bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Lactofen Application Timing on Yield and Isoflavone Concentration in Soybean Seed
Authors: Nelson Kelly A. , Rottinghaus George E. , Nelson Teak E.
Published: April 2007

Postemergence application of the herbicide lactofen is known to increase phenolic compounds such as isoflavones in soybean [Glycine max (L.) Merr.] plants. We hypothesized that lactofen increases isoflavone levels in seed when applied at the R1 and R5 stages of development. Field research evaluated the effect of lactofen application timing and cultivar (‘Garst 3712’, glyphosate‐resistant; ‘Big Bubba’, high‐protein; and ‘Envy’, edamame) on crop response and seed isoflavone concentration. Lactofen at 70 g a.i. ha−1 injured soybean 7 to 15% when compared with the untreated control 7 d after treatment. Lactofen applied to Big Bubba at the R5 stage of development increased concentration of genistein 78 μg g−1 (11%), daidzein 82 μg g−1 (9%), and total isoflavones 169 μg g−1 (10%) compared with the nontreated control. Lactofen applied to Garst 3712 at the R5 stage of development increased daidzein concentration 52 μg g−1 (7%). There was no effect of lactofen on isoflavone concentration in Envy seed. Seed yield averaged across the three cultivars was reduced by 290 kg ha−1 when lactofen was applied at the R1 stage in 2002 and by 330 kg ha−1 when lactofen was applied at the R5 stage in 2004. Results suggest a late application of lactofen may increase isoflavone concentration in seed of high‐protein soybean cultivars, but this effect may be accompanied by a reduction in seed yield.
Deriving Comprehensive County‐Level Crop Yield and Area Data for U.S. Cropland
Authors: Lokupitiya Erandathie , Breidt F. Jay , Lokupitiya Ravindra , Williams Steve , Paustian Keith
Published: April 2007

Ground‐based data on crop production in the USA is provided through surveys conducted by the National Agricultural Statistics Service (NASS) and the Census of Agriculture (AgCensus). Statistics from these surveys are widely used in economic analyses, policy design, and for other purposes. However, missing data in the surveys presents limitations for research that requires comprehensive data for spatial analyses. We created comprehensive county‐level databases for nine major crops of the USA for a 16‐yr period, by filling the gaps in existing data reported by NASS and AgCensus. We used a combination of regression analyses with data reported by NASS and the AgCensus and linear mixed‐effect models incorporating county‐level environmental, management, and economic variables pertaining to different agroecozones. Predicted yield and crop area were very close to the data reported by NASS, within 10% relative error. The linear mixed‐effect model approach gave the best results in filling 84% of the total gaps in yields and 83% of the gaps in crop areas of all the crops. Regression analyses with AgCensus data filled 16% of the gaps in yields and crop areas of the major crops reported by NASS.
Accumulation and Crop Uptake of Soil Mineral Nitrogen as Influenced by Tillage, Cover Crops, and Nitrogen Fertilization
Authors: Sainju Upendra M. , Singh Bharat P. , Whitehead Wayne F. , Wang Shirley
Published: April 2007

Management practices may influence soil N levels due to crop uptake and leaching. We evaluated the effects of three tillage practices [no‐till (NT), strip till (ST), and chisel till (CT)], four cover crops [hairy vetch (Vicia villosa Roth), rye (Secale cereale L.), vetch + rye biculture, and winter weeds or no cover crop], and three N fertilization rates (0, 60–65, and 120–130 kg N ha−1) on NH4–N and NO3–N contents in Dothan sandy loam (fine‐loamy, kaolinitic, thermic, Plinthic Paleudults), and N uptake by cotton (Gossypium hirsutum L.) and sorghum [Sorghum bicolor (L.) Moench] from 2000 to 2002 in central Georgia. Nitrogen content was higher in vetch and vetch + rye than in rye and weeds. Soil NH4–N content at 0 to 30 cm was higher at harvest than at planting, and higher in NT or vetch with 120 to 130 kg N ha−1 than with other treatments. The NO3–N content at 0 to 120 cm varied with date of sampling and was higher with vetch than with rye and weeds. The NO3–N content at 0 to 10 cm was higher in CT with vetch than in NT and ST with rye or weeds. From November 2000 to April 2001 and from November 2001 to April 2002, N loss from crop residue and soil at 0 to 120 cm was higher with vetch than with other cover crops. Nitrogen removed by cotton lint was higher with rye than with other cover crops in 2000 and higher with 0 and 60 than with 120 kg N ha−1 in 2002, but N removed by sorghum grain and cotton and sorghum biomass were higher with vetch than with rye, and higher with 120 to 130 than with 0 kg N ha−1. Because of higher N supply, vetch increased soil mineral N and cotton and sorghum N uptake compared with rye, but also increased the potential for N leaching. The potential for N leaching can be reduced and crop N uptake can be optimized by mixing vetch with rye.
Spatial and Temporal Distribution of Salts on Fairways and Greens Irrigated with Reuse Water
Authors: Devitt D. A. , Lockett M. , Morris R. L. , Bird B. M.
Published: April 2007

