| With the rapid development of social economy,the appearance and the functional requirements of buildings are constantly upgraded.The innovation of building materials is an important technological means to maintain the balance between functional requirements and structural safety of buildings.As the main building materials in the present world,reinforced concrete materia has existed for more than one hundred years,the important reason for its long-term prosperity is that it contributes to the complementary advantage of the mechanical properties of the reinforcement and concrete.Fiber Reinforced Polymer(FRP for short)provide the possibility to enhance the single mechanical properties of the reinforcement.At present,there are two kinds of technologies which are used to make the product to improve the performance of reinforcement through FRP material,one is make the stronger reinforcement by twining fibers,the other is using fibers to clad steer bar to make the stronger reinforcement.The former uses polymer resin as matrix phase,its form of manufacturing reinforcement is twining fiber reinforced phase material and matrix material phase,fiber reinforced polymer bar(FRPB for short)is obtained in this way,the latter uses steer bar as matrix material phase,its form of manufacturing reinforcement is using fiber reinforced phase material to clad the matrix material phase,the steel-fiber composite bar(SFCB for short)is obtained in the second way.The common fiber reinforced phase material includes carbon fiber(C),glass fiber(G),aramid fiber(A)and basalt fiber(B).The main research object of this paper is basalt fiber reinforced polymer bar(B-FRPB for short)and steel-basalt fiber composite bar(B-SFCB for short)which take basalt fiber(B)for fiber reinforced phase material and formed by the above two kinds of technologies.There are two main considerations in choosing basalt fiber as fiber reinforced phase material: first,there are relatively few studies on basalt fiber,and there are many unknown technical spots for discussion;Second,there are natural affinity between basalt and cement-based materials,the basalt fiber is also environmental harmlessness and has economical efficiency,so it can bring great prospect in engineering application.When FRPB brings improvement of tensile strength,the material yield step almostly disappears,the limit of elongation decreases,and the material ductility is greatly reduced,which are not conducive to the ductility design of structural members.Concrete beam belongs to typical flexural members,when it replaces longitudinal steel bar with FRPB which has same cross section,the bearing capacity of normal section of the component will increase significantly,but the technical condition of applying FRPB to transverse reinforcement on large scale is still not established(the main reason is that FRPB bending process is not mature),this is not conducive to the realization of the component which follows the principle of "strong shear-weak bending".More deadly is,unlike " specification for concrete structure design",China,Europe,north American countries about the design of FRPB components in the specification(above specification which use FRPB as the research object but did not differentiated calculation differences between different reinforced phase materials,and the relevant specification of SFCB is still blank),has made clear that the existence of FRPB weakens inclined section bearing capacity of components,this make the design of component which follows the principle of "strong shear-weak bending" more difficult.In order to further refine the calculation of the shear bearing capacity of B-FRPB and B-SFCB longitudinal beam members within the inclined section and fill in the relevant research gaps,a series of failure experiments with reference significance were designed in this paper.In terms of specimen production,this paper adopted design ideas which has variable parameter,the parameter includes the low stirrup ratios(include0.19%,0.38%),high reinforcement ratios(include 1.13%,1.69%,2.25%,2.71%,3.64%),diverse shear span ratios(include 0.61,0.91,1.52,2.00,2.50,3.00),its main purpose has two: one is to ensure that can trigger component of shear failure,in order to study the bearing capacity of inclined section;Second,the influence of above parameters on the bearing capacity of the inclined section of the member is discussed through the change of parameters and the comparison conclusion.The experimental results show that the shear bearing capacity and shear ductility performance of B-FRPB longitudinal beam are inferior to that of RC beam,and when the load is similar,the B-FRPB longitudinal beam will produce wider and longer oblique cracks.When B-SFCB which is made by using basalt fiber to wrap the steel bar is used as tensile longitudinal reinforcement,compared with B-FRPB beam,B-SFCB beam maintains the characteristics of high strength,and has improved shear bearing capacity and shear ductility performance,it also enhances the ability to inhibit the development of oblique cracks.In this paper,the new type of bars are set as tensile longitudinal bar,which mainly participates in the shear load of beam members through the action of dowel action.Based on the calculation result of dowel action,the calculation formula of shear bearing capacity of B-FRPB and B-SFCB beams is given,and the calculation formula of shear bearing capacity is derived from the angle of shear mechanism,based on the truss arch model and the limit equilibrium theory which mainly considers the shear contribution of dowel action.Finally,the derivation formula is verified with the experimental data,and it is found that the derivation formula has better safety and applicability in the calculation of the shear capacity of B-FRPB and B-SFCB longitudinal reinforced beam,which can provide certain reference value for the follow-up research on the application of FRPB and SFCB in concrete beam. |
PDF Full Text Request