Experimental study of the strength and endurance of glued timber on shearing, compression and bending

Introduction. Nowadays wood is regaining its position as a material for bridges. During the first decades of the 21st century, the share of wooden bridge construction in Russia increased from 10 to 40 %. The cost of a bridge span made of glued laminated timber is 30–50 % lower than the cost of a bridge span made of precast prestressed reinforced concrete structures. Consequently, an urgent task of modern bridge construction is to expand the scope of application of glued lam-inated timber for complex and extended structures. This requires updating existing and de-veloping new regulatory documents, which, in turn, is impossible without experimental stud-ies of the actual operation of elements of building structures made of glued laminated timber.Materials and methods. The endurance limit of glued timber specimens during shearing along the fibres and com-pression across the fibres, the endurance limit of glued timber beams during bending, and control of the residual strength of specimens that did not fail after cyclic testing were studied.Results. Statistical processing of experimental results allowed us to identify the features of defor-mation and destruction of glued timber: the endurance limit for cyclic bending is up to 10 times higher than the endurance limit for cyclic shearing and compression, which once again emphasizes the high level of anisotropy of the material. This is significantly more than for other building materials.Conclusions. Static tests showed practically uniform linear operation of glued specimens during compres-sion tests across the fibres. Analysis of destruction allowed us to draw a conclusion about the reliability of adhesive joints. It was found that with an increase in humidity by 1 %, the strength decreases by 0.4 %. Consequently, for bridge structures, the issues of moisture re-sistance of glued timber remain relevant. The results of the studies were used in the develop-ment of national standards projects.

glued laminated timber, shear along the fibres, compression across the fibres, tensile strength, fatigue strength, residual strength, cycle asymmetry coefficient