Long-Term Loading Test of Reinforced Glulam Beam

Abstract

Due to creep characteristics of wood, long-term loading can cause a significant stress loss of steel bars in reinforced glulam beams and high long-term deflection of the beam midspan. In this study, 15 glulam beams were subjected to a 90-day long-term loading test, and the effects of long-term loading value, reinforcement ratio and prestress level on the stress of steel bars, midspan long-term deflection, and other parameters were compared and analyzed. The main conclusions drawn from this study were that the long-term deflection of the reinforced glulam beams accounted for 22.5%, 20.6%, and 18.2% of the total deflection respectively when the loading value was 20%, 30%, and 40% of the estimated ultimate load under the long-term loading. The higher the loading level was, the smaller the proportion of the long-term deflection in the total deflection was. Compared with ordinary glulam beams, the long-term deflection of the reinforced glulam beam was even smaller. Under the condition of the constant loading level, the total stress value of the steel bars decreased by 17.5%, 13.6%, and 9.1%, and the proportion of the long-term deflection of the beam midspan in the total deflection was 26.9%, 24.2%, and 20.6% respectively when the reinforcement ratio was 2.05%, 2.68 %, and 3.39%. With the increase of the reinforcement ratio, the stress loss of the steel bars decreased, and the proportion of the long-term deflection decreased as well. When other conditions remained constant and the prestress level of the steel bars was 0 MPa, 30 MPa, and 60 MPa, the total stress value of the steel bars decreased by 9.1%, 9.4%, and 10.2%, respectively, and the proportion of the long-term deflection in the total deflection was 20.6%, 26.1%, and 64.9%, respectively. With the increase of the prestress value, the stress loss of the steel bars increased, and the proportion of the long-term deflection increased as well.