ISERRT Research

Reaction Frame with Enclosure

Sponsor: National Institute of Justice, U.S. Department of Justice

Status: Active – Updates to be posted throughout 2016 as test and analysis results are processed

Project Summary

Natural and manmade explosive incidents have become increasingly more commonplace with an average of over 4000 incidents occurring per year.  In the criminal justice response to such events, the determination of the weight, composition, and epicenter of accidental and malicious explosions is of foremost concern during the post-blast forensic investigation.  The proposed research will leverage low-cost 3D scanning, scene reconstruction, and nondestructive evaluation tools to characterize structural and non-structural building components in the post-blast environment that serve as silent “witnesses” to the blast shock wave. This applied research will yield powerful, high fidelity surface reconstruction of scenes that will enhance techniques for estimating important characteristics about the charge size and location, while being as technologically-accessible and user-friendly as conventional photography and videography tools used by current investigators.  To complement this disruptive technology, the proposed research will develop the first blast dynamics simulator for post-blast forensic investigation to facilitate physics-based testing of investigator hypotheses against physical evidence. Using computational methods, the project will explore how such simulation codes could be used alongside the low-cost 3D scanning measurements to yield automated routines for reconstructing information on explosive charge weight, composition, and epicenter from deformation, fracture, fragmentation, and debris formation of building components.  The project leverages an existing partnership with the City of Gastonia Police Department and Bomb Squad to facilitate field experimentation and verification of the proposed technologies and methods at the UNC Charlotte Infrastructure Security and Emergency Responder Research and Training (ISERRT) Facility.  Furthermore, a mature collaborative relationship with the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) will provide a platform for demonstrating the approach in a real-world post-blast investigation course.  This unique opportunity also maximizes the dissemination of the research results to the criminal justice and law enforcement community to promote technological replacement of current rudimentary, yet scientifically grounded observational techniques.  The project will impact criminal justice research and practice by producing a significant experimental dataset evaluating this emerging low-cost technology, software codes and applied validation studies to promote a blast dynamic simulator for post-blast forensics analogous to the Fire Dynamics Simulator used in post-fire forensics, and a method for rapid, automated reconstruction of the explosive characteristics and epicenter from structural and non-structural physical evidence.

Industry Support

Support for the design of the structural façade panel reaction structure as well as donation of materials, fabrication, and transportation of the reaction structure was provided by GRATEC (Fort Mill, SC) and Union Glass and Metal, Inc. (Fort Mill, SC).  The development of this research infrastructure, critical for the experimental component of the research effort, is greatly appreciated by the project team.

Funding Acknowledgement and Disclaimer

This Web site is funded through a grant from the National Institute of Justice, Office of Justice Programs, U.S. Department of Justice.  Neither the U.S. Department of Justice nor any of its components operate, control, are responsible for, or necessarily endorse, this Web site (including, without limitation, its content, technical information, and policies, and any services or tools provided).

Publications

Whelan, M.J., Ralston, A.D., and Weggel, D.C. (2015). “Blast Testing of Cold-Formed Steel-Stud Wall Panels,” ASCE Journal of Performance of Constructed Facilities, 10.1061/(ASCE)CF.1943-5509.0000734, 04015008.

The ISERRT Facility conducted blast testing of a series of timber stud wall specimens subject to close in explosives with various charge locations.  Each wall panel was instrumented with an array of five flush-mount pressure sensors for measurement of reflected overpressures across the wall.  An additional two free-field pencil probes were positioned to measure the incident overpressure of the shock front.  Two linear displacement transducers and six shock accelerometers were installed across the wall studs to measure the dynamic response of the wall throughout the blast loading and failure of the wall system.  Regular and high-speed video was also employed to document each test.

As an additional supplement, vibration testing was also performed on each of the wall panels prior to blast testing to provide experimental data for structural identification of the exact boundary conditions and structural stiffness of each wall.  The modal properties measured during these vibration tests will serve to calibrate advanced analytical models prior to nonlinear analysis of the blast effects to yield higher fidelity simulations.  For wall specimens exhibiting only moderate damage, the vibration testing was also conducting after the blast loading to characterized the performance of the wall in the damaged condition.  This vibration characterization will help to validate the fidelity of the analytical models in the post-blast state as well as facilitate the development of novel methods for structural health monitoring and nondestructive evaluation of structural systems subject to explosive threats.

