| Modern bamboo structure is a new and green structural system mainly developed in China,and it has increased the influence toward the international structural system.However,the low bending stiffness of bamboo beam limits the span of structure and becomes a bottleneck problem for developing modern bamboo structures.Based on the researches from the timber-concrete composite structures(TCC),it is an effective direction to improve the mechanical performance and the span of bamboo flexural members by developing the glued laminated bamboo(glubam)-concrete composite structures(BCC).Most of the existing TCC/BCC research focuses on the "wet" connection of concrete,however the connection mode exhibits obvious weaknesses.For example,the construction efficiency is low,and the large shrinkage and creep of concrete slabs have significant influence on the mechanical performance of composite beams.Oppositely,the "dry" composite beam based on prefabricated concrete slab and timber/glubam beam can effectively solve the aforementioned problems.The key is to design shear connectors suitable for prefabricated construction,which is the first step for the development of the assembled glubam/bamboo-concrete composite beams.A new type of prefabricated shear connection was proposed and investigated in the this paper.The hybrid system based on reactive powder concrete(RPC)filled thin-wall steel tube composite shear connectors with high stiffness and ductility was proposed,which has the advantages of good shear resistance,simple production process and low requirements for assembly precision.20 groups of shear performance tests on the composite connectors were carried out to obtain the basic shear performance index of the connectors in this paper.And the basic structural parameters of steel tube and RPC were analyzed.The main work accomplished and the basic conclusions obtained are as follows:(1)4 groups of tests with different anchorage lengths were carried out.The influence of anchorage length ratio on shear performance of the connectors was researched.The results showed that the increase of anchorage length ratio from 1:1 to 1:2 has the most obvious effect on the ultimate shear-resistant capacity and anti-slip stiffness,with the increase of 22.3% and 17.1% respectively.And the anchorage length has met the uplift bearing requirements.The shear-resistant performance can not be improved much or even the shear-resistant capacity will be reduced when the ratio of anchorage length is further increased over 1:2.Therefore,the anchorage length ratio of 1:2 is recommended in this paper,i.e.,the thickness of the concrete slab: the anchorage length of the connector within the glubam beam = 1:2.(2)4 groups of tests with different concrete slabs were performed to investigate the influence of concrete slab thickness on shear performance of the connectors.The results showed that the concrete slab is crushed when the thickness of concrete slab is 40 mm,that will limit the shear-resistant capacity and anti-slip stiffness of the shear connector,so it is not suitable for use.When the thickness of concrete slab increases to 50 mm,the concrete slab is not crushed,and the ultimate shear-resistant capacity and anti-slip stiffness increase significantly,by 15% and 17%,respectively.Then continue to increase the thickness of concrete slab,the increase of shear-resistant performance is decreased.So it is suggested that the thickness of concrete slab should be 50 mm.(3)14 groups of tests with different measures were conducted.The influence of the diameter and the wall thickness of the steel tube on shear performance of the connectors was studied.The results showed that the shear-resistant capacity and anti-slip stiffness of the connectors are increased when the wall thickness increases,and the ductility performance is enhanced.In addition,the increase of wall thickness has a greater effect on the anti-slip stiffness than on the ultimate shear-resistant capacity.As the diameter of the steel tube increases,the ultimate shear-resistant capacity and the anti-slip stiffness increase by a greater degree,and the steel content of the shear connector is decreased,the ductility becomes worse.Therefore,in this paper,it is recommended to adopt the form of shear connector with the steel tube diameter of 25 mm and the steel tube wall thickness of0.9 mm under the condition of the concrete slab thickness of 50 mm and the anchorage length ratio of 1:2.(4)Compared with the typical groove connectors,the shear-resistant efficiency in per unit area of the composite connector is higher.Compared with the typical dowelled connectors,the shear stiffness of the composite connector is significantly improved,and the failure mode is ductile.Therefore,the composite connector effectively combines the high ductility of the dowelled connector with the high stiffness of the groove connector.It is suitable for assembly construction and also has outstanding advantages in performance.The results from the proposed research will contribute to the further development of modern bamboo structures.The composite structure is expected to have good application prospects in new green buildings and renovations of older buildings. |
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