Nowadays, composite structures based on wood are frequently used. In civil engineering, mostly timber-concrete composite structures are used, particularly in reconstruction of old timber girder floor structures or manufacture of new ones at the reconstruction of old buildings in areas exposed to frequent earthquakes. In new buildings it is mainly glued laminated timber or lumber, while in reconstruction square timber is used. A timber beam is coupled with a concrete slab made either of conventional or a lightweight concrete. Best results are achieved by coupling timber with lightweight aggregate concrete that has all the properties similar to the timber except for its strength that is much higher and comparable to that of conventional concrete. This paper analyzes a composite timber-lightweight aggregate concrete structure. The basic girder is a T-cross section, with the web made of glulam, and flange made of lightweight concrete with expanded clay aggregate (Liapor). The two materials are coupled by means of mechanical fasteners, allowing joint action of the composite section. Quality of coupling has been determined by experimental tests carried out at the Laboratory of the Technical Mechanics Institute, Faculty of Civil Engineering in Zagreb. Finite element method was used for modelling of composite structures using ABAQUS software. The aim of this study was to determine the advantages of using timber-lightweight aggregate concrete composite structure, compared to solutions in which timber-conventional concrete composite structure or reinforced concrete slab are used.
