JP7674201B2 - A method for predicting the occurrence of rutting on the surface of concrete slabs. - Google Patents

Description

The present invention relates to a method for predicting when ruts will occur on the surface of a concrete slab.

In recent years, with the expansion of mail order business, it is necessary to move many loads in a short time in large logistics warehouses. Transporting loads by automatic guided vehicles (AGVs) has become essential. For example, in one logistics warehouse, hundreds of AGVs run around almost all day and throughout the year in a warehouse of over 10,000 ^m2 . It is required to load as many loads as possible onto the AGVs and transport them as fast as possible. Therefore, in places where AGVs run frequently, the tracks of the AGV wheels can be seen in a short period of time, and the surface wears away over time, forming ruts about 2 mm to 5 mm deep.

These ruts increase the vibrations and shocks that AGVs experience when they are traveling, leading to damage to the AGV and failures and malfunctions of onboard equipment.

One possible measure to prevent ruts on concrete slabs is to soften the material on the AGV wheel surface or to select a hard material (for example, metal plate such as iron or stainless steel) whose surface does not easily wear away. However, improving AGVs is fundamentally difficult from the construction side. On the other hand, in large logistics warehouses, changing to more expensive floor materials would significantly increase costs, so at present, relatively inexpensive specifications such as applying a surface reinforcing material to the concrete slab are the basis. At this stage, it is not clear what type of slab specifications will be able to withstand repeated AGV runs and for how long.

The following Patent Document 1 proposes a method for diagnosing or predicting concrete deterioration. This method aims to diagnose or predict the type of deterioration occurring in the concrete being diagnosed (e.g., deterioration caused by alkali aggregate reaction (ASR), delayed ettringite formation (DEF), frost damage, fire damage, salt damage, or rebar corrosion due to neutralization, etc.) and the degree (magnitude) of concrete deterioration. Furthermore, when multiple types of deterioration have occurred in the concrete being diagnosed, the method aims to diagnose the main causes (factors) of concrete deterioration from each type of deterioration, the degree of each deterioration, and the degree of each deterioration.

JP 2021-18233 A

However, the method described in Patent Document 1 does not address cracks that occur when the wheels of an AGV repeatedly run over a concrete surface.

In view of the above circumstances, the present invention provides a method for predicting the time when ruts will appear on the surface of a concrete slab, which can predict the period from when the surface breaks down to when ruts grow by measuring the initial microscopic cracks that appear on the concrete surface.

In order to achieve the above object, the present invention employs the following means.
In other words, the method of the present invention for predicting the time when ruts will appear on the surface of a concrete slab involves running vehicles under different conditions over a number of test specimens with different concrete conditions, measuring the number of times the vehicle runs until the concrete surface is maintained in a healthy state and the number of times the vehicle runs until fine cracks appear on the concrete surface, combining the concrete conditions and the vehicle conditions to prepare a number of combination models, selecting an appropriate combination model for the concrete slab on which the vehicle will run, and predicting the time when ruts will appear on the surface of the concrete slab based on the results of the combination model.

In the method for predicting the time when ruts will appear on the surface of a concrete slab configured in this way, vehicles under different conditions are run on multiple test specimens to prepare multiple combination models in advance. An appropriate combination model can be selected, and based on the results of the combination model, the time when ruts will appear on the surface of a concrete slab on which a vehicle will actually run can be predicted. Therefore, by measuring the initial microscopic cracks that appear on the concrete surface, it is possible to predict the period until the surface breaks down and grows into ruts.

In addition, in the method of predicting the occurrence time of ruts on the surface of a concrete slab according to the present invention, the concrete conditions may be one or a combination of the concrete mix, the type of aggregate, the finishing method, the type of surface reinforcement material, and the amount of application of the surface reinforcement material.

In the method for predicting the occurrence of ruts on the surface of a concrete slab configured in this way, a combination model is prepared using one or more combinations of concrete mix, aggregate type, finishing method, type of surface reinforcement material, and amount of surface reinforcement material applied as concrete conditions. Based on the specific concrete conditions, it is possible to more accurately predict the occurrence of ruts.

In addition, in the method of predicting the occurrence time of ruts on the surface of a concrete slab according to the present invention, the vehicle conditions may be one or more combinations of the wheel shape, the material of the wheel, and the load.

In the method for predicting the occurrence of ruts on the surface of a concrete slab configured in this way, a combination model is prepared using one or more combinations of the wheel shape, wheel material, and load weight as vehicle conditions. Based on the specific vehicle conditions, it is possible to more accurately predict the occurrence of ruts.

