JP2023106945A - Pull-out testing device - Google Patents

Abstract

A pull-out test apparatus capable of simultaneously applying a uniform tensile load to a plurality of bars protruding from a concrete structure is provided. A pull-out test apparatus (1) includes a pair of channel steels (30) extending along a row of reinforcing bars (90) on both sides of the row of a plurality of reinforcing bars (90), spaced apart from each other and fixed to each other, and a pair of channel steels (30). a plurality of pairs of wedge-shaped jigs 50 that sandwich the reinforcing bars 90 in the sandwiching direction from the pair of channel steels 30 to the reinforcing bars 90, and whose thickness in the sandwiching direction gradually decreases as the concrete structure 99 is approached; Between the pair of channel steels 30, the reinforcing bars 90 and the pair of wedge-shaped jigs 50 are sandwiched in the sandwiching direction. 40 , and a hydraulic jack 10 that applies a load to the pair of channel steels 30 in a direction that separates the pair of channel steels 30 from the concrete structure 99 . [Selection drawing] Fig. 2

Description

The present invention relates to a pull-out test apparatus.

In order to design the reinforcing bars embedded in the concrete structure so that they cannot be pulled out from the concrete structure, it is necessary to confirm the pull-out strength of the reinforcing bars in advance. Therefore, for example, the pull-out test apparatus disclosed in Patent Documents 1 and 2 is used to perform the pull-out test of the reinforcing bar. The pull-out test apparatuses disclosed in Patent Documents 1 and 2 apply a tensile load to a single reinforcing bar.

Japanese Patent No. 3048994 Japanese Patent No. 5464581

By the way, usually, a plurality of reinforcing bars are embedded in a concrete structure. Close spacing between rebars creates a clump effect. The group effect means that a plurality of reinforcing bars affect each other through a concrete structure, and these reinforcing bars act as one group.

In order to investigate the influence of the group effect of multiple rebars, it is necessary that these rebars are equally tensile-loaded at the same time. However, the pull-out test apparatuses of Patent Literatures 1 and 2 cannot simultaneously apply a uniform tensile load to a plurality of reinforcing bars.

Therefore, the present invention has been made in view of the above circumstances, and provides a pull-out test apparatus capable of simultaneously applying a uniform tensile load to a plurality of bars such as reinforcing bars protruding from a concrete structure. for the purpose.

A pull-out test apparatus for solving the above problems is embedded in a concrete structure and along both sides of a row of a plurality of bars arranged so as to protrude from the concrete structure. between a pair of long members spaced apart from each other and fixed to each other and the pair of long members extending in the direction of holding the pair of long members to the bar, a plurality of pairs of wedge-shaped jigs whose thickness in the sandwiching direction gradually decreases as the concrete structure is approached; a plurality of pairs of wedge-shaped bases that sandwich the tools, and whose thickness in the sandwiching direction gradually decreases as the distance from the concrete structure increases; and a load application unit that applies the load to the elongated material.

According to the above, the plurality of pairs of wedge-shaped jigs sandwich the plurality of reinforcing bars between the pair of elongated members, and the plurality of pairs of wedge-shaped foundations form the plurality of pairs of wedges between the pair of elongated members. Since the thickness of the wedge-shaped base in the clamping direction gradually decreases as it separates from the concrete structure, and the thickness of the wedge-shaped jig in the clamping direction gradually decreases as it approaches the concrete structure, the load applying portion When a load is applied to a pair of elongated members, the clamping force with which the pair of wedge-shaped jigs sandwiches the respective bars increases. Therefore, no slippage occurs between the wedge-shaped jig and the bar, and the applied load of the load applying portion simultaneously acts on the plurality of bars as a uniform tensile load. Therefore, it is possible to investigate the influence of the group effect of a plurality of bars on the pull-out strength of these bars.

According to the present invention, the applied load of the load applying portion simultaneously acts on a plurality of bars as a uniform tensile load, and the effect of the group effect of the plurality of bars on the pull-out strength of these bars can be investigated.

