS

[0025] Embodiments of the present disclosure will now be described with reference to the drawings, wherein:

[0026] FIG. 1 shows a longitudinal section through a spreading anchor in an installed condition;

[0027] FIG. 1a is a detail of FIG. 1;

[0028] FIG. 2 shows a spreading anchor deformed by elongation;

[0029] FIG. 3 shows a spreading anchor deformed by bending; and

[0030] FIG. 4 shows an adhesive anchor.

DETAILED DESCRIPTION

[0031] FIG. 1 shows a spreading anchor installed in a bore 20 of a concrete wall 2 to fix an object to the wall 2, with an anchor plate 3 of the object being shown having a throughbore 30. For this purpose, a nut 4 and a washer 5 is used to press the anchor plate 3 against the wall 2. The spreading anchor comprises an anchor sleeve 10 and a threaded bolt 1. Threaded bolt 1 has several portions, namely a threaded portion 11, a shank or stretching portion 12, and a spreading portion 13. A support portion 14 may be provided for connecting the threaded portion 11 to the shank 12. If good ductility in the transverse direction is important, the support portion 14 is omitted to provide a clearance 22 around the shank portion 12 of the threaded bolt, as illustrated in FIG. 2. The support portion 14 (if present) has an outer diameter corresponding to the inner diameter of the anchor sleeve 10. Compared thereto, the shank or stretching portion 12 has a reduced cross section, which may range from 70 to 90% of the full cross section. Spreading portion 13 is connected with stretching portion 12 through a shoulder 15 and has, except for the shoulder 15, a tapering or conical shape with a base cross section corresponding to the cross section of the bore 20. Anchor sleeve 10 is slotted at its end adjacent to the spreading portion, and the slots 17 (FIG. 1a) may have a triangular shape, but other slot shapes are likewise possible, for example with a circular 20 recess at the bottom of the slot. Due to these slots 17, the lower end of anchor sleeve 10 is divided into individual spreading segments 18, which may be separated from the rest of the anchor sleeve 10 by a bending notch 19. The inner surface of the anchor sleeve 10 may be of a uniformly round cylindrical shape, but it is also possible to provide a wall thickening 18a in the region of the spreading segments 18. The contour of the thickened wall portion at least partially follows the outline of the spreading body 13 and prevents the ends of the spreading segments from digging into the spreading body during spreading of the spreading segments.

[0032] FIG. 2 shows another embodiment of a spreading anchor, in a longitudinally stretched state thereof. Portions corresponding to those of the embodiment of FIG. 1 are designated by the same reference numerals. The illustrated spreading anchor is configured for a drilled hole 20 having an undercut 21. Furthermore, the threaded bolt 1 is formed in two parts, namely by having the spreading portion 13 screwed to the shoulder 15 of threaded bolt 1 by means of a screw neck 16. While the shank portion 12 is made of ductile material, portions 11, 15, 16, 13 have a lower ductility. In contrast to the embodiment of FIG. 1, there is no support portion 14 provided, so that there exists a radial clearance 22 between shank portion 12 and anchor sleeve 10. At the inlet end of clearance 22, a guide ring (not shown) may be provided, which consists of crushable material to allow for lateral displacement of the shank 12, as shown in FIG. 3. The latter shows the spreading anchor of FIG. 2 with the shank portion 12 bent, as it can be caused by impact forces transversely to the longitudinal extent of the anchor.

[0033] FIG. 4 illustrates an adhesive anchor 23, which is connected to a shank 12 of a threaded bolt which serves as the anchor fastening element. Adhesive anchor 23 is fixed in the bore 20 of a concrete wall 2 by means of an adhesive 24. The shape of the adhesive anchor 23 is adapted to this purpose. The remaining portions correspond to those of threaded bolt 1 of FIG. 1 or 2.

[0034] The particularity of the anchor fastening element according to the present disclosure is the use of a material of enhanced ductility for certain portions or regions of the element. A ductile material refers to a material which exhibits elastic characteristics up to a certain load, the yield strength or yield point, and which is plastically deformable when exceeding the yield point up to an ultimate strength or breaking limit. The ductility indicates the ratio between the maximum deformation and the elastic deformation of a material body. In conjunction with the present disclosure it is intended that different portions of the anchor fastening element exhibit a different ductile behavior, either by using two materials of different ductility, or by differently dimensioning or differently treating portions of the respective part so that it behaves like materials of different ductility.

[0035] A material particularly suitable for the threaded bolt 1 is wrought iron steel, i.e. a steel with a low carbon content. By carburization in the region of threaded portion 11 and spreading portion 13, the hardness of the material may be increased and thus the deformability (local ductility) thereof may be reduced, so that a threaded bolt is formed like one made of two materials of different ductility. The shank or stretching portion 12 which is left unhardened has a much higher ductility than threaded portion 11 or spreading portion 13, so that the deformation of the anchor fastening element in the event of an overload substantially occurs only in the shank portion.

[0036] A ductile material likewise suitable for the threaded bolt 1 is a copper alloy such as bronze or brass. With such material, portions of different strengths and thus of different ductility may likewise be obtained by appropriate treatment.

