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April 30, 2009

Long-span truss structures for low-vibration environments

Historically, waffle slabs have been widely used in the process floor design in semiconductor production facilities.  In a less stringent vibration environment, concrete joist slab with stiffeners could be a suitable design option. In both of the two approaches, the effectiveness of vibration control in floor structures would be substantially reduced when the column span increases. As a result, it is technically difficult and financially inefficient to adopt conventional waffle slab or stiffened joist slab in a facility design with large open areas.  On the other hand, long-span truss structures are quite common in a number of industrial settings, for example, bridges, large factory buildings, etc. Heretofore, the approach has received little attention in the US for vibration-sensitive applications, but has been employed in Asia for over a decade for facilities engaged in semiconductor and flat panel (LCD/TFT) production, where large open spaces are of great value, and spans can reach over 30m (97 ft). The article presents the vibration analysis and test results of a long-span truss facility recently constructed in Asia. In addition, the article discusses the current state of the design and analysis philosophies, including space planning, “reverse engineering” of equipment loading, and structural optimization.  

N. Tang, H. Amick, and M. Gendreau, "Long-span truss structures for low-vibration environments," Proceedings of ASCE/SEI Structures 2009 Congress, Austin TX, USA (30 April to 2 May 2009), pp. 2829-2835