According to the method of predicting the time when ruts will appear on the surface of a concrete slab according to the present invention, by measuring the initial microscopic cracks that appear on the concrete surface, it is possible to predict the period until the surface breaks down and grows into ruts.

1 is a graph showing the relationship between the number of repeated runs of the AGV wheels and the amount of wear (wheel rut depth) on the concrete surface. 1 is a photograph showing the (1) sound condition of a concrete surface. 1 is a photograph showing the state of microcracks (2) on the surface of concrete. 1 is a photograph showing the state of ruts (3) on a concrete surface. This is a photograph showing the state of the expansion of rut depth on the concrete surface (4). FIG. 1 is a diagram showing the relationship between the number of repeated runs for each combination (1) sound, (2) occurrence of fine cracks, and the amount of applied load.

The following describes a method for predicting when ruts will occur on the surface of a concrete slab according to an embodiment of the present invention. For example, the method for predicting when ruts will occur will be described for ruts that will occur on the surface of a floor slab of a building such as a large logistics warehouse where AGVs (vehicles) run.

As the AGV wheels repeatedly run over the concrete, the concrete surface is gradually damaged, and initially microcracks appear. These microcracks grow into ruts as the destruction progresses in the depth direction. Note that microcracks are less than 0.1 mm (the width that can be seen with a magnifying glass) to about 0.5 mm in size.

Figure 1 is a graph showing the relationship between the number of repeated runs of the AGV wheels and the amount of wear (track depth) on the concrete surface. Note that the areas shown in Figure 1, (1) sound, (2) fine cracks, (3) tracks, and (4) tracks with increasing track depth, are based on the graph for a load of 400 kgf.

Figure 2 shows a photograph of (1) an example of a healthy road. Figure 3 shows a photograph of (2) an example of fine cracks. Figure 4 shows a photograph of (3) an example of ruts (a ruler is shown in the center of the photograph). Figure 5 shows a photograph of (4) an example of ruts with increasing depth (a ruler is shown in the center of the photograph, and the width of the ruts in this photograph is approximately 5 cm).

As shown in Figure 1, before the wheels run over the concrete, the surface is crack-free and in a sound state (see "(1) Sound"). As the wheels run over it repeatedly, microcracks appear on the concrete surface (see "(2) Microcracks appear"). The number and width of the microcracks gradually increase, but they do not progress in the depth direction for a while. After that, the concrete surface begins to break down, and ruts appear in the depth direction little by little (see "(3) Ruts appear"), and then the depth of the ruts increases (see "(4) Increasing rut depth").

In logistics warehouses, when the condition progresses from (3) ruts occurring to (4) rut depth increasing, the area requiring repairs must be divided, the program must be changed to prevent AGVs from entering, and a period of about one week must be allowed for the repair material to fully harden. There are concerns that this work will lead to a decrease in the amount of movement of the logistics warehouse. On the other hand, because a certain amount of area must be reserved for repairs, a vicious cycle is created in which many areas that are repaired at the same time are left unattended until the condition progresses to (4) rut depth increasing. Therefore, it is ideal to check the slabs of logistics warehouses while they are in the condition of (2) microcracks occurring, and repair them partially in a short period of time.

The relationship between (1) soundness and (2) occurrence of microcracks is shown in the image in FIG. 6 as an example. The horizontal axis of FIG. 6 indicates the number of repeated runs of the AGV while maintaining (1) a sound state. In other words, the horizontal axis of FIG. 6 indicates the number of repeated runs of the AGV from (1) a sound state until (2) microcracks begin to occur. The vertical axis of FIG. 6 indicates the number of repeated runs of the AGV from (2) the beginning of the occurrence of microcracks until (3) the beginning of the occurrence of ruts. The number of repeated runs from (1) soundness until (2) occurrence of microcracks is obtained for each combination model by changing the concrete conditions and AGV conditions (vehicle conditions). The concrete conditions are the concrete mix, the type of aggregate, the finishing method such as polishing, the type of surface reinforcement material, and the amount of application of the surface reinforcement material. The AGV conditions are the shape of the wheel (flat or drum type), the material of the wheel surface (hardness), and the load (weight of the AGV). The relationship between (1) the sound length and (2) the length at which microcracks appear is that if the concrete surface is extremely hard and the wheel load is relatively small, the sound length (1) will not change to microcracks (2), and ruts will not appear permanently. Also, the more repeated runs that are made from (1) a sound state (a clean state with absolutely no cracks on the concrete slab surface) until (2) microcracks appear, the more repeated runs will be made from (2) a state where microcracks have appeared until these cracks gradually grow larger, the surface of the concrete slab begins to collapse, and (3) ruts begin to appear.

