General Mitchell International Airport

Hinman contracted with Engberg Anderson (EA) to provide blast consulting services for the renovation of the Baggage Claim building at the General Mitchell International Airport (GMIA) in Milwaukee, WI. The building is being renovated to accommodate the change in airport security after the World Trade Center attack. Once renovated, the main façade of the baggage claim building that extends approximately 600-feet along a pick-up roadway, will have large glass curtainwall systems and ribbon windows supported by precast panels as an exterior façade. The airport’s objective was to ensure that if local damage occurs, the structure would not collapse or be damaged to an extent disproportionate to the original cause of the damage, allowing for evacuation while minimizing occupant injuries. The airport defined two threat types from which Hinman based its assessment. The airport did not define clear criteria guidelines to follow, and the limited budget played a significant role in determining the final performance and agreed blast upgrades.

Hinman performed non-linear dynamic analyses to determine proof-of-concept designs for the window systems and precast panels which would result in less than 10% façade failure, and no structural collapse.

Hinman worked with the client and design team to determine achievable protection levels within the project budget. It was determined economically unfeasible to protect the entire structure and facade from damage under the defined threats, so upgrades were focused on the new perimeter structure of the building and replacement façade systems. In the early stages of design, multiple cost-benefit options were evaluated to assist with client decision making. Once decisions were finalized as to which components were to be hardened for blast and to what extent was acceptable, Hinman continued to work with EA and the structural engineer to find economical solutions. Hinman performed non-linear dynamic analyses to determine proof-of-concept designs for the window systems and precast panels which would result in less than 10% façade failure, and no structural collapse.

A perimeter barrier study was also performed, which included a vehicle approach speed analysis to determine possible speeds at impact for different vehicle sizes. Appropriate protective barriers in the client could determine whether they wanted to spend their budget on perimeter barriers. In the end, the client decided to focus its available budget on the blast hardening of the façade renovation.

Hinman presented its preliminary analysis in a meeting at the project site and also provided a 60% and a final report. Included in the reports was a summary of the entire design process, including relevant background information on blast analysis, levels of protection, as well as design results. The results included element sizes and reactions where relevant for the proof-of-concept designs and their expected level of damage under the defined threats. Figures showing a 3D model of the building were provided which showed contour plots of the blast pressures on the building as well as the extent of expected façade damage. Hinman also provided glazing and precast performance specifications that would result in connections being engineered to limit the load to primary members to prevent structural collapse.