Blast Walls and Detonation Shields

Services/Work Provided

• Blast Effects Analysis and Vulnerability Assessment (BEA/VA)
• Design and Evaluation of Effectiveness of Blast Walls and Detonation Shields
• Perimeter Site Security Recommendations
• Design and Construction Drawings

Description

In the BEA/VA studies considered by Karagozian & Case in high threat regions, there is often a requirement for the use of blast walls and/or detonation shields. The design of these features is gradually predicated on the availability of local materials and the ability of the analyst to tailor the situation into a workable and effective solution. For protection purposes such walls/shields cover a large extent of the facility and must work in a severe blast and penetration environments because the blast/penetration threats they are likely to encounter will be severe.

K&C has performed blast vulnerability assessments and designs for blast walls and detonation shields at several facilities located throughout the world. For example, the facility indicated in the figure to the left is located in Baghdad, Iraq. It is four stories with a reinforced concrete frame structure and a building façade consisting of unreinforced masonry infill walls with window openings. The scope of work included:

• Reviewing available construction documents and photographs.
• Conducting a detailed Blast Vulnerability Assessment of the “as-built” facility.
• Developing retrofit concepts to enhance the level of protection of the facility.
• Providing analysis and construction details for retrofits and upgrades.

After reviewing construction drawings, K&C evaluated how the building responded to a range of charge weights and standoff distances. Retrofit options for the structural and non-structural components were provided to protect from vehicle-borne IEDs. Additionally, concept designs were developed for blast-resistant barriers to provide shielding to the structure. An overhead protection system (detonation/blast shield) was also installed to protect against indirect fire from mortars. 

Protection from a Pressure Vessel Rupture

Services/Work Provided:

• Explosive Safety
• Protection from Tank Rupture
• Vulnerability Assessment
• Mitigation Concepts
• Design and Construction Drawings

Description:

The rupture of storage tanks and pressure vessels and the resulting risks to nearby facilities and personnel have been addressed by K&C on several occasions for a wide range of circumstances. Upon rupture, gas pressures and vessel fragments and other form of debris emanating from the rupture can potentially damage equipment or injure personnel in the vicinity. To address such risks, K&C would generally perform a study to assess the situation and make recommendations.  The elements of such a study would include:

• Determining the type of explosion/rupture and amount of blast pressure/debris released.
• Calculating debris throw including: trajectories, amounts, and sizes.
• Assessment of the risks to the facility and personnel from air blast and debris.
• Designing alternatives and developing costs to mitigate the risks.
• Prepare design and construction drawings of the concepts chosen by the client.

There are several ways that pressure vessels might fail, and a variety of simplified and advanced methods for estimating the ensuing risks may be used depending on the complexities of a particular problem. In particular, the calculation shown was developed from a Computational Fluid Dynamics (CFD) analysis where the physics of the actual problem is modeled quite precisely.  Such precision is often needed to get realistic estimates of the threat because of the complexities involved in determining the consequences and threat environment represented by such events. In the case shown, the calculation indicates the gas pressure released when a small area of the tank’s wall failed, causing debris and high pressure gases to be relased. The magnitude of has pressure propagated and the debris thrown calculated with the model shown were used to design the walls surronding this space to protect personnel housed in adjacent spaces.

Curtain Wall Vulnerability Analysis Software

Services/Work Provided:

• Development of software to perform blast effects vulnerability analyses for curtain walls.
• Creation of LS-DYNA models to simulate blast response of curtain walls.
• Design a tool for enhancing the blast resistance of new curtain walls
• Present options to retrofit existing curtain walls. 

Description:

Determining the blast resistance of curtain walls (CW's) can be complicated because they are often quite complex and generally afford minimal resistance to blast.  Also, they are comprised of widely different forms that are not easily reduced to some form of simplified analytic model.  However, curtain walls are a major source of risks were a blast to occur and a key item whose improvement could afford much greater protection.

To address this risk, K&C created a computer code, BEA_CW (Blast Effects Analysis for Curtain Walls) that allows a user to rapidly enter the basic properties of a CW system and then generate an LS-DYNA finite element model for predicting its response to a blast load. This is done in such a way that the used LS-DYNA is transparent to the user.

Security upgrades generally involve retrofitting a building’s windows, CW's, and other façade components to enhance their blast resistance.  Several retrofit options provided by BEA_CW include the use of film and polymer panels, cable and fabric catcher systems, and the use of stronger mullions. 

K&C performed blast analyses of many CWs for this project to develop the modeling strategies employed in BEA_CW. K&C also validated the analysis capability afforded by BEA-CW by comparing experimented and analytic results to several types of CWs subject to blast loads. Based on the results, our team developed the necessary coding to implement the automated generation of the LS-DYNA models and the generation of CW upgrades. 

Blast Consulting Services

Services/Work Provided:

• High-Fidelity Physics-Based (HFPB) Analysis
• Recommendations for Construction Detailing
• Review for Compliance with Security Criteria

Description:

Karagozian & Case offers blast consulting services to assist design teams when considering blast loading.  Currently, K&C is working on the design of a new Mental Health Building and Parking Garage at a Veteran’s Affairs Facility. The structures are to meet the requirements of the Physical Security Design Manual for VA Facilities (Mission Critical for the Mental Health Building; and Life Safety for the Parking Structure).

K&C is providing calculations including simplified engineering models (SDOF) and high-fidelity physics-based (HFPB) finite element models of building components and their connection details to meet the blast design requirements. Based on the calculation results, construction detailing was provided to assist the design team in developing construction drawings for the building envelope (walls, fenestration, atria and roof), structural framing system, and perimeter site security.