Design and assessment of reinforced concrete columns in uplift due to internal building detonations

Abstract

Current research with respect to the protection of civilian infrastructure against complex blast loading conditions is primarily focused towards the effect of external explosive sources. As a consequence, the general literature on internal building detonations and specifically in the context of protective design and assessment of structures against these loading conditions is incomplete. Existing guidelines developed for comparatively noncomplex external explosive blast remain unconservative when applied to internal building detonations due to blast wave confinement and complex interaction with structural components. In particular, reinforced concrete (RC) columns in internal blast environments are subjected to time-variant uplift forces coupled with lateral pressures leading to destabilisation and a critical loss of structural integrity. Research presented in this thesis provides an original understanding towards: (i) – the influence of transient uplift forces on the vulnerability of RC columns subject to lateral blast pressures and, (ii) – design and assessment of RC columns against the effect of time-variant coupled uplift and lateral blast pressures due to internal building detonations.

Research in this thesis is based on advanced uncoupled Euler-Lagrange numerical modelling splitting the structural and flow solvers for maximum integrity and accuracy. High-resolution simulations of complex flow fields are analysed using the hydrocodes Air3D and Autodyn, whilst Extreme Loading for Structures [ELS] based on the Applied Element Method is used for modelling the transient-dynamic structural response of columns. These numerical techniques are comprehensively ratified and underwritten, both qualitatively and quantitatively, using published independent experimental test data. Verified numerical modelling is subsequently used to conduct a set of comprehensive parametric studies covering both vented (frangible perimeter walls causing pressure venting) and contained (non-frangible perimeter walls causing repetitive wave reflections) internal blast environments. Results of these parametric studies are thoroughly analysed with the use of multi-variable nonlinear regression analysis techniques and are presented in the form of separate assessment and design charts. This thesis also presents a set of column hazard charts developed based on the parametric studies. These hazard charts provide threshold combinations of TNT Equivalency and critical radial distance corresponding to different column damage levels ranging from ‘No Damage’ through ‘Low Damage’ and Moderate Damage’ to ‘Imminent Structural Collapse’. The output of this research will be of direct relevance to both practitioners and researchers involved with protective design of civilian and military buildings.

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ORCID for Simon Clubley: orcid.org/0000-0003-3779-242X

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