Method and device for determining an anchoring force

Abstract

Method for determining an anchoring force (V) at a pressure point (P) of a fastening system, wherein the fastening system comprises a retaining body (110) that can be fixed to a substrate (50) via a fastening means (60) and the fastening means (60) provides a maximum tensile force (Z) on the retaining body (110) fixed by the fastening means (60), comprising the following steps: Determine (S110) a coefficient of friction between the holding body (110) and the substrate (50); Determine (S120) an inclination (α) of a compression strut (D) to the substrate (50), wherein the compression strut (D) defines an effective force direction resulting from the anchorage force (V) and maximum tensile force (Z) and the inclination (α) depends at least on the coefficient of friction; and Determine (S130) the anchoring force (V) from the maximum tensile force (Z) and the inclination (α) of the compression strut (D).

Description

[0001] The present invention relates to a method and a device for determining an anchoring force. In particular, the invention relates to a verification method for fastenings of timber structures to concrete and masonry. background

[0002] Structural engineers often face the challenge of verifying the load-bearing capacity of fixings for beam-shaped supports. For example, consider a horizontally arranged wooden beam supporting roof rafters during an extension (e.g., a carport) to an existing building. The load-bearing capacity can be described by the anchorage force, which defines the maximum force that can act on the attached structure.

[0003] Current methods for determining anchorage force are based on the assumption that the component to be attached is made of metal and rests directly on the substrate without an intermediate layer. In this case, the load that the fastening bears can be determined using leverage. Even if the component to be attached is not made of metal (e.g., when fastening wooden structures), methods that take the effect of the lever arm into account can be used.

[0004] Fig. Figure 5 shows an example of a conventional fastening method where an attachment 80 is not directly fastened to a substrate 50 (e.g., a concrete wall), but rather an anchor bolt 90 is used to fasten the attachment 80 to the exemplary concrete wall 50. In the example shown, the attachment can be made of wood, for instance. As mentioned, the anchoring force V defines the maximum force that can act on the attachment without the anchor bolt 90 being pulled out of the substrate 50. In known methods, this anchoring force V is determined using the leverage and the strength of the exemplary concrete wall 50. Thus, based on the underlying material of the substrate 50, proof of the sufficient anchoring force V for a desired application can be provided.

[0005] Other conventional methods are known for specific connections such as notched joints. Fig. Figure 6 shows an example of a possible notch connection between a concrete wall 50 and a wooden part 70. In the example shown, the notch connection is formed by a notch in the wooden part 70 and a projection in the concrete wall 70, with fastening elements 30 holding the wooden part 70 to the wall 50. Due to the notches, the wooden part 70 cannot move laterally along the wall 50, and movement perpendicular to the wall is prevented by the fastening elements 30. However, such a notch connection is uneconomical to produce but can provide a high anchorage force. DE 101 39 271 A1 discloses a device for anchoring an attachment to a substrate. Other methods are known for determining the anchorage force for pin-shaped metallic fasteners, where the anchorage force is demonstrated by shear. These are wood-to-wood connections or steel-to-wood connections.

[0006] A disadvantage of the known methods is that they are generally very complex and uneconomical. Therefore, there is a need for further verification methods for the stability analysis of anchorage forces. In particular, there is a need for a verification method suitable for concrete-timber connections or masonry-timber connections. Summary

[0007] At least some of the aforementioned problems are solved by a method for determining an anchoring force according to claim 1 and a device according to claim 9. The dependent claims define further advantageous embodiments of the method.

[0008] The present invention relates to a method for determining an anchoring force at a pressure point of a fastening system. The fastening system comprises a retaining body that can be fixed to a substrate by means of a fastener. The fastener provides a maximum tensile force on the retaining body fixed by the fastener. The method comprises the following steps: determining a coefficient of friction between the retaining body and the substrate; determining the inclination of a compression strut to the substrate, wherein the compression strut defines an effective force direction resulting from the anchoring force and the maximum tensile force, and the inclination depends on the coefficient of friction; and determining the anchoring force from the maximum tensile force and the inclination of the compression strut.

[0009] The fastener(s) can include various types of fasteners (screws, bolts, rivets, dowels, etc.) with or without adhesive bonds. As long as the supporting element withstands the load, the anchoring force is simply the force with which the supporting element is subjected. It acts, for example, vertically downwards. Although both forces act in opposite directions, they are equal in magnitude (force = counterforce), and a distinction between these two forces is not always made in the following discussion. In the following, the term anchoring force is used specifically for the force exerted on the supporting element by the support (which rests on the supporting element).

