Office Buildings Located in a High Threat Environment

Services/Work Provided:

• Site Survey & Investigation
• Blast  Effects Analysis and Vulnerability Assessment (BEA/VA)
• Design Proposal and Cost Estimate
• Security Recommendations for Site

Description:

Karagozian & Case has performed numerous BEA/VA studies for facilities located throughout the world. In fact, K&C has been awarded a long term agreements with government agencies and non-government organizations (NGOs) related to performing BEA/VA studies and developing protective designs for facilities.

Typically, an existing facility is evaluated by K&C as to its vulnerabilities to blast and other forms of threats (e.g. FE/BR protection). Recommendations are then provided to enhance its protection. Cost estimates are presented for each enhancement option. Based on the client's choice, K&C then develops the final design and prepares a set of drawings suitable for construction.

For example, some results from a study performed by K&C in the Middle East for an NGO facility are shown. The building consists of seven floors of office space and one level of underground parking. It is a reinforced concrete frame structure with a building façade consisting of a combination of insulated glazing units and unreinforced masonry infill walls. The scope of work included:

• Conducting a site visit to gather detailed information and building characteristics.
• Performing a detailed Blast Effects Analysis of the “as-built” facility to assess its vulnerabilities.
• Developing three alternative retrofit concepts and cost estimates to enhance the level of protection of the facility.
• Providing a set of construction documents for implementation of selected retrofit design

FE/BR Enhancements for Embassy Facilities

Services/Work Provided

• Field survey to assess site security protection
• Evaluation of existing Forced Entry and Ballistic Resistant (FE/BR) protection
• Retrofit/Replacement designs for FE/BR protection
• Evaluate existing structural conditions (location, type of construction, condition of materials, etc.) to determine and guide necessary upgrades to FE/BR doors, windows, and walls.
• Prepare report for site survey/assessment
• Construction Documents

Description:

K&C has been awarded several contracts to evaluate and improve security at embassies so that the facility and its occupants are better prepared to sustain security related threats such as forced entry, fire from small ammo and RPGs, and blast. To begin, the structural conditions (location, type of construction, condition of materials, etc.) are evaluated to assess the current FE/BR protection.

This generally involves assessing whether the doors, windows, and walls meet the applicable FE/BR criteria, if not determining ways that they may be brought into compliance. This often involves developing concepts to upgrade or replace the windows, wall, or door that fails to afford sufficient protection. Once K&C’s suggestions are approved, design and construction documents for the upgrades are produced. This work sometimes includes supervision/inspection of the construction to ensure compliance with K&C’s design. The photos to the left are of a typical FE/BR entrance, door, and window installation of the sort designed by K&C.

Reinforced Concrete Columns Retrofit

Services/Work Provided:

• Vulnerability Assessment for Reinforced Concrete Columns (RC)
• Column Retrofit Design
• Tests to Validate Design Concepts
• Construction Documents
• Construction Administration

Description:

The blast resistance of RC columns can be markedly enhanced by using CFRP (carbon fiber reinforced polymer) to wrap RC columns. The process of wrapping a column with CFRP is shown to the left. K&C has pioneered the use of CFRP to enhance both strength and ductility of RC columns subject to blast loads. Also displayed are photos of blast effects tests that were conducted by K&C to validate this enhancement. Steel jacket retrofits have also been developed which are particularly effective protecting RC columns from near-contact and in-contact detonations. Both the use of CFRP and steel jacket retrofits have been validated in a series of blast effects tests conducted by K&C.

K&C has developed special purpose software to design FRP wrap and steel jacket retrofits for both VBIED and PBIED threats. This software provides a quiet and easy means to evaluate an existing columns performance under blast and evaluate different options for enhancing its blast resistance.

During construction, K&C can also provide supervision on site to ensure that the CFRP wrap and steel jacket designs are installed properly. K&C has also developed an easily used fast running design code to evaluate the vulnerability and design retrofit options for RC columns.

