A448

Commercialization of Instrument for Micro-Inch Measurement of Crack Width in Support of Thrust in Remote Monitoring for Bridge Management (continuation of Triggered, Real Time Display of Infrastructure)

Charles Dowding
Northwestern University
847-491-4338
c-dowding@northwestern.edu

Chuck Howe
Geotechnical Engineering Section
Materials & Research Laboratory
MNDOT
1400 Gervais Avenue
Maplewood, MN 55109
612-779-5602

Walt Vanderpool (City of Las Vegas project)
Kleinfelder Engineers
6380 Soputh Polaris Ave
Las Vegas, NV
702-736-2936 ext 107
wvanderpool@kleinfelder.com

Prof. Catherine Aimone (State regulatory project)
New Mexico Institute of Technology
Soccoro, NM, 87801
(505) 835-5346
caimone@mailhost.nmt.edu

Alvin Budd
Vice President of Adminstration
GeoSonics
PO Box 779
Warrendale, PA 15095
724-934-2900

There are two main divisions of this project: 1) autonomous measurement of micro-inch vibratory and long-term crack movement and 2) autonomous graphical display of the results via the Internet. Its successes in 2) autonomous graphical display compliment and support other ITI Bridge Monitoring projects. For instance, instrumentation of the Sturgeon Bay Bridge is built around the concept of Internet display with the server software developed through this project. With regard to micro-inch sensing, the ultimate goal is to cooperatively develop with GeoSonics and other manufacturers of vibration instruments a remotely operable and accessible instrument to measure micro-inch changes in crack width.

Public concern over construction and traffic vibration-induced CRACKING has led to the search for a radically new approach to vibration control. This project to develop Autonomous Crack Monitoring (ACM) equipment and software for real-time monitoring and internet display of crack response and weather supports development of such a new approach to monitor and control construction induced vibration. The new instrument will automatically record and allow comparison with long-term changes in crack width as well as those produced by ground motion. Internet based, real-time public access to these data is fundamental to this new approach.

Measurement of micro-inch changes in crack width from environmental and vibratory effects provides information in a visual form that can be understood by lay bodies and regulatory administrators who control vibration limits, which ultimately control construction of transportation facilities. The present approach of correlating time histories of ground motion and past observations of cracking is simply too difficult for most jurors and village and county regulatory boards to understand. Use of such a system will allow an understanding of relationships between vibratory and environmental effects not now possible and potentially may avoid payment of 10's of millions of dollars in claims and construction delays each year.

Industrial and regulatory interest in this concept is strong. Formal coordination of parallel codeployment efforts with GeoSonics, a world leader in the manufacture of vibration monitoring instrumentation, demonstrates the potential for its immediate application. For instance, a beta test model for on site polling has already been deployed by GeoSonics for one of their clients. Vulcan Materials Corp. has loaned ITI the use of a home (adjacent to one of its quarries) for use in the development of the ACM system. This year the ACM on site polling equipment has been integrated with White Industrial Seismographs in a nation-wide study of the response of atypical structures

A joint project has been developed with the City of Las Vegas and Kleinfelder to assess the relative vibratory effect of vibratory roller excitation during widening of one of their arterial roadways. Effects of vibratory rollers have become the object of a sufficient number of complaints that the City wished to quantify the issue. The city has purchased a house for ACM instrumentation that is contiguous to the right of way. This project begins this spring and construction should be completed by the end of the summer.

A roadway aggregate producer in Connecticut has provided a house and will pay Aimone & Assoc. for the collection of house response and crack data while the blasting techniques are varied widely. This unique opportunity will allow further integration of White Seismographs and Somat technology. Should this combination continue to prove easy to install, it may provide an alternative path to commercialization of the ACM approach to vibration monitoring.

April 1 – September 30, 2002

1. Assess Vibratory Roller Impact: April through September

2. Integration of ACM with eismograph: April through June

3. Documentation of Server Code: June through September

Current Year = $70,916 3-Year Total = $228,200

Graduate Students

· Laureen McKenna and Micky Snider are working on measurements of the response of atypical structures, qualification testing of specialty sensors, and the City of Las Vegas project. McKenna’s MS thesis is to be published in April of 2002; Snider’s in 2003.

Undergraduate Students

· David Kosnik, junior at Northwestern University, and Mat Kotowsky, junior at the University of Illinois, will develop server side programs and supporting documentation that are critical to the success of this project

Continuation of "Triggered, Real Time Display of Infrastructure Response"

Industrial and regulatory interest in this concept is strong. Formal coordination of parallel codeployment efforts with GeoSonics, a world leader in the manufacture of vibration monitoring instrumentation, demonstrates the potential for its immediate application. For instance, a beta test model for on site polling has already been deployed by GeoSonics for one of their clients. Vulcan Materials Corp. has loaned ITI the use of a home (adjacent to one of its quarries) for use in the development of the ACM system. This year the ACM on site polling equipment has been integrated with White Industrial Seismographs in a nation-wide study of the response of atypical structures sponsored by State regulatory agencies.

It is anticipated that this project will continue significant interaction with the ITI Bridge NDE Users Group to ensure thorough integration with ITI and State DOT activities. Details of the activities of this group are described in the proposal submitted by David Prine on behalf of the ITI Remote Bridge Monitoring group. This coming year the User's Group will meet several times as a continuation of the tradition of holding both regional and national meetings.

A specific user group in the field of construction vibrations has been developed. This group is connected via the Constvib listserv that is accessed through the ACM web site: http://www.iti.northwestern.edu/acm/. This group is some 300 large and from time to time exchange messages concerning vibration issues of mutual interest.

Presentations were made at several locations to assess reaction to this thrust. In January 2002 a presentation entitled "A Radical New Approach to Vibration Monitoring and Control" was made at the 4rd Biennial Blasting Vibration Technology Conference, in Key West FL (which is sponsored by Geosonics). In December the Mueser Rutledge lecture was given in New York City on the topic of "Monitoring and Control of Construction Vibrations". In July a presentation on "Urban Blasting" was given at an NSF workshop at the annual meeting of the American Rock Mechanics Association. In April of 2001 a lecture on "Internet Based Monitoring of Structural Response" was given at Duke University in Durham, NC.

Commercialization of micro-inch crack measurement products will be conducted by advertisement through the following channels: (1) technical journal articles, (2) instrumentation, vibration, civil, geological, explosives, quarrying, mining, and construction magazines, (3) direct marketing to operators through the codeployment partner, GeoSonics, (4) GeoSonics and Northwestern University www sites, and (5) short courses and seminars.

Specifically, the micro-inch instrument allows comparison of changes in crack width from weather and environmental effects (long term) with those from construction vibration (short term). This comparison has the capability of showing that current regulatory controls permit less distortion than that which occurs from natural and habitation effects. Such a simple comparison is urgently needed as the general public has too little ability to understand the abstract complexity of the current system of control by measurement of ground motion. The public is interested in cracking, not abstract comparison of time histories of ground motion. They feel vibration but do not sense the long-term weather response. Thus some mechanism is needed to allow the neighbors of traffic and construction vibration to compare these two phenomena, both of which produce strains that can lead to cracking.