[0010] It is understood that the force does not act on only one point of the object being held. However, the force can be approximated by a point force. This approximation, which will also be used below, significantly simplifies the calculation and often yields satisfactory results.

[0011] According to further examples, determining the anchoring force is based on the following relationship: V=Z / tan α.

[0012] It goes without saying that this relationship can be used directly or indirectly (e.g. by rephrasing it in another form).

[0013] Optionally, determining the inclination of the compression strut involves using a reference table or an approximation formula. The reference table can, for example, refer to at least one substrate (or specify multiple substrates) or to the coefficient of friction. The same applies to the support element or its material. Furthermore, the tensile force can be included as a parameter in the table. Thus, each row / column can refer to a different tensile force or a different material for the substrate and / or the support element. These parameters can be taken into account in the approximation formula so that the inclination can be calculated directly after inserting the corresponding coefficient of friction.

[0014] Due to the vertically applied force, the friction between the support and the substrate will not be constant. This generally complicates the calculation. However, it is possible to use an effective description, which simplifies the determination of the inclination. For this purpose, an effective friction area can be defined such that constant friction acts within it, while friction outside the effective friction area is negligible. The effective friction area can, for example, encompass a region of maximum friction between the support and the substrate and be chosen to achieve the same result. Therefore, determining the inclination optionally includes determining a frictional force between the support and the substrate as a function of an effective friction area and / or the coefficient of friction and / or other parameters.It is understood that the definition of the effective friction area is an approximation, which is ideally chosen so that the associated error lies within a tolerance threshold range.

[0015] Optionally, the fasteners include at least one fastening element (e.g., one or more screws, bolts, etc.). The retaining body includes, for example, a lower edge, and the effective friction surface can extend from the lower edge towards the fastening element. The inclination can then be determined by ensuring that the compression strut points to a center point or centerline (parallel to the substrate) of the effective friction surface.

[0016] The effective friction surface can have a vertical height, and the fasteners can include one or more fasteners. For example, the vertical height might be less than the distance from the bottom edge of the retaining body to the fasteners. The effective friction surface can then be determined using the following formula: A=B*L where B is the width of that part of the holding body that is held by the at least one fastening element. If several fastening elements are formed, B can, for example, represent the average distance between the fastening elements.

[0017] Optionally, the vertical height can be determined using a reference table or an approximation formula and depends on the geometry of the mounting body and the materials of the substrate and the mounting body. The reference table and / or the approximation formula can be determined, for example, through trials / tests.

[0018] This method, or at least parts thereof, can also be implemented or stored in the form of instructions in software or on a computer program product, wherein the stored instructions are capable of executing the steps of the method when the method is running on a processor. Therefore, the present invention also relates to a computer program product with software code (software instructions) stored on it, configured to execute one of the methods described above when the software code is executed by a processing unit. The processing unit can be any type of computer or control unit that includes a suitable microprocessor capable of executing software code.

[0019] The present invention also relates to the processing unit or a device, in particular a data processing device, for determining an anchoring force at a pressure point of a fastening system, wherein the fastening system comprises a retaining body that can be fixed to a substrate by means of a fastening element, and the fastening element provides a maximum tensile force on the retaining body fixed by the fastening element. This device comprises: a module for determining a coefficient of friction between the retaining body and the substrate; a module for determining an inclination of the compression strut to the substrate, wherein the compression strut defines an effective force direction resulting from the anchoring force and the maximum tensile force, and the inclination depends on the coefficient of friction; and a module for determining the anchoring force from the maximum tensile force and the inclination of the compression strut.These modules can be implemented, in particular, as software modules in a computer (or other data processing equipment).

[0020] The present invention is based on the idea of ​​calculating connections between wood and concrete or masonry (or another substrate) under transverse tensile loads, such as brackets, using a frame model. This frame model takes into account boundary conditions of the fastening, such as the geometry of the timber structure, the type of anchoring substrate, the roughness of the surface / contact areas, the use of plastered surfaces, and the type of fastener (e.g., via its friction or bearing surfaces or the applied tensile force). By using material-specific parameters, the results can be transferred to different materials / fasteners. In particular, a different load transfer model is used in conjunction with the attachment (e.g., the support body) than that used in known methods.

