JPH07128159A - Detection apparatus of effective stress of concrete - Google Patents

Abstract

PURPOSE:To provide a high-precision stress detector by composing its case from a meshlike body of low elastic coefficient, and water-permeable isolating sheets which isolate concrete attached to both face of the body to isolate its inside from outside in terms of the stress of concrete. CONSTITUTION:Concrete which is filled into a case body 50 is isolated surely, in terms of a stress, from concrete, to be measured, around an apparatus by isolating sheets 52, 53. In addition, the concrete which is filled into the case body 50 can maintain the same state regarding individual points such as the material age, the water content state, the temperature and the stress state of the concrete, to be measured, around the apparatus due to the water permeability of the isolating sheets 52, 53 and of a core case 51. In addition, when the concrete is deformed, a deformation force acts on the case body 50. However, since the elastic coefficient of the core case 51 is extremely small, the existence of the core case 51 does not have a bad influence on the deformation force of the concrete, and the stress degree of only the concrete can be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an effective stress detecting device for concrete.

[0002]

2. Description of the Related Art Japanese Patent Publication No. 58-1736 discloses an effective stress detecting device of this type. This effective stress detector has the same quality as the concrete to be measured, as shown in Fig. 3.
A long and narrow case body 10 that is open at both ends to be filled with concrete of the same age, and is attached to one open end of the case body 10,
It comprises a connecting body 20 with a flange 21 that is fixed to the concrete to be measured, and a load cell 30 attached to the other open end of the case body 10 and having a flange 31 that is fixed to the concrete to be measured. The case body 10 includes a core case 12 having a large number of small holes 11 for allowing water to move between concrete inside and outside the case, a lid 13 that can be filled with concrete to be measured at the time of installation, and a core case 12 and an inside of the lid 13. The filter paper 14 is provided to insulate concrete inside and outside the case by stress. The connecting body 20 and the load cell 30 are provided with the adhering bodies 40, 40 for firmly connecting with the concrete with which the case body 10 is filled. The adhering bodies 40, 40 are rod bodies each having a tip end divided into two and expanded, and are arranged at the axial center position of the case body 10.

[0003]

The above-mentioned conventional effective stress detecting device has the following problems.

<A> Since the core case 12 constituting the case body 10 is a rigid body having punch holes formed in a steel plate through which water can move, the case body 10 has a relatively high elastic coefficient. Therefore, when the concrete is deformed, the case body 1
The stiffness of 0 resists and the stress is not correctly transmitted to the load cell 30.

<B> Each of the adhering bodies 40, 40 can secure the contact area with the concrete by branching the tip end into a bifurcated shape, but the concrete pillar l _C inside the case body 10 can be secured.
Disturbs the stress state of and reduces the measurement accuracy. Furthermore, since the rod-shaped adhering body 40 extending to the load cell 30 lengthens the length of the load cell 30, the apparent elastic modulus of the load cell 30 is increased and the stress sensitivity becomes excessive.

<C> Since the core case 12 constituting the case body 10 directly adheres to the concrete to be measured outside the case, the stress insulation cannot be sufficiently performed, and the measurement accuracy deteriorates.

<D> The filter paper 14 which insulates the inner concrete of the case body 10 from stress is excellent in water permeability, but is easily broken when absorbing water or filling concrete.
There is room for improvement in terms of stress insulation effect.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object of the present invention is to provide the following concrete effective stress detecting device. An effective stress detector for concrete that can improve measurement accuracy. An effective concrete stress detector that can reliably insulate the stress transmitted to the concrete inside and outside the case without inhibiting the moisture movement of the concrete.

[0009]

[Means for Solving the Problems] The present invention relates to a cylindrical case body filled with concrete of the same quality and age as the measured concrete, and the case body attached to one open end of the case body. Load detecting load cell having an adhering means for adhering concrete to the other end and an adhering means for adhering concrete to the other end, and concrete attached to the other open end of the case body and filled in the case body at one end. In an effective stress detecting device, the case body comprises a net-like core case with a small elastic coefficient, and It is an effective stress detecting device characterized in that it is laminated on both sides of a case, and is constituted by a water-permeable sheet that insulates concrete inside and outside the case in a stress manner.
Further, the present invention is the effective stress detecting device, wherein the attaching means for attaching the concrete filled in the case body is a ring-shaped spring member.

[0010]

Embodiment 1 An embodiment of the present invention will be described below with reference to the drawings.

<B> Configuration of effective stress detecting device

FIG. 1 shows a vertical sectional view of an effective stress detecting device for converting stress into a load. Incidentally, in describing the present embodiment,
The same parts as those of the above-described base technology will be described with the same reference numerals. That is, in the effective stress detecting device, the connecting body 20 to which concrete is fixed inside and outside the case is attached to one open end of the case body 50 of which both ends are open, and the load cell 30 is attached to the other open end of the case body 50. Adhesives 40, 40 that are fixed to the concrete filled in the case body 50 are fixed to the connecting body 20 and the load cell 30. The basic structure of this embodiment is substantially the same as the above-described prerequisite technique of the present invention, but the structure of the case body 50 is different from that of the above-described effective stress detection device.

