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Bridges & Structures

High Performance Steel Designers' Guide

10.0 Acknowledgement

12.0 Appendices

Appendix A | Appendix B | Appendix C

APPENDIX A - Sample HPS Special Provisions

A sample HPS Special Provisions is posted on the AISI website: www.steel.org/infrastructure/bridges. It serves as a very helpful guide in preparing project specific special provisions for HPS projects.

APPENDIX B - Research Problem Statement Format and Sample Statement

B.1 RESEARCH PROBLEM STATEMENT FORMAT (For submission through AASHTO to NCHRP)

I. PROBLEM NUMBER
(Do not put anything under this category in the first stage. NCHRP will assign a number upon submittal.)

II. PROBLEM TITLE
(A suggested title, in as few words as possible.)

III. RESEARCH PROBLEM STATEMENT
(A statement of general problem or need - one or two paragraphs should suffice.)

IV. RESEARCH PROPOSED
(A statement of the specific research proposed and how it relates to the general problem statement in III above. Include a clear and specific statement of the objectives that are expected to be met by this particular research.)

V. ESTIMATE OF PROBLEM FUNDING AND RESEARCH PERIOD
(Recommended Funding: An estimate of the funds necessary to accomplish the objectives stated in IV above. As a general guideline, the present cost for research usually averages between $75,000 and $100,000 per person-year.)
(Research Period: An estimate of the number of months of research effort, including three months for preparation of a draft final report, necessary to the accomplishment of the objectives in IV above.)
(Note: These estimates may be changed by the AASHTO Standing Committee on Research in order that the problem will fit into the broad program.)

VI. URGENCY, PAYOFF POTENTIAL, IMPLEMENTATION AND SUPPORT FOR BUSINESS NEEDS
(Statements concerning the urgency of this particular research in relation to highway transportation needs in general and the potential for payoff from achievement of project objectives should be given.)
(A statement should be included that describes the anticipated product(s) from the research (e.g., recommended specification language, new instrumentation, or recommended test methods). The anticipated steps necessary for implementation of the research product should also be delineated (e.g., Will recommended specification language be considered for adoption by a committee within AASHTO? Will an industry group have to adopt a new test method or revise their current practices or equipment?). This information should be as specific as possible, noting particular documents that may be made obsolete. Any institutional or political barriers to implementation of the anticipated research products should also be identified.)
(A statement identifying the Thrust/Business Need that will be addressed by this research (refer to NCHRP 20-7, Task 121). What building blocks are addressed?)

VII. PERSON(S) DEVELOPING THE PROBLEM
(A statement of the specifics (name, title, address, telephone number, etc.) of the person(s) having developed the problem in all its detail. This information is needed to facilitate communications when coordination between submitters is required for development of a single second-stage submittal to reflect submittals that are duplicates or are very similar in nature.)

VIII. PROBLEM MONITOR
(This should be left blank at the first-stage submittal stage. It will be dealt with if a second-stage submittal is tendered.)

IX. DATE AND SUBMITTED BY
(Show date of submission and by whom problem is submitted.)

MAIL OR E-MAIL SUBMISSION TO:
Malcolm T. Kerley, P.E.
Chairman, AASHTO Technical Committee for Research (T-11)
Virginia DOT
1401 E. Broad Street
Richmond, VA 23219
FAX: 804/786-2988
E-MAIL: kerley_mt@vdot.state.va.us

PLEASE SEND COPY TO:
David B. Beal, Senior Program Manager
National Cooperative Highway Research Program (NCHRP)
2101 Constitution Avenue, N.W.
Washington, DC 20418
FAX: 202/334-2006
E-MAIL: dbeal@nas.edu

B.2 SAMPLE RESEARCH PROBLEM STATEMENT

I. PROBLEM NUMBER

II. PROBLEM TITLE
Improving the Fatigue Performance of Steel Highway Bridges by the Use of Ultrasonic Impact Treatment (UIT).

III. RESEARCH PROBLEM STATEMENT
The service life of welded steel highway bridges is controlled by the fatigue performance of welded details. This is true for all grades of steel from M270 Grade 36 through Grade 100. Regardless of the grades of steel, the fatigue resistance of the components and welded details are subject to the same code provisions for fatigue design based on the detail categories. In other words, the fatigue resistance is the same for all strengths of steels when they are connected and welded in the same way. For example, the commonly used fillet-welded connections with welds normal or parallel to the direction of stress is classified as Detail Category E for fatigue consideration, no matter whether the steel is 36 ksi., 50 ksi. or 70 ksi. This is quite a penalty for the higher strength steels, including the new high performance steel. In terms of fatigue thresholds or allowables, Detail Category E has a threshold of 4.5 ksi., Detail Category D has a threshold of 7.0 ksi. and Detail Category C has a threshold of 10 ksi. If a Category E detail can be improved to a Category C detail, there is a significant gain in fatigue strength, resulting in more cost effective use of the higher strength steels.

