Experimental Tests And Analysis Of GluBam-concrete Composite Beams

As a new composite system,GluBam/bamboo-concrete composite(BCC)beams consist of two parts,an upper concrete slab tied to a lower glubam beam by means of shear connectors.The shear connectors transmit the shear and prevent or reduce the relative slip between the lower fibre of the slab and the upp er fibre of the glubam beam depending on the efficiency of the connection;the concrete slab,mainly subjected to compression,takes advantage of the high compression strength and stiffness of concrete;the glubam beam,mainly subjected to tension and bend ing,benefits from the high tension strength to weight ratio of glubam.Compared to glubam-only beams,BCC beams are possible to significantly increase the strength and stiffness,effectively enlarge the span,considerably improve the acoustic separation,thermal mass and susceptibility to vibration.Therefore,the investigation on the basic mechanical properties of BCC beams is essential,which can be applied extensively to the exsiting building and new construction.This paper has carried out the research on the push-out tests,full-scale bending tests as well as the finite element analysis.The main research contents in this paper are as follows:Firstly,the push-out tests of dowel connector and notched connector were conducted.This paper selected threaded rod glued-in bamboo beam,and 200 mm length rectangular notch reinforced with screw as dowel connection,respectively.The major mechanical properties such as load-slip curves,shear bearing capacity and anti-slip stiffness were measured and evaluated.The test results indicate that: For the dowel connector,the diameter of rod equal to 18 mm is a critical value for the shear-slip behavior and seems to be a reasonable choice;the quality grade of threaded rod has not substantive effect on the mechanical properties and composite action;the action of the waterproof layer laid at the interface is temporary and it can be removed for improving the composite effect.For the notched connector,a longer length of notch is essential to improve the shear strength and stiffness.Furthermore,five full-scale GluBam-concrete composite beams were designed as SM-2?SC-18-25?NC-100-12?NC-200-8?NC-200-12 specimens,and tested to collapse under 4-point bending load.The load-midspan deflection curves,load-relative slip curves,strain distribution and the degradation curves of composite action were also obtained.Experimental results indicate that the SM and SC specimens exhibited brittle behavior due to the finger joint fractured.On the other hand,NC and PNC specimens exhibited a recovery of strength after the load decreased at peak load following the yielding of a connector.The sufficient number and optimized spacing of connectors in the beam can enhance the composite action of BCC beams significantly.As for the NC specimens,the beam with the longer notch performed better in stiffness and load-carring capacity.The tensile strength of concrete,also the strength of finger joint at the middle region and bonding strength of GluBam layers have great influence on the composite action of BCC beams.At the end,the finite element analyses of total GluBam-concrete composite beams were also presented.The concrete slab,glubam beam and connections were simulated by the three-dimensional solid modeling.Moreover,the characteristic of interface was comparatively well simulated,the outcomes of linear-elastic load-midspan curves were also obtained.The results of the finite element analysis were roughly the same as the experimental results,and the results showed a good accuracy.