bed structure

Abstract

To provide a floor structure that can suppress deformation of components in high-temperature environments without being restricted by working space or installation weight. [Solution] A floor structure having multiple members and fixed to a wall structure, comprising: a plurality of first members fixed to the wall structure via a first fixing portion; and a second member whose end faces are fixed to the plurality of first members via a second fixing portion, wherein the second member is provided with a notch.

Description

Technical Field

[0001] The present invention relates to a floor structure fixed to a wall structure provided as mechanical equipment.

Background Art

[0002] In work sites such as factories, situations where materials, products, equipment, etc. that generate high-temperature heat are handled frequently occur. Therefore, various mechanical equipment provided at the work site receives heat from materials, etc. that generate high-temperature heat (hereinafter also referred to as "heat-generating substances"), and thermal stress is generated in the members constituting the mechanical equipment. When the stress load caused by the thermal stress is large, deformation of the member occurs, and when the deformation is large, damage to the equipment accompanied by the development of cracks is caused. Therefore, technologies for preventing or suppressing deformation of equipment members based on thermal stress have been conventionally studied.

[0003] For example, Patent Document 1 discloses a configuration in which in a structure in which a plurality of members having different coefficients of thermal expansion are fastened via fastening members, a thermal stress absorption portion that absorbs displacement caused by thermal stress is provided in a part of the member having a large coefficient of thermal expansion.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the configuration disclosed in Patent Document 1, since it is necessary to provide a thermal stress absorption portion that is bent outward, it is necessary to increase the size of the structure. Therefore, in a work site where there are restrictions on the work space, it becomes difficult to apply as mechanical equipment. In addition, the weight of the structure increases by providing a bent thermal stress absorption portion, and it also becomes difficult to apply in a work site where there is a weight limit.

[0006] The present invention has been made in view of the above circumstances, and its objective is to provide a floor structure that can suppress deformation of components in a high-temperature environment without being restricted by working space and installation weight. [Means for solving the problem]

[0007] [1] A floor structure having a plurality of members and fixed to a wall structure, wherein the plurality of members comprises a plurality of first members fixed to the wall structure via a first fixing portion, and a second member whose end faces are fixed to the plurality of first members via a second fixing portion, and the second member is provided with a notch. [2] The floor structure according to [1], wherein the notch is an elongated slit provided along the end face of the second member. [3] The floor structure according to [2], wherein round holes are provided at both ends of the slit portion. [4] The floor structure according to [2] or [3], wherein the second member is made of SS400 steel and the first fixing part and the second fixing part are fillet welded, and the slit part is provided such that the stress load due to thermal stress in the first fixing part is 100 MPa or less. [Effects of the Invention]

[0008] According to the present invention, deformation of components can be suppressed in high-temperature environments without being restricted by workspace and installation weight. [Brief explanation of the drawing]

[0009] [Figure 1] This is a plan view showing an example of the schematic configuration of the crane device in this embodiment. [Figure 2] This is a perspective view showing an example of the general configuration of a conventional floor structure. [Figure 3] This is a plan view showing an example of the schematic configuration of the floor structure in the present invention. [Figure 4]This figure shows an example of the schematic configuration of a conventional floor structure created in the embodiment. [Figure 5] This is a diagram (SN diagram) showing the relationship between the normal stress range and the number of stress cycles. [Modes for carrying out the invention]

[0010] The embodiments of the present invention will be described below with reference to the drawings. First, a crane device 10 to which the present invention can be applied will be described with reference to Figure 1. Figure 1 is a plan view showing an example of the schematic configuration of the crane device 10 in this embodiment.

[0011] As shown in Figure 1, the crane device 10 comprises a tongs travel section 1, a wall structure 2, and a floor structure 3. The wall structure 2 corresponds to the girder section of the crane device 10. The floor structure 3 corresponds to the deck section of the crane device 10. The floor structure 3 is fixed to the wall structure 2. The tongs travel section 1 has a tongs mechanism 1a. The floor structure 3 functions as a workspace for workers and also as a place to install wiring and other components connected to various equipment. The tongs mechanism 1a hangs down in the depth direction (corresponding to the downward direction in the vertical direction) of the drawing and has tongs capable of gripping objects being transported.