Masonry Walls

Services/Work Provided:

• Blast Effects Analysis and Vulnerability Assessment (BEA/VA) Studies
• Design of Blast Effects Mitigation Concepts
• Cost Estimates
• Design Drawings Construction Supervision

Description:

K&C generally uses results computed with high-fidelity physics-based (HFPB) finite element models that can simulate the response of a masonry wall due to blast loads. Such analyses are performed to assess both its vulnerability and the capability of the proposed retrofit because the response of such walls in terms of failure is often quite complex and easily designed incorrectly. An example of an HFPB model is shown, and while such models might seem complex, they can be generated and operated by K&C’s experiences staff for the same cost and time that others would need to perform simplified engineering analyses. The enhanced accuracy afforded by HFPB analyses is worth more and would cut down the cost of construction. Based on the analysis results, design recommendations, mitigation options, and cost estimates are provided.

For example, one of our previous projects was to enhance the protection afforded by control rooms within a refinery in the event of a vapor cloud explosion (VCE). These rooms are typically constructed of concrete block walls with light reinforcement. Studies were conducted to assess the vulnerability of existing control room structures for specific VCE threats. Based on using an HFPB model, K&C determined that the rooms provided insufficient blast resistance. However, because of the equipment, conduit/piping, and the need to maintain operations, it was difficult to access the structure or markedly change it. Here, the HFPB modeling proved itself invaluable by allowing K&C to add just the right amount of CFRP (carbon fiber reinforced polymer) fabric strengthening to hold the wall in place, when both too much and too little CFRP would cause the wall to fail.

Low Cost Blast Resistant Façades

Services/Work Provided:

• Development of Design Concepts
• Blast Effects Testing
• Blast-Resistant Wall and Window Designs
• Construction Drawings for Design

Description:

This project included development of new concepts for providing and constructing blast-resistant façades for new and existing facilities. Potential ideas were screened and evaluated using high-fidelity physics-based (HFPB) finite element models which simulate the behavior of the façade during a blast load. The performances of the most successful concepts were then validated in blast effects tests.

Results from blast tests for two of these concepts are shown in the photos. The first image shows an example of a cable catching system and the second shows a thin plate catcher system. Both ideas are intended to prevent entry of debris into a facility as proved by the results from tests shown and in other tests conducted by K&C. Each façade was constructed with lightweight conventional materials. They both provided a remarkably high level of blast resistance. The thin plate catcher system provided an order of magnitude more blast resistance than any other product or concept available and was achieved using conventional sheet metal for the panel used to capture the wall debris, (see test photos).

 Due to increased ductility and inherent strength such systems provide, they performed better than façades using materials that were heavier, more expensive, and difficult to install. The design concepts validated under this project have been installed in several facilities to provide protection against terrorist bomb attacks.

Enhanced Blast Resistance for Existing Glass Curtain Walls

Services/Work Provided:

• Vulnerability assessment
• Concepts for mitigation of blast threats
• Construction documents
• Blast effects tests to validate designs
• Development of designs and costs to enhance blast protection

Description:

Glass curtain wall systems are common to many public venues such as airport terminals, auditoriums, and atriums.  K&C has developed a unique and proven system for enhancing the blast protection of glass curtain walls that is based on preventing the debris that would be generated by a blast load from entering the facility by catching it with a network of cables (e.g., as shown in photo to the left).

In particular, the departure level façade at Terminal 3 Changi Airport in Singapore was retrofitted with a K&C designed cable catcher system.  This façade is over 300 m long by 15 m tall, and is comprised entirely of laminated glass.

The study phase of this project included a comprehensive threat/vulnerability assessment of the curtain walls on the three different levels of the terminal and allowed the owner to evaluate and understand the performance of the existing curtain wall across a range of charge weights and standoff distances. The study also presented mitigation solutions that spanned a breadth of protective levels (from low to high); ROM level cost estimates were developed for each mitigation solution.

For the design phase, K&C provided a final design for the preferred mitigation system and developed the construction drawings for its installation.  K&C also assisted the installation contractor by answering their questions and resolving issues that arose during installation.  The design parameters for the final designs were selected based on sophisticated models of the entire wall and cable catcher system that were used to calculate the blast response, which are shown to the left.

