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