It is a perspective view of a pull-out test apparatus. It is a side view of a pull-out test apparatus. 3 is a cross-sectional view showing the III-III plane shown in FIG. 2 as viewed in the direction of the arrow; FIG. FIG. 3 is a sectional view showing the plane IV-IV shown in FIG. 2 as viewed in the direction of the arrow; FIG. 4 is a perspective view of a rebar, a pair of wedge jigs and a pair of wedge foundations;

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Various technically preferable limitations are attached to the embodiments described below for carrying out the present invention, but the scope of the present invention is not limited to the following embodiments and illustrated examples.

1. Reinforcement and Concrete Structure FIG. 1 is a perspective view of a pull-out test apparatus 1 that applies a tensile load to a plurality of reinforcements 90 . FIG. 2 is a side view of this pull-out test apparatus 1. FIG. FIG. 3 is a cross-sectional view showing the III-III plane shown in FIG. 2 as viewed in the direction of the arrow. FIG. 4 is a sectional view showing the plane IV-IV shown in FIG. 2 as viewed in the direction of the arrow. FIG. 5 is a perspective view of a pair of wedge-shaped bases 40 and a pair of wedge-shaped jigs 50 of the pull-out test apparatus 1. FIG.

The multiple reinforcing bars 90 are steel bars. These reinforcing bars 90 are partially embedded in the concrete structure 99 and protrude from the concrete structure 99 to stand. These rebars 90 are linearly arranged in a row at intervals and parallel to each other. A plurality of protruded joints 91 are provided on the peripheral surface of the reinforcing bar 90 along the circumferential direction of the reinforcing bar 90 and are provided at intervals in the longitudinal direction of the reinforcing bar 90 . In addition, below, let the direction along the row|line of the reinforcing bar 90 be the front-back direction.

The concrete structures 99 are civil engineering or architectural structures such as foundations, beams, slabs, footings, harbor structures, embankment bodies, buildings, power generation equipment, substation equipment, buildings, and viaducts.

2. Configuration of Pull-out Test Apparatus (1) Outline of Pull-out Test Apparatus The pull-out test apparatus 1 is a device that simultaneously applies a tensile load to a plurality of reinforcing bars 90 and increases the tensile load under load control. The pull-out test apparatus 1 records the tensile load while the tensile load is increasing, and also measures and records the displacement of the reinforcing bar 90 due to the tensile load. The number of reinforcing bars 90 to which the pull-out test apparatus 1 applies a tensile load is three in the example shown in the figure, but is not limited to this, and may be any number.

The pull-out test apparatus 1 includes two hydraulic jacks 10, a base plate 20, a pair of channel steels 30, a plurality of reinforcing steel plates 35, 37, a plurality of bolt nut fasteners 36, 38, a plurality of pairs of wedge-shaped bases 40, a plurality of A pair of wedge-shaped jigs 50 , a plurality of steel plates 60 , a displacement sensor 80 and a control device 85 are provided.

(2) Hydraulic Jacks As shown in FIGS. 1 and 2, the hydraulic jacks 10 as load applying units are arranged on the concrete structure 99 in front of the head and behind the rear end of the row of the reinforcing bars 90 . there is Hydraulic jack 10 is an actuator that lifts base plate 20 and channel steel 30 by taking reaction force from concrete structure 99 . As a result, the hydraulic jack 10 applies a load to the base plate 20 and the channel steel 30 in a direction separating the base plate 20 and the channel steel 30 from the concrete structure 99 .

As shown in FIGS. 1 and 2, hydraulic jack 10 has cylinder 11 and rod 12 . The rod 12 is attached to the cylinder 11 so as to be able to advance and retract. The cylinders 11 are arranged on the concrete structure 99 in front of the head of the row of reinforcing bars 90 and behind the tail thereof. The cylinder 11 is installed on the concrete structure 99 so that the advancing direction and the retracting direction of the rod 12 are parallel to the longitudinal direction of the reinforcing bars 90 . The cylinder 11 advances the rod 12 upward or retracts it downward by hydraulic pressure.

Although the number of hydraulic jacks 10 is two in the example shown in the drawing, the number is not limited to this, and may be one or three or more. Also, the arrangement of the hydraulic jacks 10 is not limited to the example shown in the drawing, and for example, the hydraulic jacks 10 may be arranged between adjacent reinforcing bars 90 .