Refinery Control Rooms - Vapor Cloud Explosion Protection

Services/Work Provided:

• Assessment of blast threat
• Vulnerability assessment of control room
• Enhance blast protection afforded by control room
• Validation tests
• Design drawings

Description:

To begin, the vulnerability of existing control room and work space structures were assessed for specific VCE threats. These buildings are typically constructed of concrete block walls with light reinforcing or sheet metal over a framing system that offer very little blast resistance. Moreover, because of the equipment, conduit/piping, and the need to maintain operations, it is difficult to access the structure or markedly change it.

Mitigation options were evaluated for each of the vulnerabilities that were identified during the assessment phase. The solutions included using of fiber reinforced polymer (FRP), polymer panels, catcher systems, shotcrete and steel framing systems. Of these, FRP proved to be the most useful.

Because of the fragility of the control room’s walls, K&C used results computed with high-fidelity physics-based (HFPB) finite element models to simulate the wall’s actual responses to blast in order to select appropriate values for design parameters. This was necessary to avoid causing the wall to fail in shear due to excess FRP reinforcement.

Cargo Inspection Facility

Services/Work Provided:

• Advanced Analytic Modeling
• Innovative Design
• Blast Effects Containment
• Development of Preliminary Designs
• Costs Estimates

Description:

A hardened facility was developed for the inspection of suspicious containers detected at an entry port. This facility would allow for full containment of very large detonations (e.g., 20 to 60 Klb of TNT) and the detonation products of such an explosion. The full containment feature of the design was developed in recognition of its importance were a dirty bomb (e.g. radiation contamination, chemical or biological hazard). This facility is intended to provide a safe place to examine a suspicious container without the need of exposing the rest of the port facility to risk. In addition, the examination may be done remotely, and thus not place any personnel at risk.

The study phase included a comprehensive threat/vulnerability assessment of various designs for the containment system. This allowed the port authority to evaluate and understand the performance of the facility across a range of charge weights and design parameters. ROM level cost estimates were also developed.

The analyses conducted to design the facility used high-fidelity physics-based finite element models to simulate the dynamic response generated by a blast load. This included the structures response due to both the shock and resulting gas pressure of a contained detonation. This gas pressure governed the design, which was in excess of 700 psi. Finally, specific design parameters were selected for the containment shell and closure design.

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.

High-Fidelity Modeling of Steel Framing Systems and Components

Services/Work Provided:

• Blast Vulnerability Assessment
• High-Fidelity Physics-Based (HFPB) Analyses of Connections
• Finite Element (FE) Analysis
• Blast Resistant Design
• Design Related to the Prevention of Progressive Collapse
• Development of Special Connection Detailing

 Description:

The use of HFPB FE analysis allows K&C to properly simulate the behaviors of complicated elements of a buildings frame system. In this case, the capability of a particular building’s steel framing system and components to survive the removal of a column was assessed. This is particularly important for steel systems in determining the behaviors and failures of structural connections under blast and collapse threats. This capability is especially useful when determining the risks related to the collapse of buildings with little set back and designing the retrofits for steel conections. An example which exhibits K&C’s skills is shown to the left. Here, a detailed analysis was performed of a portion of a steel framing system to evaluate its ability to span a missing column. Several different connection types were evaluated under blast and static loads with this model.

High-Fidelity Modeling of Attachment Systems

Services/Work Provided:

• Analysis of anchorage and attachment systems
• Blast Vulnerability Assessment
• High-Fidelity Physics-Based (HFPB) Finite Element (FE) Analysis
• Validation of Analysis Tools

Description:

Detailed analyses are often needed to evaluate the capacity and failure modes of specific attachment and anchorage systems. This is particularly needed to evaluate the performance of steel connections. Here, detailed models of the bolts and welds that were used in the design of the connections were analyzed with HFPB models to assess the capability of the designs to work in a blast environment.  The analysis shown was performed to verify the ability of the HFPB FE models to capture the bolt forces and behaviors commonly found in steel frame connections. Results were verified against experimental data using the FE model shown to the left. Also presented is the sequence of responses that precede the actual failure of the bolt. Such information is both helpful in design of better attachment/anchorage systems and evaluating the capability of specific designs to perform as desired.