Browsing by Author "Lagos, Jorge"

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    Structural performance of strong timber diaphragms: High-capacity light-timber frames and cross-laminated timber
    (2024) Veliz, Fernando; Chacon, Matias F.; Lagos, Jorge; Berwart, Sebastian; Lopez, Nicol; Guindos, Pablo
    The construction of tall timber buildings is not only challenging because it requires stronger vertical lateral systems but also because it demands much Stronger Timber (ST) diaphragms in comparison to the ones required by low-rise timber construction. Two main ST alternatives exist: High -capacity Light -Timber Frame (HLTF) and Cross -Laminated Timber (CLT) diaphragms. Both approaches provide more strength, stiffness, and still have the potential to provide ductile failure than traditional timber diaphragms. However, it is unclear the structural performance differences between these two ST alternatives, which is the aim of this research. In this study, an experimental program comprising the monotonic and cyclic testing of several representative sheathing -toframing connections, plus the full-scale monotonic bending testing of six HLTF and CLT diaphragms was accomplished to characterize and compare the performance of both ST diaphragm configurations. Failure modes and mechanical properties such as stiffness, load -bearing capacity, and ductility were evaluated for all specimens. Results show that HLTF diaphragms have larger load -bearing capacity than CLT ones. Conversely, CLT diaphragms perform more ductile than HLTF ones, with a mean of /4 = 1.87 and /4 = 3.5, respectively, where the first was due mainly to high plastification of fasteners and the second to premature brittle failure of some components. Furthermore, the experimental findings were utilized to evaluate the precision of prevailing analytical and numerical models, thereby illustrating their capability to adequately represent the elastic and nonlinear responses of both ST alternatives. Finally, a sensitivity analysis of a two - story wall building with varying diaphragm (LTF, HLTF and CLT) and different light -frame shear walls (rigid and flexible) was studied. Both the diaphragms and shear walls were modeled under two different equivalent diagonal link models. The sensitivity analysis concluded that both flexible diaphragm assumption and envelope approach might not be an efficient solution, while semi -rigid approach with flexibility index eta ranging 0 - 0.5 may be expected when using ST with LTF shear walls. Finally, the diaphragm model employed enabled the validation of its elastic behavior under lateral loads, with use factors under 30% for typical setups.
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    Testing and nonlinear modelling of industrialized light-frame wooden diaphragms including optimized nailing and nonstructural sheathing
    (2023) Veliz, Fernando; Estrella, Xavier; Lagos, Jorge; Guindos, Pablo
    This article presents the outcomes of a large project towards the investigation of the lateral performance of full-scale industrialized light-frame wooden diaphragms. 10 full-scale diaphragms of 3.6 m by 2.4 m were tested under in-plane lateral loading (monotonic and cyclic), considering different sheathing, nailing, and framing. Besides, the behavior of bare slabs (without any sheathing), gypsum finishes and the potential benefits of using optimized nailing patterns instead of regularly spaced nailing was also studied. Experimental tests were non-linearly modeled using the modified Steward hysteresis model (MSTEW) and MCASHEW software. Experimental strength and stiffness results proved to be consistent with those proposed by other international campaigns, and in particular, the design principles of SDPWS fitted well with the obtained results. However, chord tensions were 30 % greater than the ones obtained by principles of engineering mechanics, which might be explained by eccentric tensile load transfer. As expected, the behavior of both sawn lumber and I-joist framed diaphragms was mainly controlled by nailing. In fact, optimized nailing patterns allowed to equal the peak capacity, increase by 20 % stiffness and 75 % ductility with 8 % less nails. Screwed gypsum finishes increased the peak capacity and stiffness by 15 %, and 20 %, respectively. The modelling approach - mainly used only in shear walls in previous investigations - proved its capability of finely reproducing the behavior of all diaphragm configurations. The numerical results were also in good agreement with the prescriptions of the SDPWS standard.