Experimental Research On Bending Fatigue Performance Of Glulam Beams

The research of Chinese modern wood structure was only in its infancy.Currently, the experimental study on the modern wooden structure mainly concentrated in the static test research,however there are a lot of research work on the dynamic performance to be done.In order to study dynamic performance of laminated wooden beam,this paper has successively developed test research on static test and fatigue test of the laminated wooden beam. A brief description of the main work in this thesis is presented here.The first, this paper engaged in the experimental study on the bend static test of three glulam beams, and summarizes the bending strength by analyzing the failure mode and stress of bond strength of laminated wooden beam.Glulam beams destruction form characterized by brittle failure in tension, the tension side mostly from pure bending of fiber breakage knag inside defect,so we can reinforce the the performance of laminated wooden beam by controlling the quality of tension surface of single plate of laminated wooden beam.The loading process of laminated wooden beam is divided into elastic stage and elastic-plastic stage.and elastic stage is the main stage.Due to the transient duration of elastic-plastic stage, so elastic stage is the main stage. Linear fit was done in load-deflection curves to 6 beam specimens which included 3 root bending static specimens and 3 root bending fatigue specimens in the elastic stage,and achieved the value of bending elastic modulus and bending rigidity.The second,this paper engaged in the experimental study on constant amplitude fatigue test by studying the influencing factors of laminated wooden beam load limit and fatigue loading times,analyzed the fatigue performance,such as fatigue failure mode,changes of fatigue stiffness,fatigue strain distribution,the degradation of fatigue residual an so on.The results showed that,the cross section sudden fracture when the bearing capacity was 65% of ultimate,which the fatigue cyclic load to 451600 times, it was concluded that specimen fatigue strength is less than 0.65 Pu.Structural bending stiffness fell, the greater the fatigue load limit on and the stiffness decreased more quickly with the increase of number of fatigue loading when the fatigue load reached to a certain value. Because of wood fiber of compression area yield in advance, the neutral axis transfers to the tension side after the laminated wooden beam under fatigue damage.However,the value of remaining bearing capacity of laminated wooden beam decreased with the upper limit the fatigue load increased when the fatigue load limit on 55% of the ultimate bearing capacity.