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The time-dependent and temperature-dependent behavior of post-tensioned concrete bridges were investigated through a case study of the St. Anthony Falls Bridge, consisting of laboratory testing of concrete time-dependent behaviors (i.e., creep and shrinkage), examination of data from the in situ instrumented bridge, and time-dependent finite element models. Laboratory results for creep and shrinkage were measured for 3.5 years after casting, and the data were best predicted by the 1978 CEB/FIP Model Code provisions. To compare the in situ readings to constant-temperature finite element models, the time-dependent behavior was extracted from the measurements using linear regression. The creep and shrinkage rates of the in situ bridge were found to depend on temperature. An adjusted age using the Arrhenius equation was used to account for the interactions between temperature and time-dependent behavior in the measured data. Results from the time-dependent finite element models incorporating the full construction sequence revealed that the 1990 CEB/FIP Model Code and ACI-209 models best predicted the in situ behavior. Finite element analysis also revealed that problems associated with excessive deflections or development of tension over the lifetime of the bridge would be unlikely. The interactions between temperature and time-dependent behavior were further investigated using a simplified finite element model, which indicated that vertical deflections and stresses can be affected by the cyclic application of thermal gradients. The findings from this study were used to develop an anomaly detection routine for the linear potentiometer data, which was successfully used to identify short-term and long-term artificial anomalies in the data.

Bridge decks are deteriorating across the state of Minnesota and limited funds are available to rehabilitate or replace them. The Minnesota Department of Transportation (MnDOT) Bridge Office is estimating construction costs well into the future to secure appropriate funding and to facilitate project programming. The rate at which bridge decks deteriorate is an important element used to estimate construction costs. MnDOT provided decades of inventory and inspection bridge data for this project. This included National Bridge Inventory (NBI) condition code data for 2601 bridges with concrete decks. Based on conversations with MnDOT, it was agreed that deck deterioration rates would be determined by the length of time bridge decks stay, or drop, at NBI condition codes. We analyzed the data to determine how many years, on average, a bridge deck remains at the various NBI condition code states. We also analyzed the data to determine what factors affect the rate of bridge deck deterioration. We looked at type of deck reinforcement (black bars, epoxy coated top bars, and all epoxy coated bars), presence of concrete overlay, average daily traffic (ADT), presence of 3 inches of cover to the top mat of reinforcement, superstructure material, and location.

Partial-depth patching mixes must rapidly gain strength to allow the roadway to be reopened to traffic quickly. A patch should also bond well to the substrate to prevent the patch from separating from the existing material and be durable enough to withstand harsh winters. The objective of the research described in this report is to develop improved guidelines for evaluation of pre-bagged commercial patching mixtures and to recommend effective construction practices. To achieve these objectives, 13 different cementitious materials were selected and tested to determine key properties including strength gain, shrinkage, bond strength, and durability. The impact of the proposed research will be a better performing patch material as well as performance criteria that can be used to compare the materials tested in this program to new materials that will certainly be developed in the future. This research was conducted in four main phases, literature review and development of a testing plan and three phases of laboratory testing campaigns. The most commonly available acceptance specification for partial-depth patching materials is the ASTM C928. This specification was followed and the outcomes of each of the recommended tests were evaluated in context of the performance of the patching materials. Several additional tests were developed and conducted to evaluate the bonding properties of patching materials; correlations between lab measured properties were also evaluated. Through aforementioned testing and analysis, a laboratory testing based acceptance procedure was developed for partial-depth patching materials to be used by MnDOT.

The current Minnesota Department of Transportation specification for coarse aggregate to be used in concrete pavements is based on either a maximum absorption of 1.75% (for Class B aggregate) or a maximum carbonate content of 30% by weight (for Class C aggregate). There is a concern that these specified limitations may reject potentially acceptable aggregates. This study is designed to evaluate the available methods for effectively characterizing the freeze-thaw (F-T) durability of aggregates. In this study, aggregates from 15 different sources in Minnesota were investigated. The experimental program included measuring the carbonate content, absorption, desorption, specific gravity, Iowa pore indices (i.e., primary pore index [PPI] and secondary pore index [SPI]), and pore size distribution of the carbonate and noncarbonate fractions. The results indicate that carbonate aggregates generally have higher absorption, lower specific gravity, and higher PPI and SPI than non-carbonate aggregates. Although there is no direct correlation between absorption, carbonate content, and SPI, a combination of high specific gravity (>2.60) and low absorption (<1.75%) often indicates a low SPI value. Carbonate aggregates generally have a much finer pore structure than non-carbonate aggregates, and the characteristics of their pore size distributions are clearly different. PPI correlates well with pores in the size range of 0.1-100 μm, and SPI correlates well with pores in the size range of 0.01-1 μm. Further res has the most significant effect on aggregate F-T which an aggregate will be truly F-T durable.

