Fiber sheet reinforced stacked beams

Abstract

To provide a stacked beam that can be easily processed and manufactured and that can improve performance. [Solution] The stacked beam is made by combining multiple upper and lower beams with dedicated wood screws that fit into wood screw holes at dedicated screw intervals that prevent axial shear misalignment, and pre-cutting both ends of the combined upper and lower beams to fit into beam support hardware that is attached to the pillar, and partially reinforcing them with fiber sheets. This improves the performance of the stacked beam and makes it possible to provide it at a low cost.

Description

[Technical Field]

[0001] This invention relates to a method for stacking wooden beams to make large beams, and in particular to a method for manufacturing large beams without fixing the beams with adhesive or compression bolts at the joint surfaces. [Background technology]

[0002] The "Act on the Promotion of the Use of Wood in Public Buildings, etc." (Act No. 36 of 2010) was enacted to promote the use of wood in public buildings, etc., in order to promote the revitalization of forests and forestry through the use of wood. The purpose of this law is to promote the use of wood, focusing on public buildings where the wooden construction rate is currently low and where future demand is expected.

[0003] Furthermore, even in low-rise wooden buildings and ordinary wooden houses, there is a demand for larger spaces, requiring beams with larger beam widths (the measurement from the top to the bottom of the beam). It is difficult to obtain such beams in solid wood, and currently the mainstream method is to use standard-sized beams made from laminated lumber or LVL. However, because laminated lumber and LVL require advanced technology for the use of adhesives and expensive specialized manufacturing equipment, large-span beams are expensive.

[0004] In order to solve the above problems, stacked beams have been developed to manufacture beams with large beam widths by stacking standard sized lumber or laminated timber beams. [Prior art documents] [Patent documents]

[0005] [Non-Patent Document 1] Tsuyoshi Hashizume et al. "Development of cedar stack beams using Shachi bolt joints," Nagano Prefectural Forestry Research Center Research Report, No. 20, 2006, pp. 117-131 [Patent Document 2] Patent Publication No. 2015-63795

[0006] The method described in Non-Patent Document 1 is a method for fastening raw beams together with metal bolts to produce beams with large beam thickness from raw beams of standard dimensions, and is a method for producing stacked beams that have an excellent appearance without being fixed with adhesive.In order to increase bending rigidity, grooves are carved into the joint surfaces of the raw beams and connecting wooden pieces called "shachi" are hammered in to prevent shear slippage.

[0007] The method described in Patent Document 2 provides a method for manufacturing large beams that can be easily machined using a pre-cut machine without fixing with adhesives or dies, and is a method for manufacturing stacked beams that includes the steps of processing unevenness into the joint surfaces of multiple material beams to be joined, combining the multiple material beams by fitting the unevenness into each other to prevent axial shear displacement, and fastening the combined multiple material beams together with fastening bolts. Summary of the Invention [Problem to be solved by the invention]

[0008] Conventional stacked beams require a process of fixing multiple material beams together with adhesive or glue, processing unevenness into the joint surfaces of the beams to be joined, and then combining the multiple material beams by fitting the unevenness into each other to prevent axial shear misalignment. As a result, the processing and manufacturing of stacked beams requires a significant amount of time and cost, and they must be manufactured in a large-scale factory.

[0009] To provide a device that can easily process and manufacture a stacked beam by eliminating the steps of processing unevenness into the joint surfaces of a plurality of material beams to be joined without fixing with adhesive or glue, and of combining the plurality of material beams by fitting the unevenness into each other to prevent axial shear displacement. [Means for solving the problem]

[0010] The stacked beam is provided with a process of drilling wood screw holes in beams with a smaller beam thickness relative to the joint surfaces of the upper and lower beams to be joined, a process of fitting the upper and lower beams together with special wood screws used in the wood screw holes and combining them with screw spacing that does not cause axial shear misalignment (two rows of slightly smaller pitches at the beam end side, and one row with a specified pitch at the center of the beam), and a pre-cut process of fitting both ends of the combined upper and lower beams into beam support hardware that can be attached to columns.

[0011] The stacked beam is provided with a plurality of upper and lower beams fastened together with dedicated wood screws, and fiber sheets having a predetermined width and length are used to reinforce the upper and lower beams in the vertical direction.

[0012] The stacked beam is provided with a fiber sheet having a predetermined width and length on both sides of a plurality of upper and lower beams fastened with the dedicated wood screws of the stacked beam, which is adhesively reinforced across the upper and lower beams in a diagonal direction symmetrically from the center of the beam.

[0013] The stacked beam is provided with a plurality of upper and lower beams fastened together with the above-described special wood screws, and is reinforced by adhesively bonding the upper and lower beams together with a U-shaped fiber sheet having a predetermined width and length on both sides and bottom surfaces of the upper and lower beams.

