JP2651378B2 - Load measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a load measuring device used for measuring a vibrating force applied to a specimen in an axial load vibration test device.

[Conventional technology]

FIG. 5 shows a side view of an axial load vibration test device and a conventional load measuring device provided in the device. 1 is a fixed wall surface, 2 is a fixed floor surface, and 3 is a specimen attached to the fixed wall surface 1. 4 is a reaction frame mounted on the fixed floor, 5 is an axial force cylinder for applying an axial force to the specimen, 6 is an accumulator for operating the coaxial force cylinder, and 7 is a horizontal direction of the coaxial force cylinder. A horizontal slide bearing 8 for allowing free movement is provided on the axial force cylinder, has a horizontal axis perpendicular to the sliding direction of the horizontal slide bearing, and is pushed forward by the air pressure of the accumulator. A load cell mounted coaxially at the front end of the rod-shaped movable part to be mounted; 9, a spherical joint mounted coaxially at the end of the load cell; and 10, a vertical slide coaxially mounted at the end of the spherical joint. The bearings are denoted by reference numerals 4 to 10 and constitute the axial force loading device. 11 is a horizontal excitation point on the specimen to be excited by a horizontal excitation device installed separately from the axial force loading device,
12 is a strain gauge.

The device with the above configuration is a simulated axial load vibration test device that assumes a case where a horizontal vibration force such as an earthquake is applied to the specimen under an axial load such as its own weight of the upper structure. The attitude of the specimen and the direction of the axial force loading are obtained by rotating the actual attitude or direction by 90 degrees.
Therefore, the fixed wall surface 1 in the present device simulates a floor surface in an actual case. In this apparatus, the specimen undergoes horizontal, vertical, and axial displacements, and the end face of the specimen in contact with the axial force loading device undergoes displacement and inclination. However, the horizontal slide bearing 7, the spherical joint 9, the vertical Due to the action of the directional slide bearing 10 and the accumulator 6, the movable portion of the axial force loading device always follows the deformation and inclination of the specimen to simulate the axial force due to its own weight of the upper structure.
The same load is applied.

In the above-described apparatus, the friction between the spherical joint 9 and the horizontal slide bearing 7 generates a reaction force in the horizontal vibration direction, acts to give an error to the measured value of the horizontal vibration force, and acts on the specimen. On the other hand, a moment which does not normally exist is added, and the evaluation accuracy is reduced. Conventionally, these values were calculated to correct the measured value of the horizontal excitation force.

The spherical joint comprises a spherical member, one connecting member for holding the spherical member, a concave spherical member for contacting the spherical member, and the other connecting member for holding the spherical member. This constitutes a moving spherical bearing. The frictional force generated in the spherical sliding portion of the spherical bearing of the spherical joint acts as a frictional moment on the center of the spherical member, and a bending moment that does not normally exist to prevent mutual rotation of the spherical sliding portion. Become.

[Problems to be solved by the invention]

During the seismic test, the specimen is subjected to horizontal excitation at the same time as it is loaded with axial force. As a result, the specimen moves by pulling the axial load device itself. The frictional drag generated in the horizontal slide bearing when the axial force loading device moves causes a horizontal excitation force measurement error. Further, at this time, a bending moment which occurs in the spherical joint and does not exist in the actual case is added to the test sample, which causes an error. Therefore, if these values can be known, the force applied to the specimen can be accurately corrected and evaluated. However, conventionally, there has been no measurement means for this.

The present invention seeks to improve the accuracy of the measurement result by calculating the horizontal shear force and the bending moment that cause the above-described error based on the measurement result.

