Nueva formulación para el cálculo de pérdidas de la fuerza de pretensado por penetración de cuñas

New formulation for the calculation of losses in prestressing force due to slipage of anchorage

For the calculation of losses in prestressing force due to slippage iof anchorage, symmetrical behaviour during tensioning and untensioning is usually assumed. This hypotesis is conceptualy wrong but, in practice, the errors introduced are admissible, from an engineering point of view. Neverthless, for unbonded tendons with surveillance programs made with the lift off test, these errors are larger than in other cases and it is necessary to calculate them. The aim of the paper is to present a new formulation to obtain the losses of prestressing force due to slipage of anchorage. For a better understanding, two examples are developed (beam and tank), and the results obtained with the new method are compared to the obtained with the usual method.