Seismic performance factors for wood frame buildings in Chile

University of Technology Sydney. Faculty of Engineering and Information Technology.Seismic performance factors are an engineering tool to estimate force and displacement demands on structures designed through linear methods of analysis. In Chile, the NCh433 standard provides the regulations, requirements, and factors for the seismic design of several structural typologies and systems. However, when it comes to wood frame structures, previous research has found that the NCh433 provisions are highly restrictive and result in over- conservative designs. Therefore, this project presents an experimental and numerical investigation aimed at proposing new, less restrictive seismic performance factors for wood frame buildings. Following the FEMA P-695 guidelines, this research embraced: (1) testing of materials, connections, and full-scale specimens, (2) developing of detailed and simplified nonlinear numerical models, (3) developing of a new FEMA P-695 ground motion set for subduction zones, and (4) analyzing the seismic performance of a comprehensive set of structural archetypes. 201 buildings were analyzed and results showed that changing the NCh433 performance factors from R = 5.5 & ∆max = 0.002 to R = 6.5 & ∆max = 0.004 decreases the average collapse ratio of wood frame structures by 13.3% but keeps the collapse probability below 20% for all the archetypes under study. Besides, it improves the cost-effectiveness of the buildings and enhances their competitiveness when compared to other materials, since savings of 40.4% in nailing, 15.9% in OSB panels, and 7.3% in timber studs were found for a 5-story building case study. Further analyses showed that the buildings designed with the new factors reached the “enhanced performance objective” as defined by the ASCE 41-17 standard, guaranteeing a neglectable structural and non-structural damage under highly recurring seismic events. Finally, dynamic results revealed that 87% of archetypes collapsed on the first and second floors, and that the minimum base shear requirement Cmin of the NCh433 standard is somewhat restrictive for soil classes A, B, and C, leading to conservative results compared to archetypes where the Cmin requirement did not control the structural design