(3) Base Plate As shown in FIGS. 1 and 2, the base plate 20 is a strip-shaped steel plate. The base plate 20 is attached to the tip of the rod 12 of the hydraulic jack 10 in a posture perpendicular to the rod 12 and the reinforcing bar 90 . A base plate 20 spans between the ends of these rods 12 . The base plate 20 has a plurality of through holes 21 through which the reinforcing bars 90 are respectively passed. The base plate 20 receives the load directly from the hydraulic jack 10. - 特許庁

(4) Channel Steel As shown in FIGS. 1 and 2, the channel steel 30 is a long material. The channel steel 30 has a U-shaped cross section orthogonal to its longitudinal direction. The channel steel 30 comprises strip-shaped flanges 31 and 32 parallel to each other and a strip-shaped web 33 provided between the long sides of the flanges 31 and 32 . The space between flanges 31 and 32 forms channel 34 .

These channel steels 30 are arranged such that their longitudinal directions are parallel to each other. As shown in FIGS. 3 and 4, the webs 33 of the channel steels 30 face each other with a space between the webs 33 and the channels 34 of the channel steels 30 face away from each other.

These channel steels 30 extend along the row of reinforcing bars 90 on both sides of the row of reinforcing bars 90 on the base plate 20 and are spaced apart from each other. These channel steels 30 are mounted on the base plate 20 . Specifically, the flanges 32 of the channel steel 30 are stacked on the base plate 20 beside the rows of the through holes 21 and the rows of the reinforcing bars 90 and fixed to the base plate 20 by fasteners 22 such as bolts. . These channel steels 30 are fixed to each other by being attached to the base plate 20 . A region between these channel steels 30, that is, between the webs 33 is a space through which a plurality of reinforcing bars 90 are vertically passed, and a plurality of pairs of wedge-shaped bases 40 and a plurality of pairs of wedge-shaped jigs 50 are arranged. It is a space where

These channel steels 30 are spanned between the ends of the rods 12 of the hydraulic jack 10 in the same manner as the base plate 20 . Channel steel 30 receives the load from hydraulic jack 10 .

Hereinafter, the direction from the channel steel 30 to the reinforcing bar 90 is referred to as the clamping direction.

(5) Reinforcing Steel Plates and Fasteners As shown in FIGS. 1-4, a plurality of reinforcing steel plates 35, 37 are affixed and secured to the web 33 by a plurality of bolt nut fasteners 36, 38, respectively, within the channel 34. It is The reinforcing steel plates 35 are arranged beside the through-holes 21 and the reinforcing bars 90, respectively. The reinforcing steel plates 37 are arranged at the longitudinal ends of the channel steel 30 . Reinforcing steel plates 35 , 37 reinforce the web 33 of the channel steel 30 .

The bolt nut fastener 36 spans from the web 33 and reinforcing steel plate 35 of one channel steel 30 to the web 33 and reinforcing steel plate 35 of the other channel steel 30 . A bolt nut fastener 36 clamps the web 33 and reinforcing steel plate 35 of one channel steel 30 and the web 33 and reinforcing steel plate 35 of the other channel steel 30 to bring them closer together. Similarly, bolt nut fasteners 38 also tighten the web 33 and reinforcing steel plate 37 of one channel steel 30 and the web 33 and reinforcing steel plate 37 of the other channel steel 30 to bring them closer together.

A pair of channel steels 30 are secured together by bolt nut fasteners 36, 38 that clamp the channel steels 30 together.

(6) Wedge-Shaped Base As shown in FIGS. 3 to 5, each wedge-shaped base 40 is shaped like a wedge, and the thickness of each wedge-shaped base 40 gradually decreases from the proximal end to the distal end of the wedge-shaped base 40. do. The proximal surface 41 of each wedge-shaped base 40 is perpendicular to the vertical surface 42 of the wedge-shaped foundation 40, and the tapered surface 43 of each wedge-shaped foundation 40 is at an acute angle to the proximal surface 41 and the vertical surface 42. constitutes The tip of the wedge-shaped base 40 refers to a corner sandwiched between the tapered surface 43 and the vertical surface 42 . The thickness of wedge-shaped base 40 refers to the distance between tapered surface 43 and elevation surface 42 .

