Applications of sustainable post-tensioned concrete slabs

Abstract

Post-tensioning is used for the last decades for different concrete elements such as slabs, beams, walls and mat foundations. For industrial and office buildings with large spans, application of post-tensioned, (PT), concrete floors is competitive to reinforced concrete. Use of PT slabs results in small sections, better serviceability, durable structures and faster construction compared to reinforced concrete construction. In some cases, it demonstrates an economic alternative to conventional concrete or steel floors. Post-tensioning concrete slabs are applied using either bonded or unbonded tendons. Bonded tendons is achieved by grouting the ducts containing the steel tendons after stressing. Consequently, the prestressing force is transmitted to the concrete by bond along the steel tendons. In unbonded tendons applications, the ducts are left after stressing without grouting and the force is transmitted at the anchorages of the prestressing steel. This paper introduces analysis, design and construction techniques of PT concrete floors. Computer model specifically made to design PT slabs satisfying the requirements of the code is introduced. Case studies carried out in Egypt and in the Gulf area in the last few years with particular application of post-tensioning are also introduced. These case studies include buildings of spans up to 24.0 ms, as well as water tank of 100,000 m3 capacity. Recommendations and design guidelines of PT concrete slabs as well as the assessment of the current Egyptian code are highlighted.