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Improved guidance for deploying refined modeling, nondestructive evaluation, load testing and long-term monitoring for the structural assessment of bridges

Description:

Background

Historically, bridge structural assessment practices have been organized hierarchically beginning with simplified (single-line girder) analysis methods followed by supplemental approaches including material sampling, refined modeling, diagnostic load testing [1], and finally proof load testing [2]. There is much wisdom in this approach as each proceeding level generally requires more resources and thus should not be employed unless the previous level was deemed (or shown to be) insufficient.

There are four important shortcomings to the current approach. First, this hierarchy does not address the specific information that each method may provide. Without a clear mapping between available approaches and the mechanisms that they may uncover/quantify, decision-makers may not be in a position to identify the most efficient path forward. The second shortcoming is related to the limited approaches that the AASHTO MBE [3] addresses. Since the practices of Diagnostic and Proof Load Testing were first formalized in the late 1990s [4], a number of different techniques have become available (as well as approaches that integrate multiple techniques). However, without their explicit inclusion within guidance documents, many decision-makers will be hesitant to employ them (even in cases where they may be more efficient and cost-effective than traditional approaches).

The third shortcoming is related to proof load testing and, in particular, its unpracticality. Of particular interest is the appropriateness of the target loads specified by the MBE, and whether such loads are reasonable if they cannot be achieved using common vehicles. Additionally, reliability methods should be used to evaluate the method for determining the target proof load. The fourth shortcoming is that the decision to model, monitor, and/or load test a bridge is often reactive and triggered based on damage, a drop-in condition, or a change in loading. There are potential benefits of identifying modeling, monitoring or load testing candidates based on the potential to reduce life-cycle costs. Such approaches have been developed for monitoring [5], and preliminary studies for load testing have been done [6]. This information should be combined and incorporated into Bridge Management Systems (such as AASHTO BrM) to provide guidance to owners that are in a position to deploy some of these structural assessment approaches in a more proactive manner.

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Literature Search Summary

Over the last two decades significant research in the realm of bridge structural assessment has been carried out throughout the U.S. funded by various state transportation agencies, NCHRP, Federal Highway Administration, the National Institute for Standards and Technology, the National Science Foundation, among others. This research includes numerous studies focused on the deployment of refined modeling, nondestructive evaluation, load testing, and monitoring to quantify and characterize the structural performance of bridges. Notable reports include: NCHRP Synthesis 453 [7], NCHRP Report 700 [8], and the FHWA Manual for Refined Analysis [9]. The ongoing project “Field Live Load Testing and Advanced Analysis of Concrete T-Beam Bridges to Extend Service Life [10]” is also relevant for this proposed work. At the international level, current research projects that aim to address more specific elements related to load testing are ongoing in the Netherlands [11] and Denmark [12], among others.

Objective:

The objective of this research is to develop improved guidance and recommendations for selecting candidates for various structural assessment techniques that include refined modeling, nondestructive evaluation, load testing, and monitoring. This guidance can then be used to improve Chapter 8 of the AASHTO MBE and a decision logic to incorporate into Bridge Management Systems such as BrM.

Benefits:

This high-priority research will provide guidance to help owners deploy the suite of available structural assessment approaches in a more cost-effective and efficient manner. Over the last several decades the traditional techniques addressed by current guidance (i.e. diagnostic and proof load testing) have been supplemented by a number of other techniques that offer different trade-offs between accuracy/completeness and cost. While these methods have the potential to improve structural assessment practice and/or reduce the associated costs, unless they are addressed by current guidance in an integrated manner, owners will be reluctant to deploy them. This research aims to fill this need and provide owners with a framework to guide the identification of candidates for the wide range of structural assessment approaches now available. The outcomes of this research will be valuable to all bridge owners. The problem statement meets the AASHTO Subcommittee on Bridges and Structures’ Strategic Plan items: 1- Extend Bridge Service Life, 4- Maintain and Enhance the AASHTO Specifications.

Related Research:

1. Olaszek, P., M. Lagoda, and J.R. Casas, Diagnostic load testing and assessment of existing bridges: examples of application. Structure and Infrastructure Engineering, 2014. 10(6): p. 834-842.

  1. Saraf, V.K., A.S. Nowak, and R. Till, Proof load testing of bridges, in Probabilistic Mechanics & Structural Reliability: Proceedings of the Seventh Specialty Conference, D.M. Frangopol and M.D. Grigoriu, Editors. 1996: Worcester, MA, USA. p. 526-529.