[0012] In the crane device 10, the tong mechanism 1a is movable in the vertical direction relative to the drawing. That is, the tong mechanism 1a is movable along the tong travel section 1. In addition, the tong travel section 1 is movable in the horizontal direction relative to the drawing. That is, the tong travel section 1 is movable along the direction in which the wall structure 2 and floor structure 3 extend. Therefore, the tong mechanism 1a is movable across the positions between the two sets of wall structures 2 and floor structure 3 shown in the vertical direction in the drawing, and below the wall structures 2 and floor structure 3.

[0013] In the field of steelmaking, during the conveyance process of products (such as slabs), a product having a weight of about several tens of tons is conveyed from the upstream side (right side toward the drawing) to the downstream side (left side toward the drawing) by the crane device 10. The conveyance of the product by the crane device 10 is repeated day and night as long as the operation is being carried out.

[0014] The crane device 10 grips a product in a high-temperature state loaded at a high place on the upstream side using the tong mechanism 1a and conveys the gripped product by moving the tong traveling unit 1 toward an arbitrary position on the downstream side. Therefore, even at a position below the floor structure 3, a product (heat-generating object) in a high-temperature state (600 to 800 °C) is loaded and temporarily placed.

[0015] The floor structure 3 receives radiant heat from the heat-generating object loaded below and generates thermal stress. The thermal stress generated in the floor structure 3 increases as the height at which the heat-generating object is loaded below becomes higher, and becomes smaller when there is no heat-generating object loaded below. Here, the temperature of the floor structure 3 may exceed 100 °C when the temperature of the heat-generating object loaded below is 600 to 800 °C.

[0016] Also, in the operation in the field of steelmaking, since the conveyance of hot slabs (heat-generating objects) is frequently performed, the position where the heat-generating object is loaded is also frequently changed. Therefore, the thermal stress generated in the floor structure 3 also changes, and as a result, the floor structure 3 is in a state where a stress amplitude is applied.

[0017] Generally, when a stress amplitude is continuously applied to a member constituting a structure, it is known that cracks and the like occur when the member reaches the fatigue limit. Regarding this phenomenon, studies have been conventionally conducted using an S-N diagram showing the relationship between the stress amplitude and the fatigue life.

[0018] Here, the conventional floor structure 300 will be described with reference to FIG. 2. FIG. 2 is a perspective view showing an example of the schematic configuration of the conventional floor structure 300. Specifically, FIG. 2(a) shows the wall structure 200 and the floor structure 300 as a conventional configuration. FIG. 2(b) shows an enlarged view of the configuration in which the wall structure 200 and the floor structure 300 in FIG. 2(a) are fixed.

[0019] As shown in FIG. 2(a), the floor structure 300 has a first member 310a and a second member 320a. The floor structure 300 is fixed to the wall structure 200. More specifically, in the floor structure 300, a plurality of first members 310a are fixed to the wall structure 200 via a first fixing portion 310b. The second member 320a is fixed to the plurality of first members 310a at both end faces N (both end faces) via a second fixing portion 320b. The first member 310a corresponds to a beam portion fixed to the wall structure 200. The second member 320a corresponds to a steel plate portion fixed to the first member 310a. Also, the first fixing portion 310b and the second fixing portion 320b correspond to welded portions where fillet welding has been performed. Note that the wall structure 200 and the second member 320a are not fixed to each other, and there is a slight gap between the wall structure 200 and the second member 320a.

[0020] Here, when a heat-generating object is loaded below the floor structure 300, due to receiving radiant heat from the heat-generating object, thermal stress due to thermal strain occurs in the second member 320a. Then, due to the generated thermal stress, the second member 320a is in a state where a stress amplitude for elongation is applied along the elongation direction T.

[0021] In this case, at the position where the second fixing part 320b is provided, a reaction force from the second fixing part 320b acts against the stress amplitude, thereby suppressing the elongation of the second member 320a. More specifically, the elongation behavior of the second member 320a is suppressed because the behavior related to elongation at both end faces is fixed by the multiple first fixing parts 310b. Therefore, the stress amplitude is transmitted to the first member 310a via the first fixing parts 310b. As a result, the first member 310a receives a compressive force due to elongation in the elongation direction T. In addition, thermal stress due to thermal strain is also generated in the second member 320a in a direction perpendicular to the elongation direction T. In this case, the second member 320a elongates in the direction opposite to the direction in which the wall structure 200 is located, without receiving a reaction force against the stress amplitude.

