A424

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

Charles H. Dowding
Northwestern University
(847) 491.4338
c-dowding@northwestern.edu

Clark Landfill - STS Consultants
Ted Buschell
Deerfield, Illinois
847.279.2473

INDOT -Division of Materials and Tests
Dan Chase
Indianapolis, Indiana
317.232.5280

IDOT - Materials and Physical Research
Riyad M. Wahab
Springfield, Illinois
217.782.7207

PennDOT - Department of Transportation
Ronald J. Clark
Uniontown, PA
274.439.7357

Field measurement of TDR cable sensitivity in soft soils can be accomplished by close monitoring of the response of the three 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.

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. An unexpected field response within the last 3 months has caused a shift in research emphasis. 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 emphasis from cable to composite.

It is especially 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.

While TDR-Tiltmeter instrumentation for active subsidence of I 70 does not involve soft soils, the importance of the project and ITI's interaction will combine to demonstrate the importance of instrumentation of critical infrastructure facilities.

1. Interpretation of cable-grout composite sensitivity in the field
2. Complete laboratory shearing of special and commercial large diameter braided cable
3. Develop a truly remotely operable instrument package for IDOT site
4. Install mine subsidence monitoring system
5. Install pier deformation monitoring system on I 57 over the Mississippi for IDOT

Three field projects are planned for late 1999 and 2000. First on line is the installation of instruments to assist PennDOT to monitor deliberate subsidence of I 70. Second on the calendar is the installation of tiltmeters on IDOT bridge piers leading to the I 57 bridge across the Mississippi. This system will need to be in place before the new year. Finally, it should be possible to schedule the deployment of a remote monitoring system on IDOT Rt 141 early this summer.

Quarter 1: Field measurement of TDR sensitivity, Shear cable/grout composite in lab, Install field remote operating system, Install/observe performance subsidence instrumentation, Install tiltmeters to monitor pier tilt.

Quarter 2: Field measurement of TDR sensitivity, Shear cable/grout composite in lab, Install field remote operating system, Install/observe performance subsidence instrumentation, Install tiltmeters to monitor pier tilt.

Quarter 3: Field measurement of TDR sensitivity, Shear cable/grout composite in lab, Install field remote operating system, Install/observe performance subsidence instrumentation.

Quarter 4: Field measurement of TDR sensitivity, Install/observe performance subsidence instrumentation.

Current year funding (incl. Indirect Cost) = $130,626

Bill Bergeson and another, unnamed graduate student will assist in field measurements and will complete laboratory testing of the compliant cable. 

Continuation of Geotech/TDR component of Condition Monitoring Thrust

TDR specific user community involvement was fostered through four mechanisms: workshops, demonstration projects, TDR-L email listserv, and installations and consulting by Dr. O'Connor. ITI and GeoTDR personnel have made presentations to the High Plains DOT Geotechnical Engineers Conference, Bridge Inspection Short Course at the University of Wisconsin at Madison, ASCE Geo-Institute yearly conference, and MIT.

Demonstration projects have been summarized elsewhere. They have mainly involved rock or stiff soils and therefore soil sites are a high priority. The LTV and CTA sites and some horizons in the INDOT sites represent unique opportunities.

The TDR listserv, 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.

Finally, 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 INDOT and CTA projects. In addition, through installation of the cables, he has provided the link between ITI researchers and IDOT for the rock causeway. Finally he was responsible for the interaction with PennDOT concerning the simultaneous use of TDR and tiltmeters to monitor controlled subsidence of I 70.

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

 A423

Minimizing Shrinkage, Creep and Cracking Damage to Concrete Bridges

Zdenek B. Bazant
Northwestern University
(847) 491.4025
z-bazant@northwestern.edu

The main objective of the present project and its proposed continuation is to build on the theoretical results of previous 20 years of theoretical investigations funded by NSF, EPRI and DoE, and introduce these results into the practice of design of bridges, as well as their maintenance and rehabilitation.

This necessitates translating the existing theoretical results into simple user-friendly algorithms or simple formulae, working out typical practical examples of calculations, presenting convincing comparisons with experiments, reducing sophisticated theoretical considerations to simple arguments preferably relying on graphical illustrations, analyzing the competing models and demonstrating their shortcomings or lack of agreement with test data, etc. This also means being active in the relevant committees of ACI and RILEM, attending the meetings, making arguments, attracting as members well educated young researchers who can vote intelligently, writing critical evaluation reports for various meetings and workshops, etc. Only in this manner can the balance in the relevant committees be slowly being tipped toward progress.

The ultimate goal is to achieve a significant revision of a number of specifications of AASHTO and other appropriate societies, as described in previous two proposals.

Although, as pointed out at the onset of this project, the success is not assured, there has already been considerable partial success. But much remains to be achieved.

During the second year of investigation, the efforts in several society committees toward introducing new research results into design codes and recommendations for creep, shrinkage and cracking in concrete bridges has met with partial success, although complete success is still not in sight. Extensive arguments and debates within the committees of ACI and RILEM led to the adoption of some of the recently established sound principles.

