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GPD Finland 2011: Blast Analysis with James Casper

Monday, April 11, 2011

Why focus a career path on building skins? The answer for Senior Structural Engineer James Casper is simple. “With typical structural engineering, your work is buried within the structure. With facades your work is out there for everyone to see and hopefully enjoy.” The Midwest native’s journey has included work on numerous projects displayed across the nation, many of which require stringent blast performance requirements to be placed upon the building skin. At GPD Finland 2011, Casper will publish and speak about the development of blast resistant curtainwall system analysis conducted for these projects.

How’d you get started as an engineer?

James Casper: I grew up on a farm, and if a farmer needs something they either build or invent it to solve the problem. I was also convinced I was going to be a pilot or astronaut from my love of airplanes, rockets and space. Engineering was that perfect mix of building things and science.

What are your day-to-day responsibilities at Enclos?

Typically providing structural engineering support for projects with forays into R&D and technical project management related tasks.

What’s the significance of this conference?

The opportunity to share and find ideas with others in the glass community, while hopefully expanding the knowledgebase of blast resistant curtainwall technology.

What makes blast design timely in 2011?

The events of the past decade have increased the awareness of blast design by both accidental and deliberate means. Blast resistant curtainwall is now a serious consideration for the same projects that would have balked at the idea in the past from cost and aesthetic impacts that result from hardening the structure. We’re seeing an overwhelming majority of the jobs out to bid — both public and private — requiring some level of blast protection today.

Below is an excerpt from Casper’s "Decoupled Sequential Single Degree of Freedom Blast Analysis" paper selected by the conference.

"Typical curtainwall analysis consists of segmenting the system into floor-to-floor spans and performing a single degree of freedom (SDOF) analysis. SDOF analysis can be done quickly, but is quite conservative. Conservative analysis in turn results in a large and costly cross section, and due to the glass fails first methodology, increases the load to structure. The other end of the spectrum is hydrocode analysis and finite element analysis. These analysis techniques can be quite precise, but are costly due to the time required to construct and analyze the models. In addition to being time intensive, specialized modeling software and modeling expertise are needed to get precise results. Sequential single degree of freedom (SSDOF) analysis offers a compromise. SSDOF analysis utilizes a series of SDOF analysis to predict the response of the system as a whole, while providing less conservative analysis for a modest increase in analysis time, allowing the structure to be hardened more economically and provide more options architecturally."

Casper will lecture on "Decoupled Sequential Single Degree of Freedom Blast Analysis" as part of the Structural Engineering Case Study program on Monday, June 20. We hope you’ll join us in Finland.