The ultrasonic impact technique was first developed in Russia. In recent years, independent assessments of the method have indicated the effectiveness of UIT in post weld treatment to improve fatigue strengths of welded details. Preliminary fatigue tests conducted at the ATLSS Center of Lehigh University indicated that the ultrasonic impact technique improved the fatigue strength of the welded details tested. For example, a Category E' (2.6 ksi) coverplated detail was improved to Category C (10 ksi) detail. Unfortunately, the details of the UIT equipment used for the tests remained confidential or proprietary.

There is no secret in the concept and mechanism of the UIT technology. The UIT process is to utilize ultrasonic waves to improve weld profile, remove stress concentration, introduce compressive residual stresses and strengthen surface layer of a weld. The ultrasonic waves vibrate at about 27,000 HZ with maximum amplitudes up to 30 microns. AUIT equipment is expected to consist of a magnetoconstriction converter, an ultrasonic wave transmitter and a special tool with holder to isolate the operator from vibration. The tool tips are designed to fit the surface conditions of the welded details.

The ultrasonic impact technique is easy to learn, uses easy to handle tool, and produces much lower noise level than air hammer peening and achieves reproducible results. It has great potential for shop and field applications in improving the fatigue resistance of new and existing welded steel bridges.

IV. RESEARCH PROPOSED
The objectives of this research is to develop practical and cost effective techniques, procedures and light hand tools for the application of ultrasonic impact treatment to predictably and significantly improve welded connections from Detail Category E (4.5 ksi.) and Detail Category E' (2.6 ksi.) to Detail Category C (10.0 ksi.) or better. The quality of the treated welds should be verifiable by visual inspection and/or other nondestructive testing methods.
The proposed research will include, but not limited to, the following tasks:

Task 1 - Perform a literature search of the state-of-the-knowledge in ultrasonic impact and other
treatments of welds for improving fatigue strength of welded structural steels.
Task 2 - Evaluate the findings from Task 1 and assess the potential for successfully meeting the
objective of the proposed research. If the potential for success and payoff is high,
proceed to Task 3. Otherwise, abort study.
Task 3 - Develop techniques, procedures and schematics for the design of light hand tools for
performing the ultrasonic impact treatment. The schematics should provide the essential
components and functions of a UIT equipment so manufacturers can further develop and
build the equipment. The techniques should rely more on science than art, such that
technicians can be trained to use the techniques and tools with repeatable results.
Task 4 - Perform laboratory and field tests together with acceptance criteria and inspection
methods to verify and refine the techniques, procedures and tools.
Task 5 - Develop Technical and Training Manuals for the application of ultrasonic treatment of
bridge welds in the shop and in the field together with acceptance criteria and inspection
techniques. The manuals should include videotape and/or computer disks for
demonstrating the techniques and procedures.
Task 6 - Prepare to conduct four training classes across the country.
Task 7 - Prepare a final report.

V. ESTIMATE OF PROBLEM FUNDING AND RESEARCH PERIOD
Estimate of Problem Funding: $350,000
Estimate of Research Period: 30 months

VI. URGENCY, PAYOFF POTENTIAL, IMPLEMENTATION AND SUPPORT FOR BUSINESS NEEDS
Many existing steel highway bridges have low fatigue category details, which are susceptible to fatigue cracking, if not already cracked. New steel bridges are designed under the constraint of Detail Category E and Detail Category E'. These details can be improved to Detail Category C by using ultrasonic impact treatment. There will be significant savings in expensive repair of existing bridges, and in effectively utilizing the higher strengths of modern steels in new bridges. The greatest benefit is in extending the service life of steel highway bridges with less disruption to the traveling public. The research results can be used immediately for fatigue retrofit of existing steel bridges and for new steel bridge design.

Thrust/Business Needs

  • Efficient Maintenance, Rehabilitation, and Construction.
  • Enhanced Specifications for Improved Structural Performance.

The associated building blocks include practical and cost effective techniques and procedures for improving the fatigue performance of welded details in existing and new steel bridges.

VII. PERSON(S) DEVELOPING THE PROBLEM

M. Myint Lwin
Structural Design Engineer
Federal Highway Administration
201 Mission Street, Suite 2100
San Francisco, CA 94105
(415) 744-2660
Myint.Lwin@fhwa.dot.gov

VIII. PROBLEM MONITOR

IX. DATE AND SUBMITTED BY
January 7, 2001

M. Myint Lwin
Structural Design Engineer
Federal Highway Administration
201 Mission Street, Suite 2100
San Francisco, CA 94105
(415) 744-2660
Myint.Lwin@fhwa.dot.gov

APPENDIX C - HPS SCOREBOARD

AISI maintains a list of HPS bridges that are being planned, under design, in fabrication, under construction and in-service. The list is posted in the AISI website: www.steel.org/infrastructure/bridges.

Updated: 07/23/2013
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000