# Behaviour Analysis of Beam-Type Timber and Timber-Concrete Composite Panels
## 2 Materials and Methods
### Laboratory Experiment  
A laboratorial experiment was carried out to validate the results obtained by the simplified design method and by finite element modelling (FEM). Three groups of laboratorial specimens were prepared. The first group of laboratorial specimens includes four specimens divided into two sub-groups with two specimens in each. This group was prepared to consider the possibility of increasing the load-carrying capacity of the CLT panels by adding the glued laminated longitudinal timber ribs. The first sub-group is presented by the two CLT panels with dimensions of 1400 mm \(\times\) 400 mm \(\times\) 100 mm. The panels consist of five timber board layers with thicknesses of 20 mm each (Figure 3). The second sub-group is presented by the two CLT panels with dimensions of 1400 mm \(\times\) 400 mm \(\times\) 60 mm, strengthened by the two glued laminated timber ribs with dimensions of 150 mm \(\times\) 80 mm. The longitudinal ribs were joined with the CLT panel by two steel teeth tapes SHARP501200 with dimensions of 1200 mm \(\times\) 50 mm \(\times\) 0.75 mm and eight steel screws TBS8140, which were provided by the company \"Rotho Blaas Baltic\" Ulbroka, Latvia (Figure 4). Figure 4: The second sub-group is presented by the two CLT panels with dimensions 1400 mm \(\times\) 400 mm \(\times\) 60 mm, strengthened by the two glued laminated timber ribs with dimensions 150 mm \(\times\) 80 mm. Figure 3: The first sub-group of the laboratory specimens—CLT panels with dimensions 1400 mm \(\times\) 400 mm \(\times\) 100 mm: A—longitudinal section; B—cross-section. The second group consists of the eight laboratory specimens, which are divided into three sub-groups: A, B, and C (Figure 5). All the sub-groups presented by the TCC specimens consist of the five-layer CLT specimens with dimensions of 600 mm \(\times\) 100 mm \(\times\) 100 mm, joined by the adhesive connection or mechanical fasteners with the concrete layer. All the boards in CLT members for all three groups of specimens are made of softwood with the C24 strength class. The strength class of the softwood was taken based on the certificate, provided by the producing company, Cross Timber Systems (Jelgava, Latvia). The moisture content of the timber was assumed to be 12%. Its mean value of the modulus of elasticity parallel to the grain was taken as 11,000 N/mm\({}^{2}\)[29]. The concrete layer with a thickness of 50 mm was presented by the Sacret BAM self-levelling mass, with strength class C20. Its modulus of elasticity was taken as 30,000 N/mm\({}^{2}\). The self-levelling mass was provided by the producing company SACRET (Rumbula, Latvia), and the mechanical properties of the self-levelling mass were taken based on the certificate provided by the material's producer. The Sacret BAM was used for the concrete layers in all the TCC specimens considered in the current study. The first sub-group includes three specimens, namely, A1, A2, and A3, and is characterised by the compliant timber-to-concrete joint realised by the steel screws TBS8140, placed in three couples (Figure 5a). Two specimens of the second sub-group are signed as B1 and B2. These specimens are characterised by the adhesive timber-to-concrete connections realised by the stone chip method with granite chips with sizes within the limits of 8 to 16 mm (Figure 5b). The granite chips were joined with the surface of CLT by the Sikadur-31 (AB) epoxy glue with strength at a shear of 16 N/mm\({}^{2}\) for the second and third groups of the laboratory specimens [28]. Three specimens of the last sub-group differed from the specimens of the second ones by the presence of the three polyethene dowels in specimens C1, C2, and C3 (Figure 5c). Specimens A2, A3, B2, C2, and C3 differ by adding the polypropylene microfibres MAPEI PP-FIBER M6 to the concrete component to decrease the brittleness of the timber-to-concrete connections.