[0014] The stacked beam is provided with a steel plate glued or screwed longitudinally to the bottom surface of the upper and lower beams fastened with the dedicated wood screws of the stacked beam described above, and a U-shaped fiber sheet having a predetermined width and length is glued and reinforced across the upper and lower beams on both sides and the bottom of the upper and lower beams.In this case, it is also possible to glue and reinforce the bottom of the beams longitudinally with a long fiber sheet instead of a steel plate. [Effects of the Invention]

[0015] The fiber sheet and special wood screws of this invention prevent misalignment and slippage at the interface of the overlapping beams, integrating the existing beams with the reinforced beams. This eliminates the need for adhesives or other fastening methods, eliminating the need to machine the uneven surfaces of the multiple material beams to be joined, and the need to fit the uneven surfaces of the multiple material beams together to prevent axial shear misalignment, thereby providing a product that can be easily processed and manufactured.

[0016] In manufacturing the stacked beam of this invention, by using wood beams that are resistant to shear, bending, and deflection for the bottom and top beams of the multiple upper and lower beams to be joined, it is possible to increase the strength of the composite beam and significantly improve its performance.

[0017] By eliminating the process required for conventional stacked beams, it is possible to significantly shorten the construction period and reduce costs for the production of stacked beams. Furthermore, the current wood screws and tools for neck length are so efficient that it is possible to do without pre-drilling the wood screw holes, and the process of drilling the wood screw holes can also be omitted.

[0018] The stacked beams of this invention can be used not only in newly constructed buildings, but also as on-site fabricated stacked beams to reinforce existing beams in renovated buildings. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a perspective view of a plurality of upper and lower beams to be joined together before they are combined. [Figure 2] FIG. 1 is a perspective view of a plurality of upper and lower beams to be joined together after being combined. [Figure 3] FIG. 1 is a perspective view showing a state in which a plurality of upper and lower beams to be joined are combined and vertically reinforced with fiber sheets. [Figure 4] FIG. 1 is a perspective view showing a state in which a plurality of upper and lower beams to be joined are combined and then diagonally reinforced with fiber sheets. [Figure 5] FIG. 1 is a perspective view showing a state in which a U-shaped fiber sheet reinforcement is applied after combining a plurality of upper and lower beams to be joined. [Figure 6] FIG. 1 is a perspective view showing a state in which the bottom surfaces of the beams are reinforced with steel plates and further reinforced with U-shaped fiber sheets after combining multiple upper and lower beams to be joined. [Figure 7] FIG. 1 is a perspective view of the upper and lower beams to be joined before they are combined. [Figure 8] FIG. 1 is a perspective view of the upper and lower beams to be joined together. [Figure 9]FIG. 1 is a perspective view showing the upper and lower beams to be joined, after being combined and vertically reinforced with fiber sheets. [Figure 10] FIG. 1 is a perspective view showing the upper and lower beams to be joined, after being combined and diagonally reinforced with fiber sheets. [Figure 11] FIG. 1 is a perspective view showing the upper and lower beams to be joined, after being combined and reinforced with a U-shaped fiber sheet. [Figure 12] FIG. 1 is a perspective view showing the bottom of the beam reinforced with a steel plate after combining the upper and lower beams to be joined, and further reinforced with a U-shaped fiber sheet. [Figure 13] 1 is a diagram of a test specimen on which a bending test was conducted on the stacked beam of the present invention. [Figure 14] shows a detailed view of test specimen 4. [Figure 15] 1 is a graph showing the relationship curve between load and central deflection in a test. [Figure 16] 1 shows the mutual load-displacement relationship measured on the side of the overlapping beam (100 mm inside from the beam support point). Table 1 shows the test results obtained by multiplying the average value of three test specimens by the coefficient of variation. Photo 1 shows the state of displacement of the fiber sheet and the state of final destruction. DETAILED DESCRIPTION OF THE INVENTION

[0020] An embodiment of the present invention will be described below with reference to the drawings. In each drawing, the same or corresponding elements are designated by the same reference numerals, and redundant explanations will be omitted. [Example]

[0021] Figure 1 is a perspective view of multiple upper and lower beams to be joined before they are assembled. Here, the lowest beam 1 and the highest beam 2 are used for beam 0. Furthermore, the lowest beam 1 and the highest beam 2 have been pre-drilled 3 for dedicated wood screws 4. This pre-drilling involves drilling a hole with a diameter equivalent to the long neck of the dedicated wood screws 4 and notching out the head of the flat head. Current dedicated long-neck wood screws and tools have such high performance that they can be used without pre-drilling, eliminating the need for the wood screw hole drilling process.

[0022] Figure 2 is a perspective view of the upper and lower beams to be joined after they have been assembled using special wood screws 4. Here, the lowermost material beam 1 and the uppermost material beam 2 are fastened to the material beam 0 using the special wood screws 4.