Cracking, Types of cracking, Width, Traffic, Vibration, Construction, Remote, Internet, Education, Public, Awareness, Instrumentation, Response, Access

A449

Commercialization of TDR Measurement of Soil Deformation in Support of ITI Thrust Area for Remote Monitoring for Bridge Management

Charles Dowding
Northwestern University
847-491-4338
c-dowding@northwestern.edu

OhioDOT Installation of TDR cables beneath I 70 near Cambridge

George Beiter
District 5 Planning and Programming
P.O. Box 306
Jacksontown, OH 43030
(740) 323-5192
George.Beiter@dot.state.oh.us

INDOT Installation of TDR cables in deforming abutment of Rt 62 & I 64 bridges

Dan Chase
Division of Materials and Tests
120 S Short Ridge Rd.
Indianapolis, IN 46219
(317) 232-5280 ext 229
DCHASE@indot.state.in.us

PennDOT Installation of TDR cables and tiltmeters along subsiding portion of I 70

David Whitlach
District Geotechnical Engineer Dist 12-0
Department of Transportation
Commonwealth of Pennsylvania
P.O Box 459
Uniontown, PA 15401
(274) 439-7357

Fl DOT/PSI Installation of TDR/tiltmeter system to monitor sinkhole deformation

John Barker
District Materials Engineer Dist 6(?)
Bartaw, FL
1-800-292-3368
john.barker@dot.state.fl.us

Ching Kuo
PSI
5801 Benjamin Dr
Tampa, FL
(813) 886-1075

CALTRANS Qualification of TDR cable for remote detection of concrete failure

Allan Chow
Toll Bridge Investigations
Structure Maintenance & Investigations
P.O. Box 23660
Oakland, CA
(510) 286-1361

Field measurement of TDR cable sensitivity in soft soils can be accomplished by installation and monitoring of the response of unique field sites. Continued potential of misapplication of the technology also points out the need for positive case studies that demonstrate the importance of the use of appropriately compliant cables.

Time Domain Reflectrometry (TDR) techniques replace other manual methods for assessing lateral movement of bridge abutments and piers. TDR’s remote operability and its inherently digital nature provide an appropriate and remotely operable method for monitoring stability of critical bridges while they await repair. Occurrence of excessive bridge pier and abutment movement is large. For instance scour induced deformation was responsible for some 40 bridge failures during the Mississippi and Missouri flooding of 1993.

Compliant cable-grout composites are necessary to maximize the use of TDR technology in soft soils. To date, TDR cables have been extensively deployed in rock and stiff soils. Recently, stiff, commercial cables installed with weak grout have been deformed with movements of 0.01 m (0.5 in) in soft lake clays. This observation has caused a shift in development emphasis from the cable itself to the reaction of the grouted hole-cable composite

It is important to further develop these special cables-grout composites for soft soils as State DOT’s are beginning to experiment independently and will require assistance to ensure that the technology is evaluated properly. Furthermore, exploratory field work with State DOT’s has revealed an overly simplistic view of installation requirements, which makes publicity of the importance of the composite view all the more critical.

Successful monitoring of mine-induced subsidence of I 70 with TDR-Tiltmeter technology for Pennsylvania DOT has lead to use of this combination of instruments for surveillance of sinkhole subsidence of SR 66 and US 27 in Florida this last year. This next six months will be employed to field test ITI developed compliant cable and bring SR 66 and the Klamath River bridges on line for autonomous, real-time display of data.

1:Field Test of Flexible Cable Developed by ITI

Monitoring of potential deformation of gas transmission lines adjacent to a deep excavation in Chicago presents an opportunity to field test the new flexible cable developed by ITI. Deformations associated with the deep excavation will be measured by slope inclinometers, pipe deflectometers, and a large number of settlement points. These measurements provide the comparisons with TDR readings that are necessary to commercialize the TDR approach. Two cables will be installed: one with a stiff, solid aluminum outer conductor, and the other with a flexible braided outer conductor. Grouts for will be specifically designed for each to maximize their response in the softer soils. Installation will take place this Spring and will be monitored during excavation this summer and fall.

2: Finalize 3D analysis

Modeling has been completed and a paper for a reviewed journal needs to be written. This article is a critical step in gaining acceptance of TDR capability in softer soils. While it has been accepted in rock and landslide materials, adoption for work in softer soils has been slow. Publication of this 3D interactive analysis should provide the scientific substantiation of the importance of matching the cable-grout composite stiffness with that of the soil.

3: Bring Florida Sinkhole Installation Online

ITI TDR instrumentation installed on and around the land bridge across the Florida sinkhole will be brought online. It has been discovered that Bell South will install a phone line to the SR 66 site without charging FlDOT. Once the phone line is brought to the site, it will be brought to the modem for polling. This site is unique in that it incorporates TDR cables to measure deformation and water level as well as tiltmeters.

April 1 to September 30, 2002

Flexible Cable Test: April – September

Bring Florida Online: May – September

Finalize 3D Analysis: July – September

Current Year = $51,965 3-Year Total = $250,362

Graduate Students: Tanner Blackburn is finishing his thesis.

Undergraduates: Dave Kosnik and Mat Kotowsky will be working with the ITI/ACM/TDR team to develop Java server side programs that are critical to the success of the automation project. Dave and Mat are juniors at Northwestern and University of Illinois respectively.

Shanna McGarry and Cristin Dziekonski were hired during the summer as ITI Summer Interns. Shanna is a Journalism/Marketing major and assisted with the production of the CD based Proceedings of TDR 2000. Crisitin is an Electrical Engineering major, focused on preparing instruments for bridge monitoring as well as TDR data acquisition

Continuation of Geotech/TDR component of Condition Monitoring Thrust

TDR specific user community involvement was fostered through five mechanisms: papers at workshops and specialty sessions, demonstration projects, TDR-L Email listserve, the TDR 2001 Symposium, and installations and consulting by Dr. O'Connor of Geo TDR.

The TDR listserve, operated by ITI, continues to serve some 150 to 200 TDR suppliers and consumers. Provision of this communication channel maintains ITI's preeminence in TDR technology. Details can be found at

http://www.iti.northwestern.edu/tdr/

Indirect support of Dr O'Connor's efforts to build GeoTDR, a company that specializes in TDR instrumentation, has been instrumental in developing ITI sponsored demonstration projects. For instance, GeoTDR installed the cables for the PennDOT and FlDOT projects. Without his assistance, PennDOT would not have been able to develop their alarm system.

TDR research will continue its interaction with the Bridge NDE User's Group to ensure thorough integration with ITI and State DOT activities. Details of the activities of this group are described in the proposal submitted by David Prine on behalf of the ITI Remote Bridge Monitoring group.

In addition to bridge monitoring, development of a TDR system to detect deformation in soil will allow further understanding of the localized shearing. Heretofore, deformation could only be measured with a resolution of 60 cm with slope indicators. When fully developed TDR technology will allow a resolution of 2 to 5 mm, which is a 100-fold increase in resolution.

Time Domain Reflectometry, Deformation, Soft Soil, Bridge Management Systems, Monitoring, Monitoring Systems, Infrastructure

A450

Allowable Deformations of Gas Mains Adjacent to Deep Excavations

Richard J. Finno
Northwestern University
847-491-5885
r-finno@northwestern.edu

An advisory committee has been established to assure the relevance of the research results. The following people are included in this committee.

Dr. Jerry Parola (Case Foundation Company) - Dr. Parola is with Case Foundation, the support system subcontractor for the Lurie Research Center excavation.

Mandoher S. S. Chawla (Department of Transportation, City of Chicago) - Mr. Chawla is the geotechnical engineer responsible for approving all building projects in Chicago.

