Experimental analysis of timber–concrete composite beam strengthened with carbon fibres

Reconstruction of old residential buildings is most often accompanied with a tendency to preserve the original features of the building, which leads to subsequent preservation of the floor elements. The ageing of the material and the consequent lower stiffness and load bearing capacity of the floor element along with the occasional change in the purpose of the facility and the consequent increase in the load require structural reinforcement of the floor elements. A possible solution lies in replacing the classic timber planks with a concrete slab and in the corresponding strengthening of the timber beam in the tensile zone. Therefore, the paper presents an experimental study performed on composite beam test samples composed of a concrete plate connected to a timber beam with dowel-type fasteners. Since the tension failure of the timber beam is the decisive resisting criterion, the beam is strengthened at the bottom of the tensile side with a carbon fibre-reinforced polymer strip. The measured results are compared with numerical results obtained by an already developed analytical model [1] based on Mohler’s simplified formulation and on European standards for timber, concrete and steel structures. Since the experimental results demonstrate a relatively low deviation and additionally a good agreement with the numerical ones, the usage of the presented analytical model can be recommended to predict proper stiffness and load bearing capacity for these types of composite floor structures.

► We experimentally tested elements composed of a concrete plate connected to a timber beam. ► The beam is strengthened at the bottom of the tensile side with a CFRP strip. ► The measured results are compared with numerical results. ► Findings are important for the renovation principles of the old residential houses with timber floors.