## Numerical Analysis

A simplified numerical model was developed in order to identify the behaviour of the plain sample F2.M. Figure 12. Numerical model: (a) detail of connection between board and beam, (b) general view of frame. Figure 13. Comparison between experimental and numerical data for the two small diagonal transducer 3 and 4 located on boarding side.

Figure 14. Comparison between experimental and numerical data for the two big diagonal transducer 7 and 8 located on the boarding side.

Figure 13. Comparison between experimental and numerical data for the two small diagonal transducer 3 and 4 located on boarding side.

The beams were modelled with two-node beam elements, while for the boards four-node shell elements were used. The two nails fastening each board at each beam were modelled by two non-linear connection elements with six DOF. These elements were joined to the beam ones through rigid-link elements. The frictional effect between boards was modelled by means of nonlinear contact points, working only in compression (Figure 12).

The beams and the boards were modelled by using the same orthotropic elastic linear material, by assuming the properties of spruce wood: E1 = 11000 N/mm2 is the longitudinal elastic modulus; E2, E3 = 367 N/mm2 are the transversal elastic moduli; Gj2 = 687 N/mm2 is the shear modulus; v12,13 = 0,46, and v21,3i = 0,03, are the Poisson coefficients in the combined directions 1,2,3 (see Fig. 12 for reference).

The law derived from push-out tests (Figure 8) was assigned to the two directions, as relative displacement of the connections elements between beam and boards. Finally, the steel frame was modelled as isotropic elastic (elastic modulus E = 210000N/mm2, and Poisson coefficient v = 0,2).

The estimations of the model were compared with the results of the experimental tests at different levels. First, the load-displacement curves obtained locally

Figure 14. Comparison between experimental and numerical data for the two big diagonal transducer 7 and 8 located on the boarding side.

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