William Walton (STS Consultants)

Dr. Paul Sabatini (GeoSyntec Consultants)

Dr. Bryan Sweeney (Haley & Aldrich, Boston)

The objectives of this proposed effort are to use the extensive monitoring data from the Lurie Research Center excavation to evaluate the effects of the deformations of gas main pipes and other utilities on the stresses in the pipes, to conduct a comprehensive stress analysis of the gas mains including the connections, and to develop rational methods to define the allowable deformations of such buried pipes when impacted by excavations in urban areas.

Deep excavations made as part of projects that modernize existing urban infrastructures affect gas main utilities located under the street since they deform with the ground adjacent to an excavation. Currently there are no universal guidelines for allowable deformations for buried gas mains adjacent to excavations. This lack of standards leads to either ignoring the possibility of damage to gas mains when an excavation is made, or arbitrarily selecting a movement criteria for an excavation project.

This project will evaluate performance data obtained from the 42 ft. deep excavation for the construction of Northwestern University’s Lurie Research Center on its Chicago campus, perform stress analyses of the gas main pipes and connections, and conduct parametric studies to develop guidelines for allowable deformations of buried pipes affected by adjacent excavations.

Four gas mains bound the excavation site. The stratigraphy generally consists of rubble fill, medium dense beach sand, soft to medium stiff clay, and stiff to very stiff clay overlying hard glacial till. The instrumentation used to monitor the ground deformation includes 149 ground surface survey points, 16 ground anchors, 30 utility settlement anchors, 8 slope inclinometers, and settlement markers in the basement of a hospital adjacent to the site.

There are four main tasks in the proposed scope of work: comprehensive literature search, evaluation of the performance data from the Lurie Research Center excavation, stress analyses of the gas main pipe and connections, and parametric studies to develop guidelines for allowable deformations of buried pipes affected by adjacent excavations.

A literature search will be conducted to find (1) case studies of performance of gas mains or other utilities in the presence of ground deformations caused by excavations, (2) analytical or numerical studies of the stresses induced in pipes by permanent ground deformations, (3) studies concerning the behavior of pipe joints in the presence of ground deformations, and, (4) local requirements concerning allowable movements of utilities. The field of lifeline engineering that has developed in response to the large impact earthquakes have on vital transportation links will be searched extensively.

2. Evaluation of the performance data from the Lurie Research Center

The three-dimensional response of the gas mains bordering the excavation will be recorded throughout the excavation.

The project team will process and interpret the observed deformations associated with the excavation process. Specific tasks include: (1) make independent predictions of movement for various sections of the excavation, (2) visit the site at least on a weekly basis, depending on the on-going activities, to detail construction progress in relation to observed movements, (3) process and interpret the performance data, (4) electronically store and plot inclinometer and optical survey data so that the development of the ground movements can be easily seen, (5) adjust predictions of movements based on performance data, and, (6) provide assessments of the progress of the work and the need to adjust construction procedures or support requirements as a function of the observed deformations.

The development of the movements as the excavation proceeds will be recorded, figures showing expected deflected shapes will be developed for each gas main throughout construction. Longitudinal bending stresses will be computed.

3. Stress analysis of gas main pipe and connections

The initial stresses in the gas mains arising from soil loads, internal pressures and live loads will be computed using a continuum mechanics approach. The stresses in the pipes, which are cast iron, will be compared to the allowable stresses in the pipes to evaluate the severity of the loading conditions imposed by the excavation-induced movements.

Detailed models of several pipe sections and their joints will be developed. This model will be a finite element simulation in three dimensions, and will include a number of the 12-ft section of cast iron pipe and the bell and spigot joints.

4. Parametric studies

After the stress analyses of the gas mains at the Lurie Research Center site have been completed, parametric studies will be conducted to extend the range of loading conditions to which those pipes were subjected. The distortions that would cause failure in the pipes will be established on the basis of these analyses.

Further parametric studies using a continuum approach will be made to extend the results of the study to other common materials used as gas main pipe.

This project runs from April 1 to September 30, 2002. It covers the first six months of a planned two-year project. Data collection, completion of the literature search, and stress analyses of the mains will begin during this six-month project. During this time, the stress analyses will focus on the initial stress conditions and development of the detailed finite element model of the gas main.

Current Year = $69,115 3-Year Total = $69,115

Two graduate students will work on the project this budget period and will focus on the literature search and analyses of the gas mains. Other students funded from different sources are also working on this project, including Jill Roboski, a PhD student, is responsible for the evaluation of the field data, Michele Calvello is finishing up his PhD and is focusing on the finite element studies, especially the automatic updating of parameters based on observed field responses, Terence Holman, a PhD student, who is working on defining the small strain behavior of the compressible glacial clays. These students will interact with the two new students working on the gas main aspects of the work.

This is the first six months of a proposed two-year project.

We propose to present our results to an advisory board consisting of practicing engineers, contractors and owner’s representatives to provide review for the results of the research and to assure that the results are relevant to engineering practice. This board has been formed as part of the PI’s National Science Foundation grant entitled "Objective updating of design predictions for supported excavations using construction monitoring data." This board meets annually, and the results of this work will be presented to them as part of the annual meeting.

The principal investigator will present the results of the study to professional societies both locally and nationally. Papers will be submitted to journals and future conferences to further disseminate the findings.

There are no universal guidelines for allowable deformations for buried pipes adjacent to supported excavations. The excavation for the Lurie Research Center represents a unique opportunity to develop much needed field performance data to evaluate the effects of excavation-induced ground movements on the in situ behavior of gas mains. When coupled with a detailed stress analysis of the gas main pipes, this data can be used to define safe limits of excavation-induced movements. The stress analyses will allow one to use the detailed field observations as a basis for more general recommendations.

Deformation, Excavation, Gas Utilities, Infrastructure

A451

Improved Condition Monitoring of Bridges: Nondestructive Evaluation of Foundations

Richard J. Finno
Northwestern University
847-491-5885
r-finno@northwestern.edu

The objectives of this project are to extend the guided wave theory to flexural wave propagation in piles and both longitudinal and flexural waves in embedded plates (representing slurry and soil mixed walls), and to continue refinement and field verification of the guided wave, longitudinal wave identification (LWI) and shear wave identification (SWI) methods.

The purpose of this project is to develop methods to non-destructively evaluate the condition of existing deep foundations and bridge piers. With previous support, a drilled shaft test section for non-destructive evaluation has been established at the National Geotechnical Experimentation Site (NGES) at Northwestern University. Experimentation at this test section and subsequent analysis and numerical simulation have defined the limits of the ability of the impulse response technique to evaluate damage to drilled shafts in both accessible and inaccessible head conditions.

This project will focus on three main areas, (1) theoretical development of the guided wave approach to consider flexural wave propagation and to consider guided waves in embedded plates, (2) continued development of the prototype system to induce and measure guided waves, and (3) continued development of the LWI and SWI methodology.

1. Theoretical developments

We will extend the guided wave theory to look at flexural wave propagation in drilled shafts and piles, which we believe to be important because of the success we have had with the shear wave identification (SWI) test. The theory will allow us to explore the limits of the approach we have developed for shear waves, much like we have done for longitudinal wave propagation in conventional impulse response tests. Application of the developed theory may also allow us to enhance the SWI methodology.

We will extend the guided wave theory to embedded plates so that we can develop techniques applicable to in situ walls, such as structural slurry walls or soil-mixed walls, that comprise part of many excavation support systems.

The question of integrity of these wall systems arose a number of times during construction of the Central Artery / Tunnel project in Boston. We will develop solutions for longitudinal and flexural wave propagation in embedded plates.