A major success has been the ACO Committee 209's approval of Model B3, previously developed at Northwestern, to be included in the forthcoming committee report that should go into the ACI Manual for Concrete Practice. But the relative status of the competing simplistic obsolete or incorrect models still remains undecided.

Another major success has been the approval by RILEM of a new testing standard for creep and shrinkage of concrete (prepared by Acker and Bazant). It has so far been approved in the form of a Draft Recommendation, which is now published and open for public discussion; if not unfavorable, approval as a RILEM Recommendation is very likely.

Extensive documents have been prepared for ACI Committee 209, and some already submitted for publication, with aim to compare various competing models on a scientific and experimental basis.

Significant work has been done on the development of a proposal to ASTM for a new standard for the modulus of rupture test, which is for example needed to characterize the onset of concrete cracking caused by shrinkage or creep stresses. A major ingredient of the present 3rd year proposal is to introduce into this ASTM standard the size effect researched under previous NSF support.

Study has also begun on the sources of excessive deflections of bridges, intended for proposing changes in the existing AASHTO recommendations.

The efforts during the 3rd year of funding will include:

1. A further push in ACI Committee 209 towards the approval of the B3 Model and rejection of the competing obsolete and simplistic models (the latter being a daunting political challenge);
2. Adoption of scientifically sound criteria and guidelines for concrete prediction models, as a basis for the preceding task;
3. Study of excessive deflection and cracking of concrete bridges on the basis of the latest research, with preparation of a draft recommendation;
4. Finalizing the proposal of a new proposed standard on the modulus of rupture test to be submitted to ASTM-C09;
5. Development of a proposal to ASTM-C09 of a new testing procedure for concrete creep and shrinkage; and
6. Preparations for Conference Concreep-6 to be held in August 2001, which will feature a scientifically based discussion of standard recommendations for design.

April 1, 2000: Project Start Date
March 31, 2001: Project End Date

Current year funding (incl. Indirect Cost) = $80,727

Postdoc - 2.5 months 
(Dr. V. Kristek or Dr. D. Novak)

Graduate Research Assistant - 6 months 
(E. Becq-Giraudon, G. Zi)

Report was prepared for publication in the proceedings of the ACI Paris Workshop on creep and shrinkage. This report presented scientifically based criteria for selecting various models, including the physical, statistical and theoretical aspects.

Study of case histories of some documented excessive deflections of large span box girder bridges. From some preliminary studies carried out this year, it appears that several phenomena normally neglected in design often grossly increase the deflections.

New standard recommendation for the conduct of creep and shrinkage tests was developed which prescribes the proper conduct of standard tests for the design of concrete bridges and other structures.

Accumulation of the statistics of creep and shrinkage test data generated around the world is very important for calibration of a good prediction Model.

 Shrinkage, Creep, Cracking, Concrete Bridges

 A425

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 Response)

Charles H. Dowding
Northwestern University
(847) 491.4338
c-dowding@northwestern.edu

Alvin L. Budd
GeoSonics, Inc.,
P.O. Box 779
Warrendale, Pennsylvania  15095
Phone: 724.934.2900

There are two goals of this project. The first is to implement and commercialize seismographic instruments that can measure micro-inch changes in crack width produced by both transient, construction vibrations and long-term environmental effects. The second is to provide via the internet these data in real time to the public in a form that allows direct visual comparison. This new approach has the potential to be a cost effective means of informing the lay public of and controlling that which is of concern, crack movement, during vibration producing construction. The detailed objectives of this project are to:

• Determine the optimal micro-inch proximity measurement system for measuring crack movement;

•Integrate proximity measurement and environmental observation with traditional vibration measurement;

• Display the comparisons of long-term and vibratory crack deformation in real time via the internet;

• Demonstrate the robustness, reliability, cost effectiveness, and limitations of micro-inch proximity measurement within structures;

• Assess the commercial potential by soliciting comments form the GeoSonics clients around the world;

• Report the results of field trials of this equipment

Public concern over construction and traffic vibration-induced cracking has led to the search for a radically new approach to vibration control. This proposal to develop 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, the Autonomous Crack Comparometer (ACC), will automatically record changes inc rack width produced by ground motion to allow direct comparison with those induced by long-term, environmental effects. Internet based, real-time public access to these data is fundamental to this new approach.

Time histories of ground motion and past correlations are simply too difficult for most jurors and village and county regulatory boards to understand. Since these public bodies control the manner in which construction activity is adjudicated and regulated, information must be provided in a form that they can understand. Measurement of micro-inch changes in crack width provides information in a visual form that can be understood by these lay bodies, and allows direct comparison of vibration and environmental effects on the same crack with the same device. Use of the ACC system will allow an understanding of this relationship not now possible and potentially may avoid payment of 10's of millions of dollars in illegitimate claims and construction delays each year.

Partnership with GeoSonics, a world leader in the manufacture of vibration monitoring instrumentation, demonstrates the potential for immediate application of these ACC instruments. For instance, a stage 0 device has already been deployed by GeoSonics for a large crushed stone quarry near Miami FL involved in potential litigation and the threat of an unusually low allowable vibration limit. This quarry is one of a group of quarries that produce some 50% of the crushed stone for the entire state of Florida. Imposition of such a restrictive vibration limit will seriously impact the cost of crushed stone for transportation usage throughout the entire state of Florida.