[0021] Advantages of exemplary embodiments arise in particular from the fact that better use of the fastening elements becomes possible, since a more precise verification of the anchoring force is enabled. Brief description of the characters

[0022] The embodiments of the present invention are better understood from the following detailed description and the accompanying drawings of the different embodiments, which, however, should not be understood as limiting the disclosure to the specific embodiments, but merely serve for explanation and understanding. Fig. Figure 1 shows a flowchart for a method for determining the anchoring force according to an embodiment of the present invention. Fig. Figure 2 shows a method of fastening a holding body to a substrate and illustrates the determination of the anchoring force according to embodiments of the present invention. Fig. Figure 3 shows the attachment of an example wooden beam to the wall using several fasteners. Fig. 4A, Fig. 4B further illustrates the principle of operation using a wooden beam that is attached to a wall. Fig. Figure 5 shows an attachment of a component to a substrate, the anchoring force of which can be determined using conventional methods. Fig. Figure 6 shows a notched joint between a concrete wall and a wooden part. Detailed description

[0023] Fig. Figure 1 shows a flowchart of a method for determining an anchoring force at a pressure point of a fastening system according to an embodiment of the present invention. The fastening system comprises a retaining body that can be fixed to a substrate (e.g., a concrete wall or masonry) by means of a fastener, wherein the fastener provides a maximum tensile force on the retaining body fixed by the fastener. The method comprises the following steps: - Determine S110 a coefficient of friction between the holding body and the substrate; - Determine S120 of an inclination of a compression strut to the substrate, wherein the compression strut defines an effective force direction resulting from the anchorage force and maximum tensile force, and its inclination depends on the coefficient of friction; and - Determine S130 of the anchoring force from the tensile force and the inclination of the compression strut.

[0024] The compression strut can originate from the point of pressure, or it can originate from a different point. The direction of the compression strut is important because the anchoring force can be determined based on its direction. Therefore, the compression strut can also be defined originating from a different point. The determined anchoring force remains unchanged.

[0025] The compression strut generally assumes a force direction resulting from the geometry of the holding body and the stress distribution between the holding body and the substrate, thus defining the maximum tensile force.

[0026] Fig. Figure 2 shows an exemplary way of attaching the retaining body 110 to the substrate 50, wherein the retaining body 110 is attached to the wall by means of fasteners 60. The retaining body 110 comprises, for example, a wooden beam which is to be attached to the exemplary masonry or concrete wall 50, wherein the Fig. Figure 2 shows a vertical cross-sectional view through the holding body 110 and the substrate 50. The fastening means 60 provide support for the holding body 110 up to a maximum possible tensile force Z.

[0027] Furthermore, friction exists between the retaining body 110 and the substrate 50, which is described by a coefficient of friction. Depending on the coefficient of friction, a compression strut D can therefore be defined when the retaining body 110 is loaded by an anchoring force V. This strut extends towards the wall 50 and intersects it at a point PM at an angle α. This angle α thus defines the inclination of the compression strut to the substrate 50. It is understood that with a (negligible) small friction between the retaining body 110 and the substrate 50, the compression strut D will point almost vertically downwards (in the Fig. 1 in the vertical position), while in the case of very high friction the compression strut D points to a point on the substrate 50 that is closer to the fastening element 60.

[0028] Thus, the compression strut D is defined by the friction between the retaining body 110 and the substrate 50. Specifically, the angle α of the compression strut D to the substrate 50 depends on the coefficient of friction between the retaining body 110 and the substrate 50. For example, depending on the chosen material, surface structure, and geometry of the retaining body 110 (e.g., its height h), the angle of inclination α can be looked up in a reference table and used to determine the compression strut D. Once the compression strut D has been defined, a force parallelogram can be constructed from a known maximum tensile force Z. This parallelogram extends, for example, from the point of compression P, where the tensile force Z points towards the substrate 50 and the anchoring force V points vertically downwards.The anchoring force V can then be derived from the parallelogram for the known compression strut D, for example, using the relationship: V = Z / tan α, where α defines the angle between the compression strut D and the surface of the substrate 50. It is understood that this relationship can also be used in a modified form; for example, the inclination can also be described by a different angle (e.g., relative to the Z-direction). Since the friction between the retaining element 110 and the substrate 50 defines the angle α, the anchoring force V can therefore be determined for a given maximum tensile force Z.

