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Abstract XVII

Steel Slag in Hot Mix Asphalt

Steel Slag in Hot Mix Asphalt Concrete
 
In September 1994, steel slag test and control sections were constructed in Oregon to evaluate the use of steel slag in hot mix asphalt concrete (HMAC). This report covers the construction and five-year performance of a pavement constructed with 30% steel slag.

Asphalt concrete can be produced and the pavement constructed readily in Oregon when crushed steel slag is used as a portion of the aggregate. If the unit cost of steel slag modified mixes is the same as conventional dense graded mixes, overall project costs may increase because of the decrease in coverage by the heavier steel slag mix. For the test section HMAC constructed with 30% steel slag, the coverage was 15% less than a conventional "B" mix. Reported increased resistance to rutting and improved skid resistance was not measured during the five years the pavements have been monitored. The differences between the two sections may not be measurable because only 30% steel slag was used in the test mix and the slag was finer than the conventional ½ - ¼" (12.7 to 6.3 mm) material it replaced. To date, both the control and test sections are performing satisfactorily.



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Seismic Protection Devices

Seismic Protection Devices - West Marquam Bridge Interchange
 
This report summarizes the seismic retrofit of the Marquam Bridge in Portland, Oregon with proprietary bearing/restraint and shock transmission devices. The retrofit was completed in 1995. The devices were supplied by FIP Industries, Inc. and included:

  • Bearing Restraint Devices (including shock transmission components); four devices at Piers #2 and #5;
  • Bearing Restraint Devices: four devices at Piers #3 and #4; and
  • Shock Transmission Devices: two on each side of Panel Point L13.
The bearing/restraint devices replaced existing bearings and required special modifications to the bridge piers and truss to accommodate jacking operations and bearing installation. After the installation was complete in 1995, Teflon shavings were discovered in the guide bar region in each of the new bearings on Pier #2 and Pier #5. The shavings were the result of the Teflon sliding element being extruded into the guide bar region. Since then, further monitoring has confirmed that the Teflon extrusion process has diminished over time. After almost five years of service, the other devices are performing satisfactorily.


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​Finite Element Modeling of Residual Stresses in Electroslag Butt Welds

Finite Element Modeling of Residual Stresses in Electroslag Butt Welds

Shop fabricated electroslag (ES) welds used in bridge construction have had a history of low toughness in the fusion and heat affected zones. In addition, conventional inspection of ES weldments under shop fabrication conditions fail to consistently detect and/or correctly size weld discontinuities. These problems have led to a Federal Highway Administration requirement for removal, re-enforcement, or re-evaluation of the integrity of ES weldments in existing Federal bridges. This study was initiated in partial response to this requirement by the Oregon Department of Transportation. The specific tasks of this study were: a) to develop an understanding of ES weld-induced residual stresses for A36 steel with an emphasis on assessment of bridge-specific weld parameters and residual stress measurement; and b) computational modeling of ES welding and the resultant stress distribution.   The ES weldments assessed in this study were those used in the fabrication of the Oregon State I-205 West Linn Bridge. This research was performed by numerical modeling based on unknown welding operation parameters. Experimental assessment of fusion zone characteristics was used as input data for the computational modeling work. Selective etching techniques were used to reveal the solidification bands formed at the fusion line interface during ESW. Analysis of these solidification bands allowed determination of weld pool profiles formed during welding, which are a direct function of the welding parameters. The results indicated that the operation procedures for all of the assessed ES welds were nominally the same.

Two-dimensional (2D) and three-dimensional (3D) models were developed using FEA methods to simulate the ESW process and to analyze the effect of operating conditions on residual stress distribution. Both Lagrangian (stationary) and Eulerian (moving) coordinate systems were assessed in the FEA analysis. Modeling using Eulerian coordinates was found to be 100 over times more efficient than Lagrangian coordinates. Thus all 3D thermal-mechanical modeling was done using Eulerian coordinates.

Both two-dimension (2D) and three-dimension (3D) thermal heat transfer ESW finite element analysis (FEA) models were developed using the Lagrangian system, only 3D thermal models were developed using the Eulerian coordinate systems. The thermal modeling effort included accounting for the latent heat of solidification. All 3D model results were in agreement, and agreed with experimentally determined ESW-induced thermal histories previously measured at the Oregon Graduate Institute.