2. Continued development of the prototype system to induce guided waves

(1)    conduct laboratory verification tests of the system. We will continue to test the prototype piles in the laboratory in a free condition to develop methods to identify small defects. We are in the process of simultaneously measuring response with multiple accelerometers to help identify the mode of vibration. We also will explore the using a triaxial accelerometer for the same purpose.

(2)    trial and optimization of the developed technique for the prototype piles installed at the National Geotechnical Experimentation Site at Northwestern. We also plan to test the piers at the Sturgeon Bay Bridge.

3. Continued development of the LWI and SWI methodology

We will develop real-time data reduction schemes so that reflections can be identified in the field, rather than in a remote location after the data has been collected, as was done for the Port Heuneme project for the Navy. We will conduct additional field tests to verify the methods. We are currently negotiating with the Navy to continue our work at the Port Heuneme Site that was cut short by the events of Sept. 11. We will also test these methodologies on the piers at the Sturgeon Bay Bridge.

The Lurie Research Center construction project at Northwestern University’s campus in Chicago also provides the opportunity to apply these techniques on wooden piles. The Center is being constructed on a site where a building supported by wooden piles was demolished, the lengths of which are unknown. We will conduct LWI and SWI tests on the piles when the upper portions of them are exposed during the excavation process. Since the wood type is not known, the propagation velocities also are unknown, and the LWI and SWI methods, with the 2 transducers placed on the sides of the piles, will allow us to measure the propagation velocity directly and hence determine the lengths of the piles.

The work for this project will take place from April 1 to September 30, 2002. Given the relatively short duration covered by this proposal, all tasks will occur simultaneously.

Given that the weather between April and September should be conducive to field testing locally, these portions of the work also will take place throughout the duration of the proposed work.

Current Year = $65,158 3-Year Total = $234,292

Hsiao-Chao Chou is expected to finish his PhD dissertation this summer. Helsin Wang , also a PhD student, is also working on the project.

Continuation of earlier project

In 1996, 1997 and 1999, the P.I. taught "Foundation Evaluation with NDE Techniques," part of a wider course entitled "Nondestructive Evaluation of Bridge Conditions," for the University of Wisconsin-Madison Department of Engineering Professional Development. He expects to teach the class again in 2001, and will continue to do so as the opportunity arises.

The PI will continue to participate in the User’s Group meetings for the Bridge Project.

Publication of results in journals and conference proceedings also will continue. H.-C. Chou will soon finish his PhD thesis and a number of papers describing the guided wave approach and verification of the theory will soon be submitted for publication.

A multiple geophone method has been developed which minimizes the effects of the surface wave reflections from intervening pile caps at the NDE test section. The impulse response technique with and without multiple geophone arrays has been used in the field at a number of bridge sites. A theory based on guided waves, describing the relation between frequency and group velocity of frequency-controlled excitations, has been developed to allow higher frequencies to be used to evaluate shafts, and, consequently, to identify smaller defects than possible with conventional techniques. In addition to the guided wave work, we have developed new methods to test piles in the field, termed longitudinal wave identification (LWI) and shear wave identification (SWI) tests, where intervening structure prevents use of impulse response techniques.

Bridge Management Systems, Infrastructure, Monitoring, Nondestructive Testing

A452

Improved Condition Monitoring for Bridge Management

David Prine
Infrastructure Technology Institute
847-491-2873
dprine@northwestern.edu

The objective of this program is to provide bridge owners with a set of advanced NDE tools so that they may better (more quantitatively and with improved repeatability) determine bridge condition, which is the primary input to a bridge management system. These tools will consist of both equipment and procedures to aid in the inspection of critical bridge components.

This project will continue the development of active monitoring technology for our remote monitoring sites, student / faculty support, large bridge instrumentation and testing, and user group activities. The project team’s student / faculty support activities continue to represent a major portion of the total staff time.

Growth of the remote monitoring technology that was started during Year 3 with the Michigan Street Bridge in Sturgeon Bay, Wisconsin will continue to be a major activity. Content will be expanded on the web page for the Sturgeon Bay remote monitoring site. The project expects to complete installation of the new fully tested instrumentation system on the Michigan Street Bridge in April or May 2002, and have the automated website up and running thereafter. Data processing / communications software that was developed and tested in the laboratory will detect and alarm for conditions set on pre-selected data thresholds, sending alerts via cell phones / pagers or other communication devices. This software, based on previous developments for the autonomous crack monitoring project and developed by one of the project’s computer science students, is ready to be installed at the Horse Creek remote site near Yreka, California.

Future strain gauge, remote monitoring, and data analysis work of the type done in 2001 when assisting Lichtenstein Associates in conducting load tests on the Hoan Bridge in Milwaukee, Wisconsin is anticipated. Current estimates by FHWA indicate that nationwide, over 400 bridges contain details similar to the Hoan Bridge, which experienced a major failure in one of its approach spans in 2000.

The user group development effort will continue its strong involvement with the user community through meetings, newsletters, and electronic communications via the Internet. The project team closely coordinates user group efforts with the Mid-West Bridge Maintenance and Inspection (BMI) working group, and applies new technologies (e.g., H.323) that allow low cost multi-point teleconferencing over the internet which can reduce DoT meeting and travel costs.

The field tests and demonstrations allow for development and refinement of the bridge monitoring technology. It also helps to forge working relationships with practitioners and provides a vehicle for strengthening the integration of the ITI staff/NU faculty team members by providing opportunity for field verification of newly emerging technology. The increased student involvement in this activity exploits the educational opportunities offered by providing hands-on experience by students under real field conditions and is becoming a major growth area. Both of these tasks (Users Group and Field Tests) also are the main marketing vehicles for additional commercialization efforts in the service area.

1. Field Tests and Demonstrations

This task is a continuation and expansion of the ongoing efforts in this area. A major portion of the effort will be focused on the continuation of the demonstration and evaluation of the remote monitoring technology that emerged in previous years’ work. We will have the Sturgeon Bay lift bridge on an automated net site during the coming year and our first active bridge monitoring system will be "on-the-air". We anticipate considerable more work using acoustic emission (AE) in the coming year. The Bryte Bend retrofit project is projected to begin during summer of 2002. Our efforts in this program will consist of applying and further refining the AE technique we developed during the retrofit design and evaluation. We will evaluate approximately 12 to 15 cross-frame connection sites prior to and immediately following retrofit to assess the effectiveness of the retrofit in alleviating fatigue crack growth. This project will also allow us to gain experience with recently acquired waveform pattern recognition software. We are negotiating with Hardesty and Hanover, a consulting firm out of New York, to perform AE testing on the roof of Miller Park the new baseball park in Milwaukee. The problem is to locate the source(s) of loud noises that occur during opening and closing of the roof.

2. User Group Development

The user group development work that was started in Year 1 and continues through the subsequent years is a vital part of this program. It continues to provide guidance to the NU researchers and a valuable source of information exchange between bridge engineers from the various states as well as keeping the bridge engineers informed of the developments of our NU researchers. Specific activities will include the application of the H.323 teleconferencing technology to special topical meetings between NU researchers and various deployment partners, participation in various committees and working groups that are organized by other infrastructure and NDE groups, and Internet activities. Additionally, we plan to archive selected presentations and make them available for free by mail (CDROM) for practitioners that do not have fast internet connections available. We will also continue to support the BMIWG meetings with this technology where appropriate.

