JPS62162940A - Method and device for uniformly distributing force in structure experiment - Google Patents

Abstract

PURPOSE:To simulate the stress distribution of a fixed border slab corresponding to actual machine design by fixing the periphery of a test body on a force application base, setting a load applied on a force application point according to the relation between force application points, and applying a uniformly distributed load by a hydraulic jack. CONSTITUTION:Four sides of the test body A on the force application base 1 are fixed by a PC steel material 6, the hydraulic jack 4 is arranged by a support frame 9 closely to the center part of the test body, and the uniformly distributed load P is placed on the test body with the reaction force of a reaction beam 3 through the operation of the jack 4. The ratio of respective loads is so set that P1:P2:P3=1:2:3. The device consists of the base 1, a pole 2, and the beam 3, so the device becomes compact and a self-balancing system whose column is buried in the base does not require a reaction force floor and the periphery of the test body is fixed to set peripheral border condition and when the stress distribution at the time of multipoint force application is a uniformly distributed load corresponding to actual machine design, the stress distribution of the fixed border slab can be simulated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for applying uniformly distributed loads to a test specimen in structural tests of slabs and the like.

"Prior Art" Conventionally, in this type of structural experiment, the following method has been generally used to simulate stress due to uniformly distributed loads.

(A) Equally distributed loading method using a hydraulic bag: A method in which a hydraulic bag is placed between the test specimen and the reaction force gantry, and a uniformly distributed load is applied to the test specimen by applying water pressure to the hydraulic bag.

(I3) Multi-point loading method using tournament loading method...
- A method of distributing the load from a force-applying device to a large number of stress points using a loading beam.

"Problems to be Solved by the Invention" However, the conventional method has the following problems to be solved.

In other words, in (A), the hydraulic bag is brought into contact with the entire surface of the test specimen to apply an evenly distributed load, so a reaction table with the same size as the test specimen is required. If yes, and the boundary condition is fixed, the reaction table has a structure that can withstand the load at the maximum proof stress of the test specimen, and has a structure that allows the test specimen to be connected using prestressing steel, etc. Therefore, there is a problem in that the size of the reaction force table becomes large. Furthermore, when a reaction floor is used instead of such a reaction table, there is a dissatisfaction with the fact that the experimental location is restricted. Furthermore, with this hydraulic bag, it is not possible to observe the progress of cracks in the test specimen on the installation surface of the hydraulic bag, and when the amount of deformation of the specimen becomes large, the hydraulic bag becomes unable to follow the deformation of the specimen. Points also occur. Moreover, with this method, it is necessary to manufacture the hydraulic bag according to the shape of the test specimen, so as the test specimen becomes larger, problems such as the need to increase the strength of the material for the hydraulic bag arise. be.

On the other hand, in case (B), when a large number of applying points are required, the height of the applying frame becomes high, and there are problems such as it is difficult and unstable to assemble the loaded rice cake etc. be. Moreover, since there is a limit to the placement of the load, the position where a reaction force can be exerted against the stress on the load is inevitably limited.
In addition, the load applied by a force-applying device replaces a uniformly distributed load with multiple concentrated loads, so it is not possible to sufficiently simulate a uniformly distributed load, and although local stress singularities do not occur, , there is a problem that the position of the recursion point is not approximated when a uniformly distributed load is applied.

The present invention effectively solves these conventional problems.The purpose of the present invention is to ensure that the stress distribution of the test specimen under multi-point application has a fixed boundary during uniformly distributed loading corresponding to the design of the actual machine. An object of the present invention is to provide a method and device for applying force that can simulate the stress distribution of a slab.

"Means for Solving the Problems" In the present invention, a test specimen is placed on a load-bearing foundation, the test specimen is fixed to the load-bearing foundation using PC steel, and a hydraulic jack is applied to the test specimen from a number of load points. This is a method of applying stress that is equivalent to a uniformly distributed load on a test specimen by applying a load to the test specimen, and in which the position of the application point is set in advance, and the load applied to the application point is adjusted in relation to each other. Each load is set in advance, and the set load is applied to the force application point.

Here, as a means to apply a uniformly distributed load to the test specimen,
A load-bearing base on which the test specimen is placed, a plurality of support columns extending upward from the load-bearing base and arranged around the load-bearing base; a reaction beam,
A large number of hydraulic jacks are arranged between the reaction beam and the test specimen to apply a load to the test specimen, and the test specimen is fixed to the loading foundation. The test specimen was fixed to a loading foundation using the PC steel material, and a load was applied to the test specimen using a large number of hydraulic jacks.

