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Strengthening Anchorage Details in Vintage
Reinforced Concrete Bridges
A Possible Titanium Application
Christopher Higgins, PhD, PEDeanna Amneus, MS Student
Laura Barker, MS StudentDecember 6, 2012
Vintage Reinforced Concrete Bridges
Many constructed in 1950s (Eisenhower Defense Highway System)
Design standards have changed since built
Loads more frequent and heavier
Many are now cracked and deficient
Research Problem
Problem with poor details (reinforcing steel terminated in locations that show cracking) that can lead to member failure
Many existing bridges with these reinforcing details cannot carry required truck loads by calculation
Need new methods to strengthen these bridges
Titanium looks promising: high strength, good stiffness match with adhesives, bendable and field adjustable, and durable. Material cost may not drive issue. Labor!
Typical Specimen Cross-Section
Typical Poor Cutoff Detail
Load Setup
(Modified from Higgins et al., 2004)
Typical Cracking at Anchorage
Typical Anchorage Failure
Retrofit Approach for Strengthening Poor Cutoff Detail: Near-Surface Mounted Reinforcing
Add External Reinforcing to strengthen beam
Near-Surface Mounted Reinforcing
Saw-Cut slots in concrete
Clean & Dry
• Epoxy placed in slots
• Insert external reinforcing in slots
Failure Modes for Carbon Fiber in NSM Application
1. Outer shell peeling2. Slip of CFRP Titanium may eliminate
these modes (with hooks)
Working with Titanium for Civil Engineering
1. Shear to length as for rebar2. Cold bend with same radius as
for steel rebar but overshoot to account for spring-back
3. Increase friction along surface to achieve better bond with epoxy
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