Task 3. Educational (EDC) Activities

This task will aid the development and growth of the educational activities started in previous years. We will continue to organize and support educational tours to various infrastructure-related locations (fabrication facilities, historical bridges, construction sites, etc.). Students and faculty are invited to participate in our field test efforts on a regular basis. ITI staff also actively supports student activities such as the AISC/ASCE Steel Bridge Competition. During 2000 we made successful use of the freshman engineering design course participants and we plan to continue to utilize this valuable resource. Both ITI and the students receive considerable benefit from these projects. The EDC projects provide these students with valuable hands on project experience with the potential of greatly expanding the capabilities of our small bridge team staff.

April 1 to September 30, 2002

Current Year = $178,418 3-Year Total = $696,645

We anticipate that both faculty and student involvement in the field test program will continue to increase dramatically. This effort has been aided by publishing notices of impending fieldwork and inviting both faculty and student participation.

Additionally, we also attempt to employ students (either work study or as temporary part-time employees) wherever possible. We also expect to continue to provide support for graduate students who are involved with research activities under the direction of our faculty partners.

During the last year’s effort the emphasis was on development of active monitoring technology for our remote monitoring sites, student / faculty support, large bridge instrumentation and testing, and user group activities. These activities will continue during the coming year. Our current student/ faculty activities continue to represent a major portion of total staff time. Growth of the remote monitoring technology that was started during Year 3 with the Michigan Street Bridge in Sturgeon Bay, Wisconsin continued. This year’s efforts have further solidified ITI’s leadership position in this area.

Two marketable products have emerged from this work. They are an improved acoustic emission bridge monitor (AEBM), and test services. The test services include application of advanced NDE such as AE, Impact Echo, TDR, and strain gauges as well as the installation and maintenance of remote monitoring systems. In year five a new approach to scour monitoring emerged which has achieved acceptance at Caltrans and resulted in a major change in their approach to solving this problem based on the ITI developed technique. This is an excellent example of successful technology transfer.

The current economic downturn has had an adverse impact on the budgets of state transportation agencies, which in turn will negatively impact our revenue. Out-of-state funding has become increasingly difficult to attain. Furthermore decentralization with the accompanying demise of the central DoT office hasn’t helped matters. The decentralization has been accompanied by an increasing dependence on consultants. We have successfully worked with major consulting firms such as Hazlet and Erdal, Wiss Janey Elstner, Michael Baker, Lichtenstein, and recently Hardesty and Hanover. We will continue to pursue and strengthen relationships with these organizations as well as actively pursue new state and municipal partners. A high and growing level of user community involvement is key to maintaining and expanding the market and insuring relevance.

A major contribution to improved condition monitoring of critical infrastructure has been made through the development of remote monitoring technology under this program. The first application occurred in 1995 in Sturgeon Bay, WI. Since then great strides have been made in system complexity and improved reliability. The numbers of long term sites and applications have continued to expand primarily because this technology addresses a need that is readily recognized by the infrastructure owners. Safe economically practical life extension of critical portions of the infrastructure demands improved condition monitoring and the remote technology provides a solution to this growing need particularly when one considers the added problem of downsizing imposed on the owners and operators by budget shrinkage. The ability to interrogate a remote site without actually sending an inspector out to the site is an obvious improvement over present methods. Overall system reliability has made order of magnitude improvements since the early days of the Sturgeon Bay system. It is now possible because of improvements in software to perform some diagnostics and maintenance of the monitoring system without dispatching an engineer to the site. As the technology evolves and our experience increases, system reliability will continue to improve but it still has a long way to go before the smart structure becomes a widely accepted reality.

We are closely coordinating our user group efforts with the Mid-West Bridge Maintenance and Inspection (BMI) working group. At three meetings of the BMI group we successfully applied new technology (H.323) that allows low cost multi-point teleconferencing over the Internet. We also used this technology for a seminar and an all day short course. The response to this technology has been very positive. We see H.323 technology as a potential solution to the travel problems that typically plague state dot workers and greatly hinder the timely interchange of information and ideas. The conferencing equipment is easy to use and relatively low cost ($4,000). Devices suitable for single person usage are available for $600 or less. The use of the Internet eliminates the high connect time costs that are part of the current DSL technology and allows much greater flexibility.

Bridge management systems, Infrastructure, Monitoring

A453

Life-Cycle Management of Steel Bridges Based on Non-Destructive Testing and Failure Analysis

Brian Moran
Northwestern University
847-491-8793
b-moran@northwestern.edu

Jan Achenbach
Northwestern University
847-491-5527
achenbach@northwestern.edu

Ed Rossow
Northwestern University
847-492-3453
e-rossow@northwestern.edu

The thrust of the project is to develop an understanding of failure mechanisms in pin-hanger connections in steel bridges and to develop guidelines for the assessment of the structural integrity of the connections.

In the project to date, a variety of finite element stress analysis and fracture mechanics templates were developed and/or customized for understanding failure mechanisms in pin-hanger connections in steel bridges. Two failure mechanisms are being investigated: 1) locking of the free rotation of the pin and failure due to plastic collapse or overload, 2) fatigue crack propagation due to thermal stressing with the eventual attainment of a critical flaw. Results for the first of these cases were obtained for the case of a Wisconsin Dells bridge and associated pin-hanger geometries and dimensions. These results indicate that the contact algorithms and the thermal stress aspects of the modeling have been correctly implemented and that they give accurate results in benchmark tests. Results also indicate that when lock up of both the upper and lower pins occurs, extensive plastic yield occurs in the pins and in the hanger. When only the lower pin locks up (the tendency is for corrosion lock up to occur first in the lower pin) significantly lower stress levels occur. A tentative outcome of this study (which we will further investigate in the early portion of the continuation) is that lock up of both pins is unsafe and lock up of the lower pin only is safe but requires monitoring of the upper pin to assure that the connection still functions adequately.

In the continuation we will carry out an analysis of fatigue crack growth in the pin and carry out risk assessments to determine failure probabilities with and without NDE inspection.

1. Complete the stress analysis of pin-hanger assembly

The assessment of corrosion induced lock-up in the Wisconsin Dells bridge pin/hanger assembly will be completed.

2. Carry out assessment of fatigue crack growth in pin –- Use of X_FEM

The analysis of cracks at safety critical locations in the pin will be carried out using standard three-dimensional finite element analysis, including detailed meshing of the crack surfaces. This will provide us with an initial estimate of fatigue crack growth characteristics in the pin. It is proposed to use the X-FEM methodology for detailed fatigue crack growth studies. The standard finite element calculations will also provide a benchmark for the X-FEM calculations. The X-FEM method will be implemented for application to practical 3D components such as bridge pins. The main theoretical developments and numerical developments of the method have been carried out in separately funded projects supported by NSF and ONR. David Houcque will work closely with Professor Moran’s post-doctoral associates and students on these projects to implement the method for bridge pins. The superelement procedure whereby the X-FEM is linked to a commercial code is currently being developed under FAA support. David Houcqe will implement this procedure for the pin/hanger problem. This will involve the development of suitable programs to model the crack geometry and the coupling of the geometry and enriched shape functions with the standard finite element program.

One issue that may need to be addressed in this analysis is whether the contact conditions change substantially during growth of the fatigue crack. This may complicate the analysis and the interface between the X-FEM and commercial (ABAQUS) codes. It may be necessary to carry out intermittent crack analyses without the use of X-FEM to assess and/or update the contact conditions.

