Tag Archives: bridge

To Corrode or Not to Corrode, a GFRP Question: GFRP Reinforcing Bars in Concrete Columns

Concrete bridge structures are typically designed to last 50 to 75 years, but seldom last half that time before needing major rehabilitation, due to degradation caused by corrosion of steel reinforcement similar to that shown in Fig. 1. Corrosion in commonly used epoxy-coated steel bars has raised concern with its use and has raised interest in the use of alternative reinforcement like fiber-reinforced polymer (FRP) bars. Glass FRP (GFRP) bars are a cost-competitive alternative to epoxy-coated steel bars and have been found to not corrode (see UDOT Report No. UT-11.16).

Photo of bridge columns showing corrosion

Fig. 1. Typical corrosion found on bridge structures

Many transportation costs and user impacts associated with typical corrosion problems could be potentially eliminated with a proactive approach of using non-corrosive reinforcement (e.g. GFRP) in the original construction of concrete elements. Experimental tests were conducted recently at the University of Utah on circular concrete columns reinforced with GFRP and/or steel longitudinal bars and GFRP confining spirals to evaluate their behavior and viability as a potential construction alternative.

One set of columns was reinforced with GFRP spirals and GFRP longitudinal bars, another set of columns was reinforced with GFRP spirals and steel longitudinal bars, and a final set of columns was reinforced with double GFRP spirals and a combination of GFRP and steel longitudinal bars (see Fig. 2). Tests were performed on 12 in. diameter short (3 ft tall) and slender (12 ft tall) columns. These are the only tests known to the authors which have investigated the stability of slender FRP-reinforced concrete columns.

Photo of GFRP columns

Fig. 2. GFRP reinforcement using in column tests.

An analytical confinement and buckling model was developed and validated against the tests to provide a means to predict the behavior and capacity of FRP-reinforced concrete columns. This enabled the analysis of additional reinforcement scenarios utilizing FRP (glass or carbon) longitudinal bars and spirals.

In general it was found that FRP spirals and FRP longitudinal bars can be a viable method of reinforcement for concrete columns, particularly in corrosive environments. FRP spirals, however, need to be placed at a closer pitch spacing to provide confinement levels similar to steel spirals due to the lower modulus of elasticity of FRP composites. On the other hand, FRP longitudinal bars can provide increased deflection capacity as compared with steel bars due to the higher tensile capacity of FRP composites.

Additional research is needed to better quantify the confining capacity of FRP spirals and the required pitch spacing needed. Also research investigating the behavior of FRP-reinforced columns under seismic loading will be an important consideration.

This guest post was written by Thomas A. Hales, PhD, SE with the UDOT Research Division and Chris P. Pantelides, PhD, SE with the University of Utah and was originally published in the UDOT Research Newsletter.

2013 Strategic Direction — Part 1

This is the first part of a 4 part series about the 2013 Strategic Direction. Please also check out Part 2: Optimize Mobility, Part 3: Zero Fatalities, and Part 4: Strengthen the Economy.

After a record breaking construction year, with more than 200 projects completed, worth just over $3 billion, what is in store for UDOT in 2013? The newly completed 2013 Strategic Direction and Performance Measures highlights accomplishments by the department in 2012 and introduces goals for 2013 and the coming years.

Key to the Strategic Direction document are the UDOT Strategic Goals. These goals ensure that we focus our efforts and capital on the most important activities. This year we have revised our goals, which include:

  • Preserve Infrastructure
  • Optimize Mobility
  • Zero Fatalities
  • Strengthen the Economy

Details on each goal will be provided in a four part series, beginning with:

Preserve Infrastructure

Preserving Utah’s multi-billion dollar investment is the single largest expenditure year to year within UDOT. Keeping the state’s bridges and pavement in good condition is the most effective way to extend the life of the transportation system. This is accomplished by applying well-timed preservation treatments to roads, and addressing critical needs first. By applying a combination of routine maintenance, preservation and minor and major rehabilitation projects, UDOT is able to utilize limited funding to maximize the pavement condition.

In 2012:

  • More than 100 preservation and rehabilitation projects were completed,
  • Approximately 350 miles, or six percent of the system, received a specific preservation or rehabilitation treatment,
  • Six critical bridges were replaced,
  • Eighty-four new bridges were built by capacity-driven project,
  • Two pedestrian bridges were built,
  • Bridge preservation and rehabilitation activities were performed on more than 170 bridges.

Please also check out Part 2: Optimize Mobility.