The asphalt mixture design and acceptance procedures for Minnesota Department of Transportation are currently governed primarily by the mixture composition requirements put forth through use of various volumetric measures (such as, air content, asphalt film thickness, aggregate gradation etc.). The asphalt binder has been required to meet performance criteria through the Superpave asphalt binder specifications. This study looked at use of laboratory performance test for asphalt mixtures. The study was conducted in three phases, first phase focused on merging the asphalt mix design records with the pavement performance data to determine effects of mix design parameters on asphalt pavement cracking performance. Second and third phase used a series of field sections across Minnesota to conduct field performance evaluations as well as laboratory tests on field cored samples. The testing for second an third phase of the study focused on using disk-shaped compact tension (DCT) fracture energy test as a laboratory performance test. The findings form he first phase of study indicated that the asphalt binder type as defined by the Superpave performance grade (PG) plays an important role in affecting the field cracking performance, majority of mixture design parameters did not indicate a consistent effect on field cracking performance, this reinforces the need for use of laboratory performance test as a mixture design tool as well as acceptance parameter. The DCT testing results showed trends consistent with previous and other on-going research studies, whereby the asphalt mixtures with higher fracture energies corresponded with pavements with lower amount of transverse cracking.

Unbonded concrete overlays are generally used to rehabilitate pavements by restoring lost ride and structural capacity. Historically, their design has been conservative (thick) due to the lack of a rational design method. In the summer of 2008, TH 53 near Duluth, MN, was rehabilitated with a thin (5-inch thick) unbonded concrete overlay. The Minnesota Department of Transportation (Mn/DOT) included the TH 53 overlay as part of a research project on thin unbonded concrete overlays. Falling weight deflectometer (FWD) measurements were taken both before and after construction. A short section of the project was instrumented with electronic sensors designed to collect environmental and load response data. The TH 53 test section is currently undergoing thorough evaluations and rigorous testing in accordance with the research project work plan. This report presents the initial baseline testing results, which include: distress survey and mapping, ride quality measurements, and structural testing. A visual distress survey, conducted in April 2009, revealed that approximately 40 transverse cracks have formed in the overlay over the nearly nine mile project length. FWD measurements indicate that the new pavement is providing good structural support.

This report includes the test results on aggregates from four taconite strata from the Mesabi iron range of Minnesota for concrete qualities including Los Angeles Rattler (LAR), absorption, flatness and elongation, magnesium sulfate, ASTM C 1260, and ASTM C 1293. The strata are identified as LC-8 Bed from United Taconite, LC-5 Bed from Ispat Inland/Mittal Steel (Laurentian Pit), LS-2 Bed from Ispat Inland/Mittal Steel (Laurentian Pit), and LUC Bed from United Taconite. A granite source, known to have moderately low expansion characteristics was also tested for comparison. All ledges tested well for Los Angeles Rattler and magnesium sulfate soundness. Ledges LS-2, LC-8, and LS-2 had excellent results for ASTM C 1260 and ASTM C 1293 expansion, while the LC-5 ledge performed very poorly. The Coal Creek fly ash used in the ASTM C 1293 tests mitigated ASR expansions much better than the slag mixes. As with any natural aggregate source, the physical and chemical properties of the taconite ledges vary. Because of the high variation in expansion potential, each potential concrete strata should be tested within a mine using ASTM C 1293. A Quality Control plan should be developed for each source. Specific gravity may be used to screen out potential deleterious strata, and should be performed frequently, perhaps on each blast. ASTM C 1260 tests should also be used on a frequent basis.

