Response of Curtain Wall Architectural Envelopes to Negative Phase Blast Effects
Date: May 31, 2011
The Need Addressed By the Project:
Reduce collateral damage to structures and protect citizens near terrorist targets by increasing the resiliency of curtain wall systems in the negative blast phase.
· Develop architectural envelopes for blast mitigation solutions in typical curtain wall configurations
· Develop and validate designs to resist the negative blast effects associated with large scale blast events
· Increase resiliency of critical infrastructure by limiting effects of an explosion near a critical building
Specifications need to consider negative phase pressure waves. While the negative phase is not always important, cases exist where negative phase could cause outward failures. Retrofit systems should be analyzed considering reduced fragment loads produced by negative phase effects. Tests that do not produce negative phase should be used in cases where negative phase can be assured to be negligible.
Significant Milestone Achievement: Testing and New Designs
With the completion of the first full scale test, the UK team was able to produce the required blast waveforms to allow for the validation and comparison of the design models and calculations. Based on the results of the first test, the model performed well. The material and grid for the models have been established for further iterations of the curtain wall design.
Project Success Story: Creation and Validation of Design Models Incorporating the Negative Blast Phase
The University of Kentucky team has successfully created and validated design models that incorporate both the positive and negative blast phases. To achieve this success, there were many notable milestones along the way. They include:
- Determination of blast loadings that are appropriate for curtain wall testing
- Generation of the desired blast waveforms
- Design and modeling of the first iteration of curtain wall systems
- Validation of design models and calculations
Through this process the UK team has created design models for two 5 ft x 10 ft curtain wall systems that take into account the positive and negative blast loading. One of these curtain wall systems was tested at the University of Kentucky’s shock tube facility. Based on the results from high explosive shock tube testing, the models and calculations have proven to be quite accurate, nearing a level of fidelity that would allow for extrapolation in the absence of test data. With the use of these models and calculations, further development of curtain wall systems can be accomplished.
At the current time, the UK team is working on the second phase of validation for design models and calculations.
The major goals and objectives are to
· Further validate the design models through full scale testing
· Evaluate current designs
· Make revisions if necessary.
Winco, Inc, the commercial partner on this project, is using these findings for marketing and for new window designs. Specifically, a retrofit system is under development for expedient installation and protection of buildings where historic site lines and architecture are desired to be maintained, but blast protection is required. Winco believes that a solid market exists for the retrofit product. In addition, the negative phase impact is suspected to be different for retrofit designs than for typical new installations.
· Winco has developed marketing materials and promoted these new window designs at:
· Winco representatives received quite a bit of interest at the show and have bids on a few jobs for new curtain walls, and are waiting customer decisions. They are actively promoting these new products in a difficult economic environment.
Other commercialization options are being considered by the project team such as the creation of a new or expansion of the current testing center for more focus on negative phase blast impacts and providing consulting services on new designs that incorporate negative phase blast test data. Interest has been strong from other manufacturers and testing labs.