Creep Behavior and Prediction of Fiber-Reinforced Polymer Reinforced Timbers Under Changing Temperature and Relative Humidity

The creep behavior of fiber-reinforced polymer (FRP) reinforced larch laminar timber was studied with respect to temperature and humidity fluctuations. There was a control group of larch laminated with two small-diameter timbers with FRP (carbon FRP (CFRP), glass FRP (GFRP)) produced; the laminated lumber had the same cross-sectional area as the two laminated lumber specimens with reinforced tensile parts. A creep test with fluctuating temperature and humidity was conducted by applying a load of 25% of the bending strength of the control specimen. A total of 8 specimens, 2 for each type, were measured for creep deformation at 9:00 am and 6:00 pm daily for approximately 14,000 h. Temperature and humidity fluctuations were measured every hour. The equilibrium moisture content and humidity of the creep test space exhibited a proportional relationship, and the moisture content of each specimen did not show a noticeable correlation with humidity and equilibrium moisture content. The average relative creep was measured as approximately 0.67 for the control, 0.4 for Glulam, and 0.43 for both the CFRP- and GFRP-reinforced specimens. Thus, the creep deformation of all the reinforced pieces was confirmed to be lower than that of the control specimen.