  2. AASHTO, The manual for bridge evaluation with 2016 interim revisions. 2nd ed. 2016, Washington, D.C.: American Association of State Highway and Transportation Officials. 1 online resource (1 b. (various pagings)).

  3. NCHRP, Manual for Bridge Rating through Load Testing. 1998: Washington, DC. p. 152.

  4. Okasha, N.M. and D.M. Frangopol, Integration of structural health monitoring in a system performance based life-cycle bridge management framework. Structure and Infrastructure Engineering, 2012. 8(11): p. 999-1016.

  5. Val, D.V. and M.G. Stewart, Chapter 10: Determination of remaining service life of reinforced concrete bridge structures in corrosive environments after load testing, in Load Testing of Bridges Volume 2: Proof Load Testing and the Future of Load Testing, E.O.L. Lantsoght, Editor. 2019, CRC Press: Boca Raton, FL.

  6. Hearn, G., State Bridge Load Posting Processes and Practices, NCHRP Synthesis 453, available from: ">https://trid.trb.org/view/1306683. 2014._ _

  7. Mlynarski, W. and A.S. Nowak, A Comparison of AASHTO Bridge Load Rating Methods,” NCHRP Report 700, Available from:_ http://www.trb.org/Publications/Blurbs/165576.aspx. 2011.

  8. FHWA, Manual for Refined Analysis - Available in draft form at: ">https://www.fhwa.dot.gov/bridge/concrete/ _2015. _

  9. Davids, B. Project 1.1: Field Live Load Testing and Advanced Analysis of Concrete T-Beam Bridges to Extend Service Life_. 2019; Available from: https://www.tidc-utc.org/knowledge-base/project-1-1-field-live-load-testing-and-advanced-analysis-of-concrete-t-beam-bridges-to-extend-service-life/.

11. Lantsoght, E., et al., Recommendations for proof load testing of reinforced concrete slab bridges, in 39th IABSE Symposium - Engineering the Future. 2017: Vancouver, Canada.

12. Schmidt, J.W., et al., High Magnitude Loading of Concrete Bridges. Special Publication, 2018. 323.

Tasks:

The following tasks will address the stated research question:

  1. Literature review and analysis of international state-of-the-art.

  2. Analyze necessary input and possible outcomes of currently available methods for refined modeling, nondestructive evaluation, load testing, and long-term monitoring, and map these results within a framework for the structural assessment of bridges.

  3. Develop a web-based tool to help decision-makers select the optimal structural assessment procedures for specific bridges. Develop long-term maintenance and hosting strategy for the tool.

  4. Evaluate current proof load testing procedures from the MBE with probabilistic studies and develop recommendations.

  5. Using the information from Tasks 2 and 3, analyze the optimal point in time for modeling, monitoring, and/or load testing a bridge by using probabilistic models. Implement timing recommendations in the tool developed in Task 2.

  6. Test, refine, and validate the developed recommendations with case studies.

  7. Develop revisions for AASHTO MBE

  8. Develop decision logic for incorporation into Bridge Management Systems such as AASHTO BrM

  9. Develop final report

Implementation:

This research will result in draft revisions to the AASHTO MBE and AASHTO BrM to help owners more effectively and efficiently deploy the various structural assessment approaches now available. In addition, this same guidance will be provided via a web-based tool to streamline its implementation in practice.

Relevance:

Potentially Interested AASHTO Councils and/or Committees T-18 Bridge Management, Evaluation, and Rehabilitation

Sponsoring Committee:AFF40, Field Testing and Nondestructive Evaluation (NDE) of Transportation Structures
Research Period:24 - 36 months
Research Priority:High
RNS Developer:Dr. Eva Lantsoght, Professor of Structural Engineering, Politécnico, Universidad San Francisco de Quito, elantsoght@usfq.edu.ec +593997111760; Dr. Franklin Moon, Professor, Civil and Environmental Engineering, Rutgers University, franklin.moon@rutgers.edu , 848-445-2870; Dr. Sreenivas Alampalli, Director, Structure Management Bureau, NYS DOT, sreenivas.alampalli@dot.ny.gov , 518-457-4544
Source Info:TRB committees
AFF40 Testing and Evaluation of Transportation Structure
AHD35 Bridge Management Committee
AHD30 Structures Maintenance Committee
Date Posted:03/05/2020
Date Modified:03/10/2020
Index Terms:Bridge management systems, Highway bridges, Nondestructive tests, Structural models, Load tests, Structural health monitoring, Structural analysis,
Cosponsoring Committees: 
Subjects    
Highways
Design
Maintenance and Preservation
Bridges and other structures

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