PSI - Issue 11

Giorgio Frunzio et al. / Procedia Structural Integrity 11 (2018) 153–160

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Prof. Ing. Giorgio Frunzio, Ing. Luciana Di Gennaro 00 (2018) 000–000

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The results show that the wood that constitutes the original structures, has excellent characteristics. In fact, the values obtained from the tests are perfectly in line with the "national chestnut wood" profile, in particular the value of bending strength and the tensile modulus comply with those of the D24 profile identified in the UNI11035 standard (Chestnut wood/Italy). The elements, for which no characteristics suitable for the profile D24 have been found, were replaced with wooden elements, of a suitable section, certified according to the European standards. Steel connectors The different wooden elements are firmly connected to each other through the insertion of stainless steel cylindrical shank connectors, placed in pre-drilled holes. The steel used for the connectors is stainless steel AISI 304 (UNIEN 10088), whose characteristic values are: medium strength (Rm) 500 – 700 MPa, Yeld strength (Rp 0,2) ≥ 190 MPa, Elongation (A) 45%, Resiliency (KV) ≥ 100 J. The finishing screed, was made by repurposing the previously removed materials, after the screening, adding lime and sand of adequate characteristics. Although the screed contributes to the distribution of loads and to the overall rigidity of the decking, it has not been considered in the calculation for the benefit of safety. Strength and deformability verifications were carried out based on the Möhler theory expressed within the Appendix B of the Eurocode n° 5. Therefore, the calculation is implemented considering the section made up of beam and plank and taking account of the connection of the two elements with finite rigidity. The handling of Möhler takes into consideration the following hypotheses: • Linear-elastic behaviour model; • Supported beam with theoretical span equal to L. For continuous beams a theoretical span equal to 0,8L. For cantilever beams a theoretical span equal to 2L; • Single wood or wood-based parts are monolithic or joined with glued "end joints"; • The single parts are connected by mechanical joints with sliding module K; • The space s between means of connection is constant or varies uniformly according to the shear stress between the values s min and s max with s max ≤ 4 s min • The load acts in the z direction, giving rise to a moment M (x) that varies sinusoidally or parabolically, as well as a shear force V (x). The method consists in determining the Effective Stiffness ( EJ ef ) of the composite system (beam and double plank) considering the connection with finite stiffness, using the relationship shown below (the subscript 1 indicates the parameters related to the double plank, the subscript 2 indicates the parameters related to the beam): ( ) = ∑ + 1 ∙ 1 1 12 + 2 ∙ 2 2 22 (1) The parameters γ 1 and γ 2 are given by: 1 = 1+ 1 2 ∙ 1 ∙ 2 1 ∙ ; 2 = 1 (2, 3) Where L is the theoretical span of the beam and s eq is the equivalent space between means of connection: = 0,75 ∙ + 0,25 ∙ (4) Parameters a , a 1 and a 2 are given by the following equations, where t indicates the distance between the two elements (beam and plank): 3. Calculation method