Development of the ability to display, in real-time, results of measurement over the internet inherent in the ACC system has is broadly applicable to other bridge monitoring activities being undertaken by ITI. This software allows instrument reading to be automatically acquired by a central computer, manipulated for calculation, and stored in a dated, internet-accessible file. These dated files are then dynamically accessed by Java script by internet choices to display current or historic comparisons by the lay public. Thus this software allows ITI to broadcast its measurement activity, in real-time, to transportation organizations and lay public around the world.

Progress Description

1. Define Optimal Micro-Inch Crack Measurement Sensor
2. Integrate the 4 Components of the System
3. Write the Required Data Acquisition Software
4. Write Internet Data Display Software
5. Build Prototypes
6. Assess Performance and Commercial Potential

Research Plan

1. Complete Study of Optimal Crack Width Sensor
2. Integrate Major Components of System
3. Complete Writing Data Analysis Software
4. Complete Writing Internet Software
5. Build Prototypes 1 & 2
6. Assess Performance and Commercial Potential
7. Write Reports

Budget Start Date: January 1, 2000
Budget End Date: January 1, 2001

Two-year schedule of research:

1st Quarter: Determine optimal crack sensor; Write data acquisition software
2nd Quarter: Determine optimal crack sensor, Write data acquisition software; Write internet software
3rd Quarter: Integrate principal components; Write data acquisition software, Write internet software, Build prototype I
4th Quarter: Integrate principal components; Write data acquisition software, Write internet software, Build prototype I, Build prototype II, Assess performance
5th Quarter: Integrate principal components; Write data acquisition software, Write internet software, Build prototype I, Build prototype II, Assess performance, Assess commercial potential, Report-Marketing
6th Quarter: Write internet software, Build prototype II, Assess performance, Assess commercial potential, Report-Marketing
7th Quarter: Assess performance, Assess commercial potential, Report-Marketing
8th Quarter: Report-Marketing

Current year funding (incl. Indirect Cost) = $61,734

Research Assistant - 1 month (prog)
Research Assistant - 8 months (inst.)

Development of the ability to display, in real-time, results of measurement over the internet inherent in the ACC system has is broadly applicable to other bridge monitoring activities being undertaken by ITI.

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) GeoSonics direct marketing to operators, (4) GeoSonics and Northwestern University www sites, (5) short courses and seminars.

The technology transfer process will begin in Tasks 6 & 7 with a market analysis of GeoSonics country-wide database as well as an assessment of world-wide market potential. Additionally, ownership of any intellectual property that results from this cooperative project will be obtained for the instrumentation. Essentially it is in GeoSonics' best interest to continue to bring new products to market. This need will drive all of the commercialization activities.

This project combines two technologies not heretofore integrated along with delivery over the internet. Internet delivery increases public access to data, which in this case should lead to greater appreciation of the relative effects of the forces affecting crack response. These data can be accessed and compared with relatively little explanation.

The device is unique in that it is the first portable instrument that will provide the ability to relate crack measurements to particle velocity seismic events on the same time scale. It combines micro-inch proximity measurement with miniaturized, digital seismograph technology.

Measurement, Cracking, Cracks, Monitoring, Bridge Management Systems, Infrastructure

 A426

Further Commercialization of 70-KSI NUCu Steel

Morris E. Fine
Northwestern University
847.491.4322
m-fine@northwestern.edu

Semyon Vaynman
Northwestern University
No Phone
svaynman@northwestern.edu

The main objectives of the follow-on, ITI-sponsored work, are:

• To further commercialization and acceptance of NUCu 70W HP steel for use in bridges
• To collaborate with Lehigh University toward development of the dual target 70/100-ksi-yield strength high performance steel

Recently, new A709 70-ksi high performance steel (HPS) was developed by the joint efforts of the Federal Highway Administration (FHWA), American Iron and Steel Institute (AISI), US Navy and leading US steel companies (US Steel, Bethlehem and Lukens). By now this A709 70W HPS steel has been used in the construction of more than 10 bridges across the country. To achieve 70-ksi-yield strength this steel needs to be quenched and tempered (Q&T). This heat-treatment not only increases the cost of the steel by 10-20%, but also limits the length of the plates or beams to 50 feet. Bridge fabricators desire longer plates because they would require less welding. Also, since this steel requires Q&T to achieve required strength it contains chromium. The CR⁺⁶ ions that form during welding are considered to be a health hazard; EPA and OSHA are contemplating restrictions on the use of Cr in steels that are to be welded.

During the past year our major efforts have been devoted toward introduction of NUCu 70W steel into infrastructure applications. The proposal prepared by IDOT with our help to use NUCu steel in retrofitting of the bridge in Illinois has been approved and funded by FHWA ($99,000). At least 80,000 lbs of the steel will be ordered from Oregon Steel Mills and then fabricated and installed in the bridge by Missouri Fabricators. Our participation in this project is extremely important for further commercialization of NUCu steel. Pending the performance of the steel during bridge fabrication and the results of IDOT's welding and other tests, NUCu 70W steel will be recommended by IDOT for use in other bridges in Illinois and the information will be supplied to other states.

