Influence of the cracking moment of two reinforced concrete beams obtained through fiber optic sensors in the determination of their instant deflections = Influencia del momento de fisuración de dos vigas de hormigón armado obtenido mediante sensores de fibra óptica en la determinación de sus flechas instantáneas

Abstract

This article investigates the measurement of the real instantaneous deflection using a displacement transducer, and with fiber optic sensors embedded and welded to the corrugated rebars in order to determine the real cracking moment of the concrete. Two reinforced concrete beams simply resting on the support with point loading in the center of the span have been tested, at which point the maximum deflection is reached. Both the sensors and the displacement transducer have been placed in the center of the span. Different loading steps have been applied to the beams, using a loading cylinder, and the measurement of the load applied has been determined using a loading cell. During the loading process of the beams, the real moment at which they cracked has been determined, and which determines the change from the gross inertia to the cracked inertia in the study of the deflections. Two expressions have been deduced that modify the formula of the instantaneous deflection and demonstrate that they are valid to determine in a much more precise way the instantaneous deflections on simply resting on the support concrete beams. Future lines of research will concentrate on studying the instantaneous deflections of more complex beams, and thus obtain expressions that more closely approximate their actual behaviour.