[0022] Therefore, as shown in Figures 2(a) and 2(b), a crack L occurs at the first fixing part 310b that fixes the first member 310a to the wall structure 200. This phenomenon is caused by the stress amplitude accompanied by elongation along the elongation direction T being applied to the second member 320a, which has received radiant heat from the heat generating material.

[0023] More specifically, although both the first member 310a and the second member 320a receive radiant heat from the heat-generating material, the second member 320a is larger than the first member 310a in terms of size along the extension direction T. Therefore, the amount of displacement due to thermal stress is also larger for the second member 320a than for the first member 310a. As a result, the first member 310a is subjected to a pressing force based on the displacement of the second member 320a, and a crack L occurs in the first fixed part 310b.

[0024] If a crack L occurs in the first fixed section 310b, it becomes impossible for workers to perform tasks on the floor structure 300 from a strength standpoint. This would halt operations using the crane equipment, requiring a significant amount of time for equipment repair work, and drastically reducing productivity in factories and other facilities.

[0025] Based on the above circumstances, the inventors conducted temperature measurements and thermal stress analysis in the floor structure in order to clarify the mechanism of crack generation due to stress amplitude caused by thermal stress.

[0026] First, the inventors measured the temperature of the floor structure 300 while a high-temperature slab (heat-generating material) was being transported by a crane device. Specifically, by measuring the infrared radiation emitted from the floor structure 300, they generated a temperature distribution image (thermography) based on the measured infrared radiation information and confirmed the temperature distribution of the floor structure 300.

[0027] As a result, it was confirmed that in the second member 320a, which corresponds to the steel plate portion, the temperature on the lower side, which is closer to the heat-generating material stacked below, was higher, while the temperature on the upper side was lower. Specifically, the average temperature on the lower side was 160°C, while the average temperature on the upper side was 70°C. The average temperature in the second member 320a was 100°C.

[0028] Furthermore, it was confirmed that the temperature of the first member 310a, which corresponds to the beam section, was lower than the temperature of the second member 320a, which corresponds to the steel plate section. Specifically, the temperature of the first member 310a was in the range of 50 to 60°C.

[0029] The inventors then estimated that, as the second member 320a (steel plate portion) continues to receive radiant heat from the heat-generating material, a stress amplitude with a large displacement is applied to it. As a result, they estimated that the stress load on the first fixing portion 310b, which corresponds to the base of the first member 310a, increases, and that a crack occurs when the fatigue in the first fixing portion 310b reaches its limit.

[0030] Therefore, the inventors have concluded that in order to suppress the occurrence of cracks in the first fixing portion 310b, it is effective to position the second fixing portion 320b, to which the second member 320a and the first member 310a are fixed together, at a position spaced apart from the first fixing portion 310b. Furthermore, in order to suppress the occurrence of cracks in the first fixing portion 310b, it is also concluded that it is effective to provide a notch in the second member 320a, which is subjected to stress amplitude, to absorb the displacement caused by the stress amplitude.

[0031] Next, the inventors analyzed the stress load acting on the first fixed part when the second member with a notch was used in the floor structure. In analyzing the stress load, the temperatures of the first member 310a, which corresponds to the beam, and the second member 320a, which corresponds to the steel plate, were those confirmed in the previously generated temperature distribution image (thermography).

[0032] Specifically, first, temperature distribution images (thermography) were generated by simulation analysis for floor structures using a second member without a notch, and floor structures using a second member with a notch, when heat-generating materials were loaded below. In this process, the temperature of the first member corresponding to the beam section and the wall structure corresponding to the girder section were set to 50°C. By setting the temperature of the first member and the wall structure to 50°C, the thermal stress value in the first member and the wall structure was set to "0" from the perspective of thermal stress. That is, the thermal stress value in the first member and the wall structure was set as the reference value, and the simulation analysis was performed.

[0033] Furthermore, the second component, which corresponds to the steel plate section, was set to a temperature of 100°C. At the same time, the air on the underside of the second component was set to a temperature of 160°C and a thermal conductivity of 10 W / m². 2 The temperature was set to °C. For the air on the upper surface of the second component, the temperature was set to 50°C and the thermal conductivity was set to 10 W / m². 2 It was set to °C.