The weld-induced transient temperature fields predicted by the thermal heat transfer models were used as input into the Lagrangian Coordinate 2D mechanical two dimensional analysis and into the Eulerian mechanical three dimensional analysis of the thermally-induced mechanical response resulting in estimation ES weld-induced residual stresses. The 3D modeling using Eulerian coordinates predicts low tensile or compressive residual stresses are present in the as-welded ESW condition. The 2D Lagrangian coordinate system modeling predicts yield strength or greater tensile residual stresses. Thus 2D modeling was found to give incorrect residuals stress predictions and should not be used to predict ESW-induced residual stresses.

Experimental assessment of bridge-specific residual stress fields was attempted. Coring and subsequent sectioning techniques were used to measure residual stresses associated with the ES weldments. However, the presence of continuous fusion line weld repairs perturbated the underlying ESW residual stress field. Thus, even though the results tend to support the 3D FEA residuals stress analysis, the experimental results can not be used to validate or invalidate the computational results. Surface residual stress assessment by the blind hole drilling method was unsuccessful.



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Composite Materials

Behavior of Concrete Specimens Reinforced With Composite Materials Laboratory Study
 
The main objective of this study was to investigate the interaction between FRP composite and concrete by addressing the most important variables in terms of FRP properties.  Type of fibers, thickness of the laminates, fiber orientation and FRP strengthening configuration were studies while keeping the type of concrete, steel reinforcement and geometry of the samples constant.
 
The intent of the data collection and analysis was to gather extensive information on the performance of FRP-reinforced concrete, rather than to investigate the structural behavior of FRP-reinforced members.  Appearance of first crack on the concrete, ultimate loads and the corresponding strains and deflection, and the failure modes were of main interest.
 
The FRP systems included in this study were most of those known to be currently available.  In addition, two customized FRP systems were developed using only domestically available materials.  All systems were tested under nearly identical conditions with respect to concrete strength, specimen dimensions, reinforcement, surface preparation, test methods, and analysis.
 
The ultimate strength increase at failure ranged from 18 to 545 percent, depending upon the FRP-application scheme.  The specimens showed no significant increase in stiffness prior to initial cracking of the concrete.  The FRP-strengthened specimens exhibited greater deflections prior to initial cracking of the concrete.  Following initial cracking, the behavior of the specimens was mostly influenced by the properties of the FRP laminate.  The results showed that the increase of the load-carrying capacity and the performance of the FRP-reinforced beams were strongly dependent on the FRP configuration.  The failure modes showed dependency on the stiffness and strength of the FRP reinforcement and scheme used to strengthen them.  The study suggested that the effectiveness of the FRP composite decreases as the rigidity (elastic modulus x FRP thickness) of the laminates increases.


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Microsilica Concrete Bridge Deck Overlay

Polypropylene Fiber-Reinforced Microsilica Concrete Bridge Deck Overlay at Link River Bridge
 
In 1997, ODOT overlaid the Link River Bridge with microsilica concrete, reinforced with polypropylene fibers (FMC). The manufacturer claimed the fibers would reduce plastic shrinkage and settlement cracking during the early life of the concrete, as well as reduce the formation of intrinsic cracking. The northbound lane was constructed with the FMC while the southbound lanes were constructed with plain microsilica concrete. Neither side showed much initial cracking when the curing blankets were removed. The latest inspection two years after construction found only minor cracking in the northbound lane and very little in the southbound lanes.


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Indirect Land Use and Growth Impacts

Indirect Land Use and Growth Impacts of Highway Improvements
 
The Oregon Department of Transportation undertook this study of the impacts of highway capacity improvements on land uses and growth, particularly at the urban fringe. This study was instituted to better understand the "cause and effect" relationships between highway capacity, travel demand and development patterns. The relationships of a variety of factors to resulting growth were evaluated for their ability to predict growth. Case studies of some communities were completed to provide an in-depth understanding of the pressures which drive development decisions and land use change.

This interim report provides initial findings of the study. It has found that most highway capacity increases do not cause development to be dramatically different from local land use plan guidance, or from what would have occurred in absence of the highway improvement. For Oregon, local governments hold the tools to determine development patterns, using zoning and public utilities such as water, sewer and roads.

The final phase of the study will complete additional case studies and develop guidance for transportation planners to evaluate indirect impacts of highway improvements.


