Recombinant bamboo slab seismic isolation support and manufacturing method thereof

Abstract

The present application relates to a kind of reconstituted bamboo board seismic isolation support and its manufacturing method, the seismic isolation support is provided with at least one layer reconstituted bamboo board, reconstituted bamboo board includes annular bamboo ring and rubber ring by inner layer to outer layer alternating annular nesting arrangement, and the grain direction of annular bamboo ring is consistent with its annular direction, annular bamboo ring and rubber ring are nested and are connected as a whole by annular end face hot vulcanization each other after nesting.After being selected bamboo, it is formed plane bamboo board material, then cutting is formed the bamboo board of required length, width, and tenon and mortise part is formed at the both ends of bamboo board, after being treated by high-temperature saturated steam softening, it is placed in cylindrical mould, and it is formed required annular bamboo ring after drying treatment, finally, according to the order of annular bamboo ring and rubber ring from small to large diameter, reconstituted bamboo board is formed by alternating nesting in sequence, and finally, through reconstituted bamboo board, rubber layer is sequentially stacked and connected as a whole by hot vulcanization, and shock-absorbing seismic isolation support is prepared.The support has better support stability and seismic performance.

Description

Technical Field

[0001] This invention relates to seismic isolation bearings in the field of construction, specifically a reconstituted bamboo panel seismic isolation bearing and its manufacturing method. Background Technology

[0002] Current research indicates that laminated rubber seismic isolation bearings made using traditional reconstituted bamboo panels instead of steel plates offer significant advantages such as being environmentally friendly, readily available materials, and low cost. Furthermore, the lightweight nature of reconstituted bamboo panels greatly reduces the difficulty of transportation, installation, and maintenance, making them suitable for rapid replacement after earthquakes. Therefore, this type of seismic isolation bearing has broad application prospects in rural and urban buildings. However, the in-plane anisotropy of reconstituted bamboo panels—specifically, the significant differences in elastic modulus and shear strength along the grain compared to the cross-grain direction—significantly increases the design complexity of both the seismic isolation bearings and the seismically isolated buildings. In addition, the brittle nature of reconstituted bamboo panels during failure, exhibiting sudden and cascading failures, is also detrimental to the energy absorption and safe load-bearing capacity of the seismic isolation bearings.

[0003] The main reasons for the in-plane mechanical anisotropy of traditional reconstituted bamboo boards are twofold: (1) Bamboo itself is an anisotropic material, with parallel and neat vascular bundles and consistent grain, lacking transverse connections, resulting in significant differences in mechanical properties along the longitudinal and transverse grain directions within the plane; (2) The processing method of reconstituted bamboo boards leads to their mechanical anisotropy. Specifically, as shown in the appendix... Figure 8 As shown, reconstituted bamboo board is a profile made by processing bamboo into long strips, bamboo filaments, or crushed bamboo filament bundles, drying, impregnating with glue, rolling and straightening them, laying them in a mold, and then heat-curing them under high temperature and pressure. Its most distinctive feature is that the bamboo strips, bamboo filaments, or bamboo filament bundles are all arranged in the same direction, giving it a clear longitudinal and transverse grain orientation. The tensile and compressive strength and stiffness along the longitudinal grain direction depend entirely on the bamboo material; however, along the transverse grain direction, the bamboo strips, bamboo filaments, or bamboo filament bundles are connected by glue, and their tensile and compressive strength and stiffness depend entirely on the glue. This results in a significant difference in the mechanical properties along the longitudinal and transverse grain directions, and both directions exhibit brittleness upon failure.

[0004] Furthermore, the rubber and stiffening layers of laminated rubber seismic isolation bearings used in buildings are mostly circular to uniformly bear seismic forces in any direction. When traditional reconstituted bamboo boards are cut into circles, the adhesive strength at the edges along the transverse grain is weakest, making them most prone to brittle, sudden cracking. After cracking, the transverse load-bearing capacity and shear stiffness are significantly reduced. Peripheral cracking can also trigger a chain reaction, causing rapid brittle cracking of the adhesive-bonded areas along the transverse grain from the outside in, resulting in a significant decrease in seismic isolation performance.

