Research On The Axial Compressive Performance Of FRP-bamboo Composite Structural Members

As a green building material that can be quickly regenerated,bamboo has been widely used in the construction of permanent and temporary buildings around the world.However,due to the relatively low compressive bearing capacity of bamboo and easy cracking during drying,its application is limited to low-rise building structures with small loads or small-span pedestrian bridges.Therefore,improving the compressive bearing capacity and durability of bamboo will expand the use of bamboo structures and promote the popularization and application of bamboo,a green building material,in medium and high-rise buildings or large-span bridges and other large-capacity engineering structures.The FRP-bamboo composite structural member and the FRP-bamboo-concrete composite structural member are a new composite structural member,which adopts the methods of wrapping FRP cloth and filling concrete to improve the traditional bamboo structural member.In this paper,with FRP cloth,bamboo node,and infill concrete as the main research parameters,the experimental research on the axial compression properties of FRP-bamboo composite structural members and FRP-bamboo-concrete composite structural members was carried out.That is,the axial compression tests of 12 FRP-bamboo composite structure specimens,12 FRP-bamboo-concrete composite structure specimens,4 bamboo-concrete composite structure specimens and 4 original bamboo structure specimens were carried out.The main research work and research results of this article are as follows:(1)The experimental study found that the failure mode of the FRP-bamboo composite structural member was that the specimen buckled inwards at multiple locations,causing the inner wall bamboo fiber to break and fail.There are two failure modes of FRP-bamboo-concrete composite members,namely the fracture failure of the carbon fiber cloth at the L / 2 specimen and the fracture failure of the carbon fiber cloth at the bottom of the specimen.Among them,the carbon fiber wrapping thickness is 0.167 mm,the slub specimen is the latter failure mode,and the remaining specimens are the former failure mode.(2)The rising section of the load-axial strain curve of the FRP-bamboo-concrete composite member is represented as a three-stage curve mode or a two-stage curve mode.The three-stage curve mode means that the curve of the first stage rises obliquely and linearly,and then the bearing capacity decreases slightly(second stage).The bearing capacity continues to rise after the second stage of decline until the specimen is destroyed(third stage).The stiffness of the specimen in the third stage becomes smaller and smaller than that of the first stage of the specimen.In the FRP-bamboo-concrete composite structural member,the rising section of the load-axial strain curve of the specimen without node is a three-stage curve mode.In the two-stage curve mode,there is no stage in which the bearing capacity decreases slightly.In the rising stage of the curve,the initial stiffness of the test piece is used to rise linearly,and then the stiffness of the test piece becomes smaller.The package thickness of the carbon fiber cloth in the FRP-bamboo-concrete composite member is 0.501 mm,and the load-strain curve of the specimen with node is a two-stage mode(3)The wrapping of FRP cloth can greatly improve the ultimate bearing capacity and ductility of bamboo structural members.When the wrapped thickness of CFRP cloth is 0.167 mm,the ultimate bearing capacity of FRP-bamboo composite structural members is increased by 144% and 92%,respectively,compared with the original bamboo specimens with and without bamboo node.When the thickness of the FRP cloth wraps further increased,the ultimate bearing capacity of the original bamboo structural members did not increase further.The reason was that the specimens buckled inwards and failed,while the outsourcing of the FRP cloth only prevented the specimens from buckling outwards.Within the range of the parameters studied in this paper,the CFRP cloth wrap thickness is 0.167 mm and the restraint effect is the best.(4)The ultimate bearing capacity of FRP-bamboo-concrete composite structural members increases as the thickness of CFRP cloth wraps increases.When the wrap thickness of CFRP cloth is 0.501 mm,the wrap capacity of CFRP cloth increases the ultimate bearing capacity of the test pieces node and without node by 260% and 162%,respectively.(5)Among the FRP-bamboo-concrete composite structural members,the ultimate bearing capacity of the specimen with node is greater than or equal to that the specimen without node,which shows that the slub helps to increase the ultimate bearing capacity of the FRP-bamboo-concrete composite structural member.However,the presence of the node does not affect the ultimate bearing capacity of the FRP-bamboo composite structural member.(6)The existence of concrete can improve the ultimate bearing capacity and initial stiffness of FRP bamboo composite structure,and can greatly improve the ductility of FRP-bamboo composite structure.The wrapping of FRP cloth and the existence of node do not affect the initial stiffness of the specimen.(7)The axial bearing capacity of the FRP-bamboo-concrete composite member has a combined effect,that is,the ultimate bearing capacity of the FRP-bamboo-concrete composite specimen is higher than the simple superposition of the three materials.The greater the thickness of the FRP package,the more obvious the combined effect.