Flexural behavior of full-scale AASHTO type I girders prestressed with stainless steel strands

Stainless steel is becoming a promising alternative for bridge construction to combat corrosion compared to other corrosion-resistant materials. Due to the limited ultimate strain of High-Strength Stainless Steel (HSSS) strands compared to conventional carbon steel (CS) strands, the yielding observed in CS strands—usually followed by concrete crushing at the extreme compression fiber—may not occur with HSSS strands. For this purpose, this paper provides the results of a study investigating the gap in understanding the flexural behavior of prestressed concrete girders using HSSS strands. Four full-scale 12 m (39.5 ft) long AASHTO Type I girders using the 15.75 mm (0.62 in.) duplex 2205 HSSS strands were designed, fabricated, and tested under four-point bending. The experimental program considered different variables, such as the number of strands, prestressing levels, and the type of loading applied, including monotonic and fatigue loading. Due to limited ultimate strains in HSSS, the design considered rupture of the strands at ultimate as an economical solution. However, despite design considerations for strand rupture, lower concrete strength (than the specified value) led to two girders exhibiting concrete crushing failure. Nevertheless, all girders demonstrated satisfactory performance, exhibiting significant reserve deflection and adequate strength. The girders experiencing strand rupture showed clear warning signs, such as extensive cracking and significant deflection before failure. This was followed by larger crack openings ultimately due to the rupture of all the strands. An analytical model based on strain compatibility principles was used and validated against experimental data to predict flexural behavior. Furthermore, a numerical model utilizing modified rectangular stress block parameters was employed to assess the nominal moment strength of stainless steel prestressed concrete girders. The results from both models closely matched the experimental findings.