Experimental Study On Flexural Performance Of Glued Laminated Timber Beams With Glue Line Defects

Glued laminated timber structure has many remarkable advantages,such as,its excellent mechanical properties,earthquake resistance,energy-conserving effect,and convenient construction,etc.In addition,it meeting our country's significant demand for"green building,building industrialization",is gradually favored by people.The glued interface,areas containing the wood cell wall and adhesive,is the only channel to transfer stress and strain.It is also one of the key factors to decide material strength and service life.Therefore,glued interface plays a key role in the overall performance of composite material.In this paper,employing Larix gmelini,a kind of the domestic fast growing wood,three groups of glulam beams were manufactured to study its flexural performance.The specimen in group A is in good condition,in group B has one layer glue line defect,in group C has two layers glue line defect.The glued interface defect is artificial simulated.The main research content is as follows:1.An experiment is carried out to distinguish the artificial glue line defect using ultrasonic method.The PSD-V-A comprehensive criterion is used to distinguish the position,boundary and severity of the glue line defect.By comparing with the preset position of defect,the feasibility of ultrasonic method identifying the glue line defect is verified.2.Vibration method is used to test the elastic modulus of five layers glulam beams.The result is compared with the testing results of static method.By discussing the degree of correlation between the two methods,the paper carried out analyze on the veracity of vibration method in measuring the elastic modulus of simply supported glulam beams.3.The glulam beams is tested by static bending destructive test.The measured data,such as deflection,strain,bearing capacity,etc.is collected,and the failure mode and mechanism is recorded.The paper studied the flexural behavior of glulam beams with different glue line defect.The influencing rule of glue line defect effect on the flexural behavior of glulam beams is obtained.4.A glulam beam model corresponding with static method is created using finite element analysis software ANSYS.Based on the comparison results of three kinds of working conditions,the influence of glue line defect on glulam beams is analyzed.Then,compared with the test result,the paper verified the validity of the test results.