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Structural Engineering and Mechanics
  Volume 55, Number 6, September25 2015, pages 1099-1120
DOI: http://dx.doi.org/10.12989/sem.2015.55.6.1099
 


Behaviour of continuous prestressed concrete beams with external tendons
K.H. Enoch Chan and Francis T.K. Au

 
Abstract
    External prestressing has been applied to both new construction and retrofitting of existing reinforced and prestressed concrete structures. Continuous beams are preferred to simply supported beams because of economy, fewer movement joints and possible benefits from moment redistribution. However, this paper argues that continuous prestressed concrete beams with external unbonded tendons demonstrate different full-range behaviour compared to reinforced concrete (RC) beams. Applying the same design approach for RC to external prestressing may lead to design with a lower safety margin. To better understand the behaviour of continuous prestressed concrete beams with unbonded tendons, an experimental investigation is performed in which nine such specimens are tested to failure. The full-range behaviour is investigated with reference to moment-curvature relationship and moment redistribution. The amounts of moment redistribution measured in the experiments are compared with those allowed by BS 8110, EC2 and ACI 318. Design equations are also proposed to estimate the curvature ductility index of unbonded prestressed concrete beams.
 
Key Words
    continuous beams; ductility; full-range behaviour; moment redistribution; partial prestressing; prestressed concrete; unbonded prestressing tendons
 
Address
K.H. Enoch Chan, CH2M HILL, Burderop Park, Swindon, United Kingdom
Francis T.K. Au, Department of Civil Engineering, The University of Hong Kong, Pokfulam, Hong Kong
 

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