The steel industry, FHWA and Navy have targeted development and commercialization of single steel that when air cooled from hot rolling meetings the requirements for a 70W high performance steel, but when quenched and tempered reaches the requirements of a 100W high performance steel. This is funded at Lehigh by the FHWA, the State of Pennsylvania and the steel industry. The concept is based on combining our NUCu 70W steel and a 100-ksi HP steel under development at Lehigh. A laboratory heat was produced at US Steel Company and tested at Northwestern and Lehigh Universities. Unfortunately, the targets were not reached in this heat because of lower Cu than recommended by us. Another heat with a higher copper concentration has been ordered. It will be tested at Northwestern and Lehigh Universities. If the target strength is achieved, a 150-ton commercial heat will be produced and rolled into sheets and pipes. Participation in this project is extremely beneficial to our steel marketing program. 

Our proposed work for FY 2000 includes:

• Cooperation with the IDOT, Missouri Fabricators and Oregon Steel Mills in retrofitting of I-55/I-70 Poplar Bridge in St. Clare County, Illinois with NUCu 70 steel;
• Cooperate with IDOT on evaluating the steel produced for the above. This will forward inclusion of NUCu 70W steel in the ASTM A709 specification;
• Cooperation with IDOT, FHWA, US Navy, American Iron Steel Institute to find other projects for NUCu 70W steel in Illinois and other states;
• Further participation in the long-term atmospheric exposure programs of weathering steels;
• Dissemination to potential users of the results of NUCu steel development through publications, reports, participation in conferences and meetings and also in special sessions of FHWA and Department of Transportation Research Board;
• Further marketing of NUCu steels for applications other than infrastructure. Since bridge and navy applications of structural steel represent a small market to major steel companies, additional applications such as for railroad tank cars and pipelines would increase the interest in the steel by the major steel companies;
• Participation with Lehigh University in development of a dual-target 70/100 ksi-yield steel.

Progress and Current Status

1. Use of 70-ksi-yield steel NUCu 70W Steel for Retrofitting of I-55/I-70 Poplar Bridge in St. Clare County, Illinois
2. Participation in the FHWA/AISI/US Navy HPS Program
3. Collaboration with Lehigh University on Development of a Dual Target 70W/100W Steel
4. Weatherability Study of NUCu Steel

Proposed Work

1. Use of NUCu 70 Steel for Bridge Retrofitting in Illinois
2. Cooperation with FHWA to Use NUCu 70W High Performance Steel for Bridges in Other States
3. Further Participation in the Long-Term Atmospheric Exposure Programs
4. Cooperation with Lehigh University in Development of Dual Target 70/100-Ksi-Yield Steel
5. Further Marketing of NUCu Steel for Non-Infrastructure Applications

Current year funding (incl. Indirect Cost) = $65,575

In-kind contribution to our research from IDOT (inclusion of NUCu steel into bridges in Illinois and marketing assistance by C. Hahin), Office of Naval Research (support of basic research in development of high performance steels) and Lehigh University/steel companies (production and fabrication of dual target 70/100-ksi steel) is estimated to be $219,200.

The technology transfer will continue. We will continue to collaborate with IDOT and participate in the FHWA/AISI/US Navy HPS Committee. This Committee includes steel producers, bridge engineers and representatives from FHWA and the Navy in its membership. We will continue to issue reports to this committee and others, give presentations at National Conferences, and publish papers in appropriate journals. In the past our papers and presentations led to involvement of different government and industrial partners into NUCu steel development and marketing.

Previously under ITI sponsorship we developed a 70-ksi-yield copper-precipitation-hardened, hot-rolled and air-cooled high performance steel (NU-Cu 70W) that does not require Q&T to achieve the desired mechanical properties. The concentration of the carbon is very low (less than 0.07%) resulting in better welding properties than the ASTM 709 HPS 70W Q&T, leading to further reduced cost. The health hazard from Cr+6 on welding is not present since NUCu 70W steel does not contain this element. Our steel also has improved weatherability. In accelerated weathering tests conducted by Bethlehem Steel Company, NUCu 70W steel has substantially less thickness loss than other weathering steels. Perhaps most important, eliminating the need for Q&T allows production of much longer plates so that beams can be produced in lengths up to 120 feet and even longer without splice welding.

 Steel, Bridges, Infrastructure

 A427

Improved Condition Monitoring of Bridges: Nondestructive Evaluation of Foundations

Richard Finno
Northwestern University
847.491.5885
r-finno@northwestern.edu

The objectives of this proposed work are to develop an experimental system for guided wave evaluation of deep foundations, and to continue refinement and field verification of the existing nondestructive testing methods for deep foundations.

The purpose of this work is to develop methods to non-destructively evaluate the condition of existing deep foundations and bridge piers, including the capability to determine the nature of unknown foundations of bridges. When evaluating existing foundations, the presence of a pile cap or other structure often times makes the heads of the concrete piles and shafts inaccessible and introduces uncertainties in the interpretation of the NDE results. With previous support, the capabilities of sonic logging, sonic echo, impulse response, and parallel seismic techniques have been evaluated for determining damage to accessible and inaccessible drilled shaft foundations. A drilled shaft test section for non-destructive evaluation (NDE) has been established at the National Geotechnical Experimentation Sites (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. A multiple geophone method has been developed which minimized 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, identify smaller defects than possible with conventional techniques.

