George Hearn

CONDITION DATA AND BRIDGE MANAGEMENT SYSTEMS

Automated systems for managing bridge maintenance require information on current and future needs for maintenance and repair actions. This information is often provided indirectly by condition ratings for bridge elements, which are assigned during routine bridge inspections. These ratings indicate the relative health of elements, but usually do not indicate specific types of deterioration or actions needed. Quantitative information on endurance of actions is rarely available at present, but is needed for the rational cost-benefit analysis of maintenance programmes. Condition ratings must be defined to correspond to specific maintenance actions, so that these ratings, and changes in them, can indicate necessary actions and their endurance. New condition states are defined as stages of service life, and models of them offer advantages in models of deterioration. This paper discusses new condition states, notes the correspondence between them and contemporary condition ratings in US practice. It also outlines the use of field testing to identify condition states, reviews deterioration modelling for condition states, and indicates a procedure for segmental inspection to capture quantities and locations of conditions.

DIFFERENTIAL SETTLEMENTS AND INELASTIC RESPONSE IN STEEL BRIDGE BEAMS

A proposed method for mitigation of pavement faults at bridge abutments (the “bump at the end of the bridge”) is the use of shallow foundations. Abutments on shallow foundations are expected to settle compatibly with embankments and thus to minimize pavement faults. Allowing bridge abutments to settle may reduce faults, but it creates a demand for tolerance of different settlement in bridge superstructures. Current guidelines for tolerable differential settlement of bridges are empirical only, and the application of elastic analysis of bridge superstructures to determine tolerance of settlement has not produced satisfactory results. Inelastic analysis of steel bridge beams was applied to the computation of tolerable differential settlement. Tests of inelastic rotation capacity of steel beams were reviewed and compared with the results of inelastic analyses. A model of tolerable inelastic rotation capacity in steel beams is proposed.

Performance of NDE methods in bridge inspection

The relations between data from test methods and conditions in bridge elements are considered. NDE methods are joint applications of a test and a basis for interpretation of data obtained in the test. Correct assessments of conditions of elements depend on the inaccuracy and variability in test data and on the uncertainty of correlations between attributes (what is measured) and conditions (what is sought in the inspection). A full description of the performance of NDE methods considers the relation of test data to conditions of elements. The quality of the test itself is important, but equally important is the interpretation that occurs after the test. The effects of variability in test data and uncertainty in correlations of attributes and conditions are presented in three examples of field testing methods.

State Bridge Load Posting Processes and Practices

This report is a synthesis of the practices of U.S. state governments in restricting weights of vehicles that can cross highway bridges and culverts to levels below legal loads. Bridges and culverts restricted for vehicle weights are called load posted structures. The load posting practices of bridge owners include the identification of structures to post for load, the evaluation of safe load capacities of these structures, and the implementation of restrictions on vehicle weights at structures. The synthesis gathers information on loads and posting for load from the United States Code, U.S. Department of Transportation National Bridge Inventory, states’ statutes and administrative codes, state department of transportation manuals and published advice to commercial carriers, and a survey of states’ representatives to the Subcommittee on Bridges and Structures of American Association of State Highway and Transportation Officials .

Framework for a National Database System for Maintenance Actions on Highway Bridges

This report presents a potential framework for a National Bridge Maintenance Database (NBMD). This framework provides a uniform format for collecting, reporting, and storing information on bridge maintenance actions. Use of this framework will promote compatibility of maintenance data reported by different agencies and will provide an effective means for using these data in evaluating cost and performance of alternative maintenance applications or as a basis for cost-benefit analysis and evaluation of cost and deterioration models. The material contained in the report should be of immediate interest to state bridge and maintenance engineers and others concerned with the maintenance and management of bridges.

