Disproportionate collapse prevention analysis for a mid-rise flat-plate cross-laminated timber building

Abstract

This research evaluated the probability of disproportionate collapse for a nine-storey mass timber building with a flat-plate Cross-laminated Timber floor system and Glued-laminated Timber columns. The alternate load-path analysis, a threat-independent method, was performed to quantify the damage-to-performance correlation. This nonlinear dynamic analysis considered the initial damage, herein the loss of individual ground floor columns, and the subsequent deformations at the location of the removed element. The results showed that hanging and catenary actions were the ideal collapse-resistance mechanisms to avoid brittle global floor failure. For this new load-path, a parameter sensitivity analysis demonstrated that the axial strength and stiffness of the column-to-column and the rotational capabilities of the floor-to-column connections were the most relevant design parameters. After element removal, the vertical forces, which cumulated at the top floor, were transferred to the core using effective horizontal ties. To achieve these tie forces, connections with sufficient strength, stiffness, and ductility were required. Finally, a reliability analysis showed that theoretically, the building can be designed with negligible probability of disproportionate collapse in the presence of the considered uncertainties. Nevertheless, practical and economical aspects of such a design require further investigations.