A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Balanced Design for Blast-Mitigating Window Retrofits for Historic Structures
Often, when facilities are being renovated to meet blast requirements, budgetary constraints allow for upgrading window systems only and not the conventional exterior wall components. Designs of blast-mitigating window systems in accordance with the most current Unified Facilities Criteria (UFC) for Department of Defense (DoD) facilities and Interagency Security Committee (ISC) criteria for federal facilities are based on a specific design threat located at the appropriate available standoff, and do not consider factors beyond transferring the load into the building diaphragm. Existing historic structures typically have small standoff distances which result in very large blast loads on the façade. Where windows are the only component considered for upgrade, it is generally not practical or economically sound to develop window retrofit designs based solely on the design basis threat since the walls surrounding the windows will likely be much weaker than the window upgrades. The building façade should be treated as a system, with a balanced approach to mitigate hazard from blast loading. A balanced design requires the window glazing to be weaker than the window frame, the window frame to be weaker than the anchorage, and the anchorage to be weaker than the surrounding building component. In a balanced system, overloading one component of the system will not cause failure of subsequent levels of the system. In an unbalanced system, stronger windows can cause overloading of the walls and the safety provided by the window upgrades would be negated by the high-hazard fragments from the wall components. For a retrofit of an older, historical building, the wall components must be included in the evaluation of the window system so balanced window upgrades can be developed and incorporated. This paper presents a case-study involving the determination of the appropriate level of protection that should be provided for window systems as part of an upgrade of a multi-story historic building in an urban environment (with minimal standoff), where design loads exceed the wall capacities. This paper discusses the effectiveness of limiting the window upgrades to a capacity comparable to the wall capacity. The analysis results would be useful to design professionals that work on renovations of historic federal and DoD facilities.
Balanced Design for Blast-Mitigating Window Retrofits for Historic Structures
Often, when facilities are being renovated to meet blast requirements, budgetary constraints allow for upgrading window systems only and not the conventional exterior wall components. Designs of blast-mitigating window systems in accordance with the most current Unified Facilities Criteria (UFC) for Department of Defense (DoD) facilities and Interagency Security Committee (ISC) criteria for federal facilities are based on a specific design threat located at the appropriate available standoff, and do not consider factors beyond transferring the load into the building diaphragm. Existing historic structures typically have small standoff distances which result in very large blast loads on the façade. Where windows are the only component considered for upgrade, it is generally not practical or economically sound to develop window retrofit designs based solely on the design basis threat since the walls surrounding the windows will likely be much weaker than the window upgrades. The building façade should be treated as a system, with a balanced approach to mitigate hazard from blast loading. A balanced design requires the window glazing to be weaker than the window frame, the window frame to be weaker than the anchorage, and the anchorage to be weaker than the surrounding building component. In a balanced system, overloading one component of the system will not cause failure of subsequent levels of the system. In an unbalanced system, stronger windows can cause overloading of the walls and the safety provided by the window upgrades would be negated by the high-hazard fragments from the wall components. For a retrofit of an older, historical building, the wall components must be included in the evaluation of the window system so balanced window upgrades can be developed and incorporated. This paper presents a case-study involving the determination of the appropriate level of protection that should be provided for window systems as part of an upgrade of a multi-story historic building in an urban environment (with minimal standoff), where design loads exceed the wall capacities. This paper discusses the effectiveness of limiting the window upgrades to a capacity comparable to the wall capacity. The analysis results would be useful to design professionals that work on renovations of historic federal and DoD facilities.
Balanced Design for Blast-Mitigating Window Retrofits for Historic Structures
Alexander, Quincy G. (author) / Brock, Shelly N. (author) / Bryant, Larry M. (author)
Structures Congress 2014 ; 2014 ; Boston, Massachusetts, United States
Structures Congress 2014 ; 198-209
2014-04-02
Conference paper
Electronic Resource
English
Balanced Design for Blast-Mitigating Window Retrofits for Historical Structures
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