2. Forum Wood Building Baltic 2021 Behaviours of Timber-concrete Composite Members | Karina Buka-Vaivade et al.
Behaviour of timber-concrete composite members Karina Buka-Vaivade; Dmitrijs Serdjuks; Romans Vasiljevs; Jana Gerasimova; Leonids Pakrastins; Imants Mierins, Institute of Structural Engineering and Reconstruction, Riga Technical University, Latvia
Summary Behaviour of timber-concrete composite panels, with the rigid timber to concrete connection, were evaluated. The rigid connection was developed by using the granite chips as the keys. Behaviour of timber-concrete composite panels were investigated by the analytical, numerical, and experimental method. A possibility to 2.55 times decrease maximal displacements by gluing concrete layer to the cross-laminated timber panel and possibility to increase by 28.1 % load-carrying capacity of the timber-concrete composite panels by using the proposed connection production technology were stated. Key words: timber-concrete composite, rigid connection, adhesive connection, glued connection, cross-laminated timber, bending test.
1. Introduction By combining such two materials as timber and concrete, various classical disadvantages of wooden floors can be improved, such as dynamic reaction, bending stiffness, loadbearing capacity, sound insulation and structural fire safety. At the same time, timberconcrete composite (TCC) in comparison with classical reinforced concrete floors allows significantly reduce the self-weight of floor structures, the dimensions of other vertical structures and foundations and transporting costs. Effectiveness of TCC structures are dependent on the type of timber to concrete connection. Semi-rigid and rigid are two types of connections which are used now. The adhesive connection of the TCC members is more effective in comparison with the semi-rigid connections. But it is difficult to predict the quality of the obtained connection with the classical methods of continuous rigid connection production. So, the aim of study is investigation of influence of the granite chips in timber to concrete connection on the behaviour of TCC structural members subjected to flexure.
2. Methods Influence of the concrete layer on the cross-laminated timber (CLT) panel behaviour were evaluated by the laboratorian, analytical and FEM analyses; and behaviour of TCC with carbon fibre plate produced by classical rigid connection dry method and by proposed rigid connection production method. The experiment was realised with four types of specimens. The first specimen was CLT panel with length, width and thickness equal to 2000 mm, 350 mm and 60 mm. The second specimen was glued together identical to the first specimen CLT panel and precast 30 mm thick concrete C20 layer. The third specimen was like the second, but with 1000 mm x 100 mm carbon fibre plate, glued in the tension zone. The fourth specimen was identical to the third, but rigid connection was produced by the proposed method which included gluing of the granite chips to the CLT surface and then placing of fresh concrete layer. All the specimens were tested in three-point bending until the collapse.
3. Results and discussion Experimentally, numerically, and analytically obtained load-displacement curves for CLT and TCC panels with 1.8 m large span are shown in Fig. 1 (left). At a load level of 15 kN in the CLT slab are formed 28.4 mm large displacements, but in TCC panel only 11.1 mm. So, the concrete layer has a significant effect on the deformability of CLT panel.
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