Experiments And Analysis Of The Mechanical Behavior Of Bolted Joints With Slotted-in Steel Plate In Timber Structures

Joints and connections are the key areas in timber structure design and research because timber can't be welded.Steel-to-timber bolted connections are easy to assemble so they have been used very widely.Due to this,researching the mechanical behavior of Steel-to-timber bolted connections is meaningful.There is no specific and separate design method of steel-to-timber bolted connections in chinses current timber structure design code,which can't satisfy the development of chinses timber structure.By comparing and analyzing different codes,this dissertation has derived a set of formulas used in designing the Steel-to-timber bolted connections which can be used in china.Then,the reasonability of the formula has been analyzed.It is reasonable to idealize the steel as thin or thick steel.It can simplify the formula and improve the efficiency of calculation,and the error of it is acceptable.The mechanical behavior of a steel-to-timber bolted joint is researched.The load-displacement curves and moment-rotation curves of the joint in different load cased are showed in this dissertation.The experiments show that the axial compressiveforce decreases the bearing capacity of the joint.The failure of the joint is happened in the extreme row,where the timber is tore.When the axial compressiveforce is 100 k N or zero,the tear is happened in the bottom row of holes whereas when the axial compressiveforce increases to 150 k N,the timber near the highest bolt holes is tore.The deformation of bolts and bolt holes is obvious.A finite element model of the joint is built using ABAQUS software.The result of finite element analyzing is similar with the experiments,having proved the validity of the finite element model.The Stiffness of the joint derived by finite element analyzing is higher than the experiment result.The gap between bolt and hole,the defect of timber and the way of loading all could cause this phenomenon.Parameters analysis have been done to research the influence of bolt diameter,bolt size,bolt arrangement and bolt yield strength.The effect of the top supporting to the joint has also been analyzed.Research result shows that it can increase the stiffness and bearing capacity of the joint dramatically particularly when there is axial compressiveforce.As for the joint with the top supporting,the axial compressiveforce can increase its bearing capacity and stiffness,which is completely different from the joint that is without the top supporting.Due to the good deformability of timber bolted joints,it will underestimate the bearing capacity if we just consider the elastic limit bearing capacity.A new method to calculate the plastic limit bearing capacity of the joint is introduced and the result of it is more accurate.A simple empirical formula is also introduced.The stiffness of the joint that is calculated using the method in EC5 is far from the result of experiments.However,the finite element analyzing result is relatively close to the experiments.