Proposed work for this year will focus on two main areas:

1. Development of an experimental system that utilizes the guided wave approach, and,
2. Continued field testing of conventional non-destructive testing methods.

Proposed Schedule

The work for this project is broken into two main tasks:

1. Develop guided wave approach for evaluating existing concrete foundations: work will continue throughout the year on both laboratory and field testing of the system (January 1 to December 31, 2000)
2. Fieldwork at the secant pile wall in Chicago will be done through March 2000 and the fieldwork at the Art Institute is scheduled to take place. Furthermore, additional projects from the Wisconsin DOT may be forthcoming as well. Thus we expect the field work to continue throughout the year (January 1 to December 31, 2000)

Current year funding (incl. Indirect Cost) = $79,953

Ph.D. candidate (Civil Engineering Department) - Hsiao-Chou Chao

Recently, the multiple geophone approach to impulse response testing was used in the Central Artery/Tunnel project to evaluate the integrity of 3-ft and 8-ft-diameter drilled shafts and structural slurry walls. 

This past year, it also was used at the excavation at Chicago Avenue and State Street to evaluate the integrity of a secant pile wall and to obtain the time-dependent variation of the stiffness of the hardened grout.

Numerical solutions to the guided wave problem in drilled shafts have been developed and presented in Aziz Khmanifah's Ph.D. dissertation. A prototype device has been developed as part of Hsiao-Chao Chou's ongoing PhD research and has been used to verify portions of the guided wave theory for cylindrical concrete cylinders in the laboratory.

The P.I. will continue to teach a course on "Nondestructive Evaluation of Bridge Conditions" 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.

The work this year focused on development of an experimental system that utilizes the guided wave approach, and continued field-testing of conventional non-destructive testing methods.

Bridge Management Systems, Infrastructure, Monitoring, Nondestructive Testing, Infrastructure

A433

Evaluation of Capacity of Micropiles Embedded in Rock

Richard Finno
Northwestern University
847.491.5885
r-finno@northwestern.edu

TCDI
Steven Scherer
Lincolnshire, Illinois
847-634-8580

A review of existing data suggests that there are two major issues that must be addressed in an experimental program to study axial capacity of micropiles in rock:

1. Axial load tests on micropiles to rock have not been carried to failure such that one can evaluate whether the failure is caused by a structural failure of the system, or a failure of the supporting rock mass. If it is the former, then one must identify the failure mechanism of the composite micropile and compare the results with the structural design approaches, such as that given by the Chicago and Massachusetts Building Codes. If it is the latter, then one must determine the most appropriate method to compute the bearing capacity of the supporting rock mass. The most common methods used to estimate capacity (equations 4 and 6) were developed for large diameter shafts, and likely are not strictly applicable for the smaller diameter micropiles.
2. Load transfer in the rock along the side of the micropile. This is assumed to be zero in conventional design. Previous experience with axial load testing of drilled shafts has suggested that shearing resistance can be developed at certain interfaces. The qualities of these interfaces are a function of the drilling techniques used to socket the anchor in the rock. Instrumentation will be designed to adequately evaluate the load transfer characteristics in the rock socket.

This is a joint effort between the Department of Civil Engineering at Northwestern University and TCDI, a specialty geotechnical contractor based in Lincolnshire, Illinois. The purpose of the proposed work is to conduct field tests to define the capacity of micropiles embedded in rock, and to develop analytical methods to accurately predict the capacity. These foundation types are used extensively in rehabilitation work for infrastructure systems. The axial capacities of these deep foundation elements are conservatively determined by current codes and conventional design methods. Results of available field axial load tests indicate that the load deflection responses are essentially linear to code-specified design loads, suggesting that the true capacity of the piles are significantly higher than currently allowed value. The work will focus on micropiles in the Chicago area where the piles are founded in dolomite or limestone. 

To allow one to rationally design micropiles founded in rock, one must conduct load tests to failure. The proposed scope of work is designed to provide enough data to evaluate the load transfer characteristics along the side of a rock socket and the end bearing capacity of a micropile in rock characteristic of the conditions in the metropolitan Chicago area. These findings should be sufficiently general so that they would be applicable to other rock conditions.

1. It is proposed to conduct two types of axial load tests: (a) Axial load tests on lengths of micropiles installed in rock from the floor of a rock quarry in the Chicago area. (b) Axial load tests on full-length micropiles installed in rock at a site in the Chicago area to be determined.
2. It is proposed to analyze the results of the load tests in terms of load transfer characteristics along the side of the pile and its end bearing capacity, and to develop recommendations for design of rock-socketed micropiles. As a starting point, procedures developed for larger diameter drilled shafts will be evaluated, but the scale effects may necessitate the development of a new approach.

It is envisioned that a series of tests will be conducted on micropiles with lengths of 2, 4, 6 and 8 ft embedded in the floor of a local quarry. These short lengths will make instrumenting the piles a much easier task, and will provide a direct measure of the increase in bearing capacity with embedment. The load transfer data provided by the instrumentation will allow one to separate the side resistance in the rock socket from the end bearing capacity. Rock samples will be collected and intact strength of the rock will be determined in the laboratory. Bedding and joint plane orientation will be noted in the field so their effects on rock mass strength can be estimated.