[0005] In summary, there is a need to improve existing reconstituted bamboo panels, especially those used in seismic isolation bearings in the building field, so that they can exhibit in-plane mechanical isotropy and ductile failure characteristics when used in building seismic isolation bearings, thereby producing lightweight, high-performance building seismic isolation bearings. Summary of the Invention

[0006] To overcome the above-mentioned shortcomings, the purpose of this invention is to provide a reconstituted bamboo board seismic isolation bearing and its manufacturing method, thereby solving the technical problems that existing reconstituted bamboo boards are unsuitable for manufacturing laminated rubber bearings, or that the laminated rubber bearings manufactured from them have poor stability and are prone to cracking due to the in-plane mechanical anisotropy of the reconstituted bamboo board, resulting in failure of seismic isolation performance. This objective is achieved through the following technical solution.

[0007] A reconstituted bamboo seismic isolation bearing, the key structural feature of which is that the reconstituted bamboo seismic isolation bearing has at least two layers of reconstituted bamboo boards. The reconstituted bamboo boards include annular bamboo rings and rubber rings arranged in an alternating ring nested arrangement from the inner layer to the outer layer, and the direction of the grain of the annular bamboo rings is consistent with the direction of their own rings. The innermost layer of the reconstituted bamboo boards is an annular bamboo ring, and the outermost layer is a rubber ring. The annular bamboo rings and rubber rings are nested together and connected to each other by hot vulcanization of the annular end faces. Through this structure, the reconstituted bamboo board exhibits superior stability. Under seismic shear force, only a small portion of the grain within the board is perpendicular to the shear force direction. The shear force in other areas is effectively decomposed into transverse forces perpendicular to the grain direction and longitudinal forces along the grain direction. The transverse forces cancel each other out, preventing the generation of transverse inward forces. The longitudinal forces, however, cause the bamboo fibers in the reconstituted bamboo board to be under tension, creating longitudinal inward forces. Therefore, this reconstituted bamboo board possesses isotropic mechanical characteristics in the plane, exhibiting reliable load-bearing stability and producing the same seismic isolation effect under seismic forces from any direction. Furthermore, rubber rings are embedded between adjacent annular bamboo rings. These rubber rings coordinate the shear deformation of the annular bamboo rings along their thickness and horizontal circumferential directions. When local bamboo fibers reach tensile strength and experience sudden brittle fracture, the rubber rings quickly distribute the tensile force, then evenly transfer it to the entire annular bamboo ring, preventing all bamboo fibers from suddenly fracturing. This results in ductility, reducing the likelihood of sudden failure in load-bearing and seismic isolation performance.

[0008] This reconstituted bamboo panel seismic isolation bearing comprises upper and lower layers of reconstituted bamboo panels, with a rubber layer between each panel. The rubber layers are bonded to the end faces of the bamboo panels via heat vulcanization. This structure constitutes a specific implementation of a laminated rubber bearing, exhibiting superior load-bearing stability and seismic isolation performance.

[0009] The central part of the reconstituted bamboo panel seismic isolation bearing, specifically the middle of the innermost annular bamboo ring of each reconstituted bamboo panel, serves as a filling cavity, which is filled with matching sandbags. This structure further enhances the load-bearing capacity, seismic isolation, and energy dissipation and damping capabilities.

[0010] The tensile strength of the bamboo rings in the reconstituted bamboo board gradually increases from the inner layer to the outer layer. Because the tensile force on the reconstituted bamboo board varies depending on the diameter of the rings under vertical compression and horizontal shear, adapting the strength of each ring to the specified dimensions can further improve load-bearing stability and vibration damping performance.

[0011] The annular bamboo ring in the reconstituted bamboo board is formed by rolling a single piece of bamboo board or by splicing together segmented arc-shaped bamboo boards. This structure, implemented as an annular bamboo ring, is suitable for manufacturing laminated rubber supports of different sizes.

[0012] When the ring-shaped bamboo ring is formed by rolling up a single piece of bamboo, the two ends of the single piece of bamboo are connected by mortise and tenon joints. When the ring-shaped bamboo ring is formed by splicing together segmented arc-shaped bamboo pieces, the segmented arc-shaped bamboo pieces are connected by mortise and tenon joints. Through this structure, the structural connection is more reliable and convenient.

