STUDIES ON THE EFFECTS OF ENVIRONMENTAL CONDITION ON LONG-TERM DEFORMATION AND CRACK WIDTH OF REINFORCED CONCRETE MEMBERS

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Deformational and cracking behaviors of reinforced concrete beams subjected to sustained flexural load were experimentally investigated under four different environmental conditions, that is, (1) in the room with the temperature of 20(]SY.+-。[)1ﾟC and relative humidity of 60(]SY.+-。[)5%, (2) in that with 70(]SY.+-。[)5%, (3) in the laborato-ry and (4) in the feild. Furthermore, computations of time-dependent deformations and crack widths of reinforced concrete flexural member under alternating temperature and humidity were performed, using numerical method developed by authors. Main results were abtained as follows ;(1) Creep was promoted mainly by seasonal temperature rise and did not necessarily depend upon relative humidity. Drying shrinkage strain in the feild, which changed reversibly during exposure to water, resulted in nearly a half of that in the laboratory due to rainfall.(2) Both curvature and compressive strain depended closely on creep and drying shrinkage. Curvatures and compressive strains of beams with compressive reinforcement were underestimated especially in the field by analysis used effective elastic modulus method. A step-by-step method based on Whitney's rate of creep law was effective in improving the procedure in terms of accuracy to a certain extent.(3) Effective rate of drying shrinkage to increase of crack width under load in the field was larger than that in the laboratory. This means that cracks do not necessarily widen in proportion to the magnitude of drying shrinkage strain.