In the summer of 2008, after roughly fourteen years of service many of the pavement test cells at the Minnesota Road Research project (MnROAD) required rehabilitation or reconstruction. This massive construction effort was also known as "Phase II" (SP 8680-157). Among the cells that were rehabilitated was Cell 5, which is located on the mainline or interstate 94 section of the research facility. Cell 5 received a thin (4 to 5") unbonded concrete overlay. This cell was heavily instrumented with electronic sensors designed to collect environmental and load response data. In addition the pavement in this cell will be thoroughly evaluated and rigorously tested at various times during the year. The thin design, and consequently shorter life, of this overlay should produce valuable data over the life of the sensors. This report describes the physical characteristics of the new thin unbonded concrete overlay test cell 5 (sub-cells 105-405). Included in the report are the construction plans (including sensor layouts), quantities and bid prices, as well as the special provisions. The report also summarizes the results from the initial material tests, various surface characteristics measurements and other initial test results.

In September 2011 MnDOT constructed two cells in the MnROAD Mainline in continuation of the study of unbonded overlay (Cell 5) and to facilitate studies on a drainable base (Cell 6) with a longitudinal tined texture. Additionally, roller-compacted concrete shoulders were constructed in these cells to replace the preexisting asphalt shoulders. Finally, repairs were done to a thin concrete overlay of existing asphalt pavement installed in 2004 (Cell 63). This report discusses the construction procedure, instrumentation and the initial monitoring from these test cells.

The report describes the construction and design of composite pavements as a viable design strategy to use an asphalt concrete (AC) wearing course as the insulating material and a Portland cement concrete (PCC) structural layer as the load-carrying material. These pavements are intended for areas with heavy trucks and problem soils to increase the service life and minimize maintenance. The project focused specifically on thermally insulated concrete pavements (TICPs) (that is, composite thin AC overlays of new or structurally sound existing PCC pavements) and developed design and construction guidelines for TICPs. Specific research objectives include determining behavior of the layers of the TICP system, understanding life-cycle costs and the feasibility of TICPs, and incorporating the results into design and construction guidelines. Both construction and design guidelines are considered in light of the construction and performance of TICP test sections at the Minnesota Road Research project (MnROAD).

An extensive field and laboratory project was undertaken to evaluate the applicability of the concrete maturity method to predict opening to traffic criteria for portland cement concrete paving operations in Minnesota. The field study included visits to18 paving projects in the state over a three-year period. At these projects, different sensor types were evaluated. In the laboratory study, two-inch mortar cubes were tested to develop sensitivity analyses related to the proportions of cementitious materials, water-cementitious materials ratio, and other mix components. The study also evaluated different mathematical models and their ability to predict concrete strength relative to the computed maturity. In addition, a database of concrete mixes and their associated maturity curves were developed, as well as a spreadsheet for viewing maturity curves and entering new information into the database. A draft laboratory manual and a construction specification for creating and using maturity curves were developed. The results of this project include recommendations for maturity equipment, the method and ages for testing flexural beams when developing and validating maturity curves, the use of the exponential model for maturity curves, and suggestions for a construction specification and a laboratory manual. Further data collection and evaluation should be conducted by MnDOT as the method is implemented into standard practice. Appropriate modifications should then be made to ensure the method's ability to predict traffic opening and to enhance the effectiveness of paving operations.

This report describes an extensive data collection effort, spanning five years, and the subsequent data analysis to evaluate the performance of surface characteristics on portland cement concrete pavements that have been diamond ground with various grinding configurations. The data collected were analyzed and evaluated to observe the longterm performance of the surface characteristics of noise, friction, texture, and ride quality. In addition to the basic analysis and comparison of the performance with respect to the control cell, several other studies were performed such as the correction of noise data with ambient air temperatures at the individual third-octave frequencies and evaluation of trends in the data using various statistical analysis methods. In addition, other surface characteristics were measured to provide a baseline for comparison with potential future measurements, including rolling resistance and advanced texture characteristics. The surface characteristics evaluated indicated immediate changes were effected due to the grinding activity, and that over time (and due to the application of repetitive traffic) these immediate effects were diminished somewhat, in most cases. Based on the immediate and long-term performance of the various grinding configurations, recommendations are made in the report regarding the use of the configurations and areas suggested for further research.

This report examines how full-depth colored concrete performs in Minnesota roadways, and includes recommendations for improved specifications for construction and for repair of existing installations.

