DE3108802A1 - Device for anchoring a tensioning bar and for transferring the anchor force to the concrete - Google Patents

Abstract

The invention relates to a single-part anchor body for tensioning-force transfer between threaded tensioning bars and concrete. The anchor body represented in the drawing comprises a threaded steel sleeve (1) in the centre of a cone shell (2) which opens towards the supporting surface (1). In the standing region (3), the cone shell (2) is reinforced annularly. Known single-part anchor bodies comprise thick steel plates with central threaded bore. They are sensitive with respect to thread tolerances, and, in particular on the first load-bearing thread turns, overloading and carrying-force losses occur. In order to achieve a uniform concrete-surface compressor stress, a large, uneconomical thickness is required. These disadvantages are avoided according to the invention in that a threaded sleeve is supported by a cone shell only in the upper third of its height. In the sleeve region subjected to tensile loading, there is a balanced force transfer between sleeve thread and bar thread, and, in the upper sleeve region subjected to compressive loading, the bar is clamped and this reduces sensitivity to tolerances. In the same way as high permissible part-surface compressor stresses on the standing ring, pure tensile and compressive loadings in the anchor-body elements result in savings in materials. <IMAGE>

Description

The invention relates to a device for

anchoring a threaded tie rod and for transmission the anchor force on the concrete in prestressed concrete construction, consisting of a one-piece, screwed like a nut onto the tie rod, at part of its height with a Steel anchor body with internal thread.

One-piece nut-like anchor body for anchoring tension rods with a thread and for transferring the anchor force to the concrete are known.

They usually consist of a steel plate with a central bore and Inner thread.

The anchor force acting on the internal thread is generated by the steel plate transferred to a sufficiently large concrete pressure surface. To some extent evenly Achieving concrete pressures in the transfer area is a relative one thick steel plate required to keep bending deformations small.

With such plate-shaped anchor bodies there is the problem that an even loading of the tie rod in the thread area is not possible is.

Overstressing occurs, especially of the first load-bearing thread turn, on, because the anchor plate in the direction of the thickness of the expansion of the tie rod in the area unable to follow the power transmission.

This overstressing reduces the fatigue strength of the The tie rod at the anchorage drops considerably below the value specified in the approval regulations is required for tendons in prestressed concrete construction.

Attempts have therefore already been made to fix the anchor plate in the area of the internal thread to be provided with a concrete-side protruding collar in order to make the first load-bearing To relieve the tension of the tie rod.

Since the collar protruding over the plate, however, by the surrounding it Concrete is affected by the elongation of the plate in the direction of the rod, also as a result Plate bending Widening of the thread hole in the area of the first load-bearing thread turns occur that lead to horizontal relative displacements in the thread between rod and Lead anchor plate, the fatigue strength of the anchorage remains strong here impaired. An improvement in fatigue strength in the anchoring area and as even as possible a distribution of the anchor force on the supporting Concrete can therefore be used in the plate-like forms of construction that have become known up to now one-piece anchor body can only be achieved with relatively thick dimensions. the Anchor bodies are therefore very heavy and especially with larger anchor forces unwieldy, which is economically unfavorable.

The object of the invention is to provide a screwable on a tie rod, one-piece anchor body the best possible form for the transfer the bar force on the concrete, i.e. it should have the highest possible fatigue strength at the transition of the force from the rod to the anchor body and the force should be as evenly as possible from the anchor head to the right-angled to the Concrete support surface running along the rod axis can be transferred, whereby for the force distribution the most favorable possible utilization of the anchor body material and thus a lower one Material consumption and a correspondingly low weight should be achieved.

The solution to the problem is the formation of the anchor body in the form of a conical shell 2, which extends towards the concrete support surface 7 at an angle of about 450 opens. The edge of the anchor body resting on the concrete support surface is reinforced by a strong ring 3. At the tapered edge of the conical bowl a sleeve 1 with an internal thread corresponding to the rod thread is attached, the sleeve protruding beyond the thickness of the conical shell 2 on one or both sides.

With this form of the anchor body, ideal conditions result for the transmission of the force from the tie rod to the concrete.

