Introduction to Contemporary Post-tensioned Concrete and Fire

Abstract

In contemporary buildings, less is more. With new construction technologies and building materials, structures are being built with open floor plans and larger than ever before spans. Post-tensioned (PT) concrete is excellent at optimizing material usage, which helps designers meet stringent sustainability objectives while creating desirable large open spaces. PT concrete uses high strength cold-drawn prestressing steel tendons that are tensioned inside ducts in the concrete after casting. This compresses the concrete prior to loading and results in excellent control of in-service deflections which is far superior to that of conventional (non-prestressed) reinforced concrete. This tensioning process results in secondary support reactions in structural systems that balance deflection from loading. The post-tensioning process reduces the use of building materials enabling large spans. Typical PT concrete structures include bridges and buildings.

Today’s flat-slab post-tensioned buildings…with columns spaced 12 m on center and span-depth ratios of 40, are more complex and require more engineering attention than typical flat-slab buildings of 40 years ago, with columns spaced at 6 m on center and span-depth ratios of 20.

—Randall Poston and Charles Dolan (2008)