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Bend Case Study

Bend Case Study: Indirect Land Use and Growth Impacts
 
To improve environmental analysis of indirect land use impacts of highway capacity improvements, this study analyzed the land use and growth patterns of 20 Oregon communities over 20 years. Using a Geographic Information System and aerial photos, growth patterns were categorized and mapped. Factors related to land use and transportation were evaluated for their relationships to resulting growth patterns. These relationships were further investigated in four in-depth case studies of development prior to, during, and after construction of a highway capacity improvement.
 
Additional case studies are currently underway. The primary product of this research will be guidance for completing an assessment of the indirect impacts on land use and growth of a highway improvement. This assessment is required by environmental regulations, but tools and data for developing general land use forecasts is limited. The guidebook will include examples from the case studies, data types and possible sources, and guidance on using GIS tools for comparing alternative scenarios.
 
Interim reports are available via the Research Internet web site. Additional case studies and a final report are scheduled to be published in the fall of 2000.


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Fatigue Crack Modeling

Fatigue Crack Modeling in Bridge Deck Connection Details

Many steel bridges built prior to 1960 have bridge deck connections that are subject to high cycle fatigue. These connections may be nearing their fatigue limit and will require increased inspection and repair over the next 10 - 20 years. Current inspection and repair are very expensive and only address those details which contain visible cracks. The goal of this research was to develop a methodology to identify problem details – those which are nearing the end of their serviceable life, but may not yet contain visible cracks. One Oregon bridge on Interstate 5 with this problem was studied to assess the loading conditions and fatigue crack growth rate for the connection details. The objective was to use the analysis from this bridge to develop a predictive model of connection detail fatigue life, which could be applied to other bridges. Such a model could be used to guide the inspection and repair process, significantly reducing costs.

Finite element modeling methods were used to characterize the structure, and fracture mechanics was used to estimate the fatigue life of the connection details. Fatigue life estimates were found to be very conservative, and results suggested that additional field validation work would be necessary to quantify other forces on the connection details. The project resulted in a low-cost field identification methodology to identify problem details. In addition, five retrofit strategies were examined and several recommendations were made to improve the fatigue-limit estimates.

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McMinnville Case Study

McMinnville Case Study: Indirect Land Use and Growth Impacts
 
To improve environmental analysis of indirect land use impacts of highway capacity improvements, this study analyzed the land use and growth patterns of 20 Oregon communities over 20 years. Using a Geographic Information System and aerial photos, growth patterns were categorized and mapped. Factors related to land use and transportation were evaluated for their relationships to resulting growth patterns. These relationships were further investigated in four in-depth case studies of development prior to, during, and after construction of a highway capacity improvement.
 
Additional case studies are currently underway. The primary product of this research will be guidance for completing an assessment of the indirect impacts on land use and growth of a highway improvement. This assessment is required by environmental regulations, but tools and data for developing general land use forecasts is limited. The guidebook will include examples from the case studies, data types and possible sources, and guidance on using GIS tools for comparing alternative scenarios.
 
Interim reports are available via the Research Internet web site. Additional case studies and a final report are scheduled to be published in the fall of 2000.


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Sweet Home Survey


Sweet Home Business and Customer Survey
 
The results of the telephone survey are provided in this report. The survey was conducted by the University of Oregon’s Survey Research Laboratory in mid-October, 1999 to determine the impact of the highway construction on access to businesses and to judge the effectiveness of the “temporary business access” signs. The survey includes a customer survey of people living in Sweet Home and a survey of businesses located along Highway 20 in Sweet Home.

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Pressure Treated Signposts

A Comparison of Pressure Treated Wood and Cedar Signposts
 
This report compares the use of pressure treated wood and cedar for signposts. Both materials are being used by the Oregon Department of Transportation (ODOT), however sign crews are now primarily using Port Orford cedar posts.

There are two types of pressure treated posts used by ODOT, Douglas-fir treated with Ammoniacal Copper Zinc Arsenate (ACZA) and Hem-fir treated with Chromated Copper Arsenate (CCA). There are environmental concerns about the use of pressure treated wood. However, studies cited in this report have shown it is not detrimental to the environment.

Based on price data provided by pressure treated wood suppliers, the purchase price for ACZA treated Douglas-fir is slightly higher than Port Orford cedar. Some of the suppliers expressed concerns about the availability of Hem-fir posts that would meet ODOT specifications.