[0034] SS400 steel was used as the second member. The first fixing part, which secures the first member (corresponding to the beam) to the wall structure (corresponding to the girder section), and the second fixing part, which secures the second member (steel plate section) to the first member, were set as fillet welds. Here, the SS400 steel has a tensile strength of 400 to 510 N / m 2 This refers to rolled steel used for general structural purposes.

[0035] Then, by performing simulation analysis based on the various temperature setting information described above, the thermal stress generated in the second member was estimated. Subsequently, based on the estimated thermal stress information, the stress load acting on the first fixing part that fixes the first member to the wall structure was analyzed. More specifically, the stress load at the first fixing part of a floor structure using a second member without a notch, and the stress load at the first fixing part of a floor structure using a second member with a notch were estimated.

[0036] As a result, it was confirmed that the stress load at the first fixed part of the floor structure using the second member without a notch exceeded 300 MPa. On the other hand, it was confirmed that the stress load at the first fixed part of the floor structure using the second member with a notch was 100 MPa or less. This is presumed to be because the stress amplitude displacement caused by thermal stress was absorbed by the notch, resulting in a decrease in the stress load at the first fixed part.

[0037] Based on the above results, the present inventors have discovered a floor structure according to the present invention. The floor structure according to the present invention will be explained with reference to Figure 3. Figure 3 is a plan view showing an example of the schematic configuration of the floor structure according to the present invention.

[0038] As shown in Figure 3, the floor structure 3 in the present invention has a plurality of members, namely a first member 31a and a second member 32a. The floor structure 3 is fixed to the wall structure 2. More specifically, in the floor structure 3, the plurality of first members 31a are fixed to the wall structure 2 via a first fixing part 31b. The second member 32a has both end faces M (both end faces) fixed to the plurality of first members 31a via a second fixing part 32b. The first member 31a corresponds to a beam portion fixed to the wall structure 2. The second member 32a corresponds to a steel plate portion fixed to the first member 31a. The first fixing part 31b and the second fixing part 32b correspond to welded parts with fillet welding. In addition, the second member 32a is provided with a notch 32c. Note that the wall structure 2 and the second member 32a are not fixed to each other, and there is a small gap between the wall structure 2 and the second member 32a.

[0039] In this case, if a heat-generating object is placed below the floor structure 3, the second member 32a will receive radiant heat from the heat-generating object, causing thermal stress due to thermal strain. As a result of this thermal stress, the second member 32a will be subjected to a stress amplitude that elongates along the extension direction T.

[0040] Although both the first member 31a and the second member 32a receive radiant heat from the heat-generating material, the second member 32a is larger than the first member 31a in terms of its size along the extension direction T. Therefore, the amount of displacement due to thermal stress is also larger for the second member 32a than for the first member 31a.

[0041] In the floor structure 3 of the present invention, even if stress amplitudes are generated due to thermal stress and elongation occurs along the elongation direction T based on the stress amplitude, the notch 32c provided in the second member 32a can absorb the behavior related to such elongation. That is, even if thermal stress is generated in the second member 32a, the situation in which pressing force is transmitted to the first member 31a can be avoided. Therefore, deformation of the members can be prevented in high-temperature environments.

[0042] Furthermore, because the second member 32a of the floor structure 3 is configured with a notch 32c, it can be applied to various types of machinery and equipment regardless of constraints on working space and installation weight, compared to conventional technologies (see Patent Document 1) that feature configurations such as providing a thermal stress absorption section formed by bending outwards.

[0043] In this invention, the floor structure 3 preferably has a notch 32c in the second member 32a, as shown in Figure 3, which is an elongated slit provided along the end face M of the second member 32a. By adopting this configuration, even when elongation occurs along the elongation direction T based on stress amplitude, the behavior related to such elongation can be efficiently absorbed by the notch 32c while avoiding receiving a reaction force from the second fixing part 32b. Furthermore, the area in which the notch 32c is provided in the second member 32a can be kept to the minimum necessary area, and the structural strength as a workspace for workers can be maintained.

