Mass timber buildings, constructed with engineered wood products, such as Laminated Veneer Lumber (LVL), Glued Laminated Timber (Glulam), and Cross-Laminated Timber (CLT), are gaining international popularity. Despite this trend, the robustness level and progressive collapse behaviour of these structures are not well understood, and design guidelines for their robust design are still limited. So far, research on these structures has primarily involved either experimental studies on scaled substructures or numerical analyses on full-scale multi-story buildings using unvalidated finite element (FE) models, often yielding contradictory results.

This PhD research aims to bridge this knowledge gap by studying the behaviour of multistory post-and-beam mass timber buildings through FE models validated against experimental studies previously conducted at Griffith University. The robustness of such buildings is quantified, and dynamic increase factors (DIF) are determined for use in design with static analysis. Additionally, this study evaluates the accuracy of pseudostatic analysis as a cost-effective method for assessing progressive collapse and presents a comprehensive parametric study aimed at identifying measures to enhance their robustness, understanding alternative load-bearing mechanisms after column loss, and clarifying failure modes.

The findings indicate that a post-and-beam mass timber building designed according to Australian national codes can meet robustness requirements under accidental design loads if average strength values are assigned to structural components. A DIF factor between 1.7 and 1.8 is recommended for the design of these structures. Contrary to general consensus, one-bay CLT panels can provide an effective alternative load path through torsion, exhibiting slightly greater robustness compared to configurations with two-bay continuous panels. The study also reveals that while enhancing beam-to-column connections may increase robustness, such modifications must be approached with caution as they can lead to column damage and extensive collapse.