NEW BRIDGES TO CROSS

UDOT bridges on U.S. 191 over the Colorado River in Utah have received an award for excellence.

Graceful arches span the Colorado River near Moab.

 

When it came to replacing an old bridge with two new bridges across the Colorado River, the beautiful landscape near Moab called for a environmentally sensitive approach to design and construction. And, great team work also helped move the project forward to completion.

“The arched design was intended to blend in with the surrounding scenery and enhance rather than intrude upon the Red Rock Canyon Country experience of visitors” says says Jim Chandler, UDOT Region Four Resident Engineer for the project.

And, the construction method was unique. “These bridges are the first to be built in Utah using balanced cantilever construction which required a smaller less, intrusive footprint on the environment,”  says Chandler. While the old bridge required seven piers, the new bridges only needed two piers on each bridge. The smaller footprint reduced the impact on the river flood plain and on Threatened and Endangered Species in the area.

The bridges took nearly two years to complete. Because the construction method was new to Utah, “the schedule from day one was a challenge,” says UDOT Project Manager Rustin Anderson. Early on, issues with the drilled shafts used in the construction of the massive piers required special equipment to be brought in, putting the team behind schedule.

Some UDOT team members, left to right: Fran Randolph, Trans-Tech 4; Inspector Kevin Marshall, Trans-Tech 4; Russ Pogue, Trans-Tech 4 and Jim Chandler, Project Manager.

Project team members worked together and “found ways and innovations to get back on track,” says Anderson. Eventually the bridges were built on time.

Project Manager Rustin Anderson holds the award.

The American Concrete Institute has presented an Excellence in Concrete Construction Award to the team for the “innovative and excellent use of concrete.”

The design and construction team:

UDOT is the project owner. Figg Engineering of Denver Colorado provided design and construction management and inspection services. Wadsworth Brothers Construction was the prime contractor.

Bridge facts: The center span of the bridges arch 438 feet between the piers, and the end spans are 292 feet from the piers to the river banks. Over 14,000 cubic yards of concrete and over 3,000,000 pounds of steel was used.

See construction images: An on-site camera provided a view of the construction progress. Still images and a time-lapse are still available online.

About cantilever construction: In this video, UDOT Public Involvement Manager Kevin Kitchen explains the construction method.

Successful first launch

 

Crews carefully nudge the west span of the new Layton interchange into place

After rolling and sliding bridges into place, UDOT has now successfully completed it’s first launch.

Early Sunday morning, August 8, UDOT completed placement of the west span of the new Layton interchange, closing the freeway for a mere five hours. The bridge was built on the side of the freeway out of the way of live traffic. Crews used a hydraulic jack to carefully nudge the bridge into place inch by inch.

UDOT has used Accelerated Bridge Construction methods on 20 bridges since the first bridge move in 2008. ABC saves time for road users over regular construction because new bridges are built nearby then moved into place, keeping the freeway open during construction.

Read a story in the Ogden Standard Examiner for more details on the launch or watch a KSL story, below, to see a time-lapsed video and get an overview of other construction in the area.

 

Video Courtesy of KSL.com

HEAVY TRAFFIC CAUSING STRESS?

UDOT and University of Utah researchers are collecting data to find out how a new material reacts under the stress of freeway traffic.

A truck crosses Beaver Creek Bridge. Some of the equipment that measures stress is visible in the lower right corner under the bridge.

Instead of the usual steel rebar, the concrete deck panels on the Beaver Creek Bridge on US-6 are internally supported with Fiber Reinforced Polymer. The bridge has sensors that measure strain and trigger a camera to snap a photo when the bridge is stressed to a predefined limit. The photos and data collected by the sensors are part of a study that is helping University of Utah researchers and UDOT accumulate information about FRP, a material that may make make bridge decks last much longer.

“The number one cause of degradation of bridges is rusting steel inside concrete,”  says Fred Doehring, Deputy Structural Engineer at UDOT. Bridges are designed to last 75 years or longer while decks only last 40 to 45 years.

The GFRP is formed into bars that look similar to rebar. FRP has a tensile strength greater than steel but weighs much less, steel which means the grid is easy to place. Deck panels are also easier to transport.

Beaver Creek Bridge was designed by UDOT’s Rebecca Nix, who says she has really enjoyed the project. Nix is helping to evaluate the new information along with researchers.  By using FRP data collected in a real-world setting, UDOT will know how to “design based on what’s really happening.”

Rebecca Nix, Structural Designer at UDOT, stands near Beaver Creek Bridge.