3. Carry out risk assessment

A probabilistic fracture analysis of fatigue crack growth in the pin will be carried out using the computational fracture methodologies mentioned above along with First Order Reliability Methods developed by the PIs. The POD curves used will be guided by measurement models. The outcome will be a probability of failure (due to fatigue) with and without inspections. This will permit us to assess the likelihood that pins fail in fatigue.

Quarter 1: April 1- June 30

The elastic-plastic analysis for the bridge pin and a report/paper on same will be completed. Fatigue crack modeling will commence and standard and X-FEM approaches to crack modeling in the pin will be implemented.

Quarter 2: July 1- September 30

Continue assessment of cracks in pin using standard FEM and X-FEM. Begin implementation of probabilistic fracture model.

Current Year = $61,535 3-Year Total = $209,264

Graduate student: David Houcque

The project is a continuation of the current ITI funded project "Life-Cycle Management of Steel Bridges Based on Non-Destructive Testing and Failure Analysis" (Moran and Achenbach).

A high level of interest has been expressed in the work with pin-hanger assemblies. Contacts are being maintained with representatives of State Transportation Agencies, particularly with Frank Reed (Cal Tran), Phil Fish and Finn Hubbard (Wisconsin Department of Transportation), Duane P. Carlson and Burt R. Thakar (Illinois Department of Transportation) and Mark Grunert (Nevada Department of Transportation). Ed Rossow will provide guidance in the presentation and communication of this work to the bridge engineering community.

The research is on the important topic of life-cycle maintenance of safety critical components in bridges. The work addresses issues pertaining to broad capabilities for general application as well as specific issues pertaining to the development of a further understanding of the failure of bridge pins and, ultimately, how these pins can best be monitored and failures avoided.

The research for this project is based both on our original vision of the development of a methodology for life-cycle maintenance based on QNDE and life-prediction and also on insight and direction obtained during the project to date. With respect to the latter, the proposed pin lock-up model and finite element simulations are a consequence of expressed interest in the results of the simulations by ITI personnel and state DOT bridge engineers.

Types of bridges by material, Bridges, Infrastructure, Bridge management systems, Nondestructive testing, Steel, Failure analysis

A454

Further Commercialization of NUCu Steels

Morris E. Fine
Northwestern University
847-491-4322
m-fine@northwestern.edu

Semyon Vaynman
Northwestern University
Svaynman@northwestern.edu

1. Illinois Department of Transportation

2. Office of Naval Research

3. AISI/FHWA/US Navy HPS Steering Committee

The main objective of this project is to achieve further commercialization of NUCu 70W HP steel in bridges and in other applications. The American Iron and Steel Institute (AISI)/FHWA/US Navy Steering Committee on High Performance Steel has identified states that are considering the use of high-performance steel in new bridges. Our objective is to have NUCu steel used in some of these bridges.

NUCu steel has been specified for use in a new bridge over the Kaskaskia River near Vandalia, IL. Our objective is to help this application by providing support to IDOT, the selected steel producer and bridge fabricator during planning and construction of the bridge.

Several years ago the FHWA and the Navy identified a need for a high performance weatherable structural steel that would have a 70 Ksi yield strength (compared to 50 Ksi yield as in the micro-alloyed steels in common use). Lower C content for improved welding and high fracture energy at cryogenic temperatures was desired for this steel. More recently a new target of 100 Ksi yield stress was identified. Under the auspices of a FHWA/Navy/ AISI Steering Committee a new steel designated ASTM HPS 70W was developed. For the higher yield strength target Lehigh received a large contract to develop such steel and the needed structural design criteria. Both steels are martensitic steels and require rapid cooling followed by tempering. This is the traditional way the high strength steels are made.

At Northwestern several years after the development described above began, a different approach was taken to meet the target steel. Our approach was to meet the requirements by a combination of Cu precipitation hardening and grain refinement by niobium carbides. NUCu 70W steel that is air-cooled after hot rolling resulted. It has a number of advantages over the ASTM HPS 70W. The processing is simpler because a quench is not required. It has a lower equivalent carbon content and, therefore, has better weldability. It has a remarkably high fracture energy at cryogenic temperatures. It has substantially better weathering resistance than HPS 70 W steel or other weathering steels. Our current and proposed efforts are to develop markets for NUCu 70 W steel. Eighty thousand pounds of NUCu steel were used in rehab of the Poplar Street Bridge near St. Louis and it is specified for a new bridge to be built in Illinois as described below.

Under sponsorship of the Office of Naval research the precipitation hardening approach is being investigated as an alternate approach to a martensitic steel for the 100 Ksi yield stress steel target. A small laboratory heat of copper-NiAl co-precipitation hardened steel has met the 100 Ksi yield strength target. The ONR support terminates this June and we propose to market this steel to steel companies for further development.

Use of NUCu 70W Steel for New Bridge Construction over Kaskaskia River near Vandalia, IL

IDOT received approval to use NUCu steel for construction of the girders for a new bridge over the Kaskaskia River near Vandalia, IL. The contract is expected to be let in June 2002. IDOT specified NUCu 70W steel for both the 1-inch-thick webs and 1-1/2 in thick flanges. After the steel producer has been selected and the steel has been ordered we will provide guidance to the successful bidder on the steel production as well as monitor production of the steel. After assurance the specifications have been met and the steel has been shipped to the fabricator for manufacture of bridge components and installation in the bridge, we will advise on welding procedures and other phases of this project. The details will be recorded, analyzed and summarized in a report.

Preparation of a Brochure

When all of the data for steel plates recently hot rolled at US Steel Company and North Star Steel Company are available, we will prepare a marketing brochure that describes NUCu 70W steel and gives its properties. A comparison will be made with the competing Q and T (or TMCP) 70W steel developed under the AISI/FHWA/US Navy Program. The advantages of our steel over the competing steel are superior weldability, superior weatherability, less complicated processing and higher impact fracture energy at cryogenic temperatures.

Marketing of NUCu Steel for Bridges in Other States and in City of Chicago

We will further continue our marketing efforts of the steel with other states and with the City of Chicago for use in bridges. We have already contacted bridge engineers in a number of State DOT's to propose use of NUCu steel in new bridges. Ohio State DOT is considering the use of high-performance steels in some bridges. On their request Stupp Bridge Company, Bowling Green, KY welded together plates of NUCu 70W steel hot rolled at USS Gary for a Process Qualification Requirements (PQR) test

Recently AISI and FHWA identified a number of states that are planning to use high-performance steel in future bridges. We have begun to contact these states’ DOTs pointing out the advantages of NUCu 70W steel. We expect to visit many state DOTs in the next 6 months.

Pennsylvania uses unpainted weatherable steel for bridges. Since weatherability of NUCu steel is significantly better than that of any available steel on the market, we will contact Pennsylvania DOT.

Chicago DOT uses painted steel for bridges. We were previously in contact with CDOT about the use of NUCu steel for decks in Chicago bridges. We will provide CDOT with our new data on performance of painted steels and will further discuss with them the application of NUCu steel.

The recent brittle fracture bridge catastrophe in Milwaukee has increased the awareness of bridge engineers that attention has to be paid to fracture toughness of load carrying components over the temperature range experienced by the bridge. In northern states as discussed above the temperature falls considerably below the –10oF for zone 3 in the A709 specification. We have become experts in this field and plan to look into the possibility of assisting on fracture toughness problems in bridges and selection of high fracture toughness steels, especially at ultra low temperatures.