Bridge Management System with NDE

Methods for the use of NDE test data in bridge management systems are presented. NDE data are interpreted as condition states of bridge elements. Definitions of condition states are coordinated with thresholds for properties measured in tests. Thresholds for NDE tests are the boundaries of condition states. Tests are directed for particular conditions and materials. Tests offer a determination of condition of elements relative to the focus of the test. Therefore, there are redundant, overlapping determinations of condition. Tests must be selected for the elements to be interrogated and for the expected types of deterioration. The tests considered here are standard tests for the evaluation of construction materials, and the examination of bridge elements in service. While standard data thresholds are available, these are adjusted to achieve a consistent assignment of condition states for all bridge elements and for all condition states.

Element-Level Performance Measures for Bridge Preservation

Measures of performance of highway bridges with element-level data are proposed. Element-level measures focus on the preservation of deck, superstructure, and substructure elements. Element-level measures recognize relationships between bridge elements. Bridge elements (e.g., joints, wearing surfaces, coatings) affect the exposure of deck, superstructure, and substructure. Poor conditions of these elements put decks, superstructures, and substructures at risk. Risk also is increased when actions for preservation are delayed or limited. Three levels of performance were measured: good, at risk, and poor. Bridges that perform well were candidates for bridge preservation programs. Bridges at risk were candidates that needed prompt attention to preserve their current condition. Bridges that performed poorly required rehabilitation or replacement. Risk from exposure and risk from delayed preservation were recognized in element-level performance measures. The following are presented in this study: (a) examples of element-level performance measures for a population of state-owned bridges, (b) comparisons with present-day performance measures of bridges, and (c) extended use of element-level performance measures to estimate annual work quantities and funding for preservation.

Performance Measures for Bridge Preservation

A study of performance measures for bridge preservation is presented. The performance measures use National Bridge Inventory general condition ratings, element-level condition states, and average costs to identify which bridges to preserve, determine the annual need for preservation work and resources, and quantify the impacts of preservation programs on bridge conditions and program costs. The proposed measures of performance for bridge preservation are demonstrated for the inventory of state-owned bridges in Colorado.

MSE WALLS WITH INDEPENDENT FULL-HEIGHT FACING PANELS

In 1996, the Colorado Department of Transportation (CDOT) completed the construction of a unique mechanically stabilized earth (MSE) wall with an independent full-height facing (IFF) for the ramp connecting northbound Interstate-25 to Interstate -70 in Denver, Colorado. The new MSE/IFF wall has four major components: 1) a self-stable welded wire fabric (WWF) reinforced soil mass, 2) full-height concrete facing panels not attacked to the soil reinforcements (i.e., independent) that are allowed to tilt around their base, 3) flexible face anchors to provide for attachment of facing panels to the reinforced soil mass and accommodate movements of the wall system, and 4) a trench with flowfill to brace the panels during construction only (before the face anchors are placed). Since this MSE wall system is the first of its kind, it was considered experimental and a comprehensive instrumentation and monitoring program was performed. The main objective of this study was to upgrade the I-25/I-70 MSE/IFF wall for future standard use of this wall system by identifying modifications and additions to the design and construction of the I-25/I-70 MSE/IFF wall that would improve performance and save money and time. This report provides insight into material, construction, construction problems and corrective actions, monitoring, performance and design assessment of the I-25/I-70 MSE/IFF wall. The wall system performed as intended in the design. The flexibility of the MSE wall system smoothly accommodated the movements of the wall system, especially those induced by heavy compaction close to the facing, and allowed for the mobilization of tensile resistance in the WWF reinforcements, thus taking most of the lateral load off the facing panels. The average lateral earth pressure measured on the facing was a low value of 32 psf. After five years in service, the structure performance has been excellent with no signs of distress and the facing remained properly aligned.

Inventory System for Retaining Walls and Sound Barriers

An inventory system for retaining walls and sound barriers includes information about location, age, service, type, dimensions, and appraisals of a structure together with element-level models and element-level condition reports. Many of the inventory items and appraisals are adapted from the U.S. National Bridge Inventory record. Elements for walls and barriers indicate structural form and material, much like Commonly Recognized (CoRe) bridge elements. Potential uses of the inventory system in maintenance management and asset preservation are noted.