The project "Simplified Design Table for Minnesota Concrete Pavements" led to the creation of MnPCC-ME, a standalone 32-bit Windows executable program to replace the preexisting RigidPave. Whereas RigidPave was based upon the outdated AASHTO 1993 design procedure for rigid pavements, MnPCC-ME is based on MEPDG version 1.1, a mechanistic-empirical design procedure that accounts for the effects of traffic loading and environment. Furthermore, MnPCC-ME was localized for Minnesota pavements through: 1) the use of local climate data and weigh-in-motion traffic data; 2) the incorporation of previously conducted calibrations of the MEPDG for Minnesota pavements; and 3) the inclusion of advanced analysis features included in MnPCC-ME's flexible design counterpart, MnPAVE. The development and source code of MnPCC-ME is detailed in this final report.

This report presents an evaluation of wastewaters derived from concrete placement and maintenance and the preparation of best management practices (BMPs). Investigation and documentation of existing practices was done to ensure application to real situations and enhancement of constructability for all BMPs. Laboratory analysis of test specimens was done to provide characterization of factors that are likely to positively or negatively influence concrete wastewater composition. Evaluation of sedimentation and filtration through and absorption by sand and geotextile materials provides a simulation of the known control techniques. Development of a constituent occurrence and control model with a strong statistical base achieved through experimental replication supports development of BMPs that are both environmentally protective and constructible.

The Minnesota Department of Transportation (MnDOT) has developed a design for a precast composite slab-span system (PCSSS) to be used in accelerated bridge construction. The system consists of shallow inverted-tee precast beams placed between supports with cast-in-place (CIP) concrete placed on top, forming a composite slab-span system. Suitable for spans between 20 and 60 ft., the MnDOT PCSSS is useful for replacing a large number of aging conventional slab-span bridges throughout the United States highway system. The PCSSS has particular durability, constructability, and economical concerns that affect its value as a viable bridge design. To address these concerns, the performance of existing PCSSS bridges was evaluated and a review of a number of PCSSS design details was conducted. The field inspections demonstrated that design changes made to the PCSSS over its development have improved performance. A parametric design study was also conducted to investigate the effects of continuity design on the economy of the PCSSS. It was recommended that the PCSSS be designed as simply supported rather than as a continuous system.

The Minnesota Department of Transportation's (MnDOT) concrete pavement design procedure, RigidPave, is based on the 1981 American Association of State Highway and Transportation Officials (AASHTO) Interim Guide and is entirely empirically-based. The American Cement Pavement Association (ACPA) developed StreetPave based on the Portland Cement Association (PCA) thickness design method with updated information, including a new fatigue model. This study compared RigidPave to StreetPave with a review of the input variables and design inputs used by surrounding departments of transportation. Existing thin (six inches or less) concrete pavements were also evaluated, which included both city and county pavements and test cells at MnROAD. There are two primary differences between the RigidPave and StreetPave: 1) traffic is handled differently and 2) the underlying design methodology. Both are based on time-tested and proven design methodologies and provide generally similar designs. The predicted design lives of the doweled low-volume cells at MnROAD appear to be similar using either StreetPave or RigidPave. The examples provided by cities and counties typically did not contain enough known information, and therefore, required too many assumptions for analysis. The authors recommend that StreetPave is added as an alternate concrete pavement thickness design procedure for city and county projects in Minnesota. Use of the StreetPave is currently allowed by the Virginia Department of Transportation for design of secondary roads. It was also determined that RigidPave has a built-in reliability of approximately 89% due to a factor of safety that is applied to the modulus of rupture. An alternate approach to allowing StreetPave as a design option would be to incorporate the reliability knowledge of RigidPave learned as part of this project.

The camber at the time of bridge erection of prestressed concrete bridge girders predicted by the Minnesota Department of Transportation (MnDOT) was observed to often overestimate the measured cambers of girders erected at bridge sites in Minnesota, which, in some cases, was causing significant problems related to the formation of the bridge deck profile, the composite behavior of the girders and bridge deck, delays in construction and increased costs. Extensive historical data was collected from two precasting plants and MN counties and it was found that, on average, the measured cambers at release and erection were only 74% and 83.5%, respectively, of the design values. Through data collection, analysis, and material testing, it was found that the primary causes of the low camber at release were concrete release strengths that exceeded the design values, the use of an equation for concrete elastic modulus that greatly under-predicted the measured values, and thermal prestress losses not accounted for in design. Fourteen girders were instrumented and their camber measured and the program PBEAM was used to evaluate the influence of various time-dependent effects (i.e., solar radiation, relative humidity, concrete creep and shrinkage, length of cure and bunking/storage conditions) on long-term camber. Once investigated, these effects were included in long-term camber predictions that were used to create sets of both time-dependent and singlevalue camber multipliers. The use of these multipliers, along with modifications made to the elastic release camber calculations, greatly reduced the observed discrepancy between measured and design release and erection cambers.

