Dissertation Defence: Seismic Assessment and Performance-Based Design of Steel Storage Rack Structures with Novel Connection Systems

Radin Md Mahirul Hoque, supervised by Dr. Shahria Alam, will defend their dissertation titled “Seismic Assessment and Performance-Based Design of Steel Storage Rack Structures with Novel Connection Systems” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Civil Engineering.

An abstract for Radin Md Mahirul Hoque’s dissertation is included below.

Examinations are open to all members of the campus community as well as the general public. Please email shahria.alam@ubc.ca to receive the Zoom link for this exam.

Abstract

This doctoral dissertation investigates the seismic design of steel storage rack structures through the development of novel beam-to-upright joints and a new base-plate connection, supported by experimental testing, detailed numerical modelling, and performance-based seismic assessment. The overarching objective is to improve the seismic performance, reliability, and design rationality of pallet-type steel storage rack systems, which are not explicitly addressed in current Canadian seismic design provisions.

The hysteretic behaviour of proposed beam-to-upright joints is examined by investigating the influence of L-shaped tab geometry and the welded position of the beam at the end connector. Three portal-frame configurations are tested under three displacement-controlled cyclic loading protocols, resulting in nine full-scale experiments. The experimental results are used to characterize moment-rotation and lateral force-displacement responses, deformation patterns, failure modes, rotational stiffness, moment resistance, ductility, and energy dissipation capacity. A quantitative damage index is also proposed to assess and compare structural degradation under different loading protocols.

A novel base-plate connection for steel storage rack systems is proposed, and its cyclic performance is evaluated in both down-aisle and cross-aisle loading directions. An experimental program consisting of eight upright base-plate assemblies is conducted under constant axial load and displacement-controlled cyclic loading to investigate the effects of supporting floor conditions and anchor-bolt configuration. The cyclic responses are assessed in terms of stiffness degradation, strength deterioration, hysteretic energy dissipation, equivalent viscous damping, cumulative dissipated energy, and failure modes. The proposed base-plate connection is further benchmarked against existing designs reported in the literature.

Detailed finite-element models are developed using ANSYS and OpenSees to simulate the portal frames, base-plate connections, and stub column tests. The numerical models are validated against experimental results with respect to global force–displacement response, moment–rotation behaviour, stiffness, energy dissipation, damping, and observed failure mechanisms. A simplified fibre-section-based OpenSees model is subsequently developed to represent perforated thin-walled uprights and is validated against both experimental data and detailed ANSYS simulations. Full-frame rack systems are then analyzed using both platforms, and pushover responses are compared to establish modelling consistency and accuracy.

Building on the validated numerical framework, response modification factors suitable for Canadian seismic design are evaluated for steel storage rack structures. Pushover and incremental dynamic analyses are performed using concepts drawn from FEMA P695 and relevant Canadian literature, addressing the absence of code-specified response modification factors for rack systems.

The applicability of the direct displacement-based design (DDBD) methodology to steel storage rack structures is also investigated. Multiple rack framing configurations and structural heights are examined using detailed finite-element models. Simplified DDBD models are calibrated and validated against experimental and numerical results, enabling a systematic assessment of the robustness and suitability of displacement-based seismic design for rack systems.

Overall, this dissertation provides an integrated experimental-numerical–analytical framework for the seismic assessment and design of steel storage rack structures. The findings contribute new connection details, validated modelling strategies, response modification factors, and displacement-based design insights that support the development of more rational and performance-oriented seismic design procedures for steel storage rack systems.