Estimación del comportamiento en el tiempo, de vigas de hormigón de alta resistencia, a partir de ensayos en probetas

Estimation of the long-term response of high strength concrete beams, based on tests of laboratory specimens

Over the past few years, the use of high strength concrete in building construction, as well as in public works, has been increasing significantly, especially in prestressed concrete elements. The most common approach for developing these concretes is through the incorporation of silica fume and superplasticizers, along with low water-cement ratios. This leads to behavior that is considerably different from that of conven-tional concretes in the various stages of its application (workability in the fresh state, instantaneous and long-term response in the hardened state, durability). In this context, the long-term behavior can influence the structural response significantly. The extrapolation of current design codes, which have been formulated for normal concretes, can lead to considerable errors. Consequently, the present work focusses on the usefulness of estimating the long-term structural behavior of structures using the results obtained from tests on specimens of the same concretes. Moreover, the cost-effectiveness and the satisfactory precision of the results have been demonstrated in the tests up to a loading period of 90 days. The experimental results from the specimens are introduced in the structural analysis and the consequent predictions are compared with data from tests of real structural elements. The effects of various factors related to specimens and beams, in sealed and unsealed conditions, and the different hypothesses used in the calculations are also analyzed.