*2.1. Reference Experimental Approach*

The short-term mechanical performance characterization of connections and joints of typical use for TTC (or TCC) systems according to Figure 2 generally depends on several uncertainties. Most of the parameters that are of primary need for analytical calculations and design are in fact sensitive to several geometrical features and loading conditions, thus affecting the corresponding serviceability stiffness and ultimate resistance values.

**Figure 2.** Conventional experimental procedure for the mechanical characterization of TTC joints with inclined STSs.

α α ≤ α Moreover, most of the simplified methods of literature that can be used for TTC joints still lack consideration of several relevant aspects that especially in the case of timber, may have severe effects on the overall structural performance assessment (i.e., crushing or plasticity, time-dependent phenomena in the joint components, occurrence and evolution of local damage mechanisms, etc.). The actual result is thus represented by the need of extensive experimental testing in support of the required stiffness and resistance calculations [22,23]. The loading procedure recommended by the Eurocode 5 for timber structures [5], in this regard, requires for a standard PO test the repetition of 25 load cycles between 5% and 40% of the expected failure load. The specimen is then pushed further to collapse. Moreover, several test repetitions should be carried out for each joint configuration. Finally, a multitude of instruments is recommended to capture and control the specimen performance.

## *2.2. Selected Push-Out Specimens and Configurations*

The numerical study discussed herein takes into account a series of TTC joints with inclined STSs characterized by geometrical variations in the inclination, the number and the position of fasteners, the loading direction (i.e., shear-compression (α < 0) and shear-tension (0 < α ≤ 45◦ )). In accordance with Figure 3a–c, the typical TTC joint consists of three glued laminated timber elements classified

as GL24h strength class (EN 1194 [24,25]). The mechanical connection of these spruce members is ensured by double-thread, carbon steel STSs (WT-T-8.2 type [26,27]), with a total length of L=190 mm or 220 mm (Figure 3d). Four joint typologies are thus numerically investigated in this paper (S#1-to-S#4 in Figure 3, with α = var), where [6]:

≤ α ≤


**Figure 3.** TTC joints with inclined STSs under a standard PO setup. (**a**)–(**c**): selected configurations and (**d**) nominal dimensions (in mm).
