This document outlines the basis of design for the performance-based design and nonlinear response history analysis of the Framework Project in Portland, OR. Performance-based design is pursued for this project because the proposed lateral force-resisting system, consisting of post-tensioned rocking cross-laminated timber (CLT) walls is not included in ASCE/SEI 7-10 Table 12.2-1.
Project contact is Thomas Miller at Oregon State University
Summary
Understanding how roof and floor systems (commonly called diaphragms by engineers) that are built from Pacific Northwest-sourced cross-laminated timber (CLT) panels perform in earthquake prone areas is a critical area of research. These building components are key to transferring normal and extreme event forces into walls and down to the foundation. The tests performed in this project will provide data on commonly used approaches to connecting CLT panels within a floor or roof space and the performance of associated screw fasteners. Structural engineers will directly benefit through improved modeling tools. A broader benefit may be increased confidence in the construction of taller wood buildings in communities at greater risk for earthquakes.
The construction materials used in the building tall structures are responsible for extremely high carbon emissions. Therefore, to address this issue building designers are constantly looking at alternative sustainable construction materials. A new type of timber called MassTimber as a material for construction is now attracting the building designers because of its sustainability advantages. Mass-timber is an innovative type of engineered timber with improved structural properties making it suitable for the construction of tall and heavy structures. This paper is intended to study the performance of tall mass-timber buildings under the most severe dynamic loading conditions of India. Three models of mass-timber buildings are analyzed in ETABS under the seismic and wind loads according to the demands of most severe earthquake zone-V and one of the windiest regions at Bhuj, India. It is observed that the mass participation during seismic activities is considerably low and the wind loads are considerably higher than the seismic loads. It is concluded that with a suitable lateral load resisting structural system mass-timber buildings can perform adequately.
This paper begins with an overview of the state of the art in the design of multi-story mass timber structures and their lateral systems in low to moderate seismic regions. Boston, MA has been chosen as the location for a feasibility analysis of 8-, 12-, and 18- story mass timber structures. These building prototypes are used to compare the structural and environmental efficiencies and tradeoffs of replacing conventional concrete cores with mass timber braced frames and steel-timber hybrid frames. The lateral resistance of prototype configurations is evaluated through numerical analyses to understand in more detail the characteristics of an efficient mass timber lateral system. Finding an optimal timber gravity system configuration is followed by examining lateral resistance of the prototypes. The resulting designs demonstrate a practical approach to assist designers in selecting a lateral system during the early stages of conceptual design. This research was conducted in parallel with a related study for implementation of mass timber in affordable housing in Boston, enabling a comparison between composite systems and all-timber structures.