A 4‐yr study was conducted to assess the impact of reuse water on soil salinization of nine golf courses in southern Nevada: three long‐term reuse courses, three fresh‐water courses, and three courses that transitioned to reuse water during the experimental period. Four of nine fairways had positive leaching fractions (LFs) during all 4 yr, with statistical separation occurring based on 4‐yr averages (p < 0.001). Soil salinity levels followed a sinusoidal seasonal curve, with 70% of all peaks associated with summer months. Salinity contour maps (surface soil) were compared over time. More than 85% of the surface area of greens were mapped as electrical conductivity of saturation extract (ECe) < 4.0 dS m−1, whereas 64% of the fairways were mapped at ECe < 4.0 dS m−1. This salinity relationship dropped to 13% on fairways of long‐term reuse courses. Changes in the average ECe values after transition to reuse water were primarily driven by the number of days a course had been irrigated with reuse water (R2 = 0.69∗∗∗). Depth‐averaged salinity (sensors) was found to be highly correlated with LF on reuse courses (R2 = 0.86∗∗∗) and transitional courses (R2 = 0.87∗∗∗). Yearly changes in depth‐averaged sensor values on transitional courses were described by an equation that included the number of days a golf course was irrigated with reuse water, the LF, and the uniformity of the irrigation system (R2 = 0.83∗∗∗). Although deficit irrigating can be practiced for short periods, adequate LFs are essential for the long‐term success of golf courses irrigated with reuse water.
Interaction between the severity of the infection by the nematode Anguillicola crassus and the tolerance to hypoxia in the European eel Anguilla anguilla
Authors: Lefebvre François , Contournet Pascal , Crivelli Alain
Published: April 2007

An experiment was conducted to test the effect of the infection by the swimbladder nematode Anguillicola crassus on the survival of the European eel Anguilla anguilla when exposed to hypoxic conditions. Forty-four wild caught and naturally infected eels were placed in an aquarium filled with water from the fishing site (Vaccarès Lagoon, French Mediterranean coast). In this confined environment (271), under decreasing oxygen resources, the first eel death occurred after 45 h (O2 = 0.98 mg l−1) and the last one after 96 h (O2 = 0.48 mg l−1). After dissection and parasite examination, analyses revealed significant negative correlations between the time to death and various parameters of parasite pressure (e.g., number of lumen worms, parasite mass, health state of the infected organ). It was shown that the severity of damage to the swimbladder rather than the count of living parasites was the major contributing factor in explaining the variation in time to death. These semi-experimental data demonstrating an increased eel mortality rate under severe oxygen stress are discussed for their relevance under field conditions, especially during hot summer months.
Ultrastructure of the ovary, ovicapt and oviduct of the spathebothriidean tapeworm Didymobothrium rudolphii (Monticelli, 1890)
Authors: Poddubnaya Larisa , Gibson David , Olson Peter
Published: April 2007

The ultrastructural details are presented of the ovary, ovicapt and oviduct of the spathebothriidean tapeworm Didymobothrium rudolphii (Monticelli, 1890) from the intestine of the sand sole Solea lascaris. Oogonia, maturing oocytes and mature oocytes are surrounded by a syncytial interstitial cytoplasm, one of the distinctive traits of which is the presence of numerous myelin-like bodies. Oocyte inclusions comprise cortical granules and a small number of lipid droplets. The thickened, nucleated epithelium of the ovicapt lacks any apical structure and is a prolongation of the narrow ovarian epithelium. The muscular sphincter of the ovicapt is formed by a band of longitudinal muscles and bands of radial muscles at right angles to the longitudinal layer, and numerous myocytes surround the ovicapt wall. The oviduct of D. rudolphii is subdivided into three regions: (1) the proximal oviduct; (2) the fertilization chamber — the region distal to the point of entry of the duct from the seminal receptacle; and (3) the ovovitelline duct — the region distal to the point of entry of the duct from the vitelline reservoir. A comparative analysis is made between the structures of the ovary, ovicapt and oviduct of D. rudolphii and those of two other spathebothriideans, Cyathocephalus truncatus and Diplocotyle olrikii, with a discussion of ultrastructural traits that might be used as taxonomic criteria within the order Spathebothriidea.
Determination of the enthalpy of fusion of Na3FeF6
Authors: Kosa L. , Macková I. , Šimko F.
Published: April 2007

The areas of the fusion and crystallization peaks of Na3FeF6 and of four calibration substances (KCl, NaCl, Na2SO4, and K2SO4) were measured using the DSC mode of a high-temperature calorimeter. Using the measured quantities and known values of the enthalpy of fusion of the calibration substances, the enthalpy of fusion of Na3FeF6 was determined. Its value at the temperature of fusion 1224 K was 70 ± 4 kJ mol−1.
Palladium-catalyzed heck and suzuki coupling in glycerol
Authors: Wolfson A. , Dlugy C.
Published: April 2007