In this way, by testing a combination model with multiple test specimens and obtaining data on the number of repetitions from (1) soundness to (3) the appearance of ruts, this can be reflected in the selection of slab specifications that match the AGV specifications and operating conditions in actual projects, and in maintenance plans. In addition, (2) it will be possible to investigate the AGV road in actual projects when microcracks are present, and to carry out partial reinforcement according to practical application.

The procedure is as follows.
(Step 1)
- Conduct repeated wheel running tests on test specimens that combine concrete and AGV conditions.

(Step 2)
The relationship between (1) the number of repeated runs required for soundness and (2) the number of repeated runs required for the occurrence of microcracks is understood for each combination model (see Figure 6).

(Step 3)
- Present combinations of slab specifications and wheel materials that suit the AGV specifications and driving conditions.
Select a combination model that matches (is close to) the conditions of the AGV and concrete slab that will actually be used. Predict the time when ruts will occur based on the test results of the combination model.
- (2) At the stage before ruts appear, when fine cracks appear, the timing for checking the slab surface is suggested according to the number of repeated runs.
・Suggest early maintenance timing.

(Step 4)
(2) Carry out partial repairs when microcracks have developed, and extend the life of the structure before ruts form.

In the method for predicting the time when ruts will appear on the surface of a concrete slab configured in this way, an AGV is run over multiple test specimens under different conditions to prepare multiple combination models in advance. An appropriate combination model can be selected, and based on the results of the combination model, the time when ruts will appear on the surface of a concrete slab on which an AGV will actually run can be predicted. Therefore, by measuring the initial microscopic cracks that appear on the concrete surface, it is possible to predict the period until the surface breaks down and grows into ruts.

In addition, a combination model is prepared by using one or more combinations of concrete conditions among the concrete mix, aggregate type, finishing method, surface reinforcement type, and amount of surface reinforcement applied. Based on the specific concrete conditions, it is possible to more accurately predict the time when rutting will occur.

In addition, a combination model is prepared by setting one or more combinations of wheel shape, wheel material, and load capacity as AGV conditions. Based on the specific AGV conditions, it is possible to more accurately predict the occurrence of ruts.

In addition, during the design stage, slab specifications can be selected to suit the AGV's specifications and driving conditions. Wheel materials can be selected to suit the slab specifications.

In addition, (2) the time to check the slab surface can be determined based on the number of repeated runs at which microcracks appear.

It also makes it possible to determine when maintenance is required before ruts form, and to select simple, inexpensive partial repairs. This makes it possible to carry out repair work that minimizes the drop in the operating rate of the logistics warehouse.

The above describes one embodiment of the method for evaluating wind loads on exterior materials according to the present invention, but the present invention is not limited to the above embodiment and can be modified as appropriate without departing from the spirit of the invention.

For example, in the embodiment described above, a combination model was prepared with the concrete mix, type of aggregate, finishing method, type of surface reinforcement material, and amount of application of the surface reinforcement material as the concrete conditions, but the present invention is not limited to this. The concrete conditions may be one or more combinations of the concrete mix, type of aggregate, finishing method, type of surface reinforcement material, and amount of application of the surface reinforcement material.

In the embodiment described above, a combination model was prepared with the wheel shape, wheel material, and load weight as the AGV conditions, but the present invention is not limited to this. One or more combinations of the wheel shape, wheel material, and load weight may be set as the AGV conditions.

In addition, in the above embodiment, an AGV is used as an example of a vehicle, but the present invention is not limited to this. The type of vehicle can be set as appropriate.

Claims (2)

Vehicles with different conditions were run over multiple test specimens with different concrete conditions,
measuring the number of times the vehicle is driven until the surface of the concrete is kept in a healthy state and the number of times the vehicle is driven until microcracks appear on the surface of the concrete, and preparing a plurality of combination models by combining the conditions of the concrete, the conditions of the vehicle, and the number of times the vehicle is driven ;
Selecting an appropriate combination model for a concrete slab on which the vehicle runs, and predicting the time when ruts will occur on the surface of the concrete slab based on the result of the combination model;
A method for predicting the time when ruts will occur on the surface of a concrete slab , wherein the concrete conditions are one or more combinations of concrete mix, type of aggregate, finishing method, type of surface reinforcement material, and amount of application of the surface reinforcement material . 2. The method for predicting the occurrence of ruts on the surface of a concrete slab according to claim 1 , wherein the vehicle conditions are one or more combinations of the shape of the wheels, the material of the wheels, and the load.

Images