The fieldwork at the quarry will be conducted during summer 2000. It is envisioned that the earliest it will be started is in July. Several weeks will be needed at the start of the project to obtain the necessary instrumentation and arrange access to the quarry. It is estimated that the installation of the micropiles and subsequent load test in the quarry will take about 2 weeks. The exact starting date also will depend on the availability of a TCDI crew and equipment.

The full-scale load tests will be conducted at a site to be determined later, depending again upon the availability of an appropriate site, a TCDI crew and equipment. We expect that these tests will be conducted within the six months after the grant has been awarded.

The total duration of the proposed project will be one year.

Current year funding (incl. Indirect Cost) = $32,819

NU graduate student: Benoit Paineau (6 months)

The results of the study will allow one to use higher design capacities than are currently allowed, and will reveal the operative load transfer mechanisms for these foundation elements.

Infrastructure, Rock

 A428

Analysis of the Performance of the Rehabilitation of the Chicago-State Subway Station and its Effects on Adjacent Structures

Richard Finno
Northwestern University
847.491.5885
r-finno@northwestern.edu

It is the purpose of this proposal to use the data obtained from monitoring effort to check methods of predicting ground movements arising from supported excavations in soft clay, and to evaluate the soil-structure interaction between the adjacent buildings and the deforming soils. Damage to the Warde School has occurred, and an analysis of the detailed soil-structure interaction will provide information concerning levels of movement and onset of damage.

Reconstruction in urban environments is ubiquitous. Many deep excavations are made as part of projects that are intended to modernize exiting urban infrastructure. 

The Department of Transportation of the City of Chicago is modifying the subway station located at State Street and Chicago Avenue. As part of the work, a 44 ft. deep excavation has been made adjacent to the foundations of the Frances Xavier Warde School and within about 80 ft of Holy Name Cathedral. Both structures are founded on shallow foundations. The excavation support walls are located within one foot of the edge of continuous wall footings at the Warde School.

The field performance data collected by Northwestern University have been processed daily and been used to verify that the contractor's excavation and support procedures adequately restrict associated ground movement such that damage to the Warde School is minimized and damage to the Cathedral is prevented. However, a great deal more usefulness can be obtained from the data if additional analyses are conducted. These analyses are the focus of this proposal.

There are two main tasks in the proposed scope of work, finite element studies and developing guidelines for onset of damage to structures adjacent to deep excavations.

The contract for the subway reconstruction was awarded on June 1, 1999. While originally the major part of the excavation was to be completed by the beginning of September 1999, unforeseen difficulties related to utility relocation played havoc with the schedule. Excavation adjacent to the Warde School along State Street and Chicago Avenue is now scheduled for completion by march 2000, although the actual schedule has been fluid since the project started. The remaining field effort has been scaled back, and is now envisioned to consist of a weekly trip to the site to collect ground movement data.

It is envisioned that the analytical and laboratory studies will be conducted over a period of 2 years beginning on January 1, 2000. This proposal is for work to be conducted from January 1 through December 31, 2000.

Current year funding (incl. Indirect Cost) = $113,904

Two Ph.D. and at least one MS level graduate student from Northwestern University's Department of Civil Engineering will participate in the remaining fieldwork and the analytical portion of the project.

An advisory committee has been established to assure the relevance of the research results. 

Regular construction meetings take place weekly to ensure coordination among the owner (CDOT), the contractor and instrumentation specialists (WJE and Northwestern University). The results of both the completed and proposed work have been, and will continue to be, presented and discussed at these meetings.

Kristi Kawamura has completed her MS thesis, entitled "Hardening Soil Model Parameters for Compressible Chicago Glacial Clays." Two PhD theses and at least one additional MS thesis will result from this work. Papers will be submitted to Journals and the results will be presented in upcoming conferences to disseminate the findings.

While one cannot expect to develop comprehensive guidelines based on one case study which concerns only one stratigraphic condition and one building type, one can develop guidelines for the soft clay condition and a structural system consisting of a reinforced concrete frame with exterior masonry bearing walls, like the Warde School. This is a fairly common structural type and hence the guidelines will have ample applicability. Furthermore, the monitoring system can serve as a model for similar projects with different structural systems.

Rehabilitation (Maintenance), Infrastructure, Structures, Subways, Subway Stations

 A429

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

1. Determine the stress sate in the connection under design conditions. This will allow for normal rotation of the hanger due to thermal expansion and contraction.
2. Investigate the effects of "freeze-up" of the pin. The expansion of pack rust is thought to freeze the pin in place and prevent free rotation. As a result, the thermal expansion mechanism of the assembly is compromised (depending on the severity of the "freeze-up") and large torsional and elongational stresses may be induced. In fact a question of some significance, and which we believe we can shed light upon, is the extent to which pin failure is a fatigue crack driven process or whether it is primarily a stress-induced failure due to "freeze-up" of the pin.
3. Provide a stress analysis of the experiment carried out at Northwestern University on November 12 by Hogan and Komsky to investigate possible causes of unexpected ultrasonic signals observed at the so-called 6 O'clock and 12 O'clock positions on the pin. Our initial goal is to provide insight into the state of stress and deformation in the pin especially near the surfaces of contact with the hanger and web. We will investigate indicators (such as large contact stresses) of possible ultrasonic reflectors.