"Example" An embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1 and 2 show an embodiment of the force applying device of the present invention. In the figures, reference numeral I indicates a force base on which the test specimen A is placed, and numeral 2 indicates this force base L. A support column, reference numeral 3, whose base end is embedded in and whose free end extends upward from the foundation 1;
denotes a reaction beam spanned over these support columns 2 in a grid pattern, and 4 denotes a number of hydraulic jacks (nine in the example) placed between the reaction beam 3 and the test specimen A. Reference numerals 1 to 4 constitute the main members of this embodiment.

The force-applying foundation l is 4 1i protruding above the ground G.
It is mainly composed of an I-frame-shaped reinforced concrete wall 5, and a mounting surface 5a for the test specimen A is provided on the upper surface of the wall 5. ) are formed at regular intervals along the length direction of the PCI material insertion hole portion 5 extending in the length direction. Note that the drawing shows a state in which a P (J4 material 6) is placed in this insertion hole. Also, the wall portion 5 is provided with a through lower opening at the end of the PCA material insertion hole, and An entrance 8 for entering the inside of the section 5 is formed.

On the other hand, the support column 2 and the reaction beam 3 are constructed of Hjli[I, and in this embodiment, the support column 2 is arranged around the wall 5 with the flange surface 2a facing the wall 5. They are placed at equal intervals. In addition, Menki reaction force 3 is
The flange surface 2a is removably spanned over the opposing support column 2 by fixing means such as bolts and nuts, and the reaction force of these reaction beams 3 extending in the inward direction (vertical direction in FIG. 1) The beams 3 are located below the reaction beams 3 extending in the left-right direction, and are assembled at different levels.

A support frame 9 made of H steel in the form of a rectangular frame with a Hiili spanned across the middle is integrally attached to the reaction beam 3 located on the lower side. The hydraulic jack 4 is fixed.

In the embodiment, this hydraulic jack 4 includes four corners of the support frame 9,
A total of nine heads are fixed at the center of each side and at the center of the support frame 9, and a universal head 11 is attached to the rod 4a of each hydraulic jack 4 so as to be in contact with the load cell lO and the upper surface of the test specimen A. There is.

Next, a case will be described in which a structural experiment of test specimen A is performed using this apparatus.

First, as shown in Fig. 1, in order to bring the force applying device into the assembled state, set an installation location that can support the total weight of the entire device and test specimen A, and set this location. The support column 2 is placed at a predetermined position, and the reaction beam 3
The load-applying frame consisting of these support columns 2 and reaction beams 3 is pre-assembled. Next, a formwork for forming the wall portion 5 is set using the support column 2 as a reference, and a sheath pipe (embedded pipe) constituting the PC steel insertion hole is fixed in this formwork, while applying force. Set the necessary reinforcing bars for the foundation l while ensuring the required cover thickness.

Note that the set staggered reinforcing bars are set in this formwork in advance by unitizing the necessary amount of reinforcing bars into a reinforcing bar basket at a factory or the like.

Once the reinforcing cages, etc. have been set, concrete is poured into the formwork to create the wall section 5, and once the specified strength of the concrete has been achieved, the reaction beam 3 is removed and the test specimen is constructed. If the hydraulic jack 4 and the like are placed on top of the test specimen A, the apparatus shown in FIG. 1 is completed.

In the above, the location where the force applying device is installed can be arbitrarily set, regardless of whether it is indoors or outdoors, as long as the device can be installed and a structural experiment of the test specimen A can be carried out.

Also, to add a supplementary explanation here about the procedure for setting the test specimen A, this is done by removing the reaction beam 3 from the pre-assembled load-bearing frame, and placing the test specimen A on the Katsuno foundation l. However, after placing the test specimen A, a fixing and shifting procedure is added to the loading foundation l using the PC steel material 6, and this PC steel material 6 was also placed on the test specimen A during the experiment. Applied force ttfkk 7+ l lA='r
= Ll shi 8 11 ノ, j Ilr+ yo,
and --, +J 1. LIT%? ff 1
→1 No, it is something to be given.

Then, in order to carry out the structural experiment, when all the sets are completed, that is, the test specimen A is fixed to the loading foundation l by the PC'g4 material 6, and the nine hydraulic jacks 4 are attached to the test specimen A by the support frame 9. When the rod 4a is placed at a set position near the center of the rod 4a, each hydraulic jack 1 is operated with its respective set load to extend the rod 4a.