<B> Case body

The case body 50 has a core case 51 and a core case 5 that have water permeability for allowing water to move between concrete inside and outside the case and have elasticity in the longitudinal direction of the case body 50.
1 is composed of a lid for filling concrete of the same quality and age as the measured concrete, and a core case 51 and insulating sheets 52 and 53 laminated on both sides of the lid.

<B> Wick case

As shown in an enlarged view of FIG. 1, a core case 51 which allows water to move between concrete inside and outside the case body 50 is formed of a mesh body such as a wire mesh having a small expansion resistance (elastic coefficient). The reason why the core case 51 is made of a mesh is that the case 50 is actively followed when the concrete is deformed. Therefore, in addition to the porous plastic or mesh, a plate having a large number of small holes is bellows-shaped. It is also possible to use a tubular body having a small expansion / contraction resistance (elasticity coefficient) processed into.

<C> Insulation sheet

Insulating sheet 5 for stress-insulating between the concrete to be measured and the concrete filled in the case body 50.
Reference numerals 2 and 53 are materials that are water-permeable and are not easily damaged, and are preferably made of felt. Felt is suitable as an insulating material of this kind because it has a proper water permeability, is excellent in strength, and has a small expansion resistance. Further, by providing the insulating sheets 52 and 53 on both sides of the core case 51 and the lid, it is possible to prevent the core case 51 from clogging and prevent clogging of the core case 51.

[0019]

Next, a method of using the effective stress detecting device will be described.

<B> Usage

A case body 50 which constitutes an effective stress detecting device.
Fill the inside with concrete of the same quality and age as the concrete to be measured, and then bury it in the concrete at the measured point. The concrete filled in the case body 20 is reliably insulated from the concrete to be measured around the effective stress detecting device in a stress manner by the insulating sheets 52 and 53. In addition, the concrete filled in the case body 50 is an insulating sheet 52,
Due to the water permeability of 53 and the core case 51, the age, water content, temperature of the concrete to be measured around the effective stress detection device,
The same state can be maintained at each point of the stress state. Further, when the concrete is deformed, the deforming force acts on the case body 50, but since the elastic modulus of the case body 51 is extremely small, the presence of the case body 51 does not adversely affect the deforming force of the concrete, and the stress of the concrete only. The degree can be detected.

<B> Basic principle (FIG. 1)

The basic principle of the effective stress detecting device is to convert stress into a load to obtain it. The characteristics of the effective stress detector are as follows.

[0024]

[Equation 1]

[0025]

[Equation 2]

[0026]

[Equation 3]

[0027]

[Equation 4]

<C> Effect of insulating sheet

As shown in FIG. 5, when the filter paper 14 which is an insulating member is provided only on the inner surface of the case body 10, the core case 12 adheres to the concrete to be measured, and the effective stress detecting device and the concrete to be measured are attached. An error occurs due to the different elastic coefficients of. The elastic modulus Es of the case body 10 in the same 2,100,000 kgf / cm ² and the steel, the cross-sectional area As 0.76 cm ^2, modulus of elasticity Ec of 200,000 kgf / cm ² of concrete columns, the cross-sectional area
When Ac is 4 cm ² and applied load P is 400 kg, the load on each case body and concrete column is Ps,
If Pc is given, the respective loads Ps and Pc are expressed by the following general formulas (5) and (6).
Required by.

[0030]

[Equation 5]

[0031]

[Equation 6]

According to the above formula, the case body 10 has 23
The concrete column will bear the load Ps of 2 kg, and the concrete column will bear the load Pc of 168 kg. Dividing each of these shared loads by the respective cross-sectional areas As and Ac to convert into stress σs and σc, the stress σs of the case body 10 is 437 kg / cm ² ,
The stress σc of the concrete column is 42 kg / cm ² , which is an error of 58% with respect to the measured stress of 100 kg / cm ² .
On the other hand, by covering both surfaces of the core case 51 with the insulating sheets 52 and 53 as in the present invention, it is possible to avoid the adhesion of the core case 51 and the peripheral concrete to correctly transmit the stress to the concrete column. Therefore, by covering both surfaces of the core case 51 with the insulating sheets 52 and 53, the measured stress is 100 kg / cm ²
It was confirmed that there was almost no error between the stress σs of each case body 50 and the stress σc of the concrete column (error of about 4 to 5%).

[0033]

[Embodiment 2] In the above-mentioned embodiment, the case where the insulating sheets 52 and 53 are attached to both surfaces of the net-made core case 21 has been described, but the water-blocking sheet 5 is provided on both sides of the core case 12 shown in FIG.
Even if 2, 53 are attached, the stress insulation effect of concrete and the clogging prevention effect of punch metal can be achieved as in the first embodiment.

