Research On The Performance Of Larch Glulam Column Under Eccentric Load Along The Fiber

In recent years, with the prosperity of domestic economy and the concept of environment protection generally accepted in China, the domestic market of modern timber structure is swelling rapidly. However, we still need to import large amounts of timber material from abroad for domestic timber structures. In order to accelerate the progress of modern timber structure farther in China, the research of Glulam made from domestic species of fast-growing tree need to be promoted. For the purpose of getting to know the performance of Glulam column under eccentric load along the fiber, as this paper describes, we choose the larch growing in the northwest of China, gluing with resorcin resin by advanced gluing technical. The conclusions we can draw are as follows:At first, we introduced the principle and process about manufacturing Glulam, and then brought the data in the paper to be the cornerstone of the theoretic analysis of Glulam column under eccentric load, from two experiments finished previously:the experiment of performance of short Glulam column under pressure along the fiber and that of Glulam beam under bending moment. As the result of the two experiments showed, we learned that the strength and elastic modulus of this material under pressure were approximately 43.03Mpa and 14.48Gpa respectively, and the values under bending moment were about 71.99Mpaand 15.66Gpa.Secondly, we designed 24 Glulam columns divided in 8 groups through different values of length. All these columns had the same size of cross section, made from same material and produced by same manufacture process, so the slenderness ratio was the unique variable parameter we concern. We needed to analyze the performance of these groups of specimens under eccentric load in different slenderness ratios by obtaining the relationships of load -strain and load-deflection at the critical points on the specimens. The experiment showed that as the load increased constantly, the deflection of specimens increased as well, which resulted in the dramatic increase of the second-order moment of the column due to the initial eccentricity. For the contribution of moment and pressure, the pressurize side of the column would yield first, and then the fold extended to the tension side. At the end, the specimens could not stand the load anymore accompanied with a few loud and clear sounds. The carrying capacity of the specimens under eccentric load along the fiber would decrease whereas the slenderness ratio of the column increases.Moreover, in order to calculate the theoretic value of the deflection at the middle span of the column, we assumed two equations deduced from the flex line of bar under pressure. Bringing relative data into the equations, we got the value of the deflection at the middle span of the column in theory, which need to compare with the experiment results. Then referring the equation about eccentric loading in GB50005-2003 ?Timber Structure Code?, we calculated the value of carrying capacity of the columns in theory by taking into account the data from the previous experiments on the material property of larch Glulam. The result showed that the values of the eccentric-load experiment and that of theoretic calculation met each other.Finally, we used the FEA software ABAQUS to analyze the model built up with Cross-isotropic constitutive relation according the parameters of the columns in the experiment, referring the Mechanics of Compound Material. The analysis showed a result coordinated with the experiment values.