A method and apparatus for pre-tensioning a bolt that joins two parts, each end of the bolt being threaded into a respective cavity of the two parts. According to one embodiment, the bolt including a double wedge pre-tensioning element, a washer disposed at each side of the double wedge and clamping elements fastening the wedges once the desired preloading has been attained. The bolt is pre-tensioned with a tensioning tool which acts on the pre-tensioning element, reducing a distance between the wedges while increasing the distance between the two parts to be joined and reducing a distance between the outer facing surfaces of the wedges and washers. The control system measures at least one of the distances described, with the tensioning tool acting in accordance with the measured distance.

A pressure sensing device may include a body configured to distribute a load applied between first and second parts positioned one against the other, and a pressure sensor carried by the body. The pressure sensor may include a support body, and an IC die mounted with the support body and defining a cavity. The IC die may include pressure sensing circuitry responsive to bending associated with the cavity, and an IC interface coupled to the pressure sensing circuitry.

An error of an axial force detection is reduced by tensioning a bolt with a tensioning device engaged with a part of the bolt, different from a shaft portion of the bolt. A tensioning device is configured to apply upward tension to a bolt fastened to a fastened member H, and fitted with a washer. A first male thread portion is formed on an outer circumferential surface of the washer. The tensioning device includes a connection member having a first female thread portion to be engaged with the first male thread portion, a tensioning mechanism for tensioning the connection member in a state where the first male thread portion is engaged with the first female thread portion, and a tension bearer which is disposed around an outer circumference of the connection member, and bears a reaction force applied from the fastened member H in tensioning performed by the tensioning mechanism.

A method, apparatus, and system to quantify tension forces of the anchor bolts for, e.g., SLTS support structures. A sensing assembly comprising one or more washers is installed along an anchor bolt. The sensing assembly comprises two spaced-apart surfaces between which a capacitance can be measured if electrical potential is created between the surfaces. The capacitance between the surfaces can be calibrated to bolt tension based on the relative distance between the surfaces. An RFRD circuit is connected to the two surfaces. An RF interrogation signal can supply the electrical potential and allow a reading of the responsive capacitance between surfaces to convert the capacitance reading into a bolt tension. Additionally, the introduction of the battery-free RFRD allows data to be acquired wirelessly from a distance, enabling an entirely new method of inspection. With minimum additional hardware cost, it provides a cost-effective way to replace traditional bolt installation and inspection methods.

In a number of embodiment the washers of this invention have been provided with the narrowing central hole wherein the washer is being compressed during tightening thereby gripping the bolt and preventing its further turning whereas the nut and the washer are immobilized relative to each other. In another embodiments when the washer is compressed, wedges and preventing its further turning and thus preventing any increase in tightening level. Stoppers are also provided which are put on top of the embodiments with a nut having cuts along parts of its length in combination either with a flat or cup washer for compressing the nut radially and thus gripping the bolt at a predetermined axial load/torque level, as well as a nut having a cut through the middle and two footers which flexes when acted upon by axial load of predetermined level and reaction forces from the two footers gripping the bolt

A monitoring system includes a fastener. A sensor is coupled to the fastener. A circuit board is electrically coupled to the sensor. An antenna electrically coupled to the circuit board.

The present invention provides an elastic washer structure and a fastener, including: an elastic washer (1) and one or more tongues (2), where the elastic washer (1) is a sheet object with an inner hole (3), one surface of the elastic washer (1) is a convex surface, the other surface is a concave surface, a tongue (2) is disposed towards a side of the convex surface on an outer edge of the elastic washer, an angle between the tongue (2) and a surface (5) on which the outer edge of the elastic washer is located is a first angle (6), and when the convex surface of the elastic washer bears pressure, there is a negative correlation between the first angle (6) and the pressure borne by the elastic washer.

A direct tension indicating (DTI) washer. The DTI washer has an annular body and one or more U-shaped horseshoe protuberances. The annular body includes a central hole, a circumference, an outer edge, a first face, and a second face opposite from the first face. The horseshoe protuberances each have a height, an apex closest to the central hole, and an opening directed toward the outer edge. The horseshoe protuberances are integral with the annular body and struck and partially sheared from the annular body to project from the first face of the annular body and leave one or more corresponding indentations in the second face of the annular body. The horseshoe protuberances may be radially offset from their corresponding indentations. An indicating material is initially encapsulated and contained within the area on the first face defined by each of the horseshoe protuberances.

A fastening device may include a first member configured for forceful engagement with a second member. The first member may include a sensor configured to emit at least a first photo-luminescent signal to a detector when at least a predetermined first torque level is applied to the first member when the first and second members are engaged.

An error of an axial force detection is reduced by tensioning a bolt with a tensioning device engaged with a part of the bolt, different from a shaft portion of the bolt. A tensioning device is configured to apply upward tension to a bolt fastened to a fastened member H, and fitted with a washer. A first male thread portion is formed on an outer circumferential surface of the washer. The tensioning device includes a connection member having a first female thread portion to be engaged with the first male thread portion, a tensioning mechanism for tensioning the connection member in a state where the first male thread portion is engaged with the first female thread portion, and a tension bearer which is disposed around an outer circumference of the connection member, and bears a reaction force applied from the fastened member H in tensioning performed by the tensioning mechanism.