Experimental Study On Bending Behavior Of Glued Wood Beams Connected With Steel Splints And Bolts

Glulam is an indispensable material in modern wood structures.It has the advantages of reasonable force,free cross-section and shape,high strength and scattered defects.However,because the wood section size is limited by the natural size,it can not be connected like concrete pouring,nor can it be welded like steel.Therefore,the connector with excellent performance and reasonable structure is used to lengthen the glued wooden beam to improve the glued wood.The utilization and promotion of the use of glued wood in timber construction has become crucial.In this paper,the steel plywood-bolt bonded glulam beam is taken as the research object.The bending resistance of the steel splint-bolt bonded glulam beam is discussed through the combination of experimental research,theoretical analysis and numerical simulation.The main research content includes the following aspects.(1)The bending capacity test of steel splint-bolt bonded glulam beams composed of glulam,Q345 grade steel plates and bolts.Through the bending capacity test of 13 sets of 39 beams,the bolt spacing and bolt arrangement and the staggered arrangement of the two beams are derived from the bending resistance of the same plywood-steel splint-bolt glulam beam.influences.Compared with pure glulam beams,the ultimate load-carrying capacity can be increased by 4%when the steel splint-bolt-bonded glulam beams are arranged at a distance of 100 mm.When the parallel bolts are 60 mm and 80 mm,the ultimate load capacity is not as good as that of ordinary glulam.Beam.The ultimate bearing capacity is proportional to the bolt spacing,that is,as the bolt spacing increases,the ultimate load carrying capacity of the steel splint-bolt bonded glulam beam will also increase.The ultimate deformation of steel splint-bolt-bonded glulam beams with parallel bolts of 60mm,80mm and 100mm is increased by 40.4%,47.7%and 49.8%respectively compared with ordinary glulam.The arrangement of the bolts and the staggered arrangement has no significant influence on the ultimate bearing capacity of the steel splint-bolt bonded glulam beams.The plywood-bolt-bonded glulam beams have higher stiffness in the early stage than the pure glulam beams,and the later-stage stiffness is not as good as that of the pure glulam beams.The initial stiffness is proportional to the spacing of the stud bolts.Whether the two spliced beams are derived from the same glulam beam has less influence on the bending resistance of the steel splint-bolt-bonded glulam beams.(2)Two test methods for the bearing strength of the wood pin groove and two corresponding methods for determining the bearing load of the pin groove were discussed.The advantages and disadvantages of the test and the determination method were analyzed.The theoretical calculation formulas of the bearing capacity of wood pin groove in the wooden structure design codes of various countries are listed,which provides a reference for the subsequent formula derivation.(3)Using the ultimate strain design method and the constitutive model of the glulam,the calculation formula of the flexural capacity of the glulam beam is proposed.The results calculated by the bending capacity formula are compared with the experimental results:the method has a high degree of agreement.The bolt bending moment formula is deduced,and the bolt spacing between the vertical and horizontal directions is increased under the premise of meeting the requirements of the specification.The bolts with higher strength grade or larger diameter are used,and the anti-slip coefficient ?of the friction surface can be increased.Bolt bending capacity.(4)The bending performance of ordinary glulam beam and steel splint-bolt glulam beam was analyzed by ANSYS finite element software.The influence of bolt spacing and bolt arrangement on the bending behavior of steel splint-bolt glulam beam was studied.And compare with the test results.The results show that whether the bolts are arranged in parallel or staggered,the stress is the highest at the bottom row of bolt holes.The staggered and parallel arrangement of the bolts has little effect on the bending capacity.The bending capacity is proportional to the bolt spacing.The laws are consistent with the test,which fully verifies the rationality of the steel plywood-bolt bonded glulam beam design.(5)The formula for calculating the slip modulus of a single bolt connection is given for the European standard EC 5.It is found that there is a big difference between the calculated value of the stiffness of the bolted joint and the test value.The possible causes of this phenomenon are:The calculation is inaccurate,the hole of the bolt hole in the test,the influence of the loading mode,and the uneven connection of the bolts of the joint.