Experimental Study On Shear Performance Of New Connectors Of Prefabricated GluBam-Concrete Composite Beams

Prefabricated glulam bamboo-concrete composite beam is a kind of green structure that the components of it are all processed and manufactured in the factory and assembled by shear connectors on site.It has higher precision of consructing,better construction efficiency,higher bearing capacity and bending stiffness,better ductility,compared with cast-in-place glulam bamboo-concrete composite beam.The connector is the key to ensure the performance of its good mechanical properties.However,the existing connector mainly has the following problems,the groove-type connectors have large stiffness rigid but small ductility,conversely,the pin-type connectors have good ductility but too little stiffness and other composite connectors are too complicated to product as a kind of connector using for prefabricated bamboo-concrete composite structures.Therefore,it is of great theoretical and practical significance to carry out the study on the prefabricated composite bamboo-concrete composite beam and design an applicable connector for it.Our team developed a new type of connector with good mechanical properties which named steel pipe-UHPC composite shear connector,based on the existing research.In order to explore the mechanical properties and the combined performance of this new type of connector,the shear test was performed on 16 groups of new types of composite shear connectors with different parameters.Then,we proposed a set of connectors with optimized parameters by comparing and analyzing the test results.According to the shear tests,we found that the specimens mainly produced three failure modes.The failure mode(1),shear failure of the connector,was observed at the interface of the composite structure.The failure mode(2),pull-out of steel core from the anchoring head.The failure mode(3),pull-out of cylindrical end of the connector from the glued bamboo beam.As to first two failure modes,the connects can fully exert their role of resisting shear load and relative slip,and the failure has obvious symptoms,so they are ideal failure modes.The third failure mode has a very low probability whitout a law of appearance,only one example of such failure mode occurred in all the specimens of this paper,which may be caused by the poor processing quality of glued bamboo beams and the manufacturing errors of the mounting holes.The results show that:In the case of the connectors with the certain thickness UHPC shell and the same type of steel core,their shear resistance and shear stiffness increase slightly following by the increase of steel core's diameter,and their ductility will be greatly improved,the connectors with large diameter of steel cores have better ductility;In the case of the connectors with a certain diameter of steel cores and the same type of steel core,their shear resistance and shear stiffness increase significantly following by the increase of UHPC shell's thickness,but their ductility drops obviously,the connectors with thicker UHPC shell have better shear resistance;In the case of the connectors with a certain diameter of steel cores and the certain thickness UHPC shells,the shear capacity of the connectors with the rebar as the core is slightly lower than the connector with the core of the screw,and the shear stiffness is greatly reduced which is possibly due to the bond a better bond between the screw and the UHPC shell.The results of this paper provide important data for the design and calculation of the shear connection of precast glued bamboo-concrete composite beams,which lays the foundation for the further study of this new composite structure.