[0013] In this reconstituted bamboo panel seismic isolation bearing, the tensile strength of the bamboo in the annular bamboo ring of the lower layer of reconstituted bamboo panel is greater than that of the bamboo in the annular bamboo ring of the upper layer of reconstituted bamboo panel. This structure helps to further improve the stability of load-bearing capacity and the seismic isolation performance.

[0014] The manufacturing method of this reconstituted bamboo panel seismic isolation bearing includes the following steps: Step 1: First, select bamboo, remove the inner nodes and the green parts, and then perform high-temperature saturated steam softening treatment on it. Then, use a flattening roller to roll the bamboo in the direction of the grain to form a flat bamboo board without cracks. Step 2: Cut the flat bamboo board along the grain to form the required width of bamboo board, and cut it along the transverse grain perpendicular to the grain to form the required length of bamboo board, and plan the two ends of the bamboo board to form mortise and tenon joints. Step 3: Soften the bamboo board from Step 2 by using high-temperature saturated steam. Place the softened bamboo board into a steel cylindrical mold, so that the bamboo board is wrapped in a ring and the two ends of the bamboo board are connected and fixed by mortise and tenon joints. Step 4: Place the cylindrical mold along with the bamboo board into a constant temperature drying oven for drying. After drying, the ring-shaped bamboo ring is obtained. Step 5: Prepare the annular bamboo rings of the required sizes for the reconstituted bamboo board according to the process from Step 1 to Step 4. Step 6: Take a rubber ring corresponding to the size of the annular bamboo ring, and nest the annular bamboo ring and the rubber ring alternately in order of increasing diameter to form the reconstituted bamboo board. The end face of the reconstituted bamboo board is treated with hot vulcanization to connect the annular bamboo ring and the rubber ring into one piece. The end face of the reconstituted bamboo board after vulcanization is polished to form a flat end face. Step 7: The reconstituted bamboo boards are stacked from bottom to top, with a rubber layer between the upper and lower layers of reconstituted bamboo boards. The rubber layer and the reconstituted bamboo boards are bonded together by hot vulcanization, and the reconstituted bamboo board seismic isolation bearing is finally obtained.

[0015] In step one, when selecting bamboo, based on the characteristics of bamboo growth, the bamboo tip section is used to make annular bamboo rings near the outer layer of the reconstituted bamboo board, the bamboo trunk section is used to make annular bamboo rings near the middle layer of the reconstituted bamboo board, and the bamboo root section is used to make annular bamboo rings near the inner layer of the reconstituted bamboo board. Thus, the tensile strength of the bamboo in the reconstituted bamboo board gradually increases from the inner layer to the outer layer.

[0016] The cylindrical mold in step three is a stepped cylindrical mold, meaning that the cylindrical mold has an inner cylinder structure that adapts to the outer diameter of each annular bamboo ring in the reconstituted bamboo board. This method facilitates the one-time molding of annular bamboo rings of various specifications, improving production efficiency.

[0017] This invention has better load-bearing stability and vibration reduction and isolation performance. When used as a seismic isolation device, it has in-plane mechanical isotropy and ductile failure characteristics. Even if the cellulose in the reconstituted bamboo board is tensilely broken, it will not cause the seismic isolation bearing to fail immediately. It is safe and reliable to use and is suitable as a seismic isolation bearing for various types of buildings, especially rural buildings, or as a structural improvement of similar bearings. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the top surface structure of the reconstituted bamboo board of the present invention.

[0019] Figure 2 yes Figure 1 A cross-sectional structural schematic diagram.

[0020] Figure 3 This is a schematic diagram of the tenon and mortise connection structure of the annular bamboo ring of the present invention.

[0021] Figure 4 This is a schematic cross-sectional view of the overall structure of the laminated rubber support of the present invention.

[0022] Figure 5 This is a schematic diagram of the local stress structure of the reconstituted bamboo board of the present invention under horizontal seismic shear force.

[0023] Figure 6 This is a schematic diagram showing the decomposition of seismic shear force and resistance of the fibers in the reconstituted bamboo board of the present invention. In the diagram, F1 is the seismic shear force on the upper surface of the bamboo board, F2 and F3 are the decomposition forces of F1, F4 is the reverse resistance force on the lower surface of the bamboo board, and F5 and F6 are the decomposition forces of F4.

[0024] Figure 7 yes Figure 6Deformation diagram after earthquake.

[0025] Figure 8 This is a schematic diagram of the structure of an existing reconstituted bamboo board.