Means for Solving the Problems The present invention has solved the above-mentioned problems, and has a reaction frame fixed to a fixed floor surface and changing the posture of the reaction frame via a horizontal slide bearing. An axial force cylinder held so as to slide horizontally, and a rod-shaped movable portion provided in the coaxial force cylinder and having a horizontal axis perpendicular to the sliding direction of the horizontal slide bearing and pushed forward by air pressure. A load cell having a cylindrical portion to which a strain gauge is attached and one end of which is coaxially connected to the front end of the rod-shaped movable portion; and a spherical joint whose one end is coaxially connected to the other end of the load cell. An axial force loading device comprising a vertical slide bearing having one end coaxially connected to the other end of the spherical joint and the other end connected to the specimen, and a coaxial force loading device; Is a separately provided horizontal vibrating device, the free end of the specimen having one end fixed to a fixed wall surface and the other end being a free end such that its main body is coaxial with the axis of the rod-shaped movable portion. Attaching the tip of the axial force loading device to apply a load in the axial direction to the specimen, and connecting the horizontal vibration device near the free end of the specimen so as to be orthogonal to the axis of the specimen. In addition, in the axial load vibration test device that tests the vibration strength etc. of the specimen in the axial loading state by applying a horizontal excitation force, the shear force applied to the specimen and the bending moment applied to the fixed part of the specimen are measured. A load measuring device used for measurement, corresponding to one position in the axial direction of the cylindrical portion on the surface of the cylindrical portion of the load cell, where the surface of the cylindrical portion intersects a horizontal plane passing through the axis of the load cell. A pair of strain gauges provided and Two sets of strain gauges in combination with another pair of strain gauges provided corresponding to another position in the axial direction, and bending strains at the respective positions during the above-described excitation from the two sets of strain gauges. And the frictional resistance that occurs on the sliding surface of the horizontal slide bearing and the friction that occurs on the spherical bearing portion of the spherical joint that result in a measurement error from the respective bending strain and the value specific to the test apparatus. Calculate the true value of the shearing force applied to the specimen and the bending moment applied to the specimen fixing part using the means for calculating the moment and the calculation result and the axial force and horizontal excitation force set by the tester on the device. And a load measuring device for an axial load vibration test device.

[Action]

The moment and the shear force are calculated based on the bending strain obtained from the two sets of strain gauges attached to the load cell to improve the accuracy of the load measurement. Therefore, errors related to the frictional drag for moving the axial force loading device or the moment that does not normally exist, which occur in the prior art, are eliminated.

〔Example〕

FIG. 1 shows a side view of an axial force loading vibration test device and an embodiment of a load measuring device of the present invention provided in the device. The portions denoted by reference numerals 1 to 12 have the same functions as those of the prior art, and thus the description thereof will be omitted. 13 is a calculator. In this embodiment, four strain gauges 12 are provided.

FIG. 2 is an enlarged horizontal sectional view of a main part of the load measuring device of the embodiment. Reference numerals 8, 12, and 13 are the same as those described in FIG. 14 is a strain gauge. In this apparatus, two sets of a pair of strain gauges 14 at the same position in the axial direction of the load cell on the surface of the load cell which intersects a horizontal plane extending in the direction of the exciting force passing through the axis of the load cell 8 are attached to the surface of the load cell. It is. Therefore, a total of four strain gauges 14 are attached.
The bending strains λ ₁ and λ ₂ at the respective positions of the two sets of strain gauges are detected by the strain gauge 12, and the bending strains are processed by the computer 13 to calculate the shearing force f ₂ and the bending moment M _μ . It is calculated.

The principle of detecting the shearing force and the bending moment by the above-described device will be described with reference to FIGS. Third
FIG. 4 is a plan view in which a part of the specimen is modeled, and FIG. 4 is a plan view in which a part of the axial load device is modeled.

 In FIG. 3, the following equation holds.

_{f 1 = F-f 2 ......} (1) M S + W · x = F · a- (M μ + f 2 · l 1) ...... (2) However, F: a horizontal exciting force (tester device Set value; known number).

W: Axial force (value set by the tester on the device; known number).

f ₁ : The true value of the shear force applied to the specimen (value to be obtained).

f ₂ : frictional resistance of the slide bearing, etc. (error of shear force applied to the specimen; unknown in the above equation, equation (5)
(Value determined by (6)).

Ms: True value of bending moment applied to the fixed part of the specimen (value to be obtained).

m _μ : Friction moment of spherical bearing (error of bending moment applied to fixed part of specimen; unknown in the above equation,
(Values obtained by Expressions (5) and (6) described later).

a: The distance between the fixed wall surface 1 and the horizontal excitation point 11 (a value obtained by measurement when setting a specimen; a known number).

l ₁ : distance between the fixed wall surface 1 and the spherical joint 9 (value obtained by measurement when setting a specimen; known number).

x: Displacement of spherical joint (value obtained by measurement;
Known number).

In the above description of the symbol, “true value” is provided in the present apparatus. It means the value of the moment and the shear force after being corrected through the means for calculating the moment and the shear force due to the friction causing the error.

