Criterios para la determinación de plazos de descimbrado en estructuras de hormigón armado solicitadas a flexión

Determination of minimum period before striking on reinforced concrete flexural members

Reduction of the minimum period before striking of a reinforced concretestructure can lead to important economical consequences both for the contractor and for the owner. However, objectivecriteria to determine the time when shoers can be removed are not always used in practice. In the present paper a methodology to determine the minimum period before striking in reinforced concrete flexural members is presented. The method is based on the satisfaction of the serviciability and the ultimate limit states both during the construction and throughout the structure service life. A set of simple formulae are provided to determine the minimum values of certain mechanical properties of concrete which must be reached before striling, as a function of the structure dimensions, dead load ratio, amount of longitudinal and transverse reinforcements and design values of the concrete and steel strengths. The practical interest of the method is shown by means of an example consisting of a structure constructed in Barcelona before the 1992 Olympic Games, where a high velocity of construction was required. The application of the proposed method allowed to reduce the duration of the construction with respect to the one initially foreseen. The results show that for this particular case, the deformability condition was the limit state controlling the period before striking.