The Heck coupling of halobenzenes with various alkenes and the Suzuki cross coupling of halobenzenes with phenylboronic acid were successfully performed in glycerol as the reaction solvent using homogeneous and heterogeneous palladium catalysts. Glycerol is a renewable and recyclable green solvent that is able to dissolve organic substrates, inorganic bases, and palladium complexes, and that allows easy isolation of the reaction product by simple extraction with glycerol-immiscible solvents such as diethyl ether, hexane, and dichloromethane.
Econometric Analysis of Customer Retention in an Aviation Trade Organization
Authors: Thomas Jacquelyn S.
Published: April 2007

The proliferation of customer data bases is a direct consequence of firms’ drive toward efficient customer-firm interactions. With regard to customer-firm interactions, firms have focused on customer retention rates. Using a customer data base, firms try to identify the most valuable customers within that data base. After identifying these customers, firms attempt to develop strategies and tactics that increase the retention of the most valued customers and maximize the profitability of the entire base of customers. With this goal in mind, common firm practices that have arisen are the offering of rewards, free additional services, and add-on selling. The impact of rewards, additional services, and add-on selling on the customer equity of a trade association in the aviation industry is examined. In particular a model that examines the impact that these factors have on customer retention and firm profitability is developed. This model is tested on a membership data base from a service organization that offers membership rewards, additional free services, and fee-based products to aircraft owners and pilots. The findings from this research have implications for how trade associations should develop marketing programs and strategically manage and target their most valuable customers.
Alternative Means of Compliance for Composite Structural Fatigue Certification of Small General Aviation Aircraft
Authors: Zyskowski Michael K.
Published: April 2007

As the future of the general aviation industry seems to be improving, a cultural paradigm shift may be imminent with the development of an advanced, revolutionary transportation system within the United States. One significant problem with this idea has been shown to be the fatigue structural certification of small, composite airplanes. By implementing a fatigue safe-life certification method for small general aviation aircraft, reduced certification program costs may be obtained while maintaining their reliability and capability. Although acceptable only when certifying aluminum aircraft, the current method has been modified here to incorporate the use of discontinuous composite materials on a defined small general aviation aircraft. Through this modification, a simplified method for the determination of the stress-cycle curve and a new “scatter factor” methodology based on the composite material properties have been developed. By using fiberglass reinforced polyester as an example composite material family, the safe-life of small general aviation aircraft relative to composite fatigue can be determined.
Finite-Element Analysis of Portland Cement Concrete Pavements with Cracks
Authors: Roesler Jeffery R. , Khazanovich Lev
Published: April 2007

It was verified that finite-element modeling could be successfully used to analyze concrete pavements with partial-depth cracks. An existing finite-element program, ILLI-SLAB, was modified (ILSL97) to allow for partial-depth crack analysis. To model a partial-depth crack, a special line spring element was added to the finite-element code. The line spring elements mimic the behavior of a crack by acting as a rotational hinge between two continuous slabs. By using available fracture mechanics techniques, a relationship was derived between the amount of moment load transfer across a crack and the crack depth. This analytical solution was then used to formulate the element stiffness matrix for the line spring element. The deflections predicted by the new finite-element program are correct, but the stresses in the vicinity of the crack tip needed to be corrected to match the stress singularity zone in front of cracks. Several example problems were used to verify the proposed finite-element model, and an example of a typical highway loading condition was analyzed.
Structural Evaluation and Analysis of Instrumented In-Service Concrete Pavements Subjected to Heavy Dynamic Loads
Authors: Izquierdo Jorge Tito , Agrait Leandro Rodriguez , Rĺos Benjamĺn Colucci
Published: April 2007

A structural evaluation and analysis of instrumented plain portland cement concrete pavement was performed in a rural primary highway subjected to heavy dynamic loads. Two full-scale slabs were constructed and tested to verify the dynamic analysis of the computer program UPR-PAVI2, which was developed at the University of Puerto Rico at Mayagüez using finite elements. It has the capability to analyze the effect of temperature differential, dead load, and dynamic and static trucks on rigid pavements. UPR-PAVI2 can consider different soil stiffness under the slab, the slab geometry, and multiple trucks and their longitudinal paths, velocities, stiffnesses, geometries, and load distributions. The instrumented slabs included both doweled and undoweled. Their material properties were obtained through laboratory and field tests. The subbase course consisted of a cut section in limestone bedrock for the doweled slab and borrowed material from limestone rock for the fill section used in the undoweled slab. The base course was composed of two layers of nonerodable black bituminous base. The slabs were constructed with concrete with a compressive strength of 34 MPa (5,000 psi) at 28 days. A loaded truck generated the established repetitions by moving over the instrumented slabs at different velocities, producing static and dynamic deflections that were measured with a data acquisition system. The replication and behavior of the response were analyzed, and the validated data were compared with the response obtained using UPR-PAVI2. The results obtained from this simulation were in good agreement with the field data.
Early Age Performance of Continuously Reinforced Concrete Pavement with Different Types of Aggregate
Authors: Cho Yoon-Ho , Dossey Terry , Mccullough B. Frank
Published: April 2007

