Reproduction of Early Post-tensioned Bridge Girder at Anna Maria Island, FL

The girder you see is a replicate of early post‑tensioned concrete girders used in Florida in the 1950s, including those used in short‑span bridges such as the Anna Maria and Cortez bridges. These original girders were precast, post‑tensioned I‑girders featuring end blocks and were designed to sit directly on concrete pier caps with only tar paper as a separator. A notable characteristic of this vintage design is the complete absence of shear reinforcement (stirrups) outside of the end blocks. The only mild steel reinforcement was placed within approximately 3 ft of each end to protect against anchorage-related stresses.

These girders are of particular interest today because:

• They combine parabolic and straight post‑tensioning bars, an early approach to optimizing tendon profiles.
• They lack modern shear reinforcement, which has led to low structural ratings for many existing mid‑century Florida bridges.
• They were built during a period of rapid infrastructure expansion, including major bridge construction around Anna Maria Island.

This specific girder was built for a research project following original 1950s plans, along with two others which were tested to gain understanding of the shear and moment capacities.