Blast Effects Analysis

Blast effects analyses (BEAs) are used by K&C to determine the response of any given structure to blast, shock and impact loads. They can be performed by using a variety of methodologies which include:

• Q-D Charts and PI-Curves
• SDOF models
• Structural finite element models
• High-fidelity physics-based analytic models

Determining which of these techniques to use is related to the complexity of the structure being analyzed, the severity of the blast load, the response modes likely to occur, and the purpose for performing the analysis. BEAs involve two major steps:

• Computing the airblast and debris loads imparted to a building by a particular blast scenario (e.g. the airblast and debris loading generated by the car bomb (VBIED) scenario shown in the figure. In this case the debris from the breakup of the perimeter wall will contribute significantly to the threat to the facility behind it.)
• Computing the response of the facility struck with these loads in terms of window and wall damage, response of the structural framing system and the risks of its collapse, and evaluating the risks to the functions and personnel housed in the facility.

In early stages of a blast effects analysis, simpler techniques are often used to provide an initial estimate and determine if further analysis is necessary. For flexural type responses, Q-D charts and PI-curves provide effective estimates; quantity-distance charts and pressure impulse curves define the safe distances for charges for different types of components, for column responses, single degree of freedom (SDOF) models are used because of the added complexity of the column responses. In performing design studies, SDOF models are utilized because they represent a good compromise between ease of use, fidelity, and widespread availability.

Structural finite element models may be useful to provide basic information concerning the blast response of a building, but are generally not well suited for blast effects analyses. These models are also used to check compliance with progressive collapse provisions of design codes.

High-fidelity physics based (HFPB) models are applied to analytically simulate the actual behavior of a given structural system or component under blast and impact loads. Even though this type of modeling is performed by few consulting engineers, it is crucial in many studies. Unlike any other analytic tool used engineers, it provides a direct means to estimate the potential for the system to fail under the applied blast/impact loads. This essential difference between HFPB and the other analytic models cited is that actual behaviors rather than assumed behaviors are used in studying the response of the system.

K&C is so skilled in the use of HFPB techniques that we can employ them at a cost comparable to that other consultants would charge to perform analyses with other, less precise engineering models, which are often far less applicable and may lead to erroneous conclusions. K&C offers a variety of physics-based analytic software tools for simulating the response of structural systems, mechanical systems, and the response of equipment and personnel to the effects of blast, shock, and impact loads.

These codes offer a powerful means to simulate almost any blast, shock and impact response, including responses to contact and shape charges, high velocity projectiles and debris fragments, and the effects of shielding and protective barriers in terms of reducing the actual threats facing the facility or location of interest.

Description of Services

• Perform Blast Effects Analyses using a variety of analytic tools.
• Develop fragility curves for various structural and window/wall components for use in vulnerability assessments.
• Perform vulnerability assessments for structural components, equipment and MEP systems, and occupants of the facility.