Comparative Study on Flexural Behavior of Steel–Timber Composite beams and Glued Timber I-Beams

Abstract

Shear performance of glued timber I-beam in large-span structures has attracted considerable research attention. Web of glued timber I-beam demonstrating low shear strength parallel to grain is susceptible to cause shear failure in the case of small shear-span ratio. Meanwhile, tensile and compressive strength values of the timber cannot be fully utilized. The use of steel web instead of timber web was proposed in this study to enhance the efficiency of tensile and compressive capabilities of timber, improve bearing capacity of the beam, and change the failure mechanism of timber. A comparative analysis on flexural behavior between steel–timber composite (STC) I-beam with steel web and glued timber I-beam was also incorporated in this study. Six I-beams in two groups were designed in the experiment. Group A included three glued timber I-beams of the same material and group B consisted of three STC I-beams of the same size. Loading mode of three-point bending was used in the bending test of the two groups of specimens. Results show that the failure mechanism of group A is brittle shear failure along the grain while that of group B is steel web yield with shear failure along the grain in the timber flange. Ultimate load, initial stiffness, and strength reserve of group B are higher than those of group A at 79.7%, 3.2%, and 140.1%, respectively. The maximum longitudinal compressive strain of top and bottom flanges of specimens in group B is 2.08 and 2.75 times larger than those of group A when the ultimate load is reached. Error between shear strength of glued timber I-beam calculated through Rammer formula and the test result is 4.49%. Hence, the proposed method can successfully utilize tensile and compressive strengths of I-beam timbers.