[0044] Furthermore, in the floor structure 3 of the present invention, when the notch 32c is a slit with an elongated hole shape, it is preferable to provide round holes at both ends of the slit. Even when the elongation behavior based on the stress amplitude is large, the fluctuations related to such elongation can be effectively absorbed by providing a long slit, and the same effect can be obtained even when the length of the slit is short by providing round holes at both ends of the slit. In addition, since the round holes can be easily constructed, they offer excellent workability for existing facilities.

[0045] In the floor structure 3 of the present invention, it is preferable that the second member (corresponding to the steel plate portion) be made of SS400 steel, and that the first and second fixing portions be fillet welded. Furthermore, it is preferable to provide a notch (a slit portion in the shape of an elongated hole) in the second member so that the stress load due to thermal stress is 100 MPa or less when a heat generating body is placed near the floor structure 3. This is because, based on the SN diagram (see Figure 5) showing the relationship between the normal stress range and the number of stress cycles, the allowable stress load found to satisfy the desired lifespan (15 years) of the crane device 10 is 100 MPa or less.

[0046] Furthermore, the inventors have concluded that, based on the results of the embodiments described later, it is effective to, in the actual design and construction of the floor structure in the present invention, to measure the stress load on the fabricated floor structure in advance, verify equipment damage after installation on the wall structure, and estimate the critical time at which cracks will occur based on the relationship between the normal stress range and the number of stress cycles (SN diagram).

[0047] Specifically, as the first step, it was considered effective to fabricate multiple floor structures with different slit lengths, heat these floor structures using a heating device, and measure the stress load acting on the beam section to select the pattern with the minimum stress load. In this case, it is preferable to use SS400 steel for the second member (corresponding to the steel plate section) to which the slit section is applied, but other steel materials may also be used to fabricate the floor structure.

[0048] As the second step, we considered it effective to install a floor structure with the length of the slit selected in the first step onto the wall structure, and to check the occurrence of equipment damage, etc., when the floor structure is applied over a long period of operation.

[0049] As the third step, by considering the relationship between the normal stress range and the number of stress cycles (SN diagram), we estimated the critical time at which cracks would occur. This allowed us to appropriately determine whether or not the floor structure confirmed in the second step should actually be installed. We believed that by going through each of these steps, it would be possible to suppress the occurrence of cracks in the floor structure. [Examples]

[0050] Next, we will describe an example in which the stress load caused by the generation of thermal stress was measured for the floor structure of the present invention, and damage to the equipment when it was actually installed on a crane device was verified.

[0051] First, the inventors manufactured a conventional floor structure 300 (hereinafter referred to as the "conventional floor structure") as a comparative example by placing a steel plate section (corresponding to the second member 320a) on top of three beam sections (corresponding to the first member 310a), and fixing the beam sections and the steel plate sections to each other via welded sections (corresponding to the second fixing section 320b). Figure 4 shows an example of the schematic configuration of the conventional floor structure created in the embodiment. The conventional floor structure shown in Figure 4 corresponds to the conventional floor structure 300 shown in Figure 2.

[0052] Furthermore, another conventional floor structure was fabricated, and the steel plate portion (corresponding to the second member) of the additionally fabricated conventional floor structure was given an elongated slit portion, similar to the floor structure 3 according to the present invention shown in Figure 3, thereby fabricating a floor structure as an example of the present invention (hereinafter referred to as "the floor structure of the present invention"). More specifically, in the embodiment, multiple "floor structures of the present invention" with different slit lengths were fabricated.

[0053] The "length of the slit" was determined by setting the position closest to the wall structure 2 (corresponding to the girder section) in the steel plate section (corresponding to the second member 32a) as "0 mm," and measuring the length extending downward toward the drawing from that position. Specifically, a "floor structure with a slit length of 200 mm," a "floor structure with a slit length of 644 mm," and a "floor structure with a slit length of 1814 mm" were manufactured. Note that the floor structure of the present invention shown in Figure 3 corresponds to the "floor structure with a slit length of 1814 mm."

[0054] Furthermore, in the conventional floor structure and the floor structure of the present invention, strain gauges were installed at the positions where the beams are fixed to the girder section (corresponding to the wall structure) of the crane device via the first fixing section (welded section) (the upper part of the beam section as seen in the drawing).