[0026] The numbers and names in the diagram are: 1. Circular bamboo ring, 102. Mortise and tenon joint, 2. Rubber ring, 3. Rubber layer, 4. Sandbag. Implementation

[0027] The present invention will now be further described with reference to the accompanying drawings.

[0028] like Figures 1-4 As shown, the reconstituted bamboo panel seismic isolation bearing consists of reconstituted bamboo panels stacked vertically, with rubber layers 3 between each panel. The rubber layers are bonded to the end faces of the reconstituted bamboo panels via heat vulcanization. Each reconstituted bamboo panel comprises alternating rings 1 and 2 of bamboo and rubber rings arranged from the innermost to the outermost layer, with the bamboo rings' grain direction aligned with their own ring direction. The nesting structure is as follows: the innermost layer is a bamboo ring, with a first layer of rubber ring nested outside the bamboo ring, a second layer of bamboo ring nested outside the first layer of rubber ring, and so on, with several layers nested in this manner. The final outermost layer of the reconstituted bamboo panel is a rubber ring, and the nested bamboo and rubber rings are bonded together via heat vulcanization of their annular end faces. A filling cavity 101 is formed in the middle of the innermost bamboo ring of the reconstituted bamboo panel, filled with integral sandbags 4 to improve load-bearing and seismic isolation performance.

[0029] Furthermore, considering that the tensile forces on the annular bamboo rings of different diameters vary under vertical compression and horizontal shear in the reconstituted bamboo panel, the tensile strength of the bamboo material in the annular bamboo rings is set to gradually increase from the inner layer to the outer layer. This compensates for the differences in tensile force, thereby achieving better load-bearing stability and seismic isolation performance. In addition, the tensile strength of the bamboo material in the annular bamboo rings of the lower layer of the seismic isolation bearing can also be greater than that in the annular bamboo rings of the upper layer, which further improves load-bearing stability and seismic isolation performance.

[0030] The specific manufacturing method of this reconstituted bamboo panel seismic isolation bearing includes the following steps: Step one: First, select bamboo, remove the inner nodes and the green parts, and then perform high-temperature saturated steam softening treatment on it. Then, use a flattening roller to roll the bamboo in the direction of the grain to form a flat bamboo board without cracks.

[0031] Step two: Cut the flat bamboo board along the grain to form the required width, and cut it along the transverse grain perpendicular to the grain to form the required length. Then, plan the two ends of the bamboo board to form mortise and tenon joints.

[0032] Step 3: Soften the bamboo board from Step 2 by using high-temperature saturated steam. Place the softened bamboo board into a steel cylindrical mold, so that the bamboo board is wrapped in a ring, and fix the two ends of the bamboo board together with mortise and tenon joints.

[0033] Step four: Place the cylindrical mold along with the bamboo board into a constant temperature drying oven and dry it at a temperature of 105℃. After drying, a ring-shaped bamboo ring is obtained.

[0034] Step 5: Prepare the required ring-shaped bamboo rings of various sizes for the reconstituted bamboo board by following the process from Step 1 to Step 4.

[0035] Step 6: Take a rubber ring of the corresponding size of the bamboo ring and nest the bamboo ring and rubber ring alternately in order of increasing diameter to form a reconstituted bamboo board. The end face of the reconstituted bamboo board is then treated with heat vulcanization to connect the bamboo ring and rubber ring into one piece. After vulcanization, the end face of the reconstituted bamboo board is polished to form a flat end face.

[0036] Step 7: Stack the reconstituted bamboo boards from bottom to top, with a rubber layer between the upper and lower layers of reconstituted bamboo boards. The rubber layer and the reconstituted bamboo boards are bonded together by hot vulcanization, and the reconstituted bamboo board seismic isolation bearing is finally obtained.

[0037] In step one above, when selecting bamboo, based on the characteristics of bamboo growth, the bamboo shoots are used to make rings near the outer layer of the reconstituted bamboo board, the bamboo trunks are used to make rings near the middle layer of the reconstituted bamboo board, and the bamboo roots are used to make rings near the inner layer of the reconstituted bamboo board. Thus, the tensile strength of the bamboo in the reconstituted bamboo board gradually increases from the inner layer to the outer layer.