The average disposal cost for pressure treated wood based on disposal at a landfill or waste transfer facility is slightly higher than cedar. In actual practice, sign crews dispose Port Orford cedar wastes in existing waste containers, thus eliminating the added disposal fee incurred by taking it directly to a landfill or waste transfer facility.

In a survey of ODOT sign crews, they unanimously favor using Port Orford cedar posts over pressure treated posts.

In Oregon State University’s wood post studies, Port Orford cedar posts lasted an average of 20 years, whereas pressure treated wood posts remained in service one-and-a-half to three times longer than Port Orford cedar. ODOT sign crews assert that only a small number of posts are replaced because of rotting, indicating a 20 year life is adequate for a signpost.
 
Based on the information presented in this report, Port Orford cedar is the most appropriate signpost material to meet ODOT requirements.

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Soil Nailed Walls

Monitoring of Soil Nailed Walls at the Highway 217 and Highway 26 Interchange
 
Soil nailing is an innovative and cost effective technique that has received increased attention in recent years. Engineers faced with the challenge of retrofitting and maximizing the use of existing structures, minimizing new construction cost, and increasing usable space within existing rights-of-way have found that soil nail walls provide a flexible and cost-effective solution in many cases. However, the geotechnical engineering community’s understanding of the behavior of soil nail walls, especially under unique loading conditions, is still somewhat limited. As additional field data becomes available, engineers will achieve a better understanding of soil nail wall performance under a variety of loading conditions and configurations. This report summarizes the results of a soil nail wall research project completed by the Oregon Department of Transportation (ODOT).


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Scour in Weak Rock

Predicting Scour in Weak Rock of the Oregon Coast Range
 
Recent experience in the Coast Range Province of Oregon demonstrates that weak sedimentary bedrock in stream channels can be vulnerable to scour. The presence of erodible rock adjacent to bridge foundations and abutments necessitates monitoring of the channel to preclude costly repairs, or in an extreme case undermining of the foundations and bridge collapse. Current design methods are not well suited for evaluating the potential for scour in weak rock, nor can the rate of scour be estimated. A design method for the latter would be useful for identifying the depth that the foundation should be socketed into the potentially scourable rock given the design life for the bridge. In an effort to relate the rate of scour in weak sedimentary rocks to the geological and geotechnical characteristics of the rock, as well as the hydraulic characteristics of the streams, a pilot study of eleven bridge sites was conducted. Geomechanical index tests were performed on bedrock specimens and the hydraulic properties of the stream channels were evaluated. A preliminary model has been proposed wherein the rate of degradation of the stream channel is related to the abrasive resistance of the bedrock and the hydraulic power of the stream. The proposed method can be used to obtain an approximate estimate of the degradation of unobstructed channels in weak sedimentary rock due to abrasion by bedload and flood events. The effects of local, or contraction, scour were not evaluated.


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Millabrading Test Evaluation

Millabrading Test Evaluation
 
The Oregon Department of Transportation (ODOT) continues to investigate alternatives for rehabilitating the rutting in concrete pavement sections. The millabrading system was proposed as an option to reduce the middle lane rut depths in a continuously reinforced portland cement concrete pavement to improve driving conditions. Rut depths of 19 to 32 mm were measured prior to construction. The system includes a high speed rotomill with a modified drum used to level out the ruts, followed by a shotblaster with steel shot to provide a uniform, skid resistant wearing surface.
 
The following conclusions were reached following an eight-month investigation.
Construction noise levels should be considered if the grinding is to take place near a residential area. Air quality, particularly coarse particulate fallout may be a problem if the rotomilling is done for an extended period in one area.

A post construction inspection measured random rut depths of 10 to 16 mm in the middle lane. Some rutting was expected, however, not to the degree measured. Insufficient survey data may have impacted the design and subsequent outcome. Full-width treatment may have eliminated the ruts. In addition, the longitudinal joints appeared spalled. A petrographic analysis indicated that there is no micro-cracking that may be detrimental to the durability of the section. Accident data for comparison between the before and after conditions is not currently available. District Maintenance staff report no problems with the section.

Field test results indicate that in-vehicle noise levels are noticeably lower after construction. Because some of the pavement ruts still remain, the reduction in noise is dependent on where the tires hit in the lane. Pavement friction values increased following the grinding and additionally after the shot blasting. Friction values, however, have continued to decrease for the last eight months following construction. The pavement ride or roughness appears to be slightly reduced following the millabrading process. Again, since some rutting still remains, the IRI reductions are dependent on where the roughness is measured.