[0023] Although not specifically shown, the multiple upper and lower beams to be joined may be material beam 0, with either or both of the lowest material beam 1 and the highest material beam 2 being double-stacked.

[0024] 3 and 4 are perspective views of the upper and lower beams to be joined after fiber reinforcement has been applied. Fig. 3 shows a stacked beam in which fiber sheet vertical reinforcement 5 has been applied to both sides of the stacked beam after assembly using the dedicated wood screws 4 shown in Fig. 2. A The overlap beam shown in Figure 4 has fiber sheet diagonal reinforcement 6 applied to both sides of the overlap beam. B Shows.

[0025] Although not specifically shown, the multiple upper and lower beams to be joined may be material beam 0, with either or both of the lowest material beam 1 and the highest material beam 2 being double-stacked.

[0026] 5 and 6 are perspective views of the upper and lower beams to be joined, with fiber sheet U-shaped reinforcement applied. Figure 5 shows a stacked beam in which fiber sheet U-shaped reinforcement 7 is applied to both sides of the stacked beam after assembly using the dedicated wood screws 4 shown in Figure 2. C The overlap beam shown in Fig. 6 is reinforced with steel plate reinforcement 8 in the longitudinal direction at the bottom of the beam, and U-shaped fiber sheet reinforcement 7 is applied to both sides of the overlap beam. D In this case, the steel plate reinforcement 8 is attached with adhesive or small wooden screws. In this case, it is also possible to adhesively reinforce the bottom surface of the beam with a long fiber sheet 7 in the longitudinal direction instead of the steel plate 8. This serves to strengthen the bending reinforcement and has the effect of increasing the toughness until bending failure.

[0027] Figure 7 is a perspective view of an embodiment other than the above, showing the lowermost beam 1 relative to the lower beam 0 before they are joined together. Figure 8 is a perspective view of the upper and lower beams after they have been joined together. Here, the lowermost beam 1 is fastened to the lower beam 0 using special wood screws 4.

[0028] 9 and 10 are perspective views of the upper and lower beams to be joined, after they have been combined and fiber reinforced. Figure 9 shows a stacked beam in which fiber sheet reinforcement 5 is applied vertically to both sides of the stacked beam after it has been combined using special wood screws 4. A Figure 10: Layer beam with fiber sheet diagonal reinforcement 6 applied to both sides of the layer beam B Shows.

[0029] 11 and 12 are perspective views of the upper and lower beams to be joined, with fiber sheet U-shaped reinforcement applied. Figure 11 shows a stacked beam with fiber sheet U-shaped reinforcement 7 applied to both sides of the stacked beam after assembly using the dedicated wood screws 4 shown in Figure 11. C The bottom of the beam is reinforced with steel plate reinforcement 8 in the longitudinal direction, and U-shaped fiber sheet reinforcement 7 is applied to both sides of the overlap beam. D In this case, the steel plate reinforcement is attached with adhesive or small wooden screws. In this case, it is also possible to reinforce the bottom of the beam with a long fiber sheet 7 in the longitudinal direction by adhesive instead of a steel plate 8. This has the effect of strengthening bending reinforcement and increasing toughness until bending failure.

[0030] Here, we conducted a strength test on the overlapping beams shown in Figures 9 and 10, and the effects and results are shown below. This test was conducted in accordance with the test method specified in "7. Bending strength and bending Young's modulus" of the "Strength Test Manual for Structural Timber" (Japan Housing and Wood Technology Center, March 2011). The test was carried out using a full-scale strength testing machine (Tokyo Koki Seizosho WU-1000, capacity 1,000 kN). The bending test conditions were a four-point bending method with a span of 3,640 mm and a distance between load points of 280 mm, and load was applied monotonically at a rate of 5 mm per minute until failure. The bending deflection at the center of the span was measured at two points, on the front and back, using a displacement transducer with a capacity of 100 mm, and the average of these measurements was taken as the center deflection.

[0031] The test specimens were an existing beam (symmetrical mixed-grade laminated timber, strength grade E120-330, species: spruce) and an existing beam to which a reinforced beam (symmetrical mixed-grade laminated timber, strength grade E105-F300, species: larch) was integrated using wood screws for wooden structures or fiber sheets. There were four types of test specimens, ▲1▼ to ▲4▼, with three specimens of each specification. The specifications of the test specimens are shown in Figure 13. Figure 14 shows a detailed diagram of test specimen ▲4▼.

[0032] Here, specimen 1▼ represents material beam 0 as the existing beam, and specimen 2▼ represents the existing beam and the reinforced beam, with the lowest material beam 1 fastened to material beam 0 using special wood screws 4, with the screws installed in two rows on the beam end side across the beam width. Specimen 3▼ is specimen 2▼'s overlapping beam with the beam end side densely reinforced and fiber reinforcement applied vertically on both sides. Specimen 4▼ is specimen 2▼'s overlapping beam with the beam end side densely reinforced and fiber reinforcement applied diagonally on both sides.