The set load of this hydraulic jack 4 is set in advance in relation to the positions where the hydraulic jacks 4 are arranged (positions of applied points), and by taking this set load into consideration, it is evenly distributed on the test specimen A. It applies a load.

In this embodiment, the ratio of each load was set as shown in equation (a) for the two-way plate and as shown in equation (b) for the one-way plate.

P , :P , :P 3= 1 :2 :3 ・
・(I) P , :P 5”l :2
(b) In equation (a), the symbol P is the point of application of the hydraulic polisher 4 located at the center of the specimen A, as shown in Fig. 3, and P2 is the point of application of the hydraulic polisher 4 on the specimen A. P is the applying point of the hydraulic jack 4 located on the center line
In the expression (Kuchi), the symbol P4 is
As shown in FIG. 4, P is the point of application of the hydraulic jack 4 located on the center line Y-Y of the test specimen A.
- Shows the points of application of the hydraulic jack 4 at symmetrical positions on the X-ray.

The set load of the hydraulic jack 4 was determined using a study method described later.

1 action.'' Then, when the hydraulic jack 4 is operated and the rod 4a of the hydraulic jack 4 is extended by the predetermined set load, the hydraulic jack 4 receives a reaction force from the reaction beam 3, and the test specimen A receives a reaction force. A uniformly distributed load acts. Then, when a uniformly distributed load is applied to the test piece A, the test piece A gradually deforms and curves, but in this example, the test piece A is
Since the specimen A is deformed, it is possible to follow the load and deformation of the specimen A at its maximum yield strength, and it is also possible to observe cracks on the upper surface of the specimen A. Note that the lower surface of the test specimen can be observed through the entrance 8 formed in the wall 5 of the loading foundation 1.

In addition, since the surface test specimen A and the load-bearing foundation l are firmly fixed by the PC studs 6, the boundary conditions around the slab can be kept as fixed as possible, but the support of the load-bearing frame is 2 as a base for applying force! Since it is configured to be embedded in the system, it has the advantage that it can be made into a self-balancing system.

In this example, the load is applied to the test specimen A using nine hydraulic jacks 4 installed on the support frame 9. However, when performing structural experiments on test specimens with other shapes, For the test specimen, consider the location of the loading point and the set load, and apply a uniformly distributed load. In this case, if the position of the hydraulic jack 4 or the like is changed, in this embodiment, the reaction beam 3
By having a structure with different levels, assembly is simplified, and there is an advantage that the position where the reaction force can be taken against the stress acting on the reaction beam 3 can be arbitrarily set.

Next, we will explain how to consider the set load.

Study method: In this study, we conducted a parametric study of the force point positions and load values, and determined the force application method so that the stress distribution of test specimen A during multi-point force could simulate the stress distribution of the actual slab. It's about doing.

The following two cases were considered as a method for approximating the test specimen stress in the multi-point loading experiment to the stress distribution of a fixed boundary slab under uniformly distributed loads corresponding to the actual machine design.

Note that the number of applying points is nine, taking into consideration the applying device and the like.

(1) As shown in FIGS. 5 and 6, a method of dividing the test specimen into equal parts and applying force to the center point O of each part.

Note that this method is common in beam experiments with uniformly distributed loads.

(11) A method for appropriately selecting a force point position and a load value (ie, the method of the present invention).

In this method, the stress of the test specimen A is determined by changing the positions of nine stress points and sequentially applying a unit load to each stress point position. Each test piece A is applied to the unit load for each force point position.
By multiplying the stress by a factor and adding them together, the stress distribution of a fixed boundary slab under uniformly distributed load can be approximated.

In order to determine the force point position and load value using the methods (i) and (11) above, separate the two-way temporary slab test specimen and the one-way plate slab test specimen as shown in Table 1. Each case was analyzed using the finite element method.

Study results For analysis cases in which the stress distribution is examined parametrically by changing the load point position and load value, the one that most closely approximates the stress distribution of a fixed boundary slab under uniformly distributed loading shall be illustrated.

As shown in Table 1, in order to compare and examine the force distribution of each of these methods with the stress distribution of the Tokozuke Tora Slab 1. The results of the bending moments and shear forces on the slab centerline and near the edges are shown in FIGS. 7 to 1θ.

Table 1 The evaluation results are shown in Table 2.

From these evaluation tables and comparison of stress distribution, CASE
The force point position and load ratio of X2 and CASEY 2 are
It is judged that the stress distribution of a fixed boundary slab can be well approximated under uniformly distributed loads.

