| In recent years,with the improvement of national requirements in energy conservation and emission reduction,the use of new green materials is strongly advocated.Wood,as a traditional green and environment-friendly building material,is gradually favored by people.In order to solve the technical problems in the design and manufacture of load-bearing wood components for modern engineering in China,and provide technical support for the independent construction of heavy-duty engineering wood structure bridges and houses,based on the Cross laminated-timber(CLT)technology,a new type of engineering wood product developed in Europe and America in recent years,this paper presents a bidirectional CLT plate component which is suitable for the bidirectional force of bridge decks.Two kinds of bidirectional CLT plate members with different types of billet were fabricated by using xing’an larch laminate and polyurethane structural adhesive.The mechanical properties of CLT plates were studied by means of experiment and theoretical analysis.The results can be used as reference for engineering application.The main contents and results are as follows:1)Two kinds of bidirectional CLT plates with three layers and four layers glued together were made,and the bending test of the bidirectional CLT plates with four simply supported sides under the action of concentrated load in the middle span was carried out,and the failure pattern,vertical deflection and strain data in the middle span were observed.The bending failure mechanism of CLT bidirectional plate and the law of load-deflection and load-strain laws are revealed.The results show that the transverse cracks at the bottom of the plate are tensile failure under bending,the transverse cracks appear near the middle span of the bottom plate,and the cracks and sounds appear at the bottom of the front plate,which is a brittle failure.Compared with the three-layer slab,the flexural capacity of four-layer slab is increased by 22.7%,and the bending stiffness increased by 28.5%.The results show that the bearing capacity of plywood with four layers is greater than that of plywood with three layers under the same thickness.2)Based on the theory of orthotropic elastic plate,the deflection analysis and bearing capacity calculation of CLT bidirectional plate at elastic stage are carried out.The results show that in the elastic stage,the difference between the theoretical calculation value and the test value of the deflection of the three-layer plate and the four-layer plate is 12.4%and-2.97%,respectively.The numerical results are in good agreement,which shows that the calculation method adopted is reasonable and reliable.3)Abaqus finite element software was used to establish a bidirectional CLT plate model,and the mid-span deflection,stress and strain of the plate under load were analyzed,and the theoretical failure analysis mechanism of the four-sided simply supported CLT bidirectional plate was further revealed;The influences of parameters such as the number of glued layers,boundary conditions and aspect ratio on the bending performance of CLT bidirectional plates were analyzed.The results show that the deflection and tensile stress of the transverse failure of the bottom plate failure of the two sets of CLT specimens are similar to the experimental test values.The results of parameter analysis show that the more of laminated layer,the smaller the deflection under the concentrated load.However,when the number of adhesive layers is too much,the effect on its flexural strength is limited.When four-side support,the deflection of bidirectional plate is less than that of the opposite side support,so the bidirectional mechanical properties of CLT plate can be better played.When the aspect ratio of the larch CLT two-way plate is within 2:1,whether it is simply supported on the side or simply supported on four sides,the deflection of the two-way plate member increases with the increase of the aspect ratio. |
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