[0038] The cylindrical mold in step three above is a stepped cylindrical mold, meaning that the cylindrical mold has an inner cylinder structure that adapts to the outer diameter of each annular bamboo ring in the reconstituted bamboo board. This allows for the drying and molding of multiple specifications of annular bamboo rings in a single operation, improving production efficiency. Furthermore, each inner cylinder within the cylindrical mold, corresponding to the size of the annular bamboo ring, can be rolled and filled with multiple sets of annular bamboo rings at once, further enhancing production efficiency.

[0039] In steps two and three above, if the length of the flat bamboo board is insufficient to meet the required length of the annular bamboo ring (i.e., the bamboo board is not long enough to make a perfectly round annular bamboo ring), segmented curved bamboo boards can be made first. The ends of each segmented curved bamboo board are planed to form tenons and mortises. Adjacent segments of curved bamboo boards are then connected using tenons and mortises and rolled together to form the annular bamboo ring. This method is beneficial for producing laminated rubber supports of different sizes and also improves the utilization rate of bamboo, reducing resource waste.

[0040] Based on the above, the working principle of this reconstituted bamboo panel seismic isolation bearing is explained as follows: Under seismic shear force in any direction, the reconstituted bamboo panel seismic isolation bearing, such as Figure 5 , Figure 6 As shown, the shear force on the surface of the reconstituted bamboo board is perpendicular to the grain direction in only a very small portion; the shear force in other portions forms an angle with the grain direction, with a maximum angle of 90 degrees. When the in-plane shear force (such as F1 and F4) forms an angle with the grain direction, it is decomposed into transverse shear force (such as F2 and F5) perpendicular to the grain direction and longitudinal shear force (such as F3 and F6) along the grain direction. The seismic shear force F1 on the upper surface of the reconstituted bamboo board balances the opposing resistance F4 on the lower surface, thus causing the components of force F3 and F6 perpendicular to the grain direction on the bamboo fibers in the reconstituted bamboo board to cancel each other out, without generating transverse inward force; while the component of force along the grain direction causes tension on the bamboo fibers, thus generating longitudinal inward force. The state after tension is as follows: Figure 7 As shown in the diagram. This means that under shear force in any direction, the bamboo fibers in the reconstituted bamboo board are only subjected to inward forces along the grain. Therefore, the shear strength and stiffness of the reconstituted bamboo board depend on the mechanical characteristics of the bamboo fibers along the grain, thus exhibiting isotropic mechanical properties in the plane. This allows it to maintain the same seismic isolation performance when subjected to seismic forces in any direction, providing reliable load-bearing stability. Furthermore, the use of rubber rings in the reconstituted bamboo board coordinates the shear deformation of the annular bamboo ring along its thickness and horizontal circumferential direction. When a local bamboo fiber reaches its tensile strength and suddenly fractures brittlely, the rubber ring quickly distributes the tensile force, then evenly transmits the force to the entire annular bamboo ring, preventing the sudden breakage of all bamboo fibers. This results in ductility and reduces the likelihood of sudden seismic isolation failure.

[0041] The above description is intended to illustrate the technical means of the present invention and is not intended to limit the scope of the invention. Any obvious improvements or substitutions made to the present invention by those skilled in the art based on existing common knowledge also fall within the protection scope of the claims of the present invention.

Claims

1. A reconstituted bamboo board seismic isolation bearing, characterized in that... The reconstituted bamboo board seismic isolation bearing is provided with at least two layers of reconstituted bamboo board. The reconstituted bamboo board includes annular bamboo rings (1) and rubber rings (2) arranged in an alternating ring nested arrangement from the inner layer to the outer layer. The direction of the annular bamboo rings along the grain is consistent with their own annular direction. The innermost layer of the reconstituted bamboo board is annular bamboo rings, and the outermost layer is rubber rings. The annular bamboo rings and rubber rings are nested together and connected to each other by hot vulcanization of the annular end face.

2. The reconstituted bamboo board seismic isolation bearing according to claim 1, characterized in that... The reconstituted bamboo board seismic isolation bearing is provided with the reconstituted bamboo boards stacked in upper and lower layers, and a rubber layer (3) is provided between each reconstituted bamboo board. Each rubber layer is connected to the end face of the reconstituted bamboo board by heat vulcanization.