The pairs of wedge-shaped bases 40 are positioned between the webs 33 of one channel steel 30 and the webs 33 of the other channel steel 30 . Each wedge-shaped base 40 is placed on the base plate 20 in such a posture that its distal end faces upward and its proximal end faces the base plate 20 . Each wedge-shaped base 40 is oriented such that its thickness direction is the sandwiching direction. Therefore, the thickness of the wedge-shaped base 40 in the sandwiching direction gradually decreases as the distance from the concrete structure 99 increases.

Each pair of wedge-shaped bases 40 are spaced apart from each other in the pinching direction with the through holes 21 and rebars 90 between them. Elevated surfaces 42 of each pair of wedge-shaped bases 40 face opposite to each other, and tapered surfaces 43 of each pair of wedge-shaped bases 40 face each other. Therefore, a tapered space is formed between the tapered surfaces 43 of each pair of wedge-shaped bases 40 so that the width between the tapered surfaces 43 gradually decreases toward the bottom.

A proximal surface 41 of each wedge-shaped base 40 is in surface contact with the base plate 20 . The elevation 42 of each wedge-shaped base 40 is in surface contact with the web 33 of the channel steel 30 . A tapered surface 43 of each wedge-shaped base 40 slopes upward from the central portion between the pair of channel steels 30 toward the web 33 of the channel steels 30 .

(7) Wedge-shaped Jig As shown in FIGS. gradually decreases toward A base end surface 51 of each wedge-shaped jig 50 is perpendicular to a vertical surface 52 of the wedge-shaped jig 50 . A tapered surface 53 of each wedge-shaped jig 50 forms an acute angle with respect to the base end surface 51 and the vertical surface 52 . The tip of the wedge-shaped jig 50 refers to a corner sandwiched between the tapered surface 53 and the vertical surface 52 . The thickness of the wedge jig 50 refers to the distance between the tapered surface 53 and the vertical surface 52 .

A circular groove 54 is formed in the upright surface 52 of each wedge-shaped jig 50 from the distal end to the proximal end of the wedge-shaped jig 50 . A plurality of circumferential grooves 55 are formed on the inner surface of the circular groove 54 at intervals in the longitudinal direction of the circular groove 54 .

The elevations 52 of each pair of wedge jigs 50 face each other, and the circular grooves 54 of each pair of wedge jigs 50 face each other with the rebars 90 interposed therebetween. Each pair of wedge-shaped jigs 50 is positioned such that the distal end of the wedge-shaped jig 50 is directed downward and the base end of the wedge-shaped jig 50 is directed toward the base plate 20, and the wedge-shaped base of each pair is It is fitted between tapered surfaces 43 of 40 . Moreover, each pair of wedge-shaped jigs 50 is fitted between the tapered surfaces 43 of each pair of wedge-shaped bases 40 in such a posture that the thickness direction of the wedge-shaped jigs 50 is the sandwiching direction. Therefore, the thickness of the wedge-shaped jig 50 in the clamping direction gradually increases as it approaches the concrete structure 99 .

Each pair of wedge-shaped jigs 50 sandwiches each reinforcing bar 90 therebetween in the sandwiching direction. Specifically, each reinforcing bar 90 is accommodated in the circular groove 54 of each pair of wedge-shaped jigs 50, and the inner surfaces of the circular grooves 54 of each pair of wedge-shaped jigs 50 are arranged in a direction in which each reinforcing bar 90 is sandwiched therebetween. sandwiched between Since the tapered surface 53 of each wedge-shaped jig 50 is in surface contact with the tapered surface 43 of each wedge-shaped base 40, each pair of wedge-shaped bases 40 is pushed downward, and each pair of wedge-shaped jigs A clamping force is created with 50 sandwiching each rebar 90 .

When the reinforcing bars 90 are inserted into the circular grooves 54 of the pair of wedge-shaped jigs 50 , the nodes 91 of the reinforcing bars 90 are caught in the circumferential grooves 55 .