The effect of coarse aggregate on pavement performance has been attributed to the volume of aggregate used in pavement construction. The different patterns of crack development for limestone (LS) and siliceous river gravel (SRG) are a typical example of aggregate-induced variable performance in continuously reinforced concrete pavement (CRCP). An attempt was made to find a reasonable solution for pavements with SRG. As a way to solve the performance problem observed from the SRG pavement, a blended aggregates mixture was suggested. Laboratory and field tests were performed to check the feasibility of their application in pavements. From the laboratory test, a 50:50 blending ratio was suggested after considering the effect on tensile strength and thermal coefficient of expansion. Field test sections were also constructed to verify previous performance observations for the two aggregates and to provide performance data for new variables such as blended aggregates and special curing methods. Unexpectedly, the blended mixture did not improve the performance of SRG pavement; rather it experienced worse cracking than SRG alone. A controlled experiment with additional field test sections is needed to verify or disprove this finding. The only definitive finding was that selection of aggregate in the concrete pavement is a vital consideration for the design of the pavement. The CRCP8 analytical program reasonably predicted crack spacing for both SRG and LS pavements, predicting mean crack spacing of 0.99 m (3.25 ft) for SRG and 1.98 m (6.41 ft) for the limestone. These values are somewhat below the actual spacing observed at 100 days. Data collected after the first winter period will be required to calibrate the program.
Neural Network Algorithms for the Correction of Concrete Slab Stresses from Linear Elastic Layered Programs
Authors: Haussmann Louis D. , Tutumluer Erol , Barenberg Ernest J.
Published: April 2007

Elastic layered programs (ELPs) are currently being used in mechanistic-based pavement design procedures for the analysis of jointed portland cement concrete pavements. Corrections must be made to stresses obtained from ELP solutions to account for the effects of finite slab size, load location on the slab, and load transfer efficiency of the joints. A preliminary artificial neural network (ANN) model is trained and used as a tool to predict the results of a finite-element analysis program for a standard pavement section. Under identical loading conditions, the trained neural network produces stresses within 1.2 percent of those obtained from finite-element analyses. The trained ANN model is found to be very effective for correcting ELP stresses, practically in the blink of an eye, with no requirements of complicated finite-element inputs. The preliminary ANN algorithm is currently being expanded to handle more general input conditions covering a wide range of slab sizes, slab thicknesses, subgrade supports, and loading conditions. Design curves created from these ANN algorithms will eventually enable pavement engineers to easily incorporate sophisticated state-of-the-art technology into routine practical design.
Development of a Roller-Compacted Concrete Pavement Crack and Joint Spacing Model
Authors: Pittman David W. , McCullough B. Frank
Published: April 2007

The development of a mechanistically based model (CRACK) that predicts the spacing of cracks in roller-compacted concrete (RCC) pavements due to restraint of drying shrinkage and thermal contraction is presented. The model considers the RCC pavement thickness, paving lane length, base friction characteristics, climatic time-temperature regimes, as well as the RCC drying shrinkage, coefficient of thermal contraction, strength gain, and modulus of elasticity. The model also determines the tensile stresses and displacements of the RCC slab along its length, from which the crack width is predicted. The CRACK program was used to predict the crack spacing and width at four RCC pavement field sites, and the predicted results were compared with field measurements. The model tends to overpredict the observed crack spacings, in part because of the simplifying assumptions used in the model development and the fact that the model does not consider fatigue stresses from warping, curling, or traffic-related loads, which cause additional cracking. However, the predicted crack spacing provides a basis for selecting joint spacings, and the predicted crack widths may help in the design of joint sealant reservoirs.
Effect of Nonlinear Temperature Gradient on Curling Stress in Concrete Pavements
Authors: Mohamed Ashraf R. , Hansen Will
Published: April 2007

Temperature and moisture gradients can lead to significant tensile stresses at the slab top and bottom. Current techniques for assessing the internal stresses due to such gradients are based on the assumption that temperature and moisture distributions through the slab thickness are linear. However, the actual distributions of such gradients have been found to be highly nonlinear. A new closed form solution technique for calculating the stresses in a pavement slab due to nonlinear gradients is introduced. The analysis is separated into two parts. In the first, an expression is presented for calculating the self-equilibrated stresses within a cross section due to internal restraint (i.e., satisfying equilibrium conditions and continuity of the strain field within the cross section). These stresses are independent of slab dimensions and boundary conditions. In the second, the stresses due to external restraint (i.e., self-weight and subgrade reaction) are calculated using an equivalent linear temperature gradient obtained from the first part and existing closed form solutions by Westergaard or Bradbury. The solution to this step includes slab length and boundary conditions. Total internal stresses due to nonlinear gradients are obtained by using the superposition principle. The methodology has been applied to field data from two studies in which the temperature profiles were recorded throughout a 24-hr period. Linear gradient solution methods cannot accurately predict the curling stresses in concrete pavements. This is especially pronounced during nighttime and early morning hours, during which nonlinear analysis predicts tensile stress in both the slab bottom and top before the application of any traffic loading.
Modified Portland Cement Association Stress Analysis and Thickness Design Procedures
Authors: Lee Ying-Haur , Bair Jean-Hwa , Lee Chao-Tsung , Yen Shao-Tang , Lee Ying-Ming
Published: April 2007

