How Durable Are Our Highway Bridges?

Following the tragic collapse of the Sliver Bridge in December 1967, Congress passed legislation that required each state to inspect and maintain an inventory of all bridges on the Federal-aid system. Inspection standards were issued in 1971 to satisfy this mandate of Congress. Most states completed their inventory of bridges on the Federal-aid system by the end of 1973. In 1978, Congress passed the Surface Transportation Assistance Act which expanded the law to require all highway bridges on public highways to be added to the inventory. Biennial inspections of all bridges were also required to ensure the safety of the traveling public.

According to the National Bridge Inventory, there are 594,888 structures in the inventory as of December 2003: 474,515 are identified as bridges, and 120,373 as culverts. Of the 474,515, a total of 161,472 structures, or 34.0%, are classified as either structurally deficient or functionally obsolete. Structural deficiency triggered by the poor performance of the bridge material accounts for 79,519 or 16.8% of the bridges. The most prominent observation is that while reinforced and prestressed concrete make up an increasingly larger share of the bridge market, these bridge types, for almost each road or highway system, have a significantly lower rate of structural deficiency than steel or timber bridges.

For a snapshot of the bridge inventory and its performance click here.

For a detailed report on the analysis of 2003 NBI data, download Material Usage and Condition of Existing Bridges in the U.S. (SR342)

Precast Bridge Deck Panels

Precast bridge deck panels can be used in place of a cast-in-place concrete deck to reduce bridge closure times for deck replacements or new bridge construction. The panels are prefabricated at a precasting plant providing optimal casting and curing conditions, which result in highly durable decks. Precast panels can be either full-depth or partial-depth. Partial-depth panels act as a stay-in-place form for a cast-in-place concrete topping.

A recent study by the Virginia Transportation Research Center concluded with a set of recommendations for the design, detailing, and construction of the connection between full-depth precast deck panels and prestressed concrete I-beams. For the detailed research report, click here.

Interstate Structures

TRB’s Transportation Research Circular E-C104, Fifty Years of Interstate Structures: Past, Present, and Future documents some of the key legislation, specifications development, and advances in research, design, and construction for bridges and other highway structures since the signing of the Federal-Aid Highway Act of 1956. More.

Annual Bridge Professors' Seminar a Success

Twenty-nine professors from U.S. and Canadian universities met at PCA for the 9th Annual Bridge Professors’ Seminar, August 2-3. The goal of the seminar is to enhance concrete curriculum by providing educators with up-to-date resources on the design and construction of concrete bridges. The concrete bridge design seminar focused on the latest AASHTO bridge design specifications, which contain design requirements significantly different than those of the ACI 318 Building Code. Forums and open discussions enabled participants to compare notes on successful methods of teaching bridge design.

PCA and allied groups hosted the seminar; regional promotion groups, Cement Association of Canada regions, and other local industry groups sponsored the professors. Each attendee received handout materials provided by the speakers and publications related to the seminar topics to assist them in updating existing or introducing new courses.

The annual seminar is typically held on the first Thursday and Friday of August. Contact Shri Bhidé for details.

Save on LRFD Bridge Design Publications

As you may know, starting October 1, 2007, all bridges receiving federal funding will have to be designed by the LRFD specifications.
PCA is offering its two publications on the design of concrete bridges by LRFD: AASHTO LRFD Strut-And-Tie Method Design Examples (EB231) and LRFD Design of Cast-In-Place Concrete Bridges (EB232) for a limited time at a special combination price of $40. (Save $15).
Click to purchase.

The First International Conference on Recent Advances in Concrete Technology (rac07) will be held September 19-21, 2007, at the Sheraton in Crystal City, Va. The conference is being organized by the University of Maryland, Howard University, and CI-Premier PTE Ltd of Singapore, and co-sponsored by PCA.

2007 PCI National Bridge Conference
October 21-24, 2007 in Phoenix, Ariz.

ASBI 19th Annual Convention
November 4-6, 2007 in Las Vegas, Nev.

International Symposium on Ultra-High Performance Concrete
March 5-7, 2008 in Kassel, Germany
Abstracts are due August 31, 2007

2008 Concrete Bridge Conference
May 4-6, 2008 in St. Louis, Mo.