Recommendations for future use are included.


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Chloride Ion Migration


The Study of Chloride Ion Migration in Reinforced Concrete Under Cathodic Protection
 
The migration of chloride ions in concrete with steel reinforcement was investigated. Mortar blocks (15 cm x 15 cm x 17 cm) of various composition (water to cement ratio, chloride ion content) were cast with an iron mesh cathode imbedded along one face and a thermally sprayed zinc anode applied to the opposite face. Current densities of 0.033 and 0.066 A / m2 were applied to the blocks over a period of one year at constant temperature and humidity. The zinc face was covered with a pond of saturated calcium hydroxide to prevent polarization of the zinc-concrete interface. Over the course of polarization, potential vs. time curves were recorded and samples of mortar were extracted for determination of chloride concentration.
 
An ion chromatography method was developed for the analysis of small samples of mortar for chloride. The method allowed for the measurement of chloride concentration in mortar samples with a long term overall relative standard deviation of 3.2% in the concentration range 1-15 mg/L in the water extract of the mortar. Under the conditions of the study, no significant migration of chloride ions could be detected over the one-year test. This result was consistent with that which would be expected with a simple transport model of the system. Random fluctuations that were observed in the chloride concentration profiles were attributed to the inhomogeneous pore structure of the mortar on the scale of the sample size and the associated inhomogeneity in the chloride distribution. Future studies of these phenomena should be designed with larger blocks and larger samples of mortar for chloride analyses; (ii) an automatic misting device to obviate the need for the calcium hydroxide solution; and (iii) higher current densities, longer periods of polarization, or both.

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Weight-Mile Tax


Effect of Weight-Mile Tax on Road Damage in Oregon
 
Oregon’s weight-mile tax was amended in 1990 to provide for a lower tax rate for trucks weighing more than 80,000 pounds if they added axles. The additional axles within a weight class reduce the amount of road damage. The tax break was largely based on equity considerations, since trucks within a weight class tend to do less road damage if they have more axles; however, the tax reduction also created an economic incentive to add axles and thus reduce road damage. This project attempted to determine if the tax break actually led to an increase in the number of axles within weight classes, which would result in a reduction in the amount of road damage. An analysis of statistical data indicated that there has been a small increase in the number of axles in most weight classes, but it was not possible to determine if this was due to the weight-mile tax. A series of structured interviews supplemented the statistical analysis and indicated that the tax incentive was not a major determinant of truck configuration. One probable reason is that regulatory constraints limit the effectiveness of the tax incentives.
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Grants Pass Case Study

Grants Pass Case Study: Indirect Land Use and Growth Impacts
 
To improve environmental analysis of indirect land use impacts of highway capacity improvements, this study analyzed the land use and growth patterns of 20 Oregon communities over 20 years. Using a Geographic Information System and aerial photos, growth patterns were categorized and mapped. Factors related to land use and transportation were evaluated for their relationships to resulting growth patterns. These relationships were further investigated in four in-depth case studies of development prior to, during, and after construction of a highway capacity improvement.
 
Additional case studies are currently underway. The primary product of this research will be guidance for completing an assessment of the indirect impacts on land use and growth of a highway improvement. This assessment is required by environmental regulations, but tools and data for developing general land use forecasts is limited. The guidebook will include examples from the case studies, data types and possible sources, and guidance on using GIS tools for comparing alternative scenarios.
 
Interim reports are available via the Research Internet web site. Additional case studies and a final report are scheduled to be published in the fall of 2000.



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Maintenance Practice F Mix

Development of Maintenance Practices for Oregon F-Mix
 
The Oregon Department of Transportation (ODOT) produces an open-graded asphalt pavement (F-mix) unlike most open-graded pavements used in the United States. Its 25 mm maximum aggregate size and typical lift thickness of 50 mm is more like the porous asphalt pavements used in Europe. This type of pavement has been in use in Europe since the early 1980’s and widely used in Oregon only since the late 1980’s. Consequently, maintenance procedures for this type of pavement are still being developed and documented. This paper summarizes progress through March of 1999 on a study of F-mix maintenance needs and techniques being conducted by Oregon State University (OSU) and ODOT. The report includes information obtained from literature review, site investigations, and a survey of ODOT maintenance supervisors.
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