A new stress analysis and thickness design procedure for jointed concrete pavements was developed. On the basis of Westergaard’s edge stress solution and several prediction models for stress adjustments for a variety of loading and environmental (i.e., thermal curling) conditions, a modified Portland Cement Association (PCA) equivalent stress analysis and thickness design procedure was proposed and implemented in a highly user-friendly, Windows-based program, TKUPAV, for practical trial applications. The proposed approach has been further verified by reproducing results very close to the PCA’s equivalent stresses and fatigue damages using a spreadsheet program and the TKUPAV program. The possible detrimental effect of loading plus daytime curling has been illustrated in a case study, which also indicated that the effect of thermal curling should be considered in the thickness design of concrete pavements.
Compatible Approach to Concrete Strength Characterization in the Design and Construction of Concrete Pavements
Authors: Soares Jorge B. , Zollinger Dan G.
Published: April 2007

The effectiveness of a concrete pavement construction specification depends on the degree of correlation the criteria in the specification have to the material properties and behavior characteristics that govern the performance of pavements. Since concrete strength is determined on the basis of small test specimens, it is important that the strength measured in these specimens be representative of the strength within the actual configuration of a pavement system. A primary deficiency in this regard is that strengths obtained from different test specimens can be quite different from each other and from the strength of the concrete in the pavement. This fact raises the question of which specimen should serve as a representative concrete strength standard that would allow a reliable measure of concrete quality and yet provide a parameter that is compatible with design stress calculations. This deficiency is encompassed within size and geometry effects that are present when estimating strength from small test specimens. Since most distresses in concrete pavements are due to tension-induced cracking, it is only logical that tension-type tests be used to represent concrete resistance to failure. A simplified tension test method, based on the fracture mechanics theory, provides a solution to the deficiency by taking into account size and geometry effects. The method considers the geometry of the specimen from which the strength is being measured (e.g., cylinder) and the geometry of the structure to which the measured strength is being applied (e.g., pavement slab). This method makes it possible to circumvent the problem of obtaining a representative strength value from a small laboratory specimen.
Laboratory and Field Moisture Conditions for Flexible Pavement
Authors: Hassan Hossam F. , White Thomas D.
Published: April 2007

The primary source of water in pavements is from surface infiltration. Water from surface infiltration and other sources increases pavement maintenance costs and shortens pavement life. These effects can be mitigated by including a subdrainage system in the pavement design. A study of pavement subdrainage systems has been conducted that included a phase for laboratory tests for the hydraulic characteristics of materials used in three test sections built on I-469 at Fort Wayne, Indiana. The purpose of building these test sections was to evaluate the subdrainage performance and materials used in the sections. The sections differ in the permeable drainage layer as well as the filter (separation) layer. The sections were instrumented with different types of sensors. Instrumentation installed in the sections included time domain reflectometry (TDR) probes, moisture suction blocks, temperature probes, resistivity tree, and rainfall and outflow tipping buckets. Other features of the instrumentation site included an air temperature probe and access tube for a nuclear moisture content probe. The laboratory hydraulic characteristic test results on the materials are presented. Field moisture condition in the layers is also presented. Calibration equations for the TDR are developed for the field materials. A summary of three rainfall events and pavement outflow volumes recorded for the tests is presented. Recommendations are made for materials to be used in subdrainage systems.
In Situ Evaluation of Fatigue Damage Growth and Healing of Asphalt Concrete Pavements Using Stress Wave Method
Authors: Kim Yongon , Kim Y. Richard
Published: April 2007

Accurate in situ evaluation of the changes in material properties of an asphalt surface layer due to fatigue loading and rest periods is important for a better understanding of fatigue mechanisms of asphalt concrete in the field and therefore more realistic prediction of the fatigue life of asphalt pavements. A nondestructive technique based on the stress wave propagation method is presented as a means of measuring the changes in the “apparent” modulus of an asphalt surface layer due to fatigue damage growth and healing during rest periods. The method was applied to four asphalt pavements in the FHWA Turner Fairbank Highway Research Center that were loaded by the Accelerated Loading Facility to induce fatigue damage. The dispersion analysis is performed using the Short Kernel Method on the wave transients measured at different loading cycles and after rest periods. The results indicate that ( a) the test and analysis technique used provides a sensitive means of evaluating the changes in asphalt surface layer properties during fatigue loads and rest periods, ( b) the elastic modulus of the asphalt layer decreases as the number of loading cycles increases in an S-shape decaying curve, and ( c) the effective modulus of the asphalt layer increases because of the introduction of rest between loading cycles.
Flexible Pavement Overlays: The State Experience
Authors: Sebaaly Peter E. , Lani Stephen , Bemanian Sohila , Cocking Christopher
Published: April 2007

