Newsletter Highlights Research, Testing and Design

The 42nd issue of HPC Bridge Views provides an overview of Louisiana Department of Transportation and Development’s HPC research program during the last 25 years. In the mid-1970s it began with the objective of developing and producing 10,000 psi concrete using local materials and culminated in 2000 with the launching of a program to test full-size precast, prestressed girders for flexure, shear, and fatigue strength.

The issue also highlights the aircraft carrier bridges designed to support exceptionally high loads of the next generation aircraft such as Airbus 380-900 weighing more than 1.3 million pounds. The 133 to 173 ft. span bridges are designed for impact loads of 40 percent and longitudinal breaking loads of 80 percent of live load.

The newsletter concludes with the description of the creep test, namely ASTM C512. For long-span bridges, predictions of long-term deflections and prestress losses are important design considerations. The accuracy of these predictions can be improved if the modulus of elasticity, creep, and shrinkage of concrete are determined by testing.

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100-Year Bridge Design Uses HPC

The Confederation Bridge is an 8.1-mile (13-km) long bridge across the Northumberland Strait between Prince Edward Island and New Brunswick, Canada. Opened in 1997, the bridge consists of gravity-based piers and a single-cell box-girder superstructure. The aggressive environment of the Northumberland Strait includes significant amounts of annual ice that are constantly moving, high winds that result in splash and spray zones on the piers, and frequent cycles of freezing and thawing.

After extensive review and consideration of the various factors affecting corrosion, it was concluded that the most effective way to protect the structure was to utilize high performance concrete in combination with increased concrete cover to the reinforcement. More.

Self-Fabricating Nanosensors for Use as Strain Sensors in Concrete

A recently concluded PCA study examined the feasibility of using self-fabricating nanosensors as embedded strain sensors in concrete. In this study, a general procedure for preparing the sensors was developed and then the general behavior of the sensors was examined, including the drift of the sensors and the gage factors for both compression and tension. More.

Workshop to Shed Light on Rapid Bridge Construction

The benefits of accelerated bridge construction are well known. They include minimizing traffic disruption and congestion, improving work zone safety, and minimizing environmental impact. Additionally, prefabrication can improve constructability, increase quality, and lower life-cycle costs. As was seen during the FHWA-AASHTO Prefab Bridge Scanning Tour, rapid bridge construction in urban areas of Europe is almost a standard practice. In the U.S., however, it has been employed only on a few projects mainly because of a lack of knowledge and limitations on contract strategies, guide specifications, and availability of equipment and specialty contractors.

To help engineers understand this method the 2006 Concrete Bridge Conference will present “Rapid Bridge Construction—How to Get There.” This workshop will feature presentations by a panel of experts and brainstorming breakout sessions among the participants. More.

The 2006 Concrete Bridge Conference will be held May 7-10, 2006 at the Nugget Resort Hotel in Reno, Nev. in conjunction with the 2006 Post-Tensioning Institute (PTI) Technical Conference and Exhibition. The rapid bridge construction conference is scheduled for May 10 from 8:00 am to 5:00 pm. Click here for registration information.

Awards Competition Now Accepting Entries

Portland Cement Association (PCA) is seeking nominations for its tenth biennial Bridge Awards Competition. The program, co-sponsored by Roads & Bridges magazine, recognizes excellence in design and construction of concrete bridges. All types of bridges—highway, railway, pedestrian—in which the basic structural system is concrete are eligible. Entries are encouraged for cast-in-place or precast concrete bridges with short, medium, or long spans. Newly constructed, reconstructed, or widened structures qualify for the competition.

Submitted bridges will be judged by a jury of distinguished professionals, and winners will be announced at the ACI Fall Annual Convention, Nov. 5-9, 2006. There is no fee for entry, and public and private organizations may submit as many bridges as desired.
Entries are due March 31, 2006. Click here for entry form.
For more information, contact Shri Bhide at PCA 847.972.9100.

38 Issues of HPC Bridge Views Now Available Under One Cover

This 172-page volume was offered at the Seventh International Symposium on the Utilization of High-Strength/High-Performance Concrete, held in Washington, D.C., June 20-24, 2005. Topics covered include specifications; cast-in-place concrete decks; fabrication of precast, prestressed bridge components; materials technology; test procedures; research; and questions and answers about HPC. Articles are prepared by partners in the HPC implementation program, including state DOTs, universities, ready-mixed concrete suppliers, the prestressed concrete industry, material and admixture suppliers, contractors, consultants, and FHWA. It sells for only $5. Click here to order.

Question: Is there a standard mix for HPC?

Answer: The requirements for HPC differ from one state to another, from one bridge to another, and between the deck and the girders. The data indicates that there is not a standard mix for HPC for either precast, prestressed concrete girders or cast-in-place decks. Concrete mix proportions must be selected to meet the specified performance criteria using locally available materials and good construction practices. More.