[0037] As for the material of the anchor sleeve 10, especially steel will be considered. Under heavy loads in the longitudinal and transverse directions, the strength thereof will prevent the drilling hole 20 from chipping, so that the deformation energy introduced will substantially become noticeable in the shank.

[0038] If part of the impact energy during an earthquake is to be absorbed by the anchor sleeve, a copper alloy such as bronze or brass will also come into consideration as a material for the anchor sleeve. Copper alloys are very ductile and are 5 therefore able to absorb impact energy by deformation.

[0039] If the risk for chipping of the drilled hole is not very large, perhaps because the wall material consists of very strong concrete, elastomeric viscoplastic plastics will also come into consideration as a material for the anchor sleeve.

[0040] The ductility distribution in the anchor fastening element may be modified. For example, it is possible to provide a transition zone between threaded portion 11 and shank portion 12, in which the material property gradually changes from lower to higher ductility. The transition zone should come to lie in the region of the interface between attached object 3 and concrete wall 2 to reduce the risk for the threaded bolt 1 to shear off in the region of threaded portion 11, i.e. threaded portion 11 should terminate within through-bore 30.

[0041] In case of a so-called undercut anchor which is to be mounted in a drilled hole 20 having an undercut 21 (FIG. 2, 3), the threaded bolt 1 may be extended in the region of stretching portion 12 in terms of thread 16 and may extend into spreading body 13, in order to obtain a displacement of the spreading body 13 relative to threaded bolt 1 and thus also relative to the anchor sleeve 10 by rotating the threaded bolt 1 which may be formed with an Allen key (not shown). This relative displacement serves for spreading the spreading segments 18 in the undercut portion 21 of the drilled hole 20. It will be understood that for this design of an undercut anchor a locally high strength material will be selected for the thread 16 which extends into the spreading body.

[0042] The installation of the spreading anchor depends on whether the anchor is an undercut anchor for undercut drilling holes (2, 3) or a self-undercutting heavy-duty anchor (FIG. 1) which produces a certain undercut by itself during the installation process.

[0043] For a self-undercutting heavy-duty anchor, a round cylindrical drilled hole 20 is provided in an anchoring base, as shown in FIG. 1. The spreading anchor with the anchor sleeve 10 sitting on spreading body 13 is introduced into the drilled hole 20, and a relative displacement is caused between anchor sleeve 10 and threaded bolt 1 such that the spreading segment end 18 of anchor sleeve 10 slides over spreading body 13. For this operation, a setting tool may be used. It is also possible to interpose an auxiliary sleeve and to tap to the anchor sleeve 10 with a hammer to allow the spreading segments 18 to penetrate a bit into the bore wall 20. Then, the anchor plate 3 together with the object to be fastened can be attached to the anchoring base 2 using a washer 5 and a nut 4. Tightening of the threaded bolt 1 causes the spreading segments 18 to further bite into the bore wall 20 and to provide good anchoring of the spreading anchor.

[0044] If the spreading anchor is configured as a heavy-duty anchor for an extraneously undercut hole, the drilled hole 20 is formed in the anchoring base 2 using a special drill which produces an undercut 21 at the blind end into which the spreading segments 18 may be deployed. This is achieved by displacing the anchor sleeve 10 and the threaded bolt 1 relative to each other in such a manner that the spreading segment end 18 of the anchor sleeve 10 is further slid over the spreading body 13, whereby the spreading segments 18 are 14 spread apart and placed in the undercut 21. This is done in basically the same manner as with the self-undercutting heavy-duty anchor. Once the spreading segments 18 have been spread, the threaded bolt 1 may be tightened to press the anchor plate 3, whereby the material located between the spreading segments 18 and the nut 4 is clamped.

[0045] In the event of an earthquake vibrations on buildings will occur that may lead to considerable stresses of the anchor fastening element in the longitudinal or transverse directions. If the fastened object has natural frequencies that correspond to the excitation frequencies of the earthquake, this may lead to an overload of the anchor fastening element. Damping of the vibratory system of fastened object and fastening element will result in a reduction of the overload by detuning the resonance phenomenon. The anchor fastening element according to the present disclosure achieves this by absorbing vibration energy of the earthquake and converting it into deformation 20 energy of the ductile shank of the threaded bolt. Upon occurrence of an overload in the longitudinal direction of the threaded bolt, the shank portion 12 will become elongated as exaggerated at U in FIG. 2, thereby absorbing seismic energy by plastic deformation of the shank 12, and in case of seismic vibrations transversely to the anchor fastening element the shank portion 12 will be shifted by U (FIG. 3), also under absorption of energy from the seismic vibrations. The duration of earthquakes is usually less than one minute, so that the accumulated energy introduced during such an earthquake will not be sufficient to lead to a ductile fracture in shank portion 12.

[0046] If during an earthquake an anchor fastening element has been damaged, it has to be neutralized or replaced. In case of spreading anchor configurations with a screw thread 16 for attaching or shifting the spreading body 13, the threaded bolt 1 may possibly be unscrewed from the sleeve bore of anchor sleeve 10, so that a replacement of the threaded bolt appears possible. In case of configurations with the spreading body 13 fixedly attached to the threaded bolt 1, the end of the threaded bolt protruding from the anchoring base will be cut off, and a new spreading anchor will be installed at an uninjured point of the anchoring base.