The design and construction of flexible overlays has become a popular exercise. However, there is not a simple, straightforward, and yet reliable design procedure that the design engineer can implement on a routine basis. The data needed for overlay design are not easily accessible to the design engineer, and yet the accessible data are not fully reliable in most cases. The process by which the design engineers at the Nevada Department of Transportation handle overlay design is presented. The various steps followed and the obstacles that the design engineer encounters in the search for the necessary data and the final design process are described. Major assumptions must be made along the way that could significantly affect the final design. Three case studies are presented. Each project was designed using three different design methods, including the AASHTO nondestructive testing method, the AASHTO condition survey method, and the Nevada Department of Transportation (NDOT) mechanistic overlay design method. All three methods used the same data gathered by the design engineer for each project. The analysis indicates that there is a significant discrepancy between the two AASHTO methods, whereas the NDOT method and the AASHTO condition survey method agreed on one project.
Performance of a Rehabilitated D-Cracked Jointed Plain Concrete Airfield Pavement
Authors: Kumapley Robert K. , Owusu-Antwi Emmanuel B.
Published: April 2007

The results of a study conducted to assess the performance of a D-cracked pavement rehabilitated between 1986 and 1989 are presented. The original pavement, located at Forbes Field in Topeka, Kansas, consisted of a thick jointed plain concrete pavement (JPCP) placed directly on a clay subgrade and had D-cracking in the top 102 mm (4 in.). The D-cracking was removed completely by milling before the placement of a bonded JPCP overlay. The major concerns were ( a) the bonding condition between the overlay and the original JPCP, ( b) the extent of D-cracking progression in the original JPCP, if any, after rehabilitation, and ( c) the structural condition of the overlay and the original JPCP. These concerns were investigated using data from heavy weight deflectometer tests performed at the center, corner, and edge of the JPCP slabs. Cores from the rehabilitated pavement were also inspected. The results of the study indicate that, after 6 to 9 years of service, the rehabilitated JPCP is in good structural condition. Significant friction and bonding still exist between the overlay and the original JPCP layer. These results may be useful to pavement engineers considering a bonded portland cement concrete overlay for rehabilitation of D-cracked JPCP.
Implementation Feasibility of Asphalt Concrete–Overlaid Portland Cement Concrete Pavement Rehabilitation Guidelines
Authors: Hall Kathleen T. , Schutzbach Amy
Published: April 2007

Illinois Highway Research Study IHR-532 was conducted to develop project-level guidelines for evaluation, rehabilitation selection, and rehabilitation design for existing asphalt concrete–overlaid portland cement concrete (AC/PCC) pavements in Illinois. Use of these guidelines depends on data that are not normally available for network-level analysis. A study was conducted to assess the feasibility of implementing these guidelines in network-level decision making and to assess the effects that implementing these guidelines for selection of rehabilitation methods for existing asphalt-overlaid concrete pavements would have on the overall rehabilitation budget requirements for a district network of Interstate pavements, the overall network condition, and pavement network remaining life. These objectives were met by comparing the IHR-532 rehabilitation strategy (which identifies one or more rehabilitation options) with the Illinois Department of Transportation’s current rehabilitation policy, which is an AC overlay thickness of 83 mm (3.25 in.). This feasibility analysis indicated that the selection of the preferred rehabilitation strategy was strongly related to the type and condition of the existing pavement. It also indicated that the IHR-532 rehabilitation strategy and the single rehabilitation strategy yielded similar networkwide results when compared on the basis of average condition at the end of the analysis period. However, the IHR-532 rehabilitation strategy indicated greater benefit than the single rehabilitation strategy, at any budget level, when compared on the basis of network average remaining life at the end of the analysis period.
Centrifuge Testing of Plumb and Battered Pile Groups in Sand
Authors: Pinto Paulo , McVay Michael , Hoit Marc , Lai Peter
Published: April 2007

Pile groups are generally used under structures subject to heavy axial loads or large lateral forces with or without scour. The focus in this paper is only on pile groups subject to large lateral forces. Currently, little, if any, full-scale lateral load data exist on pile groups that vary pile head fixity or batter. Reported here is the summary of a series of centrifuge tests on free- and fixed-head plumb and battered pile groups. Influence of pile head constraint, pile spacing, soil density, and vertical dead load is reported for groups ranging from 3 × 3 to 3 × 7 in size. Results reveal a significant lateral resistance of fixed- over free-head pile groups; fixed-head piles develop significant axial forces; battered piles without vertical dead loads are generally no better than plumb piles; and in the case of plumb piles, the use of multipliers to represent group interaction is valid.
Innovative Load Testing of Deep Foundations
Authors: O’Neill Michael W. , Brown Dan A. , Townsend Frank C. , Abar Nariman
Published: April 2007