In addition, for evaluation, methods (i) and (ii) were compared to determine their superiority or inferiority, which was expressed as O (excellent) or △ (poor).

Table 2 "Experimental Examples" Next, the results of experiments conducted to confirm the effects of the force applying method according to the present invention will be introduced.

In this experiment, the apparatus shown in FIGS. 1 and 2 was used, and the setting conditions such as the set position of each hydraulic jack 4 and the ratio of the set loads were in accordance with the embodiment described above.

FIGS. 1I and 12 show experimental results for two-way plates, and FIGS. 13 and 14 show experimental results for unidirectional plates.

In addition, in FIG. 11 and FIG. 13, (1) the bending moment on the center line XX line of test specimen A is shown by a solid line.

(2) The bending moment on the center line YY of the test specimen A is shown by a broken line.

On the other hand, in FIGS. 12 and 14, (1) the axial force on the center line XX of the test piece A is shown by a solid line.

(2) The axial force on the center line YY to the test specimen is shown by a broken line.

As is clear from the above four experimental examples, it can be estimated that the force applying method according to the present invention can sufficiently simulate a uniformly distributed load in terms of the moment shape.

"Effects of the Invention" As explained above, according to the present invention, the following excellent effects can be achieved.

(a) Since the foundation of the force-applying device is composed of a force-applying base on which the test specimen is placed, and support columns and reaction beams extending upward from this force-applying base, the entire device can be made compact. Can be summarized.

(b) It is possible to simulate a load state that is as close as possible to the stress at the time of uniformly distributed load.

(c) Since the test specimen was fixed to the load-applying foundation using prestressed steel, the boundary conditions around the test specimen could be kept as fixed as possible.

(d) By assembling the reaction beams in a lattice shape with different levels, the assembly can be simplified, and the reaction force can be reduced against the stress acting on the loading frame consisting of the reaction beams and the support beams. You can set up to 1,000 possible positions.

(e) By making the entire apparatus a self-balancing system, a reaction floor is not required and there are no restrictions on the experimental location.

(Since the D reaction beam is compacted as a lattice beam,
The test specimen can be set,
Easier to reset.

[Brief explanation of drawings]

1 and 2 show an embodiment of the force applying device of the present invention, in which FIG. 1 is a plan view, FIG. 2 is a sectional view taken along the line ■-■ in FIG. The figure is a schematic diagram shown to explain the set load at each applying point on the two-way plate, Figure 4 is a schematic diagram shown to explain the set load at each applying point on the one-way plate, Figure 5 and Figure 6 shows the application points of other application methods shown for comparison with the application method of the present invention, and is a schematic diagram similar to Figures 3 and 4, and Figures 7 and 8, respectively. The figure is shown to explain the stress distribution on the center line of the specimen in the analysis case of a bidirectional plate, so the
Figure 8 is a graph comparing bending moments, Figure 8 is a graph comparing shear forces, and Figures 9 and 10 are shown to explain the stress distribution in a unidirectional plate.
Figure 1 is a graph comparing bending moments, Figure 1O is a graph comparing shear forces, Figures 11 and 12 are results of experiments on bidirectional plates, and Figure 11 is a graph showing bending moment distribution. , Figure 12 is a graph showing the axial force distribution, Figures 13 and 14 are the experimental results for a unidirectional plate, Figure 13 is a graph showing the bending moment distribution, and Figure 14 is the graph showing the axial force distribution. This is a graph showing. 1. Loading foundation, 2. Support column, 2a. Flange surface, 3. Reaction beam, 4. Hydraulic jack, 5. Wall,
6. PC steel material, 8. Entrance port, 9. Support frame, 10.
・Load cell.

Claims (2)

[Claims] (1) Place the test specimen on a load-bearing foundation, fix the test specimen to this load-bearing foundation using PC steel, and apply loads to the test specimen using hydraulic jacks from a number of stress points, evenly distributing the load on the test specimen. A force applying method that generates stress equivalent to a load, in which the position of the force point is set in advance, the load to be applied to the force point is set in relation to each other, and the force applied to the force point is set in advance. A uniformly distributed force application method in structural experiments characterized by applying a set load. (2) A load-bearing base on which the test specimen is placed, a plurality of support columns extending upward from the load-bearing base and arranged along the circumference of the load-loading base; It has a reaction beam spanned across the structure, and a number of hydraulic jacks placed between the reaction beam and the test specimen to apply a load to the test specimen. A uniformly distributed force applying device for structural experiments, characterized in that a PC steel material is provided to fix the body to this force applying foundation.