It is an object of the invention to provide a measuring device which, by virtue of its construction and function, provides the prerequisite for an invariable zero reading and simultaneously affords a possibility of controlling the anchor strength at small expense at any time desired. All of these systems, however, have the shortcoming that the forces are determined indirectly, i.e., by way of deforming or frequency measurement, and that the initial value (zero reading) of the measurement has to be kept constant for the duration of the measurement, i.e., as the case may be, over a period of years. Finally also the forces present in the anchor can be determined by means of the frequency of a tensioned oscillating music wire. Other measuring devices operate with pressure springs between the anchoring body and the anchoring device in this connection the magnitude of the compression of these springs is a measure for the existing anchoring forces. This method, however, is cumbersome and expensive, since a tensioning press must be set up for each measurement because it is difficult to reliably determine the point of time at which balance is established, i.e., when the force to be measured is transferred from the anchoring device to the hydraulic system. The pressure in the hydraulic system of the press that is being measured at any moment in which the anchoring body, i.e., for example, a threaded nut, can be loosened from the anchoring device, is then a measure for the force or strength in the anchor. By introducing a pressure agent in the pressure space of the press, balance with the force to be measured is then established. The simplest manner of measuring the forces in a prestressed anchor consists in mounting a hydraulic tension press such as is utilized for the tensioning of tensioning elements in the prestressed concrete construction. A particular problem in this connection is to so construct these measuring devices that they are non-sensitive against temperature, moisture, soiling and corrosion and that, above all, the measured quantity of the zero reading to which the device has been set does not change. In order to make it possible to examine the effectiveness of ground and rock anchors, measuring means or devices are necessary which over a period of years can reliably measure the forces that are present in the anchor. The invention relates to a device for measuring the anchoring forces absorbed in prestressed or rock anchors by way of anchoring devices, such as, for example, anchoring plates. Device in accordance with claim 1, where said means for applying pressure includes a closed duct in communication with said cushion and that said duct is adapted to be connected to a container filled with a pressure agent. Device in accordance with claim 3 including adjusting means for said bolt on said strap.ĥ. Device in accordance with claim 2 including a stirrup mounted on said anchoring head, a strap connected to said anchoring element, and a bolt extending between said stirrup and said switch.Ĥ. Device in accordance with claim 1, where said measuring device includes an electric switch adapted to be connected to an indicating device.ģ.
Device for indicating a change in the anchoring forces absorbed by way of anchoring means such as anchor plates in prestressed ground or rock anchors comprising an anchoring element such as a plate, an outer plate defining an abutment member disposed proximate said element, an annular pressure cushion that is flat in the condition of rest, disposed intermediate said element and said outer plate and an anchoring head having a nut proximate said outer plate in position to transfer forces directly to said outer plate, means for applying pressure to said cushion, and a measuring device arranged between said anchoring element and said outer plate for determining the start of the movement of said outer plate as pressure is applied to said cushion.Ģ.
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