The current focus on extreme event loading of structures requires a better understanding of the performance of full-scale deep foundation systems, especially at large deflections. Recently, innovative loading systems such as the Osterberg cell, the Statnamic device, and linear inertial mass vibrators and their clever applications have permitted testing of much larger foundations to failure than was possible in the past and have allowed for tests to be performed at rates of loading that closely replicate the loading events being modeled. Examples of applications of those systems are described, and exceptional recent loading tests of deep foundation systems are documented.
Enhanced in Situ Geotechnical Testing for Bridge Foundation Analysis
Authors: Mayne Paul W. , Dumas Chris
Published: April 2007

Geotechnical analyses of bridge foundations are complex because of the difficulties in addressing the highly nonlinear and anisotropic stress-strain-strength-time behavior of soils, from the nondestructive small-strain range region through to failure conditions. Often engineering practice overrelies on a single test value from soil borings [the standard penetration test (SPT) N-value] for the evaluation of all necessary geotechnical parameters, which is unrealistic. There exists, in fact, a variety of in situ measurement devices for the better definition of soil engineering properties, particularly hybrid devices such as the seismic piezocone and seismic flat dilatometer, as related to foundation applications. The importance of small-strain field stiffness measurements (i.e., shear wave velocity) is discussed and illustrated with two case studies involving the axial response of drilled shaft and driven pile foundations. The examples are reviewed within the context of elastic continuum theory but may be applied similarly for use in site-specific determinations of nonlinear spring constants and well-known t-z, p-y, or q-z curves, or all three.
Prediction of Lateral Load Response for a Pile Group
Authors: Ruesta Pedro F. , Townsend F. C.
Published: April 2007

A full-scale lateral load test of a pile group consisting of 16 (4 by 4) prestressed 76-cm-square concrete piles was conducted at Roosevelt Bridge, Stuart, Florida, during the summer of 1996. Presented are ( a) in situ test results, ( b) various p-y curves from these tests, and ( c) comparisons of various computer predictions (FLPIER, GROUP, and PIGR3D) using p-y curves tempered with results from a single-pile load test. From these comparisons, the best Class A prediction is made for the 16-pile group using FLPIER with nonlinear pile properties; p-y multipliers of 0.8, 0.4, 0.3, and 0.3 for the leading, middle, and trailing two rows, respectively; and dilatometer test—pressuremeter test p-y curves. This prediction suggests that an average load per pile of 280 kN will produce a deflection of 0.1 m (63 kips/pile at a deflection of 3.9 in.) for the test group.
Resistance Factors for Single Driven Piles from Experiments
Authors: Yoon Gil L. , O’Neill Michael W.
Published: April 2007

Present-generation resistance factors for foundations in load and resistance factor design (LRFD) do not necessarily reflect directly the variance in site-specific resistance and bias in making resistance estimates. The purpose of this paper is to describe a process whereby resistance factors can be determined from experimental data at a site and to demonstrate that process for driven piles at a specific site in overconsolidated clay. Eleven pipe piles were tested to failure in compression, and 28 cone penetrometer tests (CPTs) were performed near the piles. The CPT results were characterized through both a geostatistical method and a random sampling technique to estimate resistance factors for ultimate pile resistances using three CPT methods and two α-methods. A first-order, second-moment reliability method was applied using the interpreted bias characteristics of the design methods and the dispersion characteristics of the CPT and pile tests to relate resistance factors to selected reliability indexes. The resistance factors obtained for this site by this process were 0.50 to 0.62 for the three CPT methods and 0.30 to 0.55 for the ॅ-methods for a target reliability index of 3.5, depending on the value selected for the live load factor.
Soil-Pile-Superstructure Interaction in Liquefiable Sand
Authors: Boulanger Ross W. , Wilson Daniel W. , Kutter Bruce L. , Abghari Abbas
Published: April 2007

Soil-pile-superstructure interaction in liquefiable sand is evaluated using dynamic centrifuge model tests and pseudostatic p-y analyses. Select recordings from a recent centrifuge test are presented to illustrate typical behavior with and without liquefaction in an upper sand layer. Pseudostatic p-y analyses of single-pile systems in two recent centrifuge model tests show that the apparent reduction in p-y resistance due to liquefaction was strongly affected by changes in the relative density of the sand and drainage conditions.
Peak Undrained Resistance of Loose Sands
Authors: Norris G. , Madhu R. , Ashour M. , Valceschini R.
Published: April 2007

The peak undrained resistance (σ d,upeak) of a loose sand during liquefaction under monotonic loading does not necessarily occur on or near the Mohr Coulomb failure envelope. Instead, it occurs as that combination or product of a decreasing effective confining pressure ([Formula: see text]) and an increasing stress level ( SL). The condition in which this product is a maximum occurs at a particular point on a plot of the deviator stress (σ d) versus volumetric strain (ε v) as assessed from a drained triaxial test. A method is presented whereby a single drained test with volume change measurement can be used to assess this undrained peak. This is a refinement of a more complete effective stress method of liquefaction analysis that requires only drained triaxial testing.
Primary Results for the First Texas Mobile Load Simulator Test Pad
Authors: Chen Dar-Hao , Fults Ken , Murphy Mike
Published: April 2007