[0033] The test results, where the average value of three specimens was multiplied by the coefficient of variation, are shown in Table 1, and the load-displacement relationship is shown in Figure 15. Here, δmax is the maximum load, δmax is the central deflection at the maximum load, P10mm is the load when the deflection is 10mm, and PL / 250 is the load when the deflection reaches 1 / 250 of the span (=14.56mm). The initial stiffness K was calculated from 0.1Pmax and 0.4Pmax.

[0034] As a consideration and evaluation, the strength P when a deflection limit of 10 mm is adopted in the design 10mmCompared to the unreinforced specimen (1), which served as the benchmark, specimen (2) had almost the same performance, specimen (3) had 1.2 times the performance, and specimen (4) had 1.5 times the performance. Furthermore, a comparison of specimens (3) and (4) shows that changing the sheet angle clearly improved rigidity. For specimen (3), a change in rigidity was observed near 20 kN, which is thought to be due to the sheet and adhesive performance providing resistance from the beginning of the load, and the adhesive weakening near the beam interface causing gradual sliding and peeling. Ultimately, no visible peeling or breakage of the sheet occurred.

[0035] Figure 16 shows the load-displacement relationship measured on the side of the stacked beam (100 mm inward from the beam support point), and Photo 1 shows the sheet misalignment and final failure. The misalignment at the measurement point at Pmax was 4.2 mm for specimens 2 and 3, and 2.8 mm for specimen 4. By setting the sheet at an angle of 30° to 70°, the sheet absorbs the tensile force, significantly increasing initial rigidity and strengthening the integration of the beams. The greater the angle, the greater the tensile force acting on the sheet, which is thought to be effective in preventing shear at the beam interface (here, a 65° sheet angle was used). In all specimens, bending cracking progressed from the center of the beam, leading to failure. Since there was no mechanism to prevent brittle fracture, no improvement in toughness due to reinforcement was observed. However, reinforcement using U-shaped sheets with fiber or steel plates is likely to prevent brittle fracture and improve the toughness of the stacked beams. [Industrial Applicability]

[0036] The stacked beams of this invention are simple and have new performance and effects, and can be produced cheaply and easily without the need for manufacturing in a factory with large-scale facilities. Therefore, stacked beams can be used as beams for new construction and for extensions and renovations, and can even be manufactured on the construction site. [Explanation of symbols]

[0037] A Example of the stacked beam of this invention (reinforced with vertical fiber sheets) B Another example of the overlapping beam of this invention (reinforced with diagonal fiber sheets) C Another example of the overlapping beam of this invention (reinforced with U-shaped fiber sheet) D Another example of the overlapping beam of this invention (steel plate + fiber sheet U-shaped reinforcement) 0 Material Beam 1 Bottom beam 2 Top material beam 3 Pre-processing of wood screw holes for special wood screws 4 Special wood screws 5. Fiber sheet vertical reinforcement 6 Fiber sheet diagonal reinforcement 7. U-shaped fiber sheet reinforcement 8 Steel plate beam bottom reinforcement (long fiber sheets can also be used in place of steel plates to reinforce the beams longitudinally)

Claims

1. A process of drilling wood screw holes in beams with a small beam thickness relative to the joint surfaces of multiple upper and lower beams to be joined, and a process of combining the multiple upper and lower beams by fitting them together with dedicated wood screws used in the wood screw holes at dedicated screw intervals that do not cause axial shear misalignment; a pre-cutting step for fitting both ends of the combined upper and lower beams into beam support hardware attached to columns; A stacked beam with a.

2. A stacked beam comprising a plurality of upper and lower beams fastened together with dedicated wood screws of the stacked beam as claimed in claim 1, and reinforced by adhesively joining the upper and lower beams vertically with a fiber sheet having a predetermined width and length.

3. A stacked beam comprising a plurality of upper and lower beams fastened together with dedicated wood screws of the stacked beam as claimed in claim 1, and a fiber sheet having a predetermined width and length is adhesively reinforced across the upper and lower beams in a diagonal direction.

4. A stacked beam comprising a plurality of upper and lower beams fastened together with dedicated wood screws of the stacked beam as described in claim 1, and U-shaped fiber sheets having a predetermined width and length are adhesively reinforced across the upper and lower beams on both sides and bottom surfaces of the upper and lower beams.

5. A stacked beam comprising: a plurality of upper and lower beams fastened together with dedicated wood screws for the stacked beam described in claim 1; steel plates glued or screwed longitudinally to the bottom surfaces of the beams; and a U-shaped fiber sheet having a predetermined width and length glued across and reinforced the upper and lower beams on both sides and bottom surfaces of the plurality of upper and lower beams.

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