Experimental Investigation of Structural Performance of CLT-UHPC Composite Structures

Bridges in the United States are largely in fair condition and nearing the end of their design life. Despite targeted initiatives to replace aging bridges, the rate of replacement remains slow. Recent research has explored improved construction materials and methods to accelerate the replacement and retrofitting of existing structures. Much of this work has focused on precast concrete, where questions regarding sustainability and environmentally friendly construction remain unresolved.This research aims to provide a sustainable alternative for rapidly replacing aging bridge decks by utilizing a mass-timber product--cross-laminated timber (CLT). However, CLT alone is unsuitable for this application due to its inherent limitations. As a natural, hygroscopic material, it has lower stiffness and strength compared to conventional concrete. To overcome these limitations, CLT is combined with an ultra-high-performance concrete (UHPC) overlay to form a CLT-UHPC composite, thereby enhancing durability, strength, and stiffness.The dissertation focuses on several key aspects. First, methods for effectively combining CLT and UHPC into a composite system are investigated, along with alternatives for controlling moisture intrusion in timber. A preliminary study on small-scale specimens evaluates the interface shear strength and bending strength of the composite system. Next, reduced-scale bridge decks are constructed and experimentally tested to assess performance under serviceability and ultimate strength conditions. The fatigue performance of joint connections is also examined. Finally, beyond bridge applications, the potential use of CLT-UHPC composites in tornado shelter walls is experimentally evaluated.