Hybrid composite glulam timber reinforced using deformed steel bars and epoxy resin adhesive (RGTSB), was significantly developed in Kagoshima University. A long term laboratory investigation on a 4.5-meter-span hybrid timber beam and a non-hybrid timber beam was started from August 2011. The beam was made of RGTSB and another was of conventional glulam timber. Test in early three months promoted creep deflection in the beams, by causing mechano-sorptive creep by humidifying in test room, in order to reveal effects, which the deformed bars suppress deflection in the RGTSB beam. This paper presents the results and observations of the long-term test. The deformed bars was revealed to suppress effectively the flexural creep deformation in timber. Also a simplified calculation method is presented to predict the deflection-time curve of RGTSB beam under long-term loading, using the curve of conventional glulam timber beam. The approximations showed reasonable agreement in the results of the RGTSB beam.
