A Process for Selecting Strategies for Rehabilitation of Rigid Pavements
Author: National Cooperative Highway Research Program | Size: 3.52 MB | Format:PDF | Quality:Original preprint | Publisher: Transportation Research Board | Year: 2002 | pages: 129 | ISBN: -
State highway agencies (SHAs) are under pressure to mitigate poor pavement conditions through maintenance, rehabilitation, and reconstruction (MRR) work while accelerating construction, minimizing traffic disruption, reducing accident risk, and improving public acceptance. Much of this work is performed with limited funds. SHAs have a range of engineering processes for pavement analysis and design. These pavement-related processes focus on pavement condition and causes of pavement distress to identify appropriate pavement treatments. Pavement related processes determine "what is done." Traffic and construction management processes, nonpavement-related, are also commonly considered to identify "how the pavement treatment is accomplished." Little information is available on how to integrate these nonpavement-related processes into the MRR strategy selection process for rigid pavements. These nonpavement-related aspects of an MRR strategy have, perhaps, the greatest impact on road users and local businesses and may actually have the major influence on strategy selection for high traffic volume pavements. An integrated selection process that considers a number of potential alternatives to both the pavement- and nonpavement-related aspects of an MRR strategy is needed. This process will aid decision makers in selecting the most appropriate strategy for MRR of rigid pavement subjected to high-traffic volumes. National Cooperative Highway Research Program (NCHRP) Project 10-50A was conducted to develop this selection process. The research was conducted in two phases. The first phase determined the elements that comprised an MRR strategy and proposed a preliminary process. The second phase of the research fully developed the preliminary process. This development effort created the detailed information required to implement the steps of the process as well as the structure and format for describing the process. The proposed selection process was then demonstrated through project specific applications provided by SHAs and documented as case studies.
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Improved Live Load Deflection Criteria for Steel Bridges
Author: National Cooperative Highway Research Program | Size: 1.01 MB | Format:PDF | Quality:Original preprint | Publisher: Transportation Research Board | Year: 2002 | pages: 147 | ISBN: -
This research examined the American Association of State Highway and Transportation Officials (AASHTO) live-load deflection limit for steel bridges. The AASHTO Standard Specification limits live-load deflections to L/800 for ordinary bridges and L/1000 for bridges in urban areas that are subject to pedestrian use. This limit is also incorporated in the AASHTO Load and Resistance Factor Design (LRFD) Specifications in the form of optional serviceability criteria. This limit has not been a controlling factor in most past bridge designs, but it will play a greater role in the design of bridges built with new high performance 70W steel. This study documented the role of the AASHTO live-load deflection limit of steel bridge design, determined whether the limit has beneficial effects on serviceability and performance, and established whether the deflection limit was needed. Limited time and funding was provided for this study, but an ultimate goal was to establish recommendations for new design provisions that would assure serviceability, good structural performance and economy in design and construction.
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Repair and Rehabilitation of Bridge Components Containing Epoxy-Coated Reinforcement
Author: National Cooperative Highway Research Program | Size: 4.13 MB | Format:PDF | Quality:Original preprint | Publisher: Transportation Research Board | Year: 2002 | pages: 192 | ISBN: -
The primary goal of this effort was to address the anticipated need for premature repair and rehabilitation of concrete bridge elements containing epoxy-coated rebar (ECR). Laboratory, test yard, and field studies were conducted to evaluate and validate applicable strategies. The performance of each strategy was judged by the level of corrosion protection afforded in and outside the repair area. Based on the results of this effort, credible information available in literature, and the collective experience of the research team, a decision matrix was developed. The decision matrix matches appropriate repair and rehabilitation strategies to the damage mode, present condition, environmental exposure, and future propensity of corrosion. The evaluation of strategies was subdivided into two categories, one applicable to the mitigation of corrosion in cracks and the other to delaminations and spalls. Several possible combinations of an epoxy injection material and two corrosion inhibitors were evaluated for corrosion mitigation in both corrosion and non-corrosion induced cracks. Injection of cracks was accomplished using bisphenol A and polyamine curing agent. Of the two surface applied (migrating) corrosion inhibitors used, one contained water based amine and an oxygenated hydrocarbon and the other contained calcium nitrite as the active agent. None of the repair strategies evaluated in this category exhibited any ability to provide protection against corrosion in the two spheres of interest, i.e., directly at the crack and the area adjacent to the cracks. Various combinations of three patch materials [pre-bagged portland cement concrete (PCC), pre-bagged polymer modified silica fume concrete, and Class III PCC], three rebar coatings (epoxy coating, water based epoxy resin/portland cement coating, and water based alkaline coating with corrosion inhibitor), and four corrosion inhibitors (water based amine and an oxygenated hydrocarbon migrating corrosion inhibitor, water based amine and an oxygenated hydrocarbon admixture, calcium nitrite admixture, and a multi-component corrosion inhibitor and concrete densifier admixture) were used in the evaluation of repair strategies applicable to delaminations and spalls. No benefit was discernable from the use of admixed and migrating corrosion inhibitors in repair areas and/or areas adjacent to the repair. The best response from a corrosion protection standpoint was demonstrated by a high resistance, low permeability silica fume modified patch material and an epoxy rebar coating compatible with ECR in the repair area. The water based alkaline coating with corrosion inhibitor showed promise in providing protection in the repair area. Impressed current cathodic protection applied to slabs for over 7.2 years successfully mitigated corrosion. The control slabs continued to corrode and experience corrosion induced damage, whereas, the cathodically protected ones did not suffer corrosion induced damage. Also, the current densities used to protect black reinforcing steel were found to be adequate to protect ECR.
