# An Analysis on Finnish Wooden Bridge Practices
## 4 Results
### A Structural Design Example for Dimensioning a Girder Bridge  
An example is presented where a gilam girder bridge was dimensioned for vehicular traffic. Bridge loads are defined by national Eurocodes (SFS-EN 1990/A1, SFS-EN 1991-2, and SFS-EN 1991-1-1... 7) according to the annexes and the implementing instructions of the Finnish Railways Authority (NCCI1). The dimensioning of the wooden bridge was carried out according to the Eurocodes (SFS-EN 1995-1-1 and SFS-EN 1995-2) and their national annexes and the implementing guidelines of the Finnish Railways Authority (NCCI 5). It is worth noting that NCCI 5 (strength) is based on SFS-EN 1995-1-1 and SFS-EN 1995-2, and NCCI 1 (loads) is based on SFS-EN 1990 and SFS-EN 1991. In the example presented, the focus was on the superstructure; in this case, the purpose of the dimensioning was the glued main beams and deck structure. A structural model of the bridge structure SOriSTiK program [81] was created to determine the most critical stresses (Figure 5). Figure 5: Structural model used to determine stresses. The structural model was produced based on actual measurements. The width of the deck was chosen as 5.4 m and the length of the bridge was 10 m. The effective width of the deck is 5 m. A side plank cladding was chosen as the deck floor, in this case, the cover was modeled as an orthotropic tile element, thus transferring loads only in the transverse direction of the bridge. The gulam beams, which act as the main supports, were hinged to the foundation structure, so when looking only at the superstructure, the supports were modeled as structural joints in points. Glulam beams were modeled as rod elements. The dimensioning of the main beams was carried out with the help of loads from SOFiStk. In the structural model, the structures' weights were used as loads, and in addition, the deck floors and railings were permanent loads. Variable loads included traffic load and wind load. The traffic loads related to the LM1 and LM3 load diagrams were examined. The wind load was adjusted both longitudinally and transversely. Load combinations were performed in SOFiStK according to NCCI 1 Annex 1A. The load combinations examined according to the load combinations used were 1, 3, 6, and 7 combinations, according to the attached tables. The dimensioning of the side floor cladding was carried out manually by calculation because with SOFiStik it is easier than stated to make these stresses act on a plank by giving greater stress in the impact area. When dimensioning the deck, traffic load diagrams containing bogie loads LM1 and LM2 were considered. Of these, the condition that gave the determining strain was examined. Regarding the strength of main beams, compression/tension, shear, bending, buckling, torsion and torsional and bending + tension, bending + compression, bending + buckling, and torsion + buckling as combined stresses. In addition, the deflection of the beam and the vibration of the entire superstructure in the operating limit condition were investigated. Deck floor planks were examined for shear and bending resistance. The dimensioning example has been simplified, so it does not include all the details the designer needs to make it look like a plan or dimension. As a result of the examinations, 5 gulam beam numbers of 240 \(\times\) 1080 mm were determined. The beams were spaced 1080 mm apart and the strength class is GL30c. The dimensions and strength of the beams turned out to be such that separate roll support for the structure was not needed. Cover dimensions were chosen as 50 \(\times\) 200 mm. The strength class of saw edge plank flooring was C24. Figure 6 shows the principal diagram from the dimensioned section. Tables 4 and 5 below show the most critical stresses, corresponding strengths, and utilization rates on main beams. Figure 6: Dimensioned cross-section (all dimensions are in mm). The utilization rates of the above-mentioned break-in limit state inspections were not very high, since in this case, the deflection of the beam was the most decisive factor.