Blast response and safety evaluation of a composite column for use as key element in structural systems Ruwan Jayasooriya, David P. Thambiratnam ⇑ , Nimal J. Perera Faculty of Science & Engineering, Queensland University of Technology, GPO Box 2434, Brisbane, QLD 4001, Australia article info Article history: Received 29 May 2012 Revised 6 January 2014 Accepted 6 January 2014 Available online 6 February 2014 Keywords: Blast analysis Composite column Steel core Residual capacity Structural collapse Computer simulations Key element abstract This paper presents the blast response, damage mechanism and evaluation of residual load capacity of a concrete–steel composite (CSC) column using dynamic computer simulation techniques. This study is an integral part of a comprehensive research program which investigated the vulnerability of structural framing systems to catastrophic and progressive collapse under blast loading and is intended to provide design information on blast mitigation and safety evaluation of load bearing vulnerable columns that are key elements in a building. The performance of the CSC column is compared with that of a reinforced concrete (RC) column with the same dimensions and steel ratio. Results demonstrate the superior perfor- mance of the CSC column, compared to the RC column in terms of residual load carrying capacity, and its potential for use as a key element in structural systems. The procedure and results presented herein can be used in the design and safety evaluation of key elements of multi-storey buildings for mitigating the impact of blast loads. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction 1.1. Motivation for the present work With an increase in terrorist activity it is necessary to provide adequate capacity to vulnerable columns in buildings to mitigate the consequences of the adverse effects of blast loads. As seen in the past, a bomb explosion in a public building with a high occu- pancy results in a large number of casualties and property damage. Blast resistant design of structures has therefore attracted signifi- cant attention under the present environment of global terrorism [1–5]. Motivated by this interest, a comprehensive research pro- gram on the vulnerability of reinforced concrete structural framing systems to blast loading was undertaken. The research presented in this paper is an integral part of that research program to provide design information that can be useful in blast mitigation and safety evaluation of load bearing vulnerable columns that are key elements in a building. Key elements are defined as structural components that cause the collapse of more than a limited portion of a structure within close proximity [6]. Composite columns have been found to have the potential to mitigate the adverse effect of random and unpredictable loads [7]. This paper investigates the blast response and post blast performance of a concrete–steel composite (CSC) column under different blast load scenarios and compares the performance with that of a reinforced concrete (RC) column having the same dimensions and steel ratio, but with- out the steel core (hereafter referred to as the RC column). 1.2. Background and scope of the present work Blast resisting capacity with mitigation strategies are important for key structural elements located in critical zones where high intensity blast pressure is directly applied. Different retrofit mea- sures and design strategies have been proposed in recent investiga- tions for safety [8–12]. However, comprehensive and economical design strategies are needed for future construction of buildings to perform effectively at their post blast serviceability state, in order to protect lives and property. The blast and post blast perfor- mance of key structural elements are therefore necessary to avoid disproportionate collapse of a building. Post blast evaluation of a structure is vital for post disaster evacuation. An explosion detonated at ground level will have a critical impact on the lower storeys of the building structure [13]. Catastrophic failure of the structure will initiate at the critically damaged zone due to reduction of the load carrying capacity of the load bearing key structural components such as columns [14] and the structure may yield to progressive collapse. The well- known example is the Alfred P. Murrah Federal Building bombing incident where progressive collapse extended beyond the immedi- ately damaged zones [15]. Progressive collapse of framed struc- tures in general [16] and under column loss in particular [17,18] 0141-0296/$ - see front matter Ó 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.engstruct.2014.01.007 ⇑ Corresponding author. E-mail address: d.thambiratnam@qut.edu.au (D.P. Thambiratnam). Engineering Structures 61 (2014) 31–43 Contents lists available at ScienceDirect Engineering Structures journal homepage: www.elsevier.com/locate/engstruct