Estudo experimental da deformação ao longo do tempo de lajes contínuas e simplesmente apoiadas executadas com vigotas pré-moldadas de concreto.

Abstract

This research deals with the experimental investigation of time dependent deformations in partially precast floors with composite beam-and-block floor systems made with reinforced concrete lattice joist through the measurement of deflections of prototypes with real dimensions. It is a continuation of several researches of composite beam-and-block floor systems done in Universidade Federal de São Carlos. Besides the accompanied measurement deflections of four already existents prototypes, with ages of three and a half years, it was studied eight new prototypes built in pairs. Four prototypes are localized in an acclimatized room in other to keep the values of temperature and humidity constant, and the other four prototypes, with identical characteristics, localized inside of a covered area where the temperature and humidity vary. The climatic variations were measured and analyzed in the evaluation of time dependent deformation. In the new prototypes the strain were also accompanied in the concrete and in the reinforcement, as well as their influences in time dependent deformation. Simultaneously to the experimental study, models for predicting creep are tested for prediction of deflections along the time, including the new version of Brazilian Code for Structural Concrete (NBR6118:2003). The research also establishes the ratio of long-term deflections (infinite) to the instantaneous deformation and it evaluates how the deformation develops in composite beamand- block floor systems of different supports, wherein statically and hyperstatically structures were studied. As a conclusion in this research, conforming in others already done by the study group, it has been found the results give strongly indication that the composite beam-and-block floor systems deformations are a decisive factor in design and that the shrinkage of the concrete increases this effect.