[0029] It is understood that the anchoring force V does not necessarily have to act perpendicularly, but can be inclined towards the surface of the substrate 50. The dashed line illustrates one possibility where the force projects obliquely away from the wall. Accordingly, the direction of the compression strut D also changes, projecting further downwards. Although the following descriptions typically show the case where the anchoring force V runs parallel to the surface of the substrate 50, as mentioned, the invention is not limited to this specific case.

[0030] Fig. Figure 3 shows a top view of the substrate 50 on which an exemplary wooden beam 110 is attached. The exemplary wooden beam 110 extends horizontally and is fastened to the substrate 50 at four fastening points by fasteners 61, 62, 63, 64. The fasteners 61, 62, ... have a mean spacing B. The fasteners 61, 62, 63, 64 can, for example, comprise a screw or dowel connection, with each of the fasteners 61, 62, 63, 64 providing a maximum tensile force Z with which the support body 110 is held to the substrate 50.

[0031] The frictional force between the retaining body 110 and the underlying substrate 50 acts primarily along an effective friction surface AR. It is understood that this is an approximation, as friction acts wherever the retaining body 110 contacts the substrate 50 and also depends on the specific point of contact. However, determining the anchoring force V can be simplified by defining the effective friction surface A, assuming constant friction along this surface. For example, the friction surface A has a height L and extends horizontally over the retaining body 110. The height L can be determined, for instance, from the height h between the fastening element 61, 62, 63 and a lower edge 111 of the retaining body 110. Similarly, the distance of the pressure point P (see Figure 1) is also factored into determining the effective friction surface A. Fig. 1) from the substrate 50. Based on these parameters, the height L of the effective friction area A (or the tensile force) can again be determined using a reference table.

[0032] This means that each fastening element 61, 62, 63, 64 has an effective bearing surface of A=L*B exhibits such that the entire friction surface is given by An=n*A where n is the number of fasteners 60. Using the coefficient of friction between the material of the holding body 110 and the substrate 50, a frictional force can be determined via the applied contact force. The contact force, in turn, is a function of the tensile force Z and the force with which the holding body 110 is vertically loaded. The exact functional relationship can be determined from experiments and recorded using an effective formula or in a corresponding reference table. According to exemplary embodiments, the inclination (e.g., the angle α) of the compression strut D can therefore be determined based on parameters using the effective formula or from the reference table. The parameters include at least one of the following: the coefficient of friction, the geometry of the holding body (e.g., height, width), and the number and location of the fasteners.

[0033] Fig. Figure 4A further illustrates the operating principle using a wooden beam 110 that is attached to a substrate 50. When the wooden beam 110 is attached to the substrate 50, a maximum tensile force Z is exerted via the fasteners 60, and the resulting maximum anchoring force V can be determined according to the method of the present invention.

[0034] The Fig. Figure 4B further shows the force vectors, with the maximum tensile force Z acting towards the substrate 50, and the maximum anchoring force V pointing vertically downwards. Due to the friction between the exemplary wooden beams 110 and the substrate 50, the compression strut D is inclined towards the substrate 50. Fig.Figure 4B shows the diagram for the wooden beam 110 and also the locally acting frictional force FR. The frictional force FR increases towards the lower edge 111 of the wooden beam 110 and reaches a maximum value there. In the opposite direction, the frictional force FR decreases. For example, the frictional force FR may disappear at the position of the fastener 60 or above it, because the wooden beam can move slightly away from the substrate 50 when subjected to the anchoring force V, so that no friction acts there. However, this is not necessarily the case. It is also possible that a resultant frictional force may still act at the position of the fastener 60.

[0035] It is understood that the frictional forces FR acting locally at the various points can be effectively approximated by a constant frictional force on the previously defined friction surface. In this approximation, friction acts only in region A at the lower end of the exemplary wooden beam 110. In this approximation, the compression strut D points, for example, towards a center point of region A. The exact geometry of region A and the point PM towards which the compression strut D points can be determined, for example, through simulations and then expressed by an effective calculation formula or a reference table.

[0036] The method for determining the anchoring force can also be implemented on a computer or data processing unit on which software is installed that is trained to perform the method when the software is run on the computer or data processing unit.