[0034]

Example 3

<B> Configuration

FIG. 2 shows another embodiment in which a ring-shaped attachment 60 is used instead of the rod-shaped attachment 40 of the first embodiment. The adhering body 60 is a member for ensuring an adhering area with the concrete filled in the case body 50 and for avoiding stress concentration at the time of deforming the concrete by reducing the length of the load cell 30. For example, spring steel is formed into a ring shape. It is formed by forming. The attached body 60 is welded or bolted to the load cell 30 and the connection body 20.

<B> Influence of Length of Load Cell on Accuracy

An effective stress detecting device I (load cell length + rod-like adherent length = 40 m) equipped with a rod-like adherent 40 shown in FIG.
m) and an effective stress detection device II (load cell length + ring-shaped deposit length = 20) including the ring-shaped deposit 60 of FIG.
mm) and according to Equation 4 under the following common conditions,
The elastic modulus of the measured concrete is 10,000 kg / cm ² , 100,
^{000 kg / cm 2, 200,000kg /} cm 2, 300,000kg / cm 2,
The ratio of the apparent elastic modulus of the effective stress detecting device for concrete corresponding to the change of 500,000 kg / cm ² was calculated. The calculation results are shown in Table 1.

[0039]

[Table 1]

Generally, in the relationship between the elastic modulus of the concrete to be measured and the apparent elastic modulus of the effective stress detecting device for concrete, the closer the ratio of the two is to 1, the higher the accuracy of measurement. According to Table 1, in the case of the effective stress detecting device I using the rod-shaped adhering body 40, the measurement accuracy varies, but in the effective stress detecting device II having the ring-shaped adhering body 60, the variation occurs. Almost no value is obtained, and the ratio is extremely close to 1. This is because the apparent elastic modulus of the ring-shaped attachment 60 is so small that it can be ignored, and the apparent length of the load cell need not be increased.

[0041]

[Embodiment 4] FIG. 3 shows another embodiment in which the adhering body 60a is formed of a chain of annular bodies or spherical bodies. The adherend 60a is, for example, a connection structure or chain of a plurality of beads that resists tension but does not resist compression. Reference numeral 61 is a spring member for extending the attached body 60a when filling the concrete.

[0042]

Fifth Embodiment In FIG. 4, the load cell 30 may be set in the center of the case body 10 of which both ends are open, and the adherends 60 and 60 may be provided on both sides of the load cell 30 to reduce stress disturbance.

[0043]

Since the present invention is as described above, the following effects can be obtained.

<A> By covering both sides of the core case constituting the case body with insulating sheets, the concrete inside and outside the case can be surely insulated in a stress-free manner without impeding the moisture movement of the concrete, and the measurement accuracy is improved. improves.

<B> By forming the core case forming the case body with the mesh body having a small elastic coefficient, the case body does not adversely affect the stress distribution of the surrounding concrete, and the measurement accuracy is improved.

<C> By forming the adhering body in a ring shape, it is possible to sufficiently secure the adhering with the concrete filled in the case body, to avoid stress concentration in the adhering body, and to lengthen the adhering body in the load cell. The apparent length including can be set short. Furthermore, the concrete can be deformed following the deformation, and the measurement accuracy is further improved.

[Brief description of drawings]

FIG. 1 is an overall view of an effective stress detection device according to a first embodiment.

FIG. 2 is an overall view of an effective stress detecting device according to a third embodiment including a ring-shaped adherend.

FIG. 3 is an explanatory diagram of an effective stress detecting device according to a fourth embodiment, which is provided with another attached body.

FIG. 4 is an explanatory diagram of a fifth embodiment when the case body is open at both ends.

FIG. 5 is an explanatory diagram of an effective stress detection device on which the present invention is based.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoichi Fujiyama 1-1-25 Shinurashima-cho, Kanagawa-ku, Yokohama-shi, Kanagawa Toyoko Hermes Institute of Technology Research Co., Ltd.

Claims (2)

[Claims] 1. A means for adhering a cylindrical case body, which is filled with concrete of the same quality and age as the concrete to be measured, and a concrete body, which is attached to one open end of the case body and which is filled in the case body at one end. A load cell for load detection, which is provided with an adhering means for attaching concrete to be measured to the other end,
An effective stress, which is attached to the other open end of the case body, has an attachment means for connecting the concrete filled in the case body at one end, and a connection body having an attachment means for the concrete to be measured at the other end. In the detection device, the case body is composed of a net-like core case having a small elastic coefficient, and a water-permeable sheet that is laminated on both surfaces of the core case and electrically insulates concrete inside and outside the case, Effective stress detector. 2. The effective stress detecting device according to claim 1, wherein the attaching means that attaches to the concrete filled in the case body is a ring-shaped spring member.