[0055] Subsequently, the conventional floor structure and the floor structure of the present invention were heated to 100°C using a heating device (heater, etc.), and the stress load acting on the beam section was measured using strain gauges.

[0056] The measurement results showed that in a conventional floor structure without slits in the steel plate section (corresponding to the second member), the maximum measured stress load was 308 MPa. In contrast, in the floor structure of the present invention with slits in the steel plate section (corresponding to the second member), the maximum measured stress load was 107 MPa. More specifically, regarding the maximum stress load, it was 82 MPa for the "floor structure with a slit length of 200 mm", 67 MPa for the "floor structure with a slit length of 644 mm", and 107 MPa for the "floor structure with a slit length of 1814 mm".

[0057] Therefore, by using the floor structure of the present invention, in which a slit is provided in the steel plate portion (corresponding to the second member), it was confirmed that deformation of the member can be suppressed even when a heat generating part is placed near the floor structure, resulting in a situation equivalent to a high-temperature environment.

[0058] Next, the inventors installed both a conventional floor structure and the floor structure of the present invention on crane equipment in factories and other facilities, and confirmed the occurrence of equipment damage and other issues when these floor structures were applied over a long period of operation.

[0059] For the floor structure of the present invention installed on a crane device, a "floor structure with a slit section length of 200 mm" was adopted. That is, for the floor structure of the present invention, a floor structure with slit sections was used only in positions close to the wall structure (corresponding to the girder section). When the "floor structure with a slit section length of 200 mm" is adopted as the floor structure of a crane device, it is possible to maintain strength by shortening the length of the slit section, and it is also possible to suppress obstacles such as obstruction of walking during actual work by workers, etc.

[0060] After installing the floor structure on a crane device and conducting long-term operations, the conventional floor structure developed cracks in the first fixing part (welded joint) that secures the wall structure and the beam (first member) after approximately three months. In contrast, the floor structure of the present invention showed no cracks in the first fixing part even after approximately six months.

[0061] Based on the above results, the inventors reconfirmed the presence or absence of crack occurrence using an S / N diagram showing the relationship between stress amplitude and fatigue life. Figure 5 shows the relationship between the normal stress range and the number of stress cycles (S / N diagram). In Figure 5, the value on the vertical axis (normal stress range) corresponds to the stress load measured in the example.

[0062] As shown in Figure 5, in a conventional floor structure without slits, when a stress load exceeding 300 MPa is applied, the number of times this load is applied is 3.5 × 10⁻⁶. 4 It can be confirmed that cracks occur when the stress cycle count reaches 3.5 × 10⁻⁶. Furthermore, in the floor structure of the present invention with a slit section (length 200 mm), when a stress load of 82 MPa is applied, the number of times this action occurs is 3.5 × 10⁻⁶. 6 It can be confirmed that cracks occur when the stress cycle count reaches a certain number. In other words, it is estimated that the floor structure of the present invention has approximately 100 times more leeway in terms of stress cycle count before cracks occur compared to conventional floor structures.

[0063] Furthermore, this hypothesis is consistent with the result that cracks occurred in the conventional floor structure after a period of approximately 3 months (approximately 90 days), while no cracks occurred in the floor structure of the present invention even after a period of approximately 6 months (approximately 180 days). More specifically, it is theoretically estimated that no cracks will occur in the floor structure of the present invention even after approximately 25 years of use. [Explanation of symbols]

[0064] 1. Tongs running section 1a Tong mechanism 2 Wall structure 3 floor structure 31a First Member 31b 1st fixed part 32a Second member 32b 2nd fixed part 32c Notch L Crack T extension direction M end face

Claims

1. A floor structure having multiple members and fixed to a wall structure, Among the plurality of members, a plurality of first members are fixed to the wall structure via a first fixing portion, The device comprises a plurality of first members, the second member having both end faces fixed to them via a second fixing portion, A floor structure in which a notch is provided in the second member.

2. The floor structure according to claim 1, wherein the notch is an elongated slit provided along the end face of the second member.

3. The floor structure according to claim 2, wherein round holes are provided at both ends of the slit portion.

4. The floor structure according to claim 2 or 3, wherein the second member is made of SS400 steel and the first and second fixing parts are fillet welded, the slit portion is provided such that the stress load due to thermal stress in the first fixing part is 100 MPa or less.

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