(8) Steel Plates As shown in FIG. 1, each pair of steel plates 60 are stacked in the region between adjacent pairs of wedge-shaped bases 40 in the tightening direction of the bolt nut fasteners 36 and channel steel 30 . is sandwiched between the webs 33 of the The steel plate 60 has a through hole through which the bolt and nut fastener 36 is passed, and the steel plate 60 is sandwiched between the webs 33 of the channel steel 30 by the tightening force of the bolt and nut fastener 36 .
Each pair of steel plates 70 is sandwiched between the webs 33 of the channel steel 30 at both ends of the channel steel 30 while being superimposed in the tightening direction of the bolt nut fasteners 38 . The steel plate 70 has a through hole through which the bolt and nut fastener 38 is passed, and the steel plate 70 is sandwiched between the webs 33 of the channel steel 30 by the tightening force of the bolt and nut fastener 38 .

(9) Displacement Sensor As shown in FIGS. 1 and 2 , the displacement sensor 80 is provided on the channel steel 30 . The displacement sensor 80 is connected to a control device 85 via wiring (not shown). The displacement sensor 80 measures the displacement of the channel steel 30 in the advancing direction and the retracting direction of the hydraulic jack 10 . Displacement sensor 80 forwards a signal representing a measurement of the displacement of channel steel 30 to controller 85 .

(10) Control Device As shown in FIG. 1, the control device 85 is a computer having a CPU, a RAM, a GPU, a storage device, an input device, a display device, and the like. The control device 85 is connected to the hydraulic jack 10 via wiring. The control device 85 controls the applied load of the hydraulic jack 10 in the direction in which the hydraulic jack 10 separates the base plate 20 and the channel steel 30 from the concrete structure 99 . The control device 85 periodically records the applied load of the hydraulic jack 10 in the storage device. In addition, the control device 85 records the displacement measured by the displacement sensor 80 in the storage device in synchronization with the periodical recording of the applied load of the hydraulic jack 10 .

3. Pull-out Test Method A pull-out test method using the pull-out test apparatus 1 will be described, and the operation of the pull-out test apparatus 1 will be described.

(1) Setting First, an operator assembles the pull-out test apparatus 1 and sets the pull-out test apparatus 1 on the reinforcing bar 90 . For example, the order of assembly of the pull-out test apparatus 1 is as follows.

Hydraulic jacks 10 are installed on the concrete structure 99 in front of the head and behind the tail of the row of reinforcing bars 90 respectively.

Next, the reinforcing bars 90 are passed through the through holes 21 of the base plate 20 , and the base plate 20 is attached to the tip of the rod 12 of the hydraulic jack 10 .

Next, with the webs 33 of a pair of channel steels 30 facing and parallel to each other, the channel steels 30 are fixed by the fasteners 22 on the base plate 20 on both sides of the row of reinforcing bars 90 .

Each pair of steel plates 60 is then inserted into the gap between the webs 33 of the channel steel 30 in the region between the adjacent rebars 90 and sandwiched between the webs 33 of the channel steel 30 .

Each pair of steel plates 70 is then inserted into the gap between the webs 33 of the channel steel 30 at each end of the channel steel 30 and sandwiched between the webs 33 of the channel steel 30 .

A plurality of reinforcing steel plates 35 are then affixed to the webs 33 within the channels 34 and bolt nut fasteners 36 pass through the steel plates 60 from the web 33 of one channel steel 30 and the reinforcing steel plates 35 to the other channel steel 30 . The web 33 and the reinforcing steel plate 35 are spanned. The bolt nut fasteners 36 are then tightened such that the bolt nut fasteners 36 bring the web 33 and reinforcing steel plate 35 of one channel steel 30 and the web 33 and reinforcing steel plate 35 of the other channel steel 30 closer together. , tighten these. Thereby, a clamping force is generated in which the web 33 of the channel steel 30 sandwiches the pair of steel plates 60 therebetween. Similarly, a plurality of reinforcing steel plates 37 are affixed to the webs 33 within the channels 34 such that the bolt-nut fasteners 38 consist of the webs 33 and reinforcing steel plates 37 of the channel steel 30 on one side and the webs 33 and reinforcing steel plates 37 of the channel steel 30 on the other. 37 close together. As a result, a clamping force is generated in which the webs 33 of the channel steel 30 sandwich the pair of steel plates 70 therebetween.

Each pair of wedge-shaped foundations 40 is then placed on the base plate 20 on either side of each rebar 90 . At this time, the base end surfaces 41 of each pair of wedge-shaped bases 40 are in surface contact with the base plate 20 , the tapered surfaces 43 face each other, and the vertical surfaces 42 are in surface contact with the web 33 of the channel steel 30 .

