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Because of changes in functional or security requirements, many new or existing buildings are now required to resist blast loads. New buildings can be designed and constructed to resist defined blast loads. Existing buildings, on the other hand, would have to rely on a risk assessment to determine both its vulnerability to blast effects and the necessary measures to mitigate the unacceptable blast effects. A rapid screening methodology has been developed for conducting a preliminary assessment of buildings against external blast effects. The methodology accounts for the threat, the vulnerability of the building, the consequence of an event and the risk, which is the product of the threat and the consequence. The rapid screening methodology has been applied to several buildings and the results are reasonable. This paper presents the rapid screening methodology and its application to two federal buildings in Canada. [ABSTRACT FROM AUTHOR]

Structural retrofits to buildings can be implemented to increase the protection level to occupants from potential terrorist bombing attacks. Retrofit strategies discussed in this paper can be categorized into three groups: (i) strengthening concepts, (ii) shielding concepts, and (iii) concepts to control hazardous debris. Strengthening concepts such as span reduction and increasing member sections are considered in this paper for three common construction systems including steel, concrete, and masonry. Shielding concepts are intended to prevent structural members from being fully loaded by blast forces and range from local area applications to entire building coverage. Examples of shielding concepts include a new section of wall that shields a vulnerable portion of the building or a new structure built over an entire building. Examples of concepts to control hazardous debris include arresting or deflecting failed cladding away from critical areas with “catch systems” or internal shield systems. This paper is intended to discuss typical building retrofit strategies for primary structural members (load bearing) and secondary structural members (nonload bearing) through strengthening, shielding, or controlling hazardous debris. [ABSTRACT FROM AUTHOR]

Designers charged to develop blast-resistant structural designs must be able to address the technical aspects of the explosion process and provide structural components with sufficient strength and ductility to resist the applied pressures. The blast environment is different from those of other loads with which designers deal, and uncertainties about the actual response of structures often are higher. For these reasons, designers often have less confidence in their abilities to explain to their clients their expectations about the actual response of the building to a blast event. This paper identifies some elements of the conventional design process that do not translate directly to blast-resistant design, reasons why uncertainties in performance expectations differ from those encountered with other load sources, and the need to understand and acknowledge residual risks for the facade, the structure, and the safety of the occupants of blast resistant buildings. [ABSTRACT FROM AUTHOR]

This paper presents a unique approach that can be used for the analysis of a blast due to an internal detonation. The information in this paper focuses on understanding the blast effects in a confined environment, blast loads prediction, and response analysis using computer codes and finite element modeling methods. An example is included in which a partial segment of a steel box member is analyzed for its response to an internal blast using blast prediction tools and finite element code. [ABSTRACT FROM AUTHOR]

Accurate analysis of reinforced concrete (RC) structures under blast loading is very complicated due to the nonlinear behaviour of concrete and reinforcement and the various failure modes to be considered. Although blast loads can excite a large number of modes due to their high frequency content, practical computational tools are usually limited to single-degree-of-freedom (SDOF) models. In addition to oversimplification, SDOF models are known to give inaccurate prediction for shear forces and support reactions. This is because accurate shear force prediction typically requires accounting for modes higher than the fundamental mode. In this study, a multi-degree-of-freedom (MDOF) model is developed that takes into account the nonlinear behaviour of RC structures and the material strength and deformation dependency on the strain rate. Using this model, a series of dynamic analyses were carried out for two typical structural members, with different combination of blast pressure and impulse. The effect of varying the number of degrees of freedom (DOF) was investigated through increasing the number of nodes used to descretize each structural member. The results of the developed MDOF model were compared to the results of available SDOF models which demonstrated the deficiencies of the latter. The developed MDOF model, with few DOF, was found to be capable of accurately predicting the dynamic shear of the modeled structural members. The model was also compared to available experimental results and showed good agreement. Changing the number of DOF also affected the pressure-impulse (P-I) diagrams for the structural member significantly, especially in the impulsive regime. [ABSTRACT FROM AUTHOR]

