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UBC Theses and Dissertations

Disproportionate collapse prevention analyses for mid-rise cross-laminated timber platform-type buildings Mpidi Bita, Hercend

Abstract

Abnormal loads which can cause initial damage may trigger collapse propagation, leading to disproportionate collapse of buildings with insufficient structural robustness. To ensure structural safety, design approaches against this catastrophic collapse are embodied within the building regulations. Nevertheless, the application of existing guidelines for disproportionate collapse prevention for mid- to high-rise mass-timber buildings -as an emerging construction method- becomes unpractical and uneconomic; and research studies in this topic are scarce. This thesis contributes to the body of knowledge with respect to structural robustness and disproportionate collapse prevention for mid-rise platform-type cross-laminated timber buildings through analytical, numerical, and experimental analyses. Nonlinear dynamic numerical analyses, using the sudden element removal, are performed on twelve- and nine-storey buildings to study their responses after initial damage. The analytical approach applies linear-elastic static equilibrium to estimate the minimum strength, stiffness, and ductility to ensure structural robustness. From subsequent reliability analysis, the results show that without considerations of the complexities associated with disproportionate collapse, mid-rise cross-laminated timber platform-type buildings have a high probability of disproportionate collapse. A structural optimisation procedure is then proposed to achieve a target performance and ensure structural safety. From the worst-case scenario, novel connection detailing is then proposed to trigger catenary and hanging actions as collapse resistance mechanisms. The proposed detailing using steel tubes and rods is numerically investigated and optimised. Then, results from experimental tests confirm that when the tubes and rods are implemented as floor-to-floor detailing, mass-timber floor system can trigger catenary action as a collapse resistance mechanism following the loss of internal loadbearing wall.

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