SEISMIC AND ENERGY RETROFIT OF MULTIFAMILY LIGHT-FRAME TIMBER RESIDENTIAL BUILDINGS USING MASS PLY PANEL (MPP) WALL FAÇADE SYSTEM

: The most common type of construction in the US for single and multifamily housing is known as Light-Wood-Frame (LWF). This system has been widely used for decades, following prescriptive design rules and usually without an engineered-based analysis. Due to the evolution of knowledge on the seismic hazard in the Pacific Northwest, retrofitting these structures built before the 1990s has become a necessity. In addition, these buildings also lack the energy efficiency required to reduce our global carbon footprint. This paper presents a novel façade retrofit solution consisting of prefabricated mass ply panels (MPP) that can be rapidly applied on-site over existing building cladding to upgrade older LWF one- to three-story buildings. The structural design of an existing prototype two-story LWF building in Portland, OR is presented. Custom steel connections resist design forces following the Equivalent Lateral Force (ELF) method from ASCE 7-16. Nonlinear displacement validation is performed using analytical models (AM) and finite element models (FEM), obtaining lateral drifts of 0.50% for the design earthquake (DE) reducing the expected damage in the building. Over-strength factors are calculated, considering the contribution of existing LWF walls and steel connections. A follow-up experimental setup is described for future validation of the initial assumptions.