An FHWA Special Study: Post-Tensioning Tendon Grout Chloride Thresholds
Elevated levels of chloride were recently discovered in a commercially available pre-bagged grout product made for post-tensioned (PT) tendons. These chloride values exceed the current limits set by all of the domestic and international regulatory committees. However, there is limited information reported in the the literature pertaining to actual chloride threshold of seven-wire PT strands. For this reason, the FHWA sponsored a 6-month accelerated corrosion testing program to determine chloride threshold(s) of PT strands exposed to chloride-contaminated grout. The findings of this study should be useful to bridge owners who may be responsible for similarly affected PT bridges.
Application of Radiographic Testing to Multilayered Guesset Plate Inspection
On August 1, 2007, the I-35W bridge collapsed in Minneapolis, MN. The National Transportation Safety Board (NTSB) investigated the collapse and leveraged technical assistance from the Federal Highway Administration (FHWA). NTSB determined that the cause of the collapse was due to undersized gusset plates at a particular node location on the main truss. The plates should have been twice as thick or should have had twice the yield strength to provide adequate resistance to prevent the collapse.
Bridging the Gap: Restoring and Rebuilding the Nation's Bridges
This report was issued after the 2007 collapse of a bridge in Minnesota. The publication is intended to educate municipalities on aging bridges and how to assess and improve the quality of bridges. AASHTO, 2008.
Characterization of Bridge Foundations Workshop Report
In 2013, the Federal Highway Administration proposed a new reserach program for the characterization of bridge foundations. To narrow the focus and develop a research roadmap for the program, a workshop on "Characterization of Bridge Foundations" was held in Arlington, VA, to solicit key stakeholder input. This report presents an overview and documents the results and conclusions fo the workshop.
Covered Bridge Manual
Provides technical and historic information on preservation of covered bridges, including bridge components, engineering issues, and existing bridges. USDOT & FHWA.
FHWA study of systems and techniques to identify and characterize cracks in steel bridges structures.
Guide for In-Place Treatment of Wood in Historic Covered and Modern Bridges
Historic covered bridges and current timber bridges can be vulnerable to damage from biodeterioration or fire. This guide describes procedures for selecting and applying inplace treatments to prevent or arrest these forms of degradation. The objective of an in-place preservative treatment is to distribute preservative into areas of a structure that are vulnerable to moisture accumulation and/or not protected by the original pressure treatment. Types of field treatments range from finishes, to boron rods or pastes, to fumigants. A limitation of in-place treatments is that they cannot be forced deeply into the wood as is done in pressure-treatment processes. However, some can be applied into the center of large members via treatment holes. These preservatives may be available as liquids, rods or pastes.
Guidelines for Sampling, Assessing, and Restoring Defective Grout in Prestressed Concrete Bridge Post-Tensioning Ducts
The objectives of this study were to provide recommended guidance for grout sampling, testing, data analysis, and interpretation of results and to propose courses of action by State transportation departments where grout deficiencies are identified. Grout is a cementitious material typically used to provide corrosion protection to the prestressing strands used in post-tensioned (PT) concrete bridges. Based on collected information and data analysis, State transportation departments can evaluate if grout deficiencies are present in the tendons of their PT bridges and determine the significance of those deficiencies.
Literature Review of Chloride Threshold Values for Grouted Post-Tensioned Tendons
This document describes the outcomes of a literature review conducted by the Federal Highway Administration (FHWA) to support an ongoing laboratory study on corrosion of grouted post-tensioned (PT) bridges that are affected by chloride contaminated grouts.
Long-Term Bridge Perforamnce High Priority Bridge Performance Issues
The findings from a set of interviews and a substructure workshop were used to develop a list of 22 high priority performance issues. From this list, a shorter list of six bridge performance issues was recommended as the first group of issues for study under the LTBP Program.
LTBP Bridge Performance Primer
The performance of bridges is critical to the overall performance of the highway transportation system in the United States.The purpose of this report is to provide an understanding of what bridge performance means and the factors that influence bridge performance. It describes the various ways in which bridge owners measure and report performance. It also describes how the LTBP Program will create new measures to allow deeper analysis and understanding, which will lead to ways to improve long-term bridge performance.
Material Characterization of Field-Cast Connection Grouts
Prefabricated bridge element and system (PBES) construction concepts frequently rely on field-cast grouts to complete the connections between discrete precast concrete elements. A variety of grouts are available, each with unique performance attributes. The objective of this research is to evaluate the performance of a representative sample of grouts in terms of relevant material properties. This study both reports on the performance of eight specific grouts and provides general insight into the performance of five different types of grout. Although many of these grouts could be used in a post-tensioned connection system, the tests completed herein investigated the performance of the grouts in a non-post-tensioned condition.
Movable Highway Bridge Design Specifications Revisions
This is a 2010 revision of the 2007 publication on movable highway bridge design specifications by AASHTO. AASHTO 2010.
Real-Time Bridge Monitoring - Developing Wireless Nanosensors to Monitor Structural Integrity
With steel bridges representing approximately 34 percent of the nearly 600,000 highway bridges in the United States, continual monitoring and early detection of deterioration in these structures is vital to prevent expensive repairs or catastrophic failures. Developing a solution for autonomous crack monitoring is the goal of “Low-Cost Self-Powered Wireless Nanosensors for Real-Time Structural Integrity Monitoring of Steel Bridges,” an Exploratory Advanced Research (EAR) Program project launched by the Federal Highway Administration (FHWA) in 2009 and conducted by the Georgia Institute of Technology.
Standard Specifications for Construction of Roads and Bridges on Federal Highway Projects
These Standard Specifications for the Construction of Roads and Bridges on Federal Highway Projects issued primarily for constructing roads and bridges on Federal Highway projects under the direct administration of the Federal Highway Administration. These specifications are cited as "FP-14" indicating "Federal Project" Standard Specifications issued in 2014 and contain both United States Customary and Metric units of measure. FHWA, 2014.
Standard Specifications for Road and Bridge Construction
Provides information on road and bridge construction, including general provisions, earthwork, pavements, and incidental construction. NHDOT, 2006.
Steel Bridge Fabrication Guide Specifications
This publication explains standards for steel bridges as outlined by AASHTO. The standards are meant to achieve the highest quality of bridge design and construction. AASHTO 2008.
Ultra-High Performance Concrete Composite Connections for Precast Concrete Bridge Decks
Ultra-high performance concrete (UHPC) has been used to develop a novel composite connection detail for joining precast concrete bridge decks supporting superstructure elements. The results of the research effort and recommendations for the use of this connection detail are provided herein.
User-Friendly Guide to Timber Bridges
Guide to choosing, using, and preserving the right wood, and how to make the decision to build a timber bridge. UNH Cooperative Extension.