Dissertation Defence: Resilience-based Seismic Design of Innovative Mass Timber Buildings
April 2 at 10:00 am - 2:00 pm
Biniam Tekle Teweldebrhan, supervised by Dr. Solomon Tesfamariam, will defend their dissertation titled “Resilience-based Seismic Design of Innovative Mass Timber Buildings” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Civil Engineering.
An abstract for Biniam Tekle Teweldebrhan’s dissertation is included below.
Examinations are open to all members of the campus community as well as the general public. Please email Solomon.Tesfamariam@ubc.ca to receive the Zoom link for this exam.
ABSTRACT
This thesis aims to advance the seismic design of mass timber buildings by developing a resilience-based seismic design framework based on a multi-objective optimization approach. Utility of the proposed design methods is applied on a 20-storey innovative and resilient timber structural system.
Initially, this thesis studied the mechanics of the cross-laminated timber coupled walls (CLTCWs) system and a dual system made up of CLT shear walls and the glulam moment resisting frame (CLTW-GMRF) systems. The study established their seismic design procedure and conducted parametric studies on various design parameters to understand their structural behaviour under lateral loads. As the proposed design method relies on the continuum medium method and the equivalent static force procedure, rigorous nonlinear analyses were performed using numerical model developed in OpenSees and nonlinear static (pushover) and dynamic (time history) analyses were performed to examine the performance of the proposed systems.
Based on the findings of these two structural systems, the thesis introduced a resilient-coupled system that combines the advantages of CLTCWs and GMRF. A baseline system was designed using the proposed seismic design procedures for CLTCWs and CLTW-GMRF systems. The numerical model of the system was developed in OpenSees and its structural performance was examined using non-linear analyses. Based on the results of the analysis, key design variables were identified, multiple objective functions were defined, and a deep learning-based surrogate model was trained to optimize the seismic design of the proposed system. The results demonstrate the feasibility of the CLTCWs-GMRF system and highlight the effectiveness of the proposed multi-objective optimization-based seismic design framework.
Next, the thesis focuses on evaluating the seismic resilience of the proposed CLTCWs-GMRF system. To this end, the fragility and consequence functions of key structural components of the building were defined, allowing a probabilistic assessment of seismic loss and resilience based on the FEMA P-58 methodology and state-of-the-art repair time models. The results, from quantifying the damage state of individual structural and non-structural components to post-earthquake recovery trajectories of the entire system, were obtained and discussed. Insights from the resilience assessment were then used to develop a resilience-based design framework, leveraging multi-objective optimization to balance the trade-off between shorter post-earthquake recovery and efficient structural design. Overall, the framework underscores the potential of timber-based structural systems, particularly CLTCWs integrated with GMRFs, to deliver sustainable and resilient solutions for modern high-rise construction.