The project will continue our development of a methodology for the life-cycle management of steel bridges and will continue our investigation of specific issues pertaining to failure of pin-hanger connections. In particular, a stress analysis and fracture mechanics model of the pin-hanger assembly will be completed. The effect of "freeze-up" of the pin will be investigated with the finite element model. Thin layers of elements near the pin surface will undergo eigenstrains to simulate pack rust expansion and a frictional model between contacting surfaces will provide for sticking of the pin. The eXtended Finite Element Method (X-FEM) which permits crack modeling without explicit meshing of the crack will be implemented for the bridge pin model and fatigue crack propagation in the pin will be investigated. We will continue the development of measurement models to generate probability of detection (POD) curves to set the stage for fatigue reliability studies. These studies will yield as a final result a statement of the reduction of the probability of component failure for various inspection scenarios.

1. Complete the stress analysis of pin-hanger assembly
2. Study the effects of pin "freeze-up"
3. Assessment of cracks in pin
4. Develop X-FEM methodology for practical applications - bridge pin as testbed
5. Continue the development of measurement models

Budget Period: January 1, 2000 - December 31, 2000

We expect to have a working model of the bridge pin by mid-January, to be followed by more refined models and detailed stress analyses of the bridge and test pins.

Quarter 1: In the first quarter, the three-dimensional finite element stress analysis of the Dells bridge pin/hanger assembly will be continued for freely rotating pins and for fully frozen pins. A stress analysis of the Northwestern experiment on pin loading will be continued. Continue work on the development of measurement models.

Quarter 2: The stress analyses of the freely rotating and fully frozen pin will be completed. Begin work on the development of the pin "freeze-up" model - implement eigenstrain model for pack rust expansion and test code. Begin implementation of the X-FEM for analysis of cracks in bridge pins.

Quarter 3: Continue with "freeze-up" model - implement friction model for contact surfaces and carry out parameter study. Continue X-FEM implementation.

Quarter 4: Complete "freeze-up" model analysis. Begin crack growth simulations in bridge pins using X-FEM. Begin implementation of probabilistic framework for reliability calculations.

Current year funding (incl. Indirect Cost) = $96,573

Graduate student: David Houcque

The proposed research is a continuation of the current ITI funded project "Life-Cycle Management of Steel Bridges Based on Non-Destructive Testing and Failure Analysis" (Moran & Achenbach). It also complements the ITI project "Ultrasonic Inspection of Bridge Components" (Komsky & 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).

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.

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

 A430

Improved Condition Monitoring for Bridge Management

David Prine
Infrastructure Technology Institute
847.491.2873
dprine@northwestern.edu

Wisconsin Department of Transportation
Phil Fish
4802 Sheboygan Avenue, Rm. 601
Madison, WI  53707
608.266.8165

California Department of Transportation
1120 N Street
Sacramento, CA  94273
916-654-5266

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.

The responsiveness of this project to the needs of the user community has been a unique feature since its inception and continues to be. In the past year major strides continue to be made in gaining field acceptance and commercialization of the technologies being developed under this unique program. Contract work continues with the emphasis (customer driven) being on remote monitoring of structural stability utilizing either TDR or electronic tiltmeters. Three scour susceptible bridges have been instrumented for CalTRANS with the third completed in June 1999. This technology represents a radical departure from the current approach to scour monitoring. Scour remains the major cause of bridge collapse in the U.S. 

Considerable progress has been made in the past year in the development of improvements in remote system reliability. We are much closer to a standardized system design within the limits imposed by the highly individual nature of each bridge. Two major areas remain. They are communications from locations where telephones (wire or cellular) are non-existent and power for those locations that have no ready access to power lines. A major focus for the coming year will be on developing reliable economical solutions to these problems. Success in these problem areas will open up the application of remote monitoring systems to many new sites.

The maturity of the technologies being developed by our faculty partners, particularly in the geotechnical area, has led to increased effort on the part of ITI bridge NDE staff in support of the application of these technologies in the field. During the last 9 months ITI staff involvement in the area of field support of faculty related developments approaches 50% of the time available and this will probably continue to increase over the coming years.

1. Remote monitoring will be the major activity with further extension to the active mode (smart bridge) and implementation on the Internet.
2. Alternate communications technology will be evaluated for those test sites where neither hard wire nor cellular telephone is available. We will address the problem of providing reliable power for sites that have no access to power lines.
3. Field tests and demonstrations
4. User group development: Provide guidance to 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 users group meetings, participation in various committees and working groups that are organized by other infrastructure and NDE groups and Internet activities as well as a trade show booth.
5. Educational activities: We will continue to organize and support educational tours to various infrastructure-related locations; 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, etc.

Budget Period: January 1, 2000 to December 31, 2001

During the coming year, we will attempt to accelerate the evolution of the smart structure by continuing to expand the technology to new sites and applications while actively pursuing appropriate partnerships in the areas of structural analysis and software development.

