MODELING OF CONSTITUIVE BEHAVIOR OF WHITE FIR TIMBER TRUSSES

Wood material has found a wide use in different areas of human activity, including construction. It is a material that is used for a variety of structural forms such as beams, columns, trusses, girders, etc. In this study we have analysed first the behaviour of the timber trusses and their connection components based in mechanical properties test values. Tests are conducted for timber trusses and structural timber manufactured from white fir (Abies alba Mill.).Timber trusses in relatively small dimensions, 160 cm long, 32 cm high and with a cross section of 3x3cm are tested in order to calculate the shear strength, cause of its importance in calculating the dimensions for the construction of the timber trusses. This behaviour is also analyzed based on a mathematical model build on the basis of finite elements methods using modelling software. Knowing that the timber is an anisotropic and inhomogeneous material, for simplicity in modeling process, the material was assumed to be homogeneous and transverse isotropic with identical properties in radial and tangential directions.From the mechanical tests on timber trusses resulted that the failure of the structure occurred in the rafter tie-beam connection, because of the shear stress ?xy on the heel. The behaviour of the connections during the tests has been confirmed by similar results achieved from modelling the behaviour of the trusses with the method of the finite elements. Tension values achieved from the behaviour modelling are close to the mechanical tests results.