There are many computational techniques to model the consequences to built infrastructure when subject to explosive blast loads; however, the majority of these do not account for the uncertainties associated with system response or blast loading. This paper describes a new computational model, called “Blast-RF” (Blast Risks for Facades), that incorporates existing (deterministic) blast-response models within an environment that considers threat and (or) vulnerability uncertainties and variability using probability and structural reliability theory. The structural reliability analysis uses stress limit states and the UK Glazing Hazard Guide's rating criteria to calculate probabilities of glazing damage and occupant safety hazards conditional on a given blast scenario. This allows the prediction of likelihood and extent of damage and (or) casualties, useful information for risk mitigation considerations, emergency service's contingency and response planning, collateral damage estimation, weaponeering, and post-blast forensic analysis. [ABSTRACT FROM AUTHOR]

The blast response and ultimate resistance of reinforced concrete slabs externally strengthened with carbon fibre reinforced polymer (CFRP) laminates were investigated. Five square slab specimens, 1 m on a side, were retrofitted with 500 mm wide CFRP laminates bonded to their top and bottom surfaces. Another four nominally identical unretrofitted slabs were used as control specimens. Four of the retrofitted and the four control slabs were first subjected to the detonation of either 22.4 or 33.4 kg of explosive at a stand-off distance of 3.0 m. For reference, the fifth retrofitted slab was only statically tested to failure. Blast pressures and impulses and slab deformations were measured. After exposure to the blast, the slabs that were not completely damaged were statically tested to failure. Overall the retrofitted slabs performed better than the control slabs, but one retrofitted slab completely failed under the blast load while none of the control slabs experienced complete failure under similar load. [ABSTRACT FROM AUTHOR]

This study critically discusses the fundamental concepts used for evaluating the flexural and axial resistance of structures under blast. Simplified methods based on single degree of freedom are emphasized. The paper begins with how to estimate the blast parameters for a given charge size and standoff distance. These parameters include side-on and reflected pressures, positive phase duration, and side-on and reflected impulses. Subsequently, blast damage criteria are defined in accordance with prevailing guidelines and some of their short comings are discussed. To assess the impact of blast on the flexural safety and performance of structures, some simple methods are presented. The methods are either empirical or are based on the principles of energy and momentum conservation. The analytical results are in closed-form or in the form of pressure-impulse (P-I) diagrams. The effect of strain rate on both blast-induced flexural deflection and strength of structures, with particular emphasis on reinforced concrete structures, is discussed. [ABSTRACT FROM AUTHOR]

During the past decade, significant research has been carried out on the strengthening of reinforced concrete (RC) slabs, beams, and columns using externally bonded carbon fibre reinforced polymer (CFRP) sheets. Steel reinforced polymer (SRP) sheets have recently been proposed as an alternative to CFRP to strengthen reinforced concrete beams. This paper reports experimental and numerical results of RC beams and beam-columns transversely wrapped with SRP and tested under blast load. A total of 10 scaled RC members were tested at a variety of blast wave intensities. Detailed observations are reported and validated against numerical models created in AUTODYN for the unstrengthened RC members. The SRP wraps were resilient in the near-field blast range and enhanced the ductility of the concrete likely through enhanced confinement. Member capacity could be increased by the wraps in failure modes dominated by concrete crushing. AUTODYN appears able to reasonably predict the behaviour of the RC members when loaded by blast. [ABSTRACT FROM AUTHOR]

Recent bomb attacks on buildings have raised awareness about the vulnerability of structures to blast effects. The resiliency of structures against blast-induced impulsive loads is affected by structural characteristics that are also important for seismic resistance. Deformability and continuity of structural elements, strength, stiffness, and stability of the structural framing system and resistance to progressive collapse are factors that play important roles on the survivability of buildings under both blast and seismic loads. The significance of these structural parameters on blast resistance of reinforced concrete buildings is assessed through structural analysis. Both local element performance and global structural response are considered while also assessing the progressive collapse potential. The buildings under investigation include 10-storey moment resisting frames with or without shear walls. The blast loads selected consist of different charge-weight and standoff distance combinations. The results are presented in terms of ductility and drift demands. They indicate improved performance of seismic-resistant buildings when subjected to blast loads, in terms of local column performance, overall structural response, and progressive collapse potential. [ABSTRACT FROM AUTHOR]

An introduction to the journal is presented in which the editor discusses an article on the field of blast engineering, the blast risk assessment on buildings, and retrofit strategies as a blast response.