 On the other hand, the following equation holds in FIG.

_{λ 1 · E · Z = f} 2 · x 1 -M μ ...... (3) λ 2 · E · Z = f 2 · x 2 -M μ ...... (4) provided that x ₁ and x _2: spherical Jiyointo Distance of strain gauge.

λ ₁ and λ ₂ : bending strain at the position of the strain gauge.

E: longitudinal modulus of load cell.

Z: Section modulus of the load cell.

λ ₁ · E · Z and x ₂ · E · Z: Moment experienced by the load cell at the position of the strain gauge.

In equations (3) and (4), f ₂ and M _μ are unknown, λ
₁ and λ ₂ are measurable, x ₁ and x ₂ are numerical values derived from the layout, and E and Z are values unique to the material. Becomes

M _μ and f ₂ obtained by the equations (5) and (6) are calculated by the equation (1),
Substituting into (2), it is possible to know the true value f ₁ of the shearing force applied to the true value Ms and specimen bending moment applied to the fixing portion of the specimen by the lateral pressing force F, Yotsute thereto The accuracy of the test can be improved.

〔The invention's effect〕

In the load measuring device of the present invention, the shear force and the bending moment are calculated by applying the information from the two sets of strain gauges attached to the load cell to the calculating means,
The accuracy of the measurement result can be improved.

[Brief description of the drawings]

FIG. 1 is a side view of one embodiment of the present invention, FIG. 2 is a partially enlarged view of the above embodiment, FIGS. 3 and 4 are explanatory diagrams of calculation formulas of the above embodiment, and FIG. It is a side view. 1 fixed wall surface 2 fixed floor surface 3 specimen 4
... Reaction force frame, 5 ... Axial force cylinder, 6 ... Accumulator, 7 ... Horizontal slide bearing, 8 ... Load cell, 9 ... Spherical joint, 10 ... Vertical slide bearing, 11 ... Horizontal vibration Point, 12… Strain gauge, 13… Calculator, 14… Strain gauge.

Claims (1)

(57) [Claims] 1. A coaxial force, comprising: a reaction frame fixed to a fixed floor surface; an axial force cylinder held by the reaction force frame via a horizontal slide bearing so as to slide horizontally without changing posture; A rod-shaped movable portion provided on the cylinder and having a horizontal axis perpendicular to the sliding direction of the horizontal slide bearing and pushed forward by air pressure, and a cylindrical portion to which a strain gauge is attached and one end of which is the rod-shaped movable portion A load cell coaxially connected to the front end of the portion, a spherical joint whose one end is coaxially connected to the other end of the load cell,
An axial force loading device having a vertical slide bearing having one end coaxially connected to the other end of the spherical joint and the other end connected to the specimen, and separately from the coaxial force loading device. A horizontal vibration device is provided, one end of which is fixed to a fixed wall surface so that the main body thereof is coaxial with the axis of the rod-shaped movable portion, and the other end is a free end. Connect the tip of the axial force loading device to apply an axial load to the specimen, and connect the horizontal vibrating device near the free end of the specimen to connect it perpendicularly and horizontally to the axis of the specimen. For the measurement of the shearing force applied to the specimen and the bending moment applied to the fixed part of the specimen, an axial force applied vibration test device that tests the vibration strength etc. of the specimen in the axial loading state by applying a strong excitation force The load measuring device used, wherein A pair of strain gauges provided at the surface of the cylindrical portion where the surface of the cylindrical portion of the load cell intersects with the horizontal plane passing through the axis of the load cell at one position in the axial direction of the cylindrical portion, and Two sets of strain gauges are combined with another pair of strain gauges provided corresponding to the other position, and the bending strain at each position during the above-described excitation is detected from the two sets of strain gauges. The strain gauge, the frictional resistance generated on the sliding surface of the horizontal slide bearing and the frictional moment generated on the spherical bearing portion of the spherical joint, which are measurement errors from the respective bending strains and the values specific to the test apparatus, are measured. Means for calculation and the true value of the shear force applied to the specimen and the bending moment applied to the specimen fixing part using the axial direction and the horizontal excitation force set by the tester on the calculation result and the tester Load measuring device of the axial force loading vibration test apparatus characterized by comprising a means for output.