The remote monitoring capability will continue to advance and expand during the coming year with both active as well as passive systems coming on line.

Current year funding (incl. Indirect Cost) = $236,616

Student participation has consisted of work-study assignments and graduate student assistance with research efforts.

Of the 14 activities that are part of this project, 8 involved faculty and/or students. The student activities have mainly consisted of direct involvement in ITI bridge team projects. This type of involvement is expected to continue to grow.

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.

Considerable effort by ITI staffers was expended in two graduate research projects. The first was an outgrowth of the development effort begun in the summer of 1998 to develop compliant TDR cables. The second was a project to evaluate a remote crack monitoring system being developed by Professor Dowding for application to blast monitoring. The system is installed in the Church Street Metra station.

A total of 8 technical reports and papers were published or presented in the past year.

The user group development effort maintains a strong involvement with the user community through meetings. Newsletters, and electronic communications via the Internet have been effective in the past and efforts are underway to bring these back to previous high standards. The remote monitoring effort will make its presence known on the Internet with a "live" link to a remote monitoring test site.

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 gages as well as the installation and maintenance of remote monitoring systems. Three bridges have been instrumented and CalTRANS is planning to extend this approach to several hundred structures using the services of outside contractors.

The numbers of long term sites and applications have continued to expand primarily because technology addresses a need that is readily recognized by the infrastructure owners. Just the ability to interrogate a remote site without actually sending an inspector out to the site is an obvious improvement over present methods. The active self-interrogating remote site (smart structure) has far greater potential for positively impacting the process of condition determination.

Bridge management systems, Infrastructure, Monitoring

 A432

Feasibility Study for Commercialization of a Non-destructive, Ultra-sonic Technique for Monitoring the Setting and Hardening of Concrete

Surendra Shah
Northwestern University
847.491.3858
s-shah@northwestern.edu

K.V. Subramaniam, Assistant Professor

New York College

The objectives of this study are to perform a critical evaluation of the field applicability of the proposed technique and to perform a feasibility study for further development of a field device for assessing the in-situ hardening and strength gain of concrete. The main objectives of this feasibility study are as follows:

1. Identify industry need and barriers to acceptance of a new field test.

2. Ascertain the acceptable market price for a field device.

3. Define potential market for the field device at market price.

4. Study the possibility of developing a standardized test method for in-situ monitoring of hardening and setting of concrete, acceptable by agencies such as the American Society for Testing Materials (ASTM)

A new technique for monitoring the setting and hardening process of concrete in-situ was recently developed at the NSF Center for Advanced Cement Based Materials. This new technique is based on high-frequency ultrasonic measurements and consists of monitoring the wave reflection factor (WRF) at the interface between a steel plate and the hardening concrete. Preliminary studies have shown good correlation between the measured trends of WRF and the elastic modulus and hydration process of Portland cement concrete in the early stage (first 72 hours). The WRF technique provides a non-invasive tool for assessing early strength gain in concrete. The in-situ progression of the early hydration process can be monitored relatively easily using the WRF technique.

The outline of the proposed work for this study is as follows:

1. Assess the current state of the art in the field of testing early-age concrete including the nondestructive testing of early-age concrete

2. Conduct a literature review and an industry survey on the methods currently used in the field to determine the maturity of concrete and their shortcomings

3. Review the ultrasonic techniques currently under development to characterize the properties of fresh cement paste. Incorporate possible improvements in the proposed WRF technique.

4. Identify promising applications of the WRF technique based on the feedback from cement and admixture manufacturers, concrete suppliers, and precast component manufacturers. Identify specific needs of the industry and short-comings of the methods currently in use.

5. Collect feedback from NDE equipment manufacturers including instruments already on the market and currently in use, assessing them in terms of utility, accuracy, market acceptance and cost.

6. Identify time lines, costs, and critical milestones for further development of a field applicable test device based on the WRF technique.

This proposed feasibility study would be completed in two months

Current year funding (incl. Indirect Cost) = $14,993

One Post-Doctoral Student

A new technique for monitoring the setting and hardening process of concrete in-situ was recently developed at the NSF Center for Advanced Cement Based Materials. The preliminary development of the technique was supported by the Federal Aviation Administration Center of Excellent for Pavement Research and the Infrastructure Technology Institute.

 A few of the potential applications of this technique are listed below:

• Cement and Admixture Manufacturers

Study and document admixture effects on cement blends; Prevent cement/admixture incompatibility

• Ready-mix Suppliers

Identify material compositions and environmental conditions that could lead to early stiffening and flash setting; Optimize paving and finishing operations for a given material composition

• Precast and Paving (decks and highways)

Determine time for demolding/removal of formwork, thereby increasing productivity; Determine earliest post-tensioning time; Establish criteria for opening new or reconstructed/rehabilitated pave sections

• Prestressed Components

Determine time for application of prestress

While currently a laboratory tool, the ultrasonic WRF method shows sufficient promise for further development into a field device. Of primary importance is the development of robust field instrumentation and simpler, more operator-friendly data processing/analyzing tools.

Concrete, Monitoring, Infrastructure