Study On The Influence Of Holes On The Bending Strength Of Larix Gmelinii Plate

Larix gmelinii is an important forest resource in China with straight trunk,high longitudinal strength,tough material,and good durability,which is widely used in the parallam and wood buildings.Sometimes we need to punch the glulam beams in wooden structures.In order to ensure the structural stability of wood beam,it is necessary to calculate the weakening effect of holes on mechanical properties of wood beam.There are few studies on the effect of holes on the mechanical properties of wood.In this paper,the influences of holes in different positions and sizes on the bending strength of the board is discussed by comparing the bending strength before and after punching.The main conclusions are as follows:(1)The load interval used by universal mechanics testing machine to calculate the elastic modulus of the specimen was explored,and it was found that there was a significant correlation between the elastic modulus measured by universal mechanics testing machine and the calculated elastic modulus when the deflection difference of the specimen when the load was 800N and 1200N.(2)The relationship between MOE and MOR is investigated.There is a functional relationship between the elastic modulus and the bending strength:MOR=MOEX 0.003+81.375,R2=0.6361,which has a good correlation.Therefore,the bending strength before punching can be predicted by this formula.(3)The effect of the position of the hole in the direction of thickness on the strength of bending is discussed.The results shows that the influence of the holes on the bending strength is greatest when the hole is tangent to the bottom surface of the plate.When the hole is tangent to the central layer,it has the least influence on the bending strength.If the holes have same distance from the central layer,the hole above the central layer will have a greater influence on the bending strength.(4)The effect of the position of the hole in the direction of length on the strength of bending is discussed.The study shows that the influence on the bending strength decreases with the increase of the distance between the holes and the loading point.When the deviation of holes exceeds a certain distance,it has litter effect on the bending strength.(5)The effect of location and size of holes on elastic modulus is discussed.The study shows that the effect of holes on the elastic modulus is similar to that of the bending strength.(6)The mathematical model of the effect of the relative position and diameter of the hole in the direction of plate thickness on the bending strength is obtained.The model is proved to be reliable.