Participation in AISI/FHWA/US Navy High Performance Steel Program

Participation in the AISI/FHWA/ US Navy High Performance Steel Program is very important in our efforts to promote increased use of NUCu steel. As before we will actively participate in the quarterly meetings of this Committee in Washington, DC. We will work with this committee in further development of NUCu steel. Specifically, we will attempt to secure assistance from this committee to further develop and commercialize the 100+-ksi-yield, fracture tough, weldable and weatherable Cu/NiAl precipitation strengthened steel as an alternative to the Q & T 100+ Ksi yield strength steel developed under the committee’s sponsorship.

Additional Studies of NUCu Steel Sponsored by IDOT

IDOT is sponsoring a project entitled "Development of machining parameters as well as techniques for measuring the machinability and punchability of High Performance Steels" at Advanced Sciences, Inc., Cincinnati, Ohio. This important study will include NUCu steel among other high performance steels. The results will be sent to us and we will use them in our marketing efforts.

Marketing of NUCu Steel with US Steel Company toward infrastructure and non- infrastructure application

Since US Steel Company does not have facilities for thermo-mechanically-controlled processing (TMCP) of steel plates, they are very much interested in production of NUCu steel because of its simpler processing (air cooling from hot rolling). Additional studies will be made at USS Research Center, Monroeville, PA. The results of these studies will be given in a paper to be presented at the International Iron and Steel Society Symposium on Microalloyed Steels that will be held in October 2002. The paper will be co-authored by US Steel engineers and us.

Work with North Star Steel Company and Caterpillar toward marketing of NUCu Steel

We will continue looking into NUCu steel for non-infrastructure applications. North Star Steel Company produces steel shapes for special applications such as light and power poles and hoist and derrick beams. They have rolled the 4-inch-thick slabs that they bought and are evaluating the steel for such applications.

Caterpillar is interested in NUCu steel because it combines weldability with high strength, excellent fracture toughness and corrosion resistance. Research will be done at Caterpillar to investigate the steel during laser cutting and welding.

April - June, 2002

1. Work with US Steel, North Star Steel and Caterpillar Companies on further evaluation of NUCu Steel.

2. Prepare brochure.

3. Work with IDOT on marketing of steel in Illinois.

4. Contact State DOT’s, Chicago DOT to discuss the use of NUCu steel.

5. Participate in AISI/FHWA/Navy Committee on High Performance Steel.

6. Continue work on modified 120-ksi-yield NUCu steel (if project is funded).

7. Prepare manuscript for International Iron and Steel Society Symposium on Microalloyed Steels.

July - September, 2002

1. Contact steel producer and fabricator for Kaskaskia bridge. Discuss details for steel production.

2. Analyze data from welding and machining studies sponsored by IDOT.

3. Continue work with US Steel, North Star Steel and Caterpillar Companies on further evaluation and marketing of NUCu Steel.

4. Continue steel marketing to State DOT’s, to other agencies for non-infrastructure application

5. Continue work on modified 120-ksi-yield NUCu steel (if project is funded).

6. Study effects of temperature on NUCu steel (if project is funded by IDOT)

7. Participate in AISI/FHWA/Navy Committee

Current Year = $26,572 3-Year Total = $143,303

Our proposed work for the next six-month period is a continuation of work begun during the prior year. Everything we propose follows from work done during year 2001 and the first 3 months of 2002.

Many of our proposed activities are of the technology transfer category. These include arranging for manufacturers and users to develop data on NUCu 70W steel. The technology transfer will continue through publications, reports, presentations and personal contacts. We will continue to collaborate with IDOT and participate in the FHWA/AISI/US Navy HPS Steering Committee. This Committee includes steel producers, bridge engineers and representatives from FHWA and the Navy in its membership. We will work to expand the group of potential users that we are in contact with.

IDOT has recommended use of NUCu steel in the construction of a new bridge in Illinois. US Steel Company or Oregon Steel Mills will produce the steel. Both of these companies are familiar with NUCu steel since they previously produced NUCu steel in production heats or laboratory heats. We frequently exchange information with engineers at both steel companies. We are in contact with engineers at other steel companies through the AISI/FHWA/Navy Steering Committee. Our involvement with IDOT will continue and contact with other state DOT's and Chicago DOT has been established and will be expanded.

During 2001 we established working relationship with North Star Steel and Caterpillar. We will work closely with them to market NUCu steel for non-infrastructure application. Also we will target other steel, construction and manufacturing companies.

We plan to prepare a brochure that describes NUCu steel and its properties as well as its advantages over other high-performance steels and its use in the bridges. This brochure will be distributed to the steel producers, fabricators and to the users community.

Also we will participate in conferences and workshops. We and two collaborators from US Steel Company will present a paper at International Iron and Steel Society Symposium on Microalloyed Steels.

NUCu steel is attractive to steel companies because of its excellent mechanical and weathering properties combined with simpler processing than for ASTM A709 HPS 70W. This gives our steel a competing edge.

Since the bridge steel market is considered a small one, use of NUCu steel for applications besides bridges increases the interest of the steel manufacturers to market our steel. There is interest in high-performance steels for navy ships, tank cars, pipes, pressure vessels, construction, etc. We will continue to target these markets through presentation of papers at conferences and through the direct contacts with different companies. We have been invited to present a paper at an Iron and Steel Society Conference in a session concerned with railroad tank cars. A current problem is brittle fracture at low temperatures.

Steel, Bridges, Infrastructure

A455

The ICCML as a Novel Teaching Tool to Improve Undergraduate Education and Student Learning of Civil Engineering

Prof. Roberta Massabò
Northwestern University
847-467-4105
r-massabo@northwestern.edu

The objectives of this project are the following:

1. Develop new material and innovative pedagogy to enhance the learning of civil engineering within undergraduate curricula using the ITI and Northwestern University Department of Civil and Environmental Engineering’s Infrastructure Construction and Condition Monitoring Laboratory (ICCML). This will be achieved through the development of a new short course or new content for existing undergraduate courses and laboratories. Focus will be on structural engineering concepts.

2. Improve the existing web site of the ICCML through the incorporation of new case studies and material.

3. Investigate the possibility of using the ICCML to enhance the interest of young students toward civil engineering.

This project is the first stage of an anticipated one and one-half year program to investigate the feasibility of using the Infrastructure Construction and Condition Monitoring Laboratory (ICCML) of the Infrastructure Technology Institute (ITI), its web site, and its remotely operated web-camera as a novel teaching tool to improve undergraduate education and student learning of civil engineering. A new course or new content for existing undergraduate courses within the civil engineering program will be developed with the aim of creating a more effective learning environment and bringing knowledge from the infrastructure / building industry to university curricula. The feasibility of using the ICCML to attract young students from middle school to join civil engineering programs will also be investigated. The existing web site of the ICCML will be improved with the incorporation of new case studies and material.

This project will be the first phase of the larger project. Specific tasks include:

1. PI will learn about the ICCML, its web-site and remotely operated camera
2. Investigate how material already available could be used within civil engineering courses
3. Explore the current use of new media and new technologies in university teaching (e.g., web-based teaching, virtual reality based teaching, etc.) aimed to reach students with different learning styles and to increase knowledge retention
4. Collaborate with ITI to identify other construction sites to include in the program

April 1 to September 30, 2002

Current Year = $12,283 3-Year Total = $12,283

This initial phase of the project will be conducted by the PI. The anticipated follow-on project will be executed by a graduate student in collaboration with the PI at the Department of Civil and Environmental Engineering of Northwestern University.

This is the first six months of a proposed one and one-half year project.

