Study On Mechanical Properties Of Inclined Wood Dowel Rotation Welding Composite Beams

The dowel rotation welding technology is an ecological welding technology with a wide range of application prospects.Beech dowel was used to rotate welding SPF in this paper.There were three different insertion angles designed,including vertical dowel,45° inclined,135° inclined.The influence of different insertion angles on performance of wood dowel rotation welding joints was investigated by pull-out test and shear resistance test.And calculation formulas for the shear capacity of the dowel rotation welding specimens were proposed by the force analysis of the dowels.On this basis,four kinds of timber-timber composite beams with different connection forms were designed,including vertical penetration(V),vertical cross(VC),inclined cross(IC),inclined parallel(IP).And then the four-point load bending test was carried out on the beams to analysis the bending performance of the wood dowel rotation welding composite beams with different connection forms.The conclusions were obtained as follows:(1)The insertion angle of the dowel,welding depth,and the direction of the substrate have an influence on the welding interface.Therefor the peak load of 45° inclined tensile test specimens was 16.0% higher than that of vertical specimens,but the tensile strength was 18.0% lower than that of vertical specimens.Both the two kind of specimens had similar initial stiffness(2)The 135° inclined dowel rotation welding specimens had the highest single-shear capacity,because of the rope effect.The dowels in 45° inclined dowel specimens borne the component force of lateral force,resulting in the lowest single-shear capacity.The shear capacity calculated by GB 50005-2017,NDS-2018,Eurocode 5 had large error.The calculation error of the formulas proposed according to the force analysis of the dowel were less than 15%.2y emF =M f d for vertical connection of single shear specimens,2 siny emF =M f d ? for 45° inclination welded single shear specimens,2 sin cosy em axFM f d ? +F ? for 135° inclination welded single shear specimens,and2 2y emF =M f d for vertical welding double shear specimens.(3)Relative slip was existed between layers during the bending test of wood rotation welding composite beams,so the composite beams do not meet the plane section assumption.The failure modes of dowel were consistent with that of the shear test.(4)Under the premise of the same number of dowels,the bending initial stiffness and bending modulus of elasticity of the composite beams were similar,which were three times of control group.The influence of different connection forms on the bending initial stiffness and bending modulus of elasticity is little.The peak load,yield load,energy consumption,bending strength of group T were larger than that of other three groups,because its shear area is the largest.The bending strength of group IC is 8.9% lower than that of group VC.The bending strength of group IP is 12.4% higher than that of group VC.It shows that the inclination direction of the dowel is opposite to the sliding direction of the laminate,which has an enhanced effect on the bending resistance of the timber composite beam.