Materiales de Construcción, Vol 62, No 308 (2012)

Influence of the storage conditions on prestressing steel relaxation losses


https://doi.org/10.3989/mc.2012.04011

F. Suárez
Departamento de Ingeniería Civil: Construcción. Escuela Técnica Superior de Ingenieros de Caminos, Canales y Puertos. Universidad Politécnica de Madrid, Spain

J. C. Gálvez
Departamento de Ingeniería Civil: Construcción. Escuela Técnica Superior de Ingenieros de Caminos, Canales y Puertos. Universidad Politécnica de Madrid, Spain

J. M. Atienza
Departamento de Ciencia de Materiales. Escuela Técnica Superior de Ingenieros de Caminos, Canales y Puertos. Universidad Politécnica de Madrid, Spain

D. A. Cendón
Departamento de Ciencia de Materiales. Escuela Técnica Superior de Ingenieros de Caminos, Canales y Puertos. Universidad Politécnica de Madrid, Spain

M. Elices
Departamento de Ciencia de Materiales. Escuela Técnica Superior de Ingenieros de Caminos, Canales y Puertos. Universidad Politécnica de Madrid, Spain

Abstract


Stress relaxation losses on active reinforcement have significant impact on prestressed concrete structures. This is why relaxation tests are carried out on prestressing steel wires and strands after being manufactured. Then, these materials are coiled and stored for a long-term period, sometimes in excess of one year. The influence of these operations, carried out after manufacturing, is usually neglected. Nevertheless, some manufacturers and contractors have noticed that, sometimes, when relaxation tests are carried out after a long-term storage, the relaxation losses found are higher than those measured immediately after manufacturing. In this work, lab tests are performed to check the influence of the coiling radius and the period of storage on the relaxation test. In addition to this, an analytical model is presented to predict the results of a relaxation test carried out on a wire coiled and stored for a long-term period. This model explains the evolution on the cross-sectional stress profile along the coiling-storing-uncoiling process, as well as the influence of the residual stresses on it.

Keywords


steel; relaxation losses; coiling; storage

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References


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