University of Cambridge > > Engineering Department Structures Research Seminars > Strengthening of Beams in RC Frames using External Tendons

Strengthening of Beams in RC Frames using External Tendons

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External post-tensioning is an effective strengthening method in which tendons are being installed on the outside of a member, and the prestressing force is transferred to the member through deviators and anchorages. First, the effects of flexural and axial restraints, that is, secondary and tertiary effects, respectively, on beam strengthening in symmetrical RC frames using external tendons are examined analytically. Next, tests carried out on four single- and double-bay frames will be presented.

It is shown that secondary effects are beneficial in frames under gravity load and have no influence on the axial loads imposed on the beam due to external post-tensioning. Tertiary effects however lead to a lower increase in the load-carrying capacity and a smaller reduction in the deflection of the strengthened beam, and introduce undesirable shear forces on the supporting columns. Test results showed that external post-tensioning while increasing the ultimate strength, also led to a reduction in deflection and crack width of the strengthened beam. A stiffer load-deflection response was observed in frames with larger supporting columns, and doubly-draped tendons provided better crack control.


Dr Tan is Associate Professor in the Department of Civil Engineering at the National University of Singapore. He obtained his PhD degree from The University of Tokyo in Japan in 1985. He has more than twenty-five years of experience in teaching and research, and has published more than 170 refereed papers in the field of structural engineering. His research interests include structural concrete, FRP systems, external post-tensioning, and FRC . Professor Tan is Associate Editor of the ASCE Journal of Materials in Civil Engineering (USA) and Managing Editor of the KCI International Journal of Concrete Structures & Materials (Korea). He is also Editorial/Advisory Board Member for seven other international journals including the ICE Structures & Buildings Journal (UK). He is a Fellow of the Institution of Engineers, Singapore, and a registered professional engineer in Singapore.

This talk is part of the Engineering Department Structures Research Seminars series.

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