The pavement behavior under 630,000 axle repetitions from the Texas Mobile Load Simulator (TxMLS) was studied. During the course of TxMLS testing, nondestructive testing and in situ instrumentation (pressure cell, strain gauge, and multidepth deflectometers) were applied to monitor and assess the pavement condition. In addition, pavement distress data, such as measurements of permanent deformation, rutting, and cracking, were collected and analyzed. At the end of 630,000 axle repetitions, the maximum permanent deformation was approximately 22 mm. A forensic study was then performed by cutting a 1.8-m by 3-m trench in the middle of the test pad and three nuclear density gauge (NDG) tests were performed on top of each layer to determine the densities and moisture contents. It was found that the lime-treated gravel base (LTB) layer contributed the most to rutting. The axle-load applications increased the density of the LTB layer in the pit area, which caused the pavement structure to settle and consolidate. The highest rate of rutting was observed at the early stages of loading, between 10,000 and 20,000 axle repetitions. The higher deflections on the left wheelpath as observed from falling weight deflectometer data were probably due to the higher moisture content and the instrumented pit. NDG data showed that the LTB, lime-stabilized subgrade (LTS), and subgrade in the left wheelpath all had higher moisture contents than those in the right wheelpath.
Crack Development in Linear Tracking Test Pavements from Visual Survey to Pixel Analysis
Authors: Miradi A. , Groenendijk J. , Dohmen L. J. M.
Published: April 2007

Cracking is one of the most common and important types of pavement distress. This includes structural cracking, originating at the bottom of the bound layers and growing toward the surface, and surface-originated cracking. Descriptions of cracking and its development, both for research and for pavement management and maintenance, are limited to some global nonnumerical characterization, which is not sufficient for detailed computerized analyses. The crack pattern of the linear tracking device (LINTRACK) test Lane I was originally recorded nonnumerically on photographs and transparent plastic sheets. These data were digitized to enable scientific analysis and interpretation. Crack length, crack direction, growth speed, and percentage of cracked area were calculated from the digital data.
Effect of Initial Pavement Smoothness on Future Smoothness and Pavement Life
Authors: Smith K. L. , Smith K. D. , Hoerner T. E. , Darter M. I.
Published: April 2007

Initial pavement smoothness has an effect on the future smoothness and life of asphalt concrete (AC) and portland cement concrete (PCC), as well as AC overlays of existing AC and PCC pavements. Initial pavement smoothness has a significant effect in 80 percent of new construction (both AC and PCC pavements) and in 70 percent of AC-overlay construction. Furthermore, using two different analysis techniques, added pavement life can be obtained by achieving higher levels of initial smoothness. Combined results of roughness-model and pavement-failure analyses indicate at least a 9 percent increase in life corresponding to a 25 percent increase in smoothness from target profile index (PI) values of 7 and 5 in./mi (0.11 and 0.08 m/km) for concrete and asphalt pavements, respectively.
Backcalculation Analysis of Pavement-Layer Moduli Using Genetic Algorithms
Authors: Fwa T. F. , Tan C. Y. , Chan W. T.
Published: April 2007

Most existing iterative backcalculation programs for pavement layer moduli arrive at their solutions by minimizing an objective function related to the differences between computed and measured surface deflections. Unfortunately, the solution surface of the backcalculation problem of pavement-layer moduli is known to contain many local minima. A potentially good backcalculation procedure would be one that has a strong global search ability to overcome the problem of local minima. The genetic algorithm (GA) is a technique that satisfies this requirement. The development of a backcalculation program known as NUS-GABACK using the genetic-algorithm approach is presented, along with the formulation and operations of the program. A detailed performance evaluation of the GA-based method is made against four other programs by solving five backcalculation problems with different structural composition. It was found that NUS-GABACK performed comparably well against the other programs and demonstrated consistency in the accuracies of backcalculated moduli.
Effects of Bus Stop Design on Suburban Arterial Operations
Authors: Fitzpatrick Kay , Nowlin R. Lewis
Published: April 2007

When choosing the location and design for a particular bus stop, several alternatives are available. These alternatives include near-side, far-side, or midblock locations, and curbside or bus bay designs. Several studies have focused on choosing the optimum location of a bus stop for given situations; however, few have investigated the effects of bus stop design. The objective is to use computer simulation to determine how bus stop design influences traffic operations around a bus stop. Bus stop designs analyzed included curbside, bus bay, open bus bay, and queue jumper. The results can be used to aid in the selection of a preferred bus stop design for a given location and traffic volume. The analysis was divided into two separate studies: curbside versus bus bay/open bus bay, and queue jumper versus no queue jumper. The analysis consisted of investigating the relationships between variables such as travel time, speed, and traffic volume for given bus stop designs and locations. The bus stop locations investigated in the curbside–bus bay/open bus bay study included midblock and far-side. Results indicated that the bus bay design provided the greatest benefit at traffic volumes of approximately 350 vehicles per hour per lane (vphpl) and above; however, notable advantages in vehicle speeds were also observed at 250 vphpl. Results from the queue jumper study revealed that the queue jumper design provided significant benefits at volumes above approximately 250 vphpl.