Blast Mitigation for Structures 1999 Status Report on the DTRA/TSWG Program (2000) / Chapter Skim
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B: Blast Mitigation for Structures, Program Master Plan
B: Blast Mitigation for Structures, Program Master Plan
Pages 45-74
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B Blast Mitigation for Structures Program Master Plan
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. Cat TASK MANAGER: Doug Sunshine Defense Threat Reduction Agency 6801 Telegraph Road Alexandria, VA 223 ~ O
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This building has also been used to test ma~Irooms to protect against package bombs, windows and window retrofit methods, and vein hold venous walls for additional blast testing. To address roof and load-beanng wall collapse, a reaction structure has been constructed to test retrofit concepts.
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Validation tests were successfully conducted in Israel to verify design methods for masonry was and window retrofits that provide inexpensive systems to reduce debris hazards. The wall system uses fabrics which do not strengthen the wall, but catch the debris thus protecting people inside.
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CTS ~ Full-scale test structure to be built and tested in FY98 CTS2 Full-scale test structure to be built in FY98 and tested in FY99 DoD Department of Defense DOE Department of Energy DOS Department of State DSWA Defense Special Weapons Agency FIB Federal Bureau of Investigation FCDSWA or FC Field Command, Defense Special Weapons Agency FEMA Federal Emergency Management Agency FY Fiscal Year GSA . General Services Administration LACRO Interagency Cost Reimbursement Order MIPR Military Interdepartmental Purchase Request NFESC Naval Facility Engineer Service Center NRC National Research Council PC Personal Computer PHETS Permanent High Explosives Test Site SETA Scientific Engineering and Technical Assistance SS US Secret Service TNT Tr~nitrotoluene TWSG Technical Support Working Group UK United Kingdom US ACE United States Army Corps of Engineers USAF/WI United States Air Force Wright Laboratories WES United States Army Engineer Waterways Experiment Station WSMR White Sands Missile Range 1V
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Final products include vulnerability assessment methods for calculating blast effects, structural response and human injury. Design guidance will be developed to reduce these vuInerabilities.
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Although structural hardening and blast mitigation techniques will accomplish this, in part, the focus is on protecting people, not the structure or other assets. Injuries and death Tom bomb attacks on buildings can usually be attributed to three causes: structural collapse, flying debris, and fire/smoke propagation.
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built without blast hardening. Retrofit methods to increase blast resistance unit be applied to the structure and tested.
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on the blast loading. It will then take the validated results of the research program and either develop new computer-based methodologies or modify existing design programs to take into account the potential effects of terrorist bombs on buildings.
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They will be used for both explosive testing and methodology development." DTRA has a considerable testing infrastructure as part of the DTRA Permanent High Explosives Test Site (PHETS) at the White Sands Missile Range (WSMR)
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A number of potential techniques to mitigate the effects of bomb blasts on structures have been identified (e.g., earthquake resistance retrofit methods, application of composite materials, energy absorbing materials)
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A recent DSWA sponsored test indicated that a reinforced concrete wall failed in a manner as to cause a significant debris hazard out to several hundred feet. ' Phased computer code that provides conventional weapons calculations based on the equations and Ames of TM S-855-1 "Fundamentals of Protective Design for Conventional Weapons', A-2
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Column failure was the primary cause of structural collapse in the bombing of the Murrah Federal Building. A FEMA/ASCE reports on the Oklahoma City bombing suggests that BS% of the floor space would have been saved if the columns did not fail.
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These efforts wiD help insure the success of the full-scale structure test. Potential failure modes include column failure, slab failure due to upliR, or punching shear of the floor at the column.
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Figure 5: Exterior Wall With Window Opening, Severe Damage to Column and floor The last test was designed to maximize the uplift by leaving the bottom bays without walls and constructing solid walls on the second floor. The test results showed that the floor did receive severe uplift damage, and the column on the second floor received severe damage (similar to other solid wall test)
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to examine st~uch~ral collapse and to test retrofit methods to prevent it. Analytical studies were conducted which indicate that seismic retrofit techniques, adapted for blast loads, show promise.
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These walls are also very susceptible to collapse because of their relatively weals capability to resist horizontal loads, and because of the large surface area to attract blast loads. Analysis methods for masonry walls have been developed for some masonry was configurations, but only limited validation testing has occurred.
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There where three examples of this in the Oklahoma City bombing. During FY9S, a reaction structure was built at Tyndall AFB to hold rooftest articles.
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Although blast loads are directly considered in the design process, the robustness ofthe resulting building will prevent progressive collapse. This effort guideline development effort will be finished during FY99.
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C Debris Hazards Flying debris (e.g., glass, walls, overhead lights and utilities, other building components and fit strings)
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The UK Glazing Hazard Guide was developed In paper form as a series of charts. Dig FY98, this method was automated and coded as a computer module for use by various vulnerability codes (e.g., it has been incorporated into AT-Planner)
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This effort writ not be initiated until FY00 due to Ending constraints. The automation of the UK Glazing Hazard Guide is an interim step toward developing a complete hard and injury prediction method.
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The government has agreed to test industry products in a shock tube at Allured Baker Associates. The shock tube was chosen to perform the tests because it provides a good' consistent simulation of blast loads, and is less expensive than open-field testing.
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~ Control Wall Pre-Test~` Fabric Figure i2: Fabric wall Retrof its b. Walls With Openings 8~C~ Post-Test The fabric catch method works extremely well for masonry walls without openings.
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One must be carefi~! not to rely only on previous bombing events for injury prediction methods since, in terrorist bombings, the bomb type, yield, and configuration is usually not know precisely, and must be estimated based on observed damage.
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Potential methods including reinforced concrete walls, sacrificial walls, masonry walls with debris catchers, application of composite walIpaper, and others will be investigated. This task will take advantage of the filll-scale test structures and unit work in conjunction with the DOE mailroom initiative.
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Design guidance grill be developed dunng FYOO. Figure 13: Mailroom Test Ds-2 1 3.
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