Investigation into Mechanical Properties of Mass Timber T-Beam System

Abstract

This study proposes a new type of mass timber system in the shape of a T-beam. A well-proven and effective configuration for concrete and metal structures, T-shaped cross sections are not common for mass timber, yet they offer known inherent physical and structural efficiencies. The paper presents an analytical design comparison of major-axis bending stiffness and strength of several T-beam configurations and compares them to cross-laminated timber (CLT) configurations. The results indicate the potential for substantially higher mechanical properties using less lumber, leading to longer spans or higher loads with possibly cheaper building designs. Follow-up experimental tests for bending strength, stiffness, and shear strength were conducted on prototype 5-layer T-beams made from Eastern hemlock feedstock. A comparison of experimental values to design values for mean EIapp for both conventional 3-layer CLT and 5-layer T-beams showed good agreement, while differences between values for FbSeff were reassuringly consistent for both products taking 5% exclusion values and safety factors into consideration. The comparison helped to validate the design analysis, which indicated excellent potential for the mass timber T-beam concept.