Preliminary Bond Testing and Splicing of Titanium Alloy Bars

Abstract

The study of the interaction between reinforcement and concrete is important to ensure the composite action of the two materials. A high bond strength is desirable in the reinforcement–concrete interface to avoid pullout failure. The higher bond of reinforcing bars with concrete provides better performance and increases the capacity and service life of structural elements. Bond tests of smooth titanium alloy bars (TiABs) and 60 kips per square inch (ksi) (414 MPa) steel with concrete are conducted in accordance with the ASTM C234. Based on the experimental results, the bond strength of TiABs is generally found to be higher than that of the steel. The paper also presents some preliminary investigation for identifying appropriate and commercially available mechanical couplers for splicing the TiABs. Since TiABs are more expensive than normal rebars, it is necessary to limit their quantity and use in bridge piers (e.g., plastic hinge zone only). Products from a well-known producer of mechanical couplers in the United States are used in the research. A few mechanical couplers are investigated for splicing of #5 (15.9 mm diameter) and #6 (19.1 mm diameter) pseudo-threaded TiABs. Tensile testing is carried out in accordance with ASTM A1034 to address the 2017 AASHTO Load and Resistance Factor Design (LRFD) requirements and a suitable coupler was identified. The appropriate mechanical coupler was identified to be the coupler that is designed specifically for use with high-strength bars. It uses a cold swaged steel sleeve and is thicker.

Pullout Behavior of Titanium Alloy Reinforcing Bars in Ultra-High Performance Concrete

“…This makes TiABs an expensive material compared to steel, stainless steel, aluminum, etc. Several research institutions have carried out studies of TiABs for concrete structures applications, for example, Idaho State University (mechanical properties testing of TiABs [9], bond testing and splicing of TiABs [10], bridge columns reinforced with TiABs [11], cap beam reinforced with TiABs [12]) and Oregon State University (retrofit square column with TiABs [13], retrofit deficient reinforced concrete girders [14]).…”

Prediction of Ultimate Bond Strength between Ultra-High Performance Concrete and Titanium Alloy Bars Using a Machine Learning Approach

“…TiABs are currently just limited to aerospace industry but becoming popular for applications in concrete structures because of their exceptionally outstanding advantages. Compared to conventional reinforcing, the advantages that TiABs offer include but are not limited to higher strength, superior fatigue performance, high strength-to-weight ratio, lighter weight, lower modulus of elasticity, reduction in rebar congestion, smaller inelastic residual deformation, and excellent corrosion resistance [1]. Similarly, UHPC offers numerous advantages critical for bridge application such as exceptionally higher compressive strength, superior mechanical properties, and excellent durability compared to conventional or high-strength concrete [2].…”