Next, the upright surfaces 52 of each pair of wedge-shaped jigs 50 face each other with the reinforcing bars 90 placed between them, and the tips of each pair of wedge-shaped jigs 50 are directed downward. Each pair of wedge-shaped jigs 50 is inserted between the tapered surfaces 43 of each pair of wedge-shaped bases 40 . As a result, the reinforcing bars 90 are sandwiched between the inner surfaces of the circular grooves 54 of the wedge-shaped jig 50 , and the tapered surface 53 of the wedge-shaped jig 50 comes into surface contact with the tapered surface 43 of the wedge-shaped base 40 . Each pair of wedge-shaped jigs 50 is pushed downward, and a clamping force is generated in which each pair of wedge-shaped jigs 50 sandwiches each reinforcing bar 90 in the sandwiching direction. Also, the joints 91 of each reinforcing bar 90 are caught in the circumferential grooves 55 of each pair of wedge-shaped jigs 50 . The wedge-shaped jig 50 does not slip on the reinforcing bar 90 in the longitudinal direction of the reinforcing bar 90 .

A displacement sensor 80 is then provided on the channel steel 30 . Also, the displacement sensor 80 and the hydraulic jack 10 are connected to the control device 85 via wiring.

The order of assembly of the pull-out test apparatus 1 is not limited to the order of steps as described above.

(2) Load application The control device 85 operates the hydraulic jack 10 . The rod 12 of the hydraulic jack 10 advances from the cylinder 11 , and the hydraulic jack 10 receives a reaction force from the concrete structure 99 to apply a load in the direction separating the base plate 20 and the channel steel 30 from the concrete structure 99 . and channel steel 30. Therefore, an upward load is applied to each pair of wedge-shaped bases 40, and the clamping force with which each pair of wedge-shaped jigs 50 sandwiches each reinforcing bar 90 increases. Therefore, each pair of wedge-shaped jigs 50 does not slip on each reinforcing bar 90 in the longitudinal direction of each reinforcing bar 90 .

Since each pair of wedge-shaped jigs 50 clamps each reinforcing bar 90 with a strong clamping force, the load applied from the hydraulic jack 10 to the base plate 20 and the channel steel 30 simultaneously acts on each reinforcing bar 90 as a tensile load.

During application of the load by the hydraulic jack 10 , the controller 85 controls the hydraulic jack 10 to statically increase the applied load of the hydraulic jack 10 . Therefore, the tensile load on each reinforcing bar 90 increases statically.

During the application of the load by the hydraulic jack 10, the control device 85 periodically records the applied load of the hydraulic jack 10 in the storage device. In addition, the control device 85 records the displacement measured by the displacement sensor 80 in the storage device in synchronization with the periodical recording of the applied load of the hydraulic jack 10 .

When the tensile load of the reinforcing bars 90 reaches the pull-out capacity, these reinforcing bars 90 are pulled out of the concrete structure 99 . Therefore, the channel steel 30 is rapidly displaced, and the displacement measured by the displacement sensor 80 is rapidly increased.

After the reinforcing bar 90 is pulled out, the control device 85 stops the hydraulic jack 10 . This completes the pull-out test. After the pull-out test, the control device 85 selects the applied load when the measured displacement rises sharply, and specifies the applied load as the pull-out strength of the reinforcing bar 90 . The pull-out capacity determined in this way is influenced by the group effect of the plurality of rebars 90 . Therefore, the pull-out strength specified in this way can be used for design when reinforcing bars are densely arranged on a foundation or the like.