Unique access to an industrial building prior to, during, and immediately after detonation of an internal explosion was leveraged to obtain a remarkably extensive database of experimental measurements on the performance of the building before and after damage induced by the blast loading. Additionally, incident pressures, reflected pressures, and shock accelerations across various structural surfaces were obtained during the blast to quantify the loading and structural response. The structure tested was a two-story masonry building that advantageously provided opportunities to test the performance of a prestressed double-tee joist roof, conventional masonry walls, and an interior steel frame under blast loading.

Key features of the experimental database are:

• Multiple-Input-Multiple-Output Modal Testing of the Prestressed Double-Tee Joist Roof using a stationary array of 60 accelerometers distributed across the 12 joists during application of controlled, measured excitation produced by 2 long-stroke shakers driving reaction masses.
• Multiple-Input-Multiple-Output Modal Testing of an Internal Steel Frame using a stationary array of 58 accelerometers distributed across columns and primary beams during application of controlled, measured excitation produced by 2 long-stroke shakers driving reaction masses.
• Modal Testing of an Infill Masonry Wall by Roving Impulse Hammer Technique over 48 locations of the wall with multiple stationary accelerometers to extract modal parameter estimates of the wall prior to and after blast loading.
• Materials Characterization through Impact-Echo Technique applied at over 1500 locations across the prestressed roof joists.
• Collection of Physical Test Specimens for Destructive Testing including cores from the concrete in the roof and cores from the masonry blocks.
• Blast Observation and Measurement from high-speed synchronous data acquisition of 2 incident pressure pencil probes, 10 flush-mount reflected pressure transducers, and 8 shock accelerometers distributed across the prestressed concrete roof, masonry walls, and steel frame.

Publications

Kernicky, T., Whelan, M.J., Weggel, D.C., and Rice, C.D. (2014) “Structural Identification and Damage Characterization of a Masonry Infill Wall in a Full-Scale Building Subjected to Internal Blast Load,” Journal of Structural Engineering, Volume 141, Special Issue: Field Testing of Bridges and Buildings.

Kernicky, T., Whelan, M.J., and Weggel, D. (2014) “Experimental Modal Analysis of a Prestressed Concrete Double-Tee Joist Roof Subject to Blast,” International Modal Analysis Conference XXXII, Orlando, FL, February 2-5, 2014.

Whelan, M.J., Kernicky, T., and Weggel, D. (2014) “Structural Identification using the Applied Element Method: Advantages and Case Study Application,” International Modal Analysis Conference XXXII, Orlando, FL, February 2-5, 2014.

Kernicky, T. (2013) “Structural Identification and Damage Characterization of a Full-Scale Masonry Building Subject to Internal Blast Load,” Masters of Science Thesis, Department of Civil and Environmental Engineering, University of North Carolina at Charlotte.

Kernicky, T., Whelan, M.J., Rice, C., and Weggel, D. “Structural Identification of a Full-Scale CMU Infill Wall Subjected to Blast Loading using an Applied Element Framework,” International Workshop on Structural Health Monitoring (IWSHM), Stanford, CA, September, 2013

Publications

Ralston, A.D., Weggel, D.C., Whelan, M.J., and Fang, H. (2015) “Experimental and numerical investigations of glass curtain walls subjected to low-level blast loads,” International Journal of Computational Methods and Experimental Measurements, Vol. 3, No. 2, 121-138.

Kennedy, B.T., Weggel, D.C, and Keanini, R.G. (2013) “Experimental program and simplified nonlinear design expression for glass curtain walls with low-level blast resistance,” International Journal of Computational Methods and Experimental Measurements, Vol. 1, No. 3, 321-343.

Weggel, D.C. and Zapata, B.J. (2008) “Laminated glass curtain walls and laminated glass lites subjected to low-level blast loading,” Journal of Structural Engineering, Vol. 134, No. 3, 466-477.

Weggel, D.C., Zapata, B.J., and Kiefer, M.J., “Properties and dynamic behavior of glass curtain walls with split screw spline mullions”, Journal of Structural Engineering, Vol. 133, No. 10, 1415-1425.

Kennedy, B.T. (2008) Performance of a nearly-conventional curtain wall system subjected to blast loads. Master’s Thesis, University of North Carolina at Charlotte, Charlotte, NC.