PSI - Issue 37

Karina Buka-Vaivade et al. / Procedia Structural Integrity 37 (2022) 563–569 Karina Buka-Vaivade et al. / Structural Integrity Procedia 00 (2019) 000 – 000

564

2

© 2022 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of Pedro Miguel Guimaraes Pires Moreira Keywords: adhesive connection; rigid connection; wood-concrete composite © 2022 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of Pedro Miguel Guimaraes Pires Moreira 1. Introduction The use of timber-concrete composite (TCC) in construction is relatively new technology. The first using of TCC as structural material was at the beginning of the 20th century, and it was related with a lack of steel for concrete reinforcement (Destro et al. (2015)). Nowadays, both the discovered advantages of TCC and the problem of limited natural resources increase the interest in TCC. Today, it is used both in the design of new floors and in the renovation of wooden floors, as well as in the bridges (Holschemacher et al. (2010), Rodrigues et al. (2013)). In reinforced concrete structures subjected to the flexure, the tensile strength of the concrete is usually not observed, all tensile stresses are absorbed by the reinforcement. When the load-bearing capacity limit is reached, the concrete has cracked to about 2/3 of the cross-sectional height. Therefore, in TCC structures it is useful to replace this potentially cracked area with a timber cross-section. Despite timber is characterized by lower strength and stiffness than steel reinforcements, the use of timber with much more cross-sectional area can compensate this fact (Dias et al. (2018)). Synergy or the degree of interaction of the composite material between the two different materials occurs in the existing connection between the layers of materials. Due to the interaction of the layers, the composite material has the best properties of both materials. The composite works if two structural elements or materials are joined together thus forming a structure or material which react to the applied load as one element and has more stiffness or strength and different spectra of natural vibrations (Kirsanov et al. (2021)) compared with each of materials separately. In timber-concrete composite structures, timber elements are joined together with concrete layers, usually using special connecting elements that absorb shear stresses. The connection plays an important role in the analysis and design of the behavior of structures (Buka-Vaivade et al. (2021)). Ideally, the joint should be rigid to obtain the most efficient performance of the composite materials (Winter et al. (2016), Rodrigues et al. (2013), Fragiacomo et al. (2011), Van Der Linden (1999), Fragiacomo et al. (2018)). In practice, with mechanical connectors, it is difficult to create a perfect rigid connection. From the point of view of connection strength and stiffness, glued connection is the best solution that can ensure almost perfect performance of composite materials. Opportunity to avoid concentration of local shear and compression stresses on the timber surface (Rodrigues et al. (2013)), to create a protective layer on the timber surface from the existing moisture in the concrete (Negrão et al. (2006)), to avoid time-consuming operations (cutting, drilling, etc.), to avoid corrosion issues that are relevant for mechanical connectors (Kostic et al. (2018)) are benefits of adhesive connections. Nowadays, two technologies for the development of glued connections in TCC are known (Dias et al. (2018). "Dry" is the gluing of timber layer with a prefabricated concrete slab; "wet" - is fresh concrete placing on a freshly applied layer of glue. Each of the techniques has its advantages and disadvantages. Precast concrete is usually less cost-effective due to high transport costs, but this solution is able to speed up the overall construction process, but there are problems with quality control of the obtained adhesive connection. Cast concrete on the construction site reduces transport costs, but constantly risks the adhesive shifting during concrete pouring. This study examines the effect of non-glued areas in connection between composite layers on the shear stresses and energy absorption of the TCC elements subjected to the flexure. An alternative technology for the development of a glued connection in TCC is also offered, which would facilitate the quality control of the glued connection. 2. Materials and methods The proposed production method of rigid connection between timber and concrete layers is shown on the Fig.1 and provides preparation of timber base, applying of glue layer on timber surface, gluing of granite chips and after drying of glued layer – placing of fresh concrete. To investigate the effect of the proposed adhesive connection on behavior of TCC subjected to the flexure - two types of specimens were prepared for laboratorial, analytical, and numerical analyses.