4. Advantageous Effect (1) As described above, the pull-out test apparatus 1 according to the present embodiment is embedded in the concrete structure 99 and is arranged to protrude from the concrete structure 99. A pair of channel steels 30 extending along the row of the reinforcing bars 90 on both sides of the row, spaced apart from each other and fixed to each other, and a sandwiching direction from the pair of channel steels 30 to the reinforcing bars 90 between the pair of channel steels 30 Between a plurality of pairs of wedge-shaped jigs 50 whose thickness in the sandwiching direction gradually decreases as it approaches the concrete structure 99, and a pair of channel steels 30, the reinforcing bars 90 and A pair of wedge-shaped jigs 50 are respectively sandwiched, and a plurality of pairs of wedge-shaped bases 40 whose thickness in the sandwiching direction gradually decreases as the thickness in the sandwiching direction moves away from the concrete structure 99, and a pair of channel steels 30 are separated from the concrete structure 99. a hydraulic jack (10) for applying a directional load to a pair of channel steels (30).
Therefore, the clamping force with which the plurality of pairs of wedge-shaped jigs 50 sandwich the plurality of reinforcing bars 90 is increased. Therefore, slippage between the wedge-shaped jig 50 and the reinforcing bars 90 does not occur, and the applied load of the hydraulic jack 10 simultaneously acts on the plurality of reinforcing bars 90 as a uniform tensile load. Therefore, the influence of the group effect of the plurality of reinforcing bars 90 on the pull-out strength of these reinforcing bars 90 can be investigated.

(2) The pull-out test apparatus 1 according to the present embodiment further includes bolt-nut fasteners 36 and 38 for tightening the pair of channel steels 30 in a direction in which the pair of channel steels 30 are brought closer to each other.
As a result, it is possible to prevent relaxation of the clamping force with which the pair of wedge-shaped jigs 50 sandwich the reinforcing bar 90 .

(3) In addition, in the pull-out test apparatus 1 according to the present embodiment, the reinforcing bars 90 are accommodated in the circular grooves 54 of the pair of wedge-shaped jigs 50 and sandwiched between the inner surfaces of the circular grooves 54. In addition to good fit, slippage between the wedge-shaped jig 50 and the reinforcing bar 90 can be prevented.

(4) In addition, in the pull-out test apparatus 1 according to the present embodiment, since the pair of channel steels 30 sandwich the plurality of reinforcing bars 90, the plurality of pairs of wedge-shaped jigs 50, and the plurality of pairs of wedge-shaped bases 40, the pair of grooves The shape steel 30 is used for drawing out a plurality of reinforcing bars 90 . Therefore, the number of parts of the pull-out test apparatus 1 can be reduced.

5. Modification (1) The bar material is not limited to the reinforcing bar 90 . For example, when a plurality of anchor bolts are embedded in the concrete structure 99 instead of the plurality of reinforcing bars 90, even if the pull-out test apparatus 1 applies a tensile load to these anchor bolts at the same time as in the case of the reinforcing bars 90, good. In this case, the inner surface of the circular groove 54 of each wedge-shaped jig 50 is formed with a thread groove that meshes with the male thread of the outer peripheral surface of the anchor bolt.

(2) The long material is not limited to the channel steel 30 . For example, instead of the channel steel 30, an angle steel, an H-shaped steel, or a square steel pipe may be employed.

30... Channel steel (long material)
40... Wedge-shaped base 50... Wedge-shaped jig 90... Reinforcing bar (bar)
99 Concrete structure

Claims (3)

A pair of fixed rods that are embedded in a concrete structure and extend along the row of rods on both sides of the row of a plurality of rods arranged so as to protrude from the concrete structure, are spaced apart from each other, and are fixed to each other. a long material;
Between the pair of elongated members, each of the rods is sandwiched in a sandwiching direction from the pair of elongated members to the rods, and the thickness in the sandwiching direction gradually decreases as it approaches the concrete structure. a pair of wedge-shaped jigs;
A plurality of pairs of wedges that respectively sandwich the bar and the pair of wedge-shaped jigs in the sandwiching direction between the pair of elongated materials, and whose thickness in the sandwiching direction gradually decreases as the distance from the concrete structure increases. a mold base;
a pull-out test apparatus, comprising: a load applying unit that applies a load to the pair of elongated members in a direction that separates the pair of elongated members from the concrete structure. 2. The pull-out test apparatus according to claim 1, further comprising a fastener for tightening the pair of elongated members in a direction to bring the pair of elongated members closer to each other. Grooves are formed on surfaces facing each other of said pair of wedge-shaped jigs, said grooves facing each other, said rods being accommodated in said grooves, and said rods being sandwiched between inner surfaces of said grooves. 3. The pull-out test apparatus according to 1 or 2.

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