| Wood is a sustainable green building materials when the amount of harvested forests is balanced with stocks.Therefore,the construction is mainly based on wooden structures in foreign country,while the buildings in China are mainly brick-concrete,reinforced concrete and steel structures.These building materials consume a lot of energy,minerals and land at the expense of unsustainable building materials.In China,bamboo resources are abundant and the performance is excellent.Based on the thin outer dimensions of bamboo hollow walls,bamboo oriented strand board is one of the most effective and efficient approach for manufacturing high-quality bamboo-based composites and has the advantages of high strength and stable performance.The preparation process of bamboo oriented strand board is highly automated,and it is a kind of industrial material that can be mass-produced.At present,bamboo oriented strand board is mainly used in the fields of container floor,exterior wall finish and furniture,but it is rarely used in structural engineering.In this paper,the basic properties of the raw material Dendrocalamus giganteus Munro were first tested.The physical and mechanical properties of bamboo oriented strand board under different conditions and the finger jointing process of bamboo oriented strand board were studied.With bamboo oriented strand board as raw material,the bamboo I-beams and columns were designed and prepared,focusing on the bending performance of the bamboo I-beam,the short-beam shear strength of bamboo I-beam,the axial compression performance of the sectional column and the bolting joint performance of the bamboo oriented strand board.The study provides a theoretical basis for the design and application of bamboo in construction.The main results are as follows:?1?Through the study of air-dry density,compressive strength and bending strength of different bamboo age and bamboo stem height position,it was concluded that the air-dry and mechanical properties of bamboo increased from the age and height,and the mechanical properties of Dendrocalamus giganteus Munro could reach the performance index of building structural materials.?2?The physical-mechanical properties of bamboo oriented strand board with two distinctive orientation types including parallel aligned strand orientation?BOSL?and typical three-layer assembly with aligned strands in the face layers and orthogonally oriented strands in the core layer?BOSB?were researched.It was concluded that the board with three-layer assembly has better bending resistance,shear resistance,dimensional stability and aging resistance to moisture,which is more suitable for application in longitudinal and transverse forces,such as the webs in the I-beam and the column members.The board with parallel aligned strand orientation has superior tensile strength and compressive strength,which was more suitable for use in the flange of the I-beam and the compressed load-bearing column member.?3?In view of the available small-span bamboo oriented strand board jointed in length,the preeminent technological parameters and the impact of finger-jointing types,resin consumption and end pressure on its bending and tensile properties were investigated by means of orthogonal experiment.The results showed that the static bending strength,elastic modulus and tensile strength of finger-jointed bamboo oriented strand board were 74.05%,75.73%and64.12%of unfinger-jointed boards,respectively,when the optimal technique parameters of finger-jointing type?,glue quantity of 290 g·m-2,the pressure of 3 MPa were determined.The finger-jointing type has significant influence on the bending strength and tensile strength of bamboo oriented strand board.The influence of resin consumption and end pressure on the bending strength,elastic modulus and tensile strength is not significant.?4?Under the same flange section,the shear performance of bamboo I-beam increased less as the beam height increased from 300 mm to 400 mm.The shearing performance of the bamboo I-beam prepared by the cold-press gluing connection of flange and web was higher than that of nail-gluing beam.The bending performance test of the bamboo I-beams showed that the bending moment and ultimate bearing capacity increase,the proportional load increases,and the mid-span deflection decreases as the beam height increases.Reasonable design of the cross-sectional shape size can reduce the deflection deformation.According to the calculation formula of the shear capacity and bending stiffness of the webbed I-beam provided by CAS 086-01,the error between the calculated and experimental value was within 15%.The formula can correctly calculate the shear bearing capacity and stiffness of the bamboo I-beam.The maximum bending moment of the I-beam can be calculated with reference to the theoretical formula corresponding to the different failure modes of the I-beam,and the precision was relatively high.?5?Three different sections of bamboo columns,including solid core columns,five-core columns and hollow columns are designed and prepared.When the same cross-sectional area and different sectional form of three columns were designed,the axial compression test showed that the ultimate bearing capacity of three column with a height of 1000 mm,2000 mm and2800 mm is not obvious,but the failure mode is different,Through the eigenvalue analysis and nonlinear analysis,the constitutive model of the axial compression of the reconstituted bamboo column was established,and the buckling process of the column was simulated by the finite element software ANSYS 16.0.The simulation value and the experimental value were well fitted.?6?According to dowel bearing strength testing of bamboo oriented strand,it is concluded that the bolt diameter has no significant effect on the dowel bearing strength under the condition that the sample size meets the minimum requirement.The dowel bearing strength of BOSL by loading in the length,width and thickness directions were different,the length direction?width direction?thickness direction.Study on the bearing performance of bolted joints between boards showed that the yield load,ultimate load and stiffness of the bolted joint increase by 38.03%,100.90%and 43.66%,respectively,as the thickness of the edge member BOSL increases from 28 mm to 56 mm.The yield load and ultimate load of the bolted joint specimens with washers and nuts are significantly larger than specimens without washers and nuts under the same thickness.According to the structural characteristics and mechanical strength of the bamboo oriented strand board,the calculation formula of the bearing capacity of the bolted joints in the American standard NDS-2015 and the European standard Eurocode 5should be corrected,which is suitable for the theoretical calculation of the bearing capacity in bamboo oriented strand board connecting bolts joints. |
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