Estudio experimental de la influencia del pandeo de la armadura comprimida, en la capacidad portante de elementos de hormigón armado sometidos a flexión simple

Exoerimental investigation of the influence of compressed bars buckling in the strength capacity of reinforced concrete flexural members

Main beams of reduced depth, are a type of structural member of extraordunarily common use today, given both their construction and aesthetic advantages as a result of their depths coinciding with that of the floor supports. The fact that their depth can be reduced, leads to their load bearing being conditioned by the begaviour of their sections of vane which, in general, need to include compressed reinforcement, which, in accordance with the current regulations, erquires to dispose transversal reinforcement to comply with the minimum specified, similar, on the other hand, to other standards, in force in other countries, with the object of avoiding, according to the text, that the compressed reinforcement suffers buckling instability phenomenon. From the practical observation, we deduce that members on bending, which have compressed assembled reinforcement in the centre of the vane which is not taken into account in the calculations, with spacing distances betweem stirrups, superior to the minimums indicated by the aforementioned specifications, do not present cases of buckling of bars. This leads us to aproach the present experimental investigation into a subject on which extremely litttle appears in the technical bibliography consulted. The investigation results show that in the ultimate capacity of the expertimental sections, there is no influence of spacing distances between stirrups, obtaining in all cases failure moments superior to the theoretical. In all tests the manners of failure was similar, with buckling of the compressed reinforcement immediately before the failure and very similar diagrams of fisuration. We think, therefore, that the results of this experimentation open a way, which, when complemented, perhaps, by analysis on theoretical models and with experimentation on similar models under cyclical loads that can give more information on the begaviour under seismic risk, could provide a reconsideration of the Standards, resulting in a greater simplicity of the construction procedures.