Experimental Study On Glulam Beam-column Joints With Support

In recent ten years,the mechanical properties of long-span and multi-storey heavy timber structures have been paid more and more attention.As an important part of the internal force transfer and synergistic force of beam and column members,the mechanical properties of joints directly determine the bearing capacity and seismic performance of the structural system under static and dynamic loads.It is found that the overall lateral resistance of the timber frame structure is poor due to the limitation of the tensile strength of the wood grain and the low stiffness of the joints,which makes it difficult to guarantee the safety of the timber frame structure under earthquake action.At present,the anti-lateral stiffness measures of reinforced timber frame structures are mainly the combined application of timber frame,oblique bracing and shear wall.At present,most of the commonly used wooden beam-column structures are single-limb columns,and the connection between the beams and columns is made of steel filled plate bolts,which requires grooving of the beam ends,which causes great initial damage to the beams.In this paper,a double-column frame structure is proposed.The beam is clamped between the double-column,the joints are connected by bolts,and the joints are supported to improve the lateral stiffness of the structure.The structure is characterized by material saving and simple structure.Trial produced six full scale glulam beams-battened column frame structure nodes,four nodes specimen for the monotonic loading test,to study the node glulam initial rotational stiffness,bending strength and ductility of side resistance,on the other 2 nodes for low reversed cyclic loading test specimens,as to research in glulam node stiffness degradation,degradation of flexural bearing capacity and energy dissipation and seismic performance.Finally,ABAQUS software was used to model and analyze the four monotone loading specimens,and the best choice of bolt diameter and strength was given.The results show that:（1）The beam-column joints of unsupported frame structures are similar to articulated joints,and the damage of the beam ends is ductile,but the bending resistance is very small,so it is not suitable to be used as a structural system alone;The joints with braces significantly improve the rotational stiffness and flexural bearing capacity of the beam-column frame joints,but the failure of the beam ends shows severe splitting failure.（2）After the reinforcement measures of transverse grain constraint are adopted at the end of the beam,the joints take full advantage of the high compressive strength of the wood grain before the failure,which causes ductile failure of the joints,which meets the design requirements of "strong frame and weak support" of the wood structure;Due to the low tensile strength of the wood grain,the two joints were seriously damaged by the tensile strength of the beam grain under low cyclic loading.（3）The size of the support section has a significant effect on the rotational performance of the joints.The stiffness of the joints increases with the increase of the support section.The flexural capacity of the joints supported with small sections decreases slightly,but the ductility of the joints supported with small sections is better,and the joints have a strong flexural deformation capacity.The joints with braces have better aseismic performance.The stiffness and strength of the joints with two kinds of braces can be maintained at a higher level before failure,but the hysteretic curve of the joints with small braces is fuller,and the dissipation capacity of seismic input energy is stronger,and the aseismic performance is improved better.（4）the parameters of the finite element analysis results indicate that the node stiffness mainly depends on the support section size,the influence of bolt diameter is not big,and improve the bolt strength grade to improve the mechanical properties of the node is not big,the significance of the comprehensive comparison of each node in different bolt diameter and strength,after the initial stiffness and flexural bearing capacity under the recommended 14 mm diameter,strength grade of ordinary bolt with a magnitude of 4.8.