Grout materials and grouting practices used in post-tensioned (PT) bridge construction prior to 2003 frequently resulted in the formation of air- or water-filled pockets; termed grout voids; inside PT tendons. Grout voids have been identified as conditions that can promote a corrosive environment within PT tendons. This report details the second phase of a two-phase project that was commissioned by MnDOT to identify best practices for the investigation of PT tendon conditions in bridge structures constructed prior to 2003. This report presents information and recommendations that will assist MnDOT in selecting and developing a project approach; work plan; and budget for future inspection and repair contracts for their pre-2003 era PT bridge inventory.

The need to consider sustainability in design dictates that materials should be recycled and reused whenever possible. The Minnesota Department of Transportation (MnDOT) is quite progressive in allowing the use of recycled aggregates in new construction. While the use of recycled concrete aggregate (RCA) in the base course of new pavements is quite common in Minnesota and many other states; it is rarely used in the concrete pavement itself. In fact; Minnesota was one of the few states to build multiple trial projects and has one of the largest number of concrete pavements constructed using the RCA in the concrete itself. The performance of those pavements; most of which are still in service; has never been formally evaluated against similar conventional concrete pavements. This prompted the current research study. Additional objectives were to assess the current state of practice across the nation; conduct experimental investigations using RCA in concrete; assess the sustainability and in particular the economics of using RCA in concrete; and finally to provide some recommendations for guidelines on using RCA in concrete. It has been shown by the authors and other researchers that it is possible to create strong and durable concrete mixtures using RCA as coarse aggregate in volume replacement levels of natural coarse aggregate up to 100%.

This report describes the 7-year performance of the 60-year concrete design test cell (Cell 53) built in 2008 in the MnROAD Low Volume Road). Many characteristics of this 115-foot cell, two 12-feet wide lanes, 12 inch thick dowelled concrete test have exhibited insignificant change in performance criteria over the 5-year period. . The test cell maintained adequate skid resistance since it was constructed in 2008. Transverse joint monitoring and fault measurements also indicated insignificant faulting over the period of review. In many cases, measured properties in the inside lane of Cell 53 were significantly different from outside lane. The International Roughness Index (IRI) was not initially low but has remained relatively constant. Additionally, a slight disparity of IRI between the inside (traffic) lane and the outside (environmental) lane was evident. The IRI in the inside lane was consistently higher than the outside lane. Seasonal deflection basins created for both summer and spring dates soon after construction in 2009 and similar summer and spring dates in 2013 showed deflections below 100 microns, which also suggests good performance. The test cell displayed excellent load transfer at all of the transverse joints tested in this research. The average load transfer was approximately 0.85, which was in some cases over four times as high as another MnROAD concrete pavement test cell which was undoweled and in poor condition. The load transfer in the 60-year design cell had not shown significant decrease over time. Researchers used the Evaluation of Layer Moduli and Overlay Design (ELMOD) to determine the layer properties of the pavement test cell. Again, similar dates in both spring and summer seasons were compared for the year 2009 and 2013. Summer results exhibited a slight decrease in calculated Moduli values for the base, subbase and subgrade layers, for both the inside and outside lane. This slight decrease over the period was not interpreted as failure in the base layers. Seven years of monitoring reveal that 60-year design concrete pavement test cell has not shown any performance issues apart from those inherent in the construction process. Most Importantly, evidence of lesser strain in the concrete when compared to thinner pavements designed for a shorter service life at the research facility.

