'Mr. Liebherr' helps Duffield rise from the ground

This is the second of a series of periodic updates on the construction of Cornell's Duffield Hall, the $58.5 million nanotechnology research facility adjacent to Phillips Hall on the Engineering Quad. The author is Bob Stundtner, Cornell's Duffield Hall project manager.

There was no ceremony or fanfare, but the Duffield Hall project achieved a significant milestone on Nov. 8. After four months of site preparation and excavation, the first concrete was placed and the building started rising from the ground.

A 154-foot-tall Liebherr 316 EC-H 12 tower-crane, viewed from an entranceway in Upson Hall, is aiding in the construction of the university's new Duffield Hall on the Engineering Quad. Robert Barker/University Photography

A Liebherr 316 EC-H 12 tower-crane, the newest and most prominent member of the project team, will play a key role in placing concrete on the project. With an overall height of 154 feet, the crane is too big to be totally viewed with the project's live web cam www.duffield.cornell.edu/webcam.cfm. The jib is 213 feet long and the counter-jib is 74.5 feet. The crane can lift up to 7,715 pounds at the end of the jib, and overall it can lift 26,455 pounds at a maximum distance of up to 76 feet from the cab.

The crane traveled to Cornell from a project in Virginia and will remain on the job for about 16 months, at a monthly rental of about $13,000, plus operator costs. That makes "Mr. Liebherr" the best-paid team member on the project.

Its expensive presence is needed because Duffield Hall will be principally a reinforced-concrete structure, with the design selected to achieve the low-vibration criteria set by the User Advisory Committee. Composed of research faculty and staff, the committee was one of three advising the project team. The two other committees advised on safety-related issues and Duffield's architectural design.

Duffield Hall is designed to be generally much more stable than most facilities on campus, and in selected areas unprecedented levels of stability will be required. That is because creating nanometer-scale structures requires extremely stable environments, with temperature, humidity, electromagnetic interference and vibration rigorously controlled. The clean room and electron microscopy suite on Duffield's first floor will contain the most stable environments, including six isolated slabs for ultra-low vibration requirements.

While a reinforced-concrete structure is the best fit for the design criteria, concrete quality control -- meaning durability and the stiffness of the concrete to resist vibration -- presents special challenges. It is a challenge that Cornell has met in the past: Both Ho Plaza and the Carl A. Kroch Library are examples of concrete quality control at its highest level, and both projects often are nationally cited. Indeed, some of the standards that the American Concrete Institute has recommended to assure concrete quality are based on research conducted at Cornell.

Ken Hover, professor of civil and environmental engineering, notes that exterior concrete surfaces in Ithaca are particularly vulnerable to degradation, such as fracturing, by the area's harsh climate. Duffield, however, because it is an enclosed concrete building, is not as sensitive to climatic effects. Even so, he said, the highest level of quality control is still essential. Without question, the amount of water in the concrete is of paramount importance, said Hover. The aggregates (the sand and gravel, or rock, added to the cement), also are vital because stiffness of the concrete is determined by the stiffness of the aggregate, as well as the "paste" that holds it together.

To ensure the highest quality in construction, Hover and Brian Brown, Cornell's Duffield construction manager, recently met with representatives from the McCarthy/Welliver McGuire joint venture for the project, concrete subcontractor Murnane Building Contractors, concrete supplier W.F. Saunders and Sons, structural consultants LeMessurier and the independent testing agency Atlantic Testing.

The contractors and the supplier presented their quality-assurance plan, and by the end of the meeting most concerns were resolved. Hover recommended additional testing to monitor water content of the concrete as well as tests of the stiffness of the concrete to evaluate how well it will perform in structural elements that will be built later in the project. LeMessurier's design engineer, Reginald Roome, expressed confidence that the contractors would meet his specified requirements.