3. The reconstituted bamboo panel seismic isolation bearing according to claim 1, characterized in that... The middle part of the reconstituted bamboo board seismic isolation bearing, that is, the middle part of the innermost annular bamboo ring (1) of each reconstituted bamboo board, serves as the filling cavity (101), and the filling cavity is filled with matching sandbags (4).

4. The reconstituted bamboo panel seismic isolation bearing according to claim 1, characterized in that... The tensile strength of the bamboo material in the annular bamboo ring (1) of the reconstituted bamboo board gradually increases from the inner layer to the outer layer.

5. The reconstituted bamboo panel seismic isolation bearing according to claim 1, characterized in that... The annular bamboo ring (1) in the reconstituted bamboo board is formed by rolling a whole piece of bamboo board or by splicing together segmented arc-shaped bamboo boards.

6. The reconstituted bamboo board seismic isolation bearing according to claim 5, characterized in that... When the ring-shaped bamboo ring (1) is formed by rolling up a whole piece of bamboo board, the two ends of the whole piece of bamboo board are connected by mortise and tenon joints. When the ring-shaped bamboo ring is formed by splicing together segmented arc-shaped bamboo boards, the segmented arc-shaped bamboo boards are connected by mortise and tenon joints.

7. The reconstituted bamboo panel seismic isolation bearing according to claim 1, characterized in that... The tensile strength of the bamboo material in the annular bamboo ring (1) of the lower layer of the reconstituted bamboo board seismic isolation bearing is greater than that of the bamboo material in the annular bamboo ring of the upper layer of the reconstituted bamboo board.

8. A method for manufacturing a reconstituted bamboo panel seismic isolation bearing as described in claim 1, characterized in that... The production method includes the following steps: Step 1: First, select bamboo, remove the inner nodes and the green parts, and then perform high-temperature saturated steam softening treatment on it. Then, use a flattening roller to roll the bamboo in the direction of the grain to form a flat bamboo board without cracks. Step 2: Cut the flat bamboo board along the grain direction to form a bamboo board of the required width, and cut it along the transverse grain direction perpendicular to the grain direction to form a bamboo board of the required length. Then, plan the two ends of the bamboo board to form a tenon and mortise joint (102). Step 3: Soften the bamboo board from Step 2 by using high-temperature saturated steam. Place the softened bamboo board into a steel cylindrical mold, so that the bamboo board is wrapped in a ring and the two ends of the bamboo board are connected and fixed by mortise and tenon joints. Step 4: Place the cylindrical mold along with the bamboo board into a constant temperature drying oven for drying. After drying, the ring-shaped bamboo ring (1) is obtained. Step 5: Prepare the annular bamboo rings of the required sizes for the reconstituted bamboo board according to the process from Step 1 to Step 4. Step 6: Take a rubber ring (2) corresponding to the size of the annular bamboo ring, and nest the annular bamboo ring and the rubber ring alternately in order of increasing diameter to form the reconstituted bamboo board. The end face of the reconstituted bamboo board is treated by hot vulcanization to make the annular bamboo ring and the rubber ring become one piece. The end face of the reconstituted bamboo board after vulcanization is polished to form a flat end face. Step 7: The reconstituted bamboo boards are stacked from bottom to top, and a rubber layer (3) is set between the upper and lower layers of reconstituted bamboo boards. The rubber layer and the reconstituted bamboo boards are connected together by hot vulcanization, and finally the reconstituted bamboo board seismic isolation support is obtained.

9. The method for manufacturing the reconstituted bamboo board seismic isolation bearing according to claim 8, characterized in that... In step one, when selecting bamboo, according to the growth characteristics of bamboo, the bamboo tip section is used to make an annular bamboo ring (1) near the outer layer of the reconstituted bamboo board, the bamboo trunk section is used to make an annular bamboo ring near the middle layer of the reconstituted bamboo board, and the bamboo root section is used to make an annular bamboo ring near the inner layer of the reconstituted bamboo board. Thus, the tensile strength of the bamboo in the reconstituted bamboo board gradually increases from the inner layer to the outer layer.

10. The method for manufacturing the reconstituted bamboo board seismic isolation bearing according to claim 8, characterized in that... The cylindrical mold in step three is a stepped cylindrical mold, that is, the cylindrical mold has an inner cylinder structure that is adapted to the outer diameter of each annular bamboo ring (1) in the reconstituted bamboo board.

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