[0037] Exemplary embodiments of the present invention offer the following advantages. A wide range of applications is opened up, as these embodiments make it possible for the first time to determine the maximum possible anchoring forces of wood fixings to concrete or masonry. The model allows for the consideration of various influencing factors. These include, for example: the geometry of the fixing body 110 or the substrate 50, the type of anchoring base (e.g., whether it is masonry or concrete), the roughness of the surface / contact areas (and thus the coefficient of friction), application on plastered surfaces, and the transferability to other fixing devices. This flexibility allows exemplary embodiments of the present invention to be applied to many fixings or to be used directly with minor adjustments.

[0038] The features of the invention disclosed in the description, claims and figures may be essential for the realization of the invention, either individually or in any combination. Reference symbol list 50 subsurface 60 Fasteners 61, 62, Fasteners 70 wooden part with notch 80 Attachment part 90 anchor bolts 110 retaining bodies 111 Lower edge of the holding body D pressure strut P pressure point V (maximum) anchoring force Z (maximum) tensile force α Angle of inclination An effective friction surface B mean distance between the fasteners L Height of the effective friction surface H Distance of fastening elements from the lower edge of the mounting body

Claims

[1] Method for determining an anchoring force (V) at a pressure point (P) of a fastening system, wherein the fastening system comprises a holding body (110) which can be fixed to a substrate (50) via a fastening means (60) and the fastening means (60) provides a maximum tensile force (Z) on the holding body (110) fixed with the fastening means (60), comprising the following steps: Determining (S110) a coefficient of friction between the holding body (110) and the substrate (50); Determining (S120) an inclination (α) of a compression strut (D) to the ground (50), wherein the compression strut (D) defines an effective force direction resulting from the anchoring force (V) and maximum tensile force (Z), and the inclination (α) depends at least on the friction coefficient; and Determine (S130) the anchoring force (V) from the maximum tensile force (Z) and the inclination (α) of the compression strut (D). [2] Method according to claim 1, wherein the determination (S130) of the anchoring force (V) is based on the relationship: V=Z / tan α based. [3] The method of claim 1 or claim 2, wherein determining (S120) the inclination (α) of the compression strut (D) comprises using a lookup table or an approximate formula. [4] Method according to one of the preceding claims, wherein determining (S120) the inclination (α) comprises determining a friction force (FR) between the holding body (110) and the ground (50) as a function of the friction coefficient and an effective friction surface (A), wherein the effective friction surface (A) is defined such that there is a constant friction there and outside the effective friction surface (A) the friction is negligible and comprises an area of maximum friction between the holding body (110) and the base (50). [5] Method according to claim 4, wherein the fastening means (60) comprise at least one fastening element (61, 62, 63, 64), the holding body (110) has a lower edge (111) and the effective friction surface (A) extends from the lower edge (111) towards the fastening element (61, 62, 63, 64), and wherein the determination of the inclination (α) is carried out such that the pressure strut (D) points to a center point or center line (M) of the effective friction surface (A). [6] Method according to claim 4 or claim 5, wherein the friction surface (A) has a vertical height (L) and the fastening means (60) comprises at least one fastening element (61, 62, 63, 64) and the determination of the effective friction surface (A) is given by the following formula: A=B*L, wherein B is a width of a part of the holding body (110) held by the at least one fastening element (62). [7] Method according to claim 6, wherein the vertical height (L) can be determined by a look-up table or an approximate formula and depends on a geometry of the holding body (110) and the materials of the substrate (50) and the holding body (110). [8] A computer program product having software stored thereon which is adapted to carry out the method according to any one of claims 1 to 7 when the software is executed on a data processing unit. [9] Device, in particular data processing device, configured to determine an anchoring force (V) at a pressure point (P) of a fastening system, wherein the fastening system comprises a holding body (110) which can be fixed to a substrate (50) via a fastening means (60), and the fastening means (60) provides a maximum tensile force (Z) on the holding body (110) fixed by the fastening means (60), having the following features: Module configured to determine (210) a coefficient of friction between the holding body (110) and the substrate (50); Module configured to determine (220) an inclination (α) of a compression strut (D) to the ground (50), wherein the compression strut (D) defines an effective force direction resulting from the anchoring force (V) and maximum tensile force (Z), and the inclination (α) depends at least on the friction coefficient; and Module configured to determine (230) the anchoring force (V) from the maximum tensile force (Z) and the inclination (α) of the compression strut (D).

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