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Author: Hughes, W Eccles, K Harwood, D Potts, I Hauer, E | Size: 2.33 MB | Format:PDF | Quality:Original preprint | Publisher: Transportation Research Board | Year: 2004 | pages: 303 | ISBN: -
This report documents and presents the results of a study to develop an annotated outline, prototype chapter, and work plan for the first edition of the Highway Safety Manual (HSM). The purpose of the HSM will be to provide the best factual information and tools, in a useful and widely accepted form, to facilitate roadway planning, design, and operational decisions based upon explicit consideration of their safety consequences.
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Geofoam Applications in the Design and Construction of Highway Embankments
Author: Stark, T D Arellano, D Horvath, J S Leshchinsky, D | Size: 10.32 MB | Format:PDF | Quality:Original preprint | Publisher: Transportation Research Board | Year: 2004 | pages: 792 | ISBN: -
This report is a comprehensive document that provides both state-of-the art knowledge and state-of-the-practice design guidance for the use of geofoam in roadway embankments and bridge approaches. This document presents a design guideline or procedure as well as an appropriate material and construction standard, both in AASHTO format. It is anticipated that this document will encourage greater and more consistent use of expanded polystyrene (EPS)-block geofoam in roadway embankments. The ultimate benefit of this is an optimization of both the technical performance as well as cost of EPS-block geofoam embankments. It is anticipated that designers will be more willing to consider EPS-block geofoam as an alternative for construction of embankments over soft ground using the design methodology and construction standard presented herein. The research has confirmed that EPS-block geofoam can provide a safe and economical solution to problems with construction of roadway embankments on soft soils. This report is designed to produce a single source of information on the present knowledge of geofoam usage in roadway embankments.
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Design and Construction Guidelines for GRS Bridge Abutments with a Flexible Facing
Author: Wu, Jonathan T H | Size: 1.81 MB | Format:PDF | Quality:Original preprint | Publisher: Transportation Research Board | Year: 2004 | pages: 83 | ISBN: -
The capability of DYNA3D/LS-DYNA for analyzing the performance of segmental facing geosynthetic-reinforced soil (GRS) bridge abutments was critically evaluated. To achieve the purpose of evaluating the analytical tool, it was necessary to compare the analytical results with experimental or field-measured results that involve the critical components of the problem on hand. This means that it is necessary to select closely related case histories of which the measured results are reliable, the placement density and moisture conditions of the fill are well monitored, and the material parameters (stress-strain-strength and volume change behavior of the soil and load-deformation properties of the reinforcement) are well documented. Following an extensive search and careful consideration, five case histories that involved critical components of segmental GRS abutments were selected for the evaluation. The first two experiments involved spread footings on sand. They were included as part of the verification study because it was considered important to examine the adequacy of DYNA3D and the extended two-invariant geologic cap model in terms of their capability to predict failure loads of spread footings on unreinforced and reinforced soils.
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Author: Wagner, Chad R | Size: 7.27 MB | Format:PDF | Quality:Original preprint | Publisher: Transportation Research Board | Year: 2006 | pages: 299 | ISBN: -
The main purpose of National Cooperative Highway Research Program (NCHRP) Project 24-14 was to collect field data from which processes affecting scour magnitude in contracted bridge openings could be identified, to support verification of physical and numerical model studies, and to improve guidelines for applying scour-prediction methods at contracted bridge sites. The objectives were accomplished by the collection and analysis of data at 15 bridge sites. A combination of real-time and post-flood data collection activities provided comprehensive field data sets. Detailed directional velocity data were collected throughout the reaches affected by the bridge where flood and site conditions permitted (4 of 15 sites). In addition, streambed, stream bank and floodplain material properties were described. Raw data were reduced and assembled into a database accessible through the World Wide Web (http://ky.water.usgs.gov/Bridge_Scour/BSDMS/index.htm). Scour predictions based on the methods provided in HEC-18 were compared to the observed scour at each site. Flow velocity and depth data obtained from real-time investigations along with post-flood topographic surveys were used to develop and calibrate two-dimensional hydraulic models (RMA-2 and FESWMS) at two sites. One-dimensional hydraulic models (HEC-RAS or WSPRO) were developed for all sites where sufficient cross sectional data were collected or available. The velocities obtained from numerical simulations were compared to measured velocities. The observations and measured data demonstrate the inaccuracies of the current scour prediction methods as specified in HEC-18 related to contraction scour and abutment and the effectiveness of the Melville and Dongol method for predicting scour at a pier with debris. Measured flow-velocity distributions and those computed from the one-dimensional and two-dimensional models were compared. Scour topography computed with the two-dimensional hydraulic model and two-dimensional sediment-transport model were compared. Recommendations for future research that will advance scour-prediction methods were provided, including suggested modifications to the Strategic Plan for Scour Research (NCHRP Project 24-8). Appendix A contains 10 case studies.
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Service Life of Corrosion-Damaged Reinforced Concrete Bridge Superstructure Elements
Author: Sohanghpurwala, Ali Akbar | Size: 735 KB | Format:PDF | Quality:Original preprint | Publisher: Transportation Research Board | Year: 2006 | pages: 57 | ISBN: -
The primary product of this effort was the development of a manual titled "Manual on Service Life Prediction of Corrosion-Damaged Reinforced Concrete Bridge Superstructure Elements." This manual provides a protocol for assessing the condition of reinforced concrete bridge superstructure elements subjected to corrosion-induced deterioration, predicting the remaining service life of such elements using the developed service life model, and quantifying service life extension for such elements expected from alternative maintenance and repair options. This report documents the data utilized in the development and validation of the service life model presented in the manual.
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