The results of the project will be used as a vehicle to transfer knowledge from the building / infrastructure industry to undergraduate curricula, and to offer undergraduate students a tool for active learning and the opportunity of being "virtually" present on sites of otherwise restricted construction projects.

The potential of the ICCML, its web site and remotely operated web-cameras is enormous. The cameras can offer remote access to construction sites that would otherwise be restricted. They allow virtual presence on sites of large and interesting construction and retrofitting projects, in different locations in the United States and during critical times of the construction. Free access to the information incorporated in the web site can provide learning opportunities on building and infrastructure design, construction, maintenance and retrofitting, on new monitoring technologies and on management of large projects and public infrastructures. The results of the project will be used as a vehicle to transfer knowledge from the building/infrastructure industry to undergraduate curricula, and to offer undergraduate students a tool for active learning and the opportunity of being "virtually" present on sites of otherwise restricted construction projects.

Education and Training, Civil Engineering, Virtual Reality, Infrastructure

A456

Introducing Size Effect Into Design Practice and Codes for Concrete Infrastructure

Prof. Zdenek P. Bazant
Northwestern University
847-491-4025
z-bazant@northwestern.edu

The overall objectives of the project are:

1. Capitalizing on two decades of basic research funding of the principal investigator (PI)’s research of size effect at Northwestern University, demonstrate practical applications to design and testing.
2. Based on the general theory already developed, construct simple design formulae for the size effect in various basic type of failure, suitable for use in design firms.
3. Work in engineering societies, particularly ACI, RILEM and FIB (AASHTO co-opts their approach), to introduce changes in the respective code articles, one by one, beginning with the diagonal shear failure of reinforced concrete and with the flexural failure of plain concrete.
4. Formulate a statistically correct structure of load factors for the code, suitable for use after the size effect is taken into account in code provisions.
5. Formulate test procedures for concrete strength and fracture taking the size effect into account, and propose improved testing standards to ASTM and RILEM.
6. Articulate the reasons and promulgate the necessary changes by tutorial presentations at conferences.

This is the first six months of a proposed three and one-half year project that will focus on the introduction of size effect, and along with it fracture mechanics background, into practical design and codes for concrete structures. This is important not only for large-span pre-stressed concrete box bridge girders and box girders of cable-stayed bridges, but also for the supporting piers and foundation plinths, as well as for road and airport pavements, earth-retaining walls, tunnel linings and dams (which often carry highways).

The design practices for ductile failures are not affected, but those guarding against brittle failures, which currently still are based on the plasticity based theory of limit states, need to be updated for size effect according to fracture mechanics and random strength statistics. The basic theory (summarized in the principal investigator’s two recent books) is now ripe for practical application. However, simple design formulas for particular design problems need to be developed and proper material testing procedures instituted. Moreover, clear and convincing articulation for the need for updates to codes will need to be made to the relevant committees of ACI, RILEM and FIB (followed by AASHTO).

Major tasks for these six months of the project are:

1. As a member of ASTM Committee C-04 (Concrete) and subcommittee on strength testing, argue for the proposed new modulus of rupture test updated for size effect, and prepare an improved formulation of the standard.
2. As a member of ACI Committee 447, Shear and Torsion, prepare a proposal for an improved design formula for designing against the diagonal shear failure of beams, and articulate the reasons for it.
3. As a member (and founder and former chairman) of ACI Committee 446, Fracture of Concrete, argue for a sound method for the fracture energy test, a correct method from the size effect viewpoint (the result should be a recommendation from this committee to ASTM). Present convincing arguments at the upcoming ACI convention in Detroit. Prepare a statistical study justifying the proposed testing method and evaluation procedure.
4. As chairman of the RILEM Committee QFS, Quasibrittle Fracture Scaling, work on the state of art report and incorporate in it sound recommendations on the size effect in reinforced and plain concrete structures, based on the theoretical researches at Northwestern.
5. Present a paper at the First International Conference on Bridge Maintenance, Barcelona, July 2002 (chaired by D. Frangopol) on the need to revise the structure of load factors for bridges, particularly the load factor for self weight, and do it in tandem with the introduction of size effect (this is an invited paper).
6. Initiate a statistical study aimed at rational prediction of failure loads of an extremely small failure probability, which would agree with extreme value statistics and could conceivably replace the empirical load factors current used in the design codes for buildings and bridges.
7. Present a paper at ACI Detroit on the confining reinforcement of reinforced concrete (tied, spiral and tubular) columns (including bridge columns) that is needed to suppress strain-softening response of concrete and thus to eliminate size effect.
8. As member of the US National Committee on Theoretical and Applied Mechanics, collaborate on the Committee’s goal of finding ways to improve the transfer of theoretical results into practice (the main topic on the agenda for the upcoming meeting of the Committee at VPI in June).
9. As chairman of the NSF International Workshop on Durability (Prague, July 2002), steer the Workshop to focus, among other problems, on durability of bridges (often impaired by fracturing).

April 1 to September 30, 2002

Current Year = $60,388 3-Year Total = $60,388

Postdoctoral: Dr. D. Novak or Dr. I. Carol

Graduate Research Assistant: G. S. Pang

This is the first six months of a proposed three and one-half year project.

Much of the focus of this project is on technology transfer through advancing updates to codes, advancement of new design and testing methods, and presentations at conferences. The PI will be active in the relevant committees of ASTM, ACI and RILEM. Activities include promoting new and updated codes, design recommendations and testing methods as part of the ASTM Committee C-04 (Concrete) and subcommittee on strength testing; ACI Committee 447 (Shear and Torsion); ACI Committee 446 (Fracture of Concrete); RILEM Committee QFS (Quasibrittle Fracture Scaling). Additional transfer activities include: presenting a paper at the First International Conference on Bridge Maintenance; presenting a paper at ACI Detroit; and collaborating on the U.S. National Committee on Theoretical and Applied Mechanics’ efforts to find ways to improve the transfer of theoretical results into practice (main topic of June 2002 meeting).

According to the classical theories of failure such as elasticity with a strength limit of plastic limit analysis, a structure fails when the maximum stress reaches a certain critical value that is independent of structure size. This simple concept is valid for many situations, for example the bending failure of a steel girder or the failure of tensile reinforcement in a reinforced concrete beam. In modern concrete structures, however, there are many situations where this simple concept breaks down and the apparent material strength (or nominal strength) decreases with increasing structure size. This is called the size effect.

There are two physical causes of size effect: 1) the statistical cause, consisting in the randomness of material strength; and 2) the deterministic cause, consisting in the release of strain energy from the structure during crack propagation.

The basic theory of the statistical size effect, formulated by Weibull in 1939, is no longer believed to be the only explanation of the size effects observed experimentally in concrete structures. A theory is now generally accepted by the leading researchers that deterministic size effect exists and is in fact dominant for all quasibrittle materials, not only concrete, but also rocks, ice, tough ceramics and fiber composites. However, the theory has not yet penetrated concrete practice, especially not the design codes.

The basic theory of the deterministic size effect was developed largely at Northwestern by the PI, under a series of grants from NSF, AFOSR and ONR. It was presented in a recent textbook (Bazant and J. Planas, Fracture and Size Effect, CRC Press, Boca Raton 1998), and the advanced aspects in a monograph just published (Bazant, Size Effect on Structural Strength, Hermes-Penton, London 2002). The present project is aimed at bringing this new theory into practice.

Concrete, Infrastructure, Fracture Mechanics, Design Standards