The anchor body forms a rotationally symmetrical support system, which from a pressure ring (sleeve), a pull ring (reinforced shell edge) and the two rings connecting one another, lying in the outer surface of the conical shell oblique struts is formed. All parts of the support system are only axially on Push or pull stressed. So it occurs when the bar force is transmitted hardly any bending stresses on the concrete, so that full utilization of the cross-sections is given at every point. (In contrast to bending stress).

With a cone inclination of about 450, the cheapest ones continue to occur Relationships between the size of the force and the material volume of the individual support members, see above that the material expenditure for the anchor body is to a minimum.

The outer surface of the cone can be distributed over the circumference, radial slots are interrupted without significantly affecting the load-bearing capacity.

The sleeve attached to the top of the conical shell and acting as a pressure ring ensures an even introduction of the force from the rod to the anchor body, since the sleeve can largely follow the elongation of the rod, whereby a Overstressing of the first load-bearing threads of the tie rod is avoided.

In addition, the sleeve, which acts as a pressure ring, is still pressed together radially. Depending on the thread play, it can be supported on the tie rod. A horizontal one Relative displacement between the thread teeth of the sleeve and tie rod is thus largely reduced or even switched off, whereby the permanent threshold strength is increased significantly in the thread area.

Appropriately, the approach of the conical shell is approximately in the upper third placed at the height of the sleeve. The sleeve is thus further down over the cone shell before than up. The sleeve acts like a collar or collar nut, their favorable behavior in the case of permanent threshold loads as a result of the constant force transfer is known.

The constant transfer of force from the tie rod to the sleeve can be known in a Way can be improved by the fact that the outer diameter of the downwards about the Cone shell protruding part of the sleeve to the lower edge of the sleeve decreases towards.

The part of the sleeve protruding above the conical shell can seen on the outside polygonal, for example hexagonal, are delimited so that a key for turning the anchor body during the tensioning process is set here can be.

In Fig. 1 and 2, the inventive embodiment of the anchor body shown.

Fig. 1 shows a section through the rotationally symmetrical anchor body up to the axis of symmetry (rod axis), Fig. 2 represents the anchor body accordingly up to half in the view.

Through the anchor body, the bar force 6 is perpendicular to it Transfer running concrete support surface 7. For this purpose the with a Inner thread 9 provided sleeve 1, the outer diameter of which is constant or downwards can be decreasing.

The sleeve 1 is approximately in the upper third of its height through the cone shell 2 supported. The bevels that develop in the conical shell at about 450 and compression struts running radially in plan are supported against the tension ring 3, the lower surface of which rests on the concrete 7. The anchor force is even here distributed on the annular pressure transmission surface, because of the favorable Area ratio, relatively high concrete pressures are permissible.

With the embodiment of the one-piece anchor body according to the invention an optimal material utilization is possible. The opposite of the known, plate-like and anchor bodies subject to bending stressed by finer training in the manufacturing costs are no longer disadvantageous, since the Manufacturing takes place by forging or pressing, whereby the shape does not play an essential role more plays.

Claims (5)

DEVICE FOR ANCHORING A TENSION ROD AND TRANSMISSION THE ANCHOR FORCE ON THE CONCRETE PATENTANS 1. Device for anchoring a threaded tie rod and to transfer the anchor force a support surface made of concrete at right angles to the rod axis from a one-piece, nut-like screwed onto the tie rod, to one Part of its height with an internal thread, steel anchor body, thereby characterized in that the anchor body consists of a conical shell (2), which is opens towards the support surface (7) at an angle of approximately 450 and in the contact area with a ring-like reinforcement that also forms the concrete bearing surface (3) is provided and that at the upper, tapered end of the cone shell one with a Internal thread (9) provided over the thickness of the conical shell on one or both sides protruding sleeve (1) is attached. 2. Device for anchoring according to claim 1, characterized in that that the approach of the conical shell (2) on the sleeve (1) approximately in the upper third of the Sleeve height is. 3. Claim as 1. and / or 2., characterized in that the conical shell (2) has holes (4) or narrow slots (5) distributed on the circumference. 4. Apparatus as in claim 1 to 3, characterized in that the part of the sleeve (1) protruding upwards over the conical shell (2) on the outside of the The floor plan is bounded by a polygon (8). 5. Apparatus according to claim 1 to 4, characterized in that the outside diameter of the sleeve (1) is variable in height, e.g. according to the the lower edge of the sleeve decreases.