GNGTS 2019 - Atti del 38° Convegno Nazionale

466 GNGTS 2019 S essione 2.2 the modal analysis and obtain the Backbone Curves development) and the definition of the inter-story drift limits for each performance level (i.e IO, LS, CP). The general steps for the multistory Modal DBD procedure, in accordance with those formulated by Pang and Rosowsky (2009) are explained below and in Fig. 1. Fig. 1 - Flowchart for multi-story Modal - DBD procedure (Pang and Rosowsky, 2009). Some observation concerning the Blockhaus log-walls are necessary in order to understand their mechanical behavior and validate the main hypothesis for the Modal-DBD application. These log-walls are well known for having both partition and load-bearing features, so they performs a key role as lateral force resisting system in log-haus structures. The friction phenomena, the mounting gaps and the corner joints are the main components that influences the in-plane response and led to a non-linear response. The main assumption to apply the Modal-DBD requires proving the shearwall’stiffness K tot proportional to their length L . This hypothesis has been validated by using an analytical simplified formulation proposed in (Sciomenta et al, 2018) here summarized: where μ is the is the static friction coefficient, p is the vertical load, δ i represents the displacement of the i-th log each log, with i=2..n . and δ top is the top displacement that include also the presence of small gaps in the corner joint region. Case of study. The Modal-DBD has been applied to a three-story Blockhaus structure. The plan of the structure is symmetrical in the longitudinal direction (Walls P2 and P4) and