Pavement base layer quality is vital for long term performance. Low stiffness and shear strength can result in loss of support and increased tensile stresses under loads. To maintain uniform support under concrete pavements and ensure satisfactory performance, a stable, non-erodible, drainable base layer is necessary. The primary objective of this report is to quantify the aggregate base properties required for concrete pavement foundations in accordance with currently established layer thickness requirements. The effects of properties of different base layers on concrete pavement performance were evaluated, based on an the mechanical and hydraulic properties of typical base materials collected from previous MnDOT studies and relevant literature. Field measured environmental data from the MnROAD test facility was collected and used for calibration purposes. The effects of environmental conditions on long-term concrete pavement performance were evaluated accordingly. Data from the LTPP SPS-2 study and MnROAD test cells were analyzed to evaluate the effects of design and site factors on performance. Improved aggregate classes were established, considering gradation, aggregate shape properties and drainage characteristics. Field test data were analyzed to assess the effectiveness of open-graded aggregate bases in providing structural stability. The analytical gradation analysis and the discrete element modeling approach for engineering aggregate shape and gradation were used to predict field performance. The findings from the study were synthesized to recommend revisions for performance-related specifications for aggregate bases supporting concrete pavements. The results would ideally help design cost effective base types and thicknesses suitable for both concrete and asphalt pavements.

In pavement infrastructure, functional characteristics are mainly preponderant over structural characteristics as the former typically govern pavement rehabilitation, maintenance and reconstruction decisions. Evidently, agencies invest in provision or restoration of friction (skid resistance) and make policies to minimize traffic noise. Most agencies accept (or reject) construction projects based mainly on initial ride quality. Consequently, this study examined various concrete textures imparted on new pavements in the 2007, 2010 and 2011 MnROAD test cell construction and monitored their ride quality, friction, tire pavement noise, visual conditions and acoustic impedance over time. The study successfully developed an in-situ impedance tube evaluation method for pervious concrete for a proxy to material and hydraulic conductivity condition. It also created tenable time-series equations for the progression of the various texture characteristics and developed a friction degradation model based on traffic and texture type. Advanced data analysis showed that longitudinal texturing and negative textures were strongly associated with pavement quietness. Investment analysis revealed that certain surfaces produced noise reduction of 6 decibels over the transverse time. Those textures including pervious concrete and diamond grinding were found to be cost-beneficial for noise abatement consideration. This research also associated rectangular texturing with anomalous laser-induced ride-quality measurements. Further analysis also accentuated a correlation of pavement condition to surface acoustics thus recommending the development of impedance tube for pavement joint condition monitoring. Additionally, This research recommended drag pre-textured longitudinal-tining as the optimal texture for durability, quietness and skid resistance based on the overall research results.

The Minnesota Department of Transportation has reported erection cambers of many prestressed concrete bridge girders that were much lower than anticipated. A previous University of Minnesota study (ONeill and French, MN/RC 2012-16) attributed the discrepancies to inaccurate estimates of the concrete strength and stiffness at release and strand force loss due to temperature during fabrication. The objective of this study was to further investigate the effects of temperature on strand force and camber during precast, prestressed girder fabrication and to make recommendations for the design and fabrication processes to reduce the potential loss of prestress due to temperature effects during fabrication and to improve the release camber estimation. A thermal effects analysis was developed based on four key steps in the girder fabrication process: tensioning, concrete-steel bond, release, and normalization. The study included fabricating six short prestressed concrete segments released at early ages to determine the time/temperature associated with bonding the prestressing strand to the concrete. To investigate the non-recoverable prestress losses during girder fabrication, four sets of girders (MN54 and 82MW) were instrumented with thermocouples, strain gages, and in some cases load cells, that were monitored during the fabrication process to separate the thermal and mechanical strain components. Effects investigated included casting during a cold season, casting during a warm season, casting with the free length of strand covered, and casting with different bed occupancy during any season. A recommended procedure for adjusting strand force during tensioning was proposed to account for non-recoverable strand force changes due to temperature changes between tensioning and bond.

The current empirical methods for determining traffic-opening criteria can be overly conservative causing unnecessary construction delays and user costs. The research described here recommends innovative mechanisticbased procedures for monitoring concrete early age development and evaluating the effect of early traffic opening on long-term damage accumulation. The procedure utilizes recent developments in nondestructive testing to optimize traffic opening timing without jeopardizing pavement longevity. These tasks were achieved via extensive field and laboratory experiments allowing for the analysis of variables such as curing condition and loading type with respect to the effect of early loading of concrete. The results of these efforts culminated in the development of a program that analyzes the effect of design and opening time decisions on pavement damage. The deliverable can be utilized by transportation agencies to make more informed decisions.