bluuebunny/crossref_metadata_2025 huggingface dataset:
Methodology for Improving Weak Foundations by Lateral Consolidation
Authors: Ta-Teh Chang Dave , Chang Jeffery C. I. , Chang Jung-Yang
Published: April 2007

Leader Administration College planned to build its administration building on the campus located at An-Nan district, Tainan, Taiwan. A geological survey showed that the soil underneath the foundation of the administration building was consolidated soft clay, including a portion of stratified sand layer. The differential settlement was estimated to be greater than 1/200. Lateral consolidation was chosen to reduce the differential settlement to 1/250.
Discrete Element Modeling of Asphalt Concrete: Microfabric Approach
Authors: Buttlar William G. , You Zhanping
Published: April 2007

Micromechanical modeling has tremendous potential benefits in the field of asphalt technology for reducing or eliminating costly tests to characterize asphalt-aggregate mixtures for the design and control of flexible pavement structures and materials. In time, these models could provide a crucial missing link for the development of true performance-related specifications for hot-mix asphalt. A microfabric discrete element modeling (MDEM) approach is presented for modeling asphalt concrete microstructure. The technique is a straightforward extension of a traditional discrete element modeling (DEM) analysis, in which various material phases (e.g., aggregates, mastic) are modeled with clusters of very small, discrete elements. The MDEM approach has all the benefits of traditional DEM (e.g., the ability to handle complex, changing contact geometries and the suitability for modeling large displacements and crack propagation). These models also allow for the simulation of specimen assembly (e.g., laboratory compaction of the asphalt mixture). By modeling inclusions such as aggregates with a “mesh” of small, discrete elements, it is also possible for one to model complex aggregate shapes and the propagation of cracks around or through aggregates during a strength test. A commercially available DEM package was used to demonstrate the usefulness of the MDEM approach. A method was also presented to obtain the properties of the matrix material in an asphalt mixture, which is typically difficult to determine experimentally. This study was limited to two-dimensional analysis techniques and involved the simulation of small test specimens. Follow-up studies involving larger specimen models and three-dimensional modeling capabilities are under way.
Correlation of Fine Aggregate Imaging Shape Indices with Asphalt Mixture Performance
Authors: Masad Eyad , Olcott Dana , White Thomas , Tashman Laith
Published: April 2007

This study addresses the relationship between fine aggregate shape properties and the performance of hot-mix asphalt. Aggregate shape was expressed as three independent properties: form, angularity, and texture. Image analysis procedures and indices were developed to capture these properties. The indices were measured for 22 aggregate samples. The samples were related to the hot-mix asphalt rutting resistance measured under wet and dry conditions in the Purdue wheel-tracking device. Among the different aggregate shape properties, texture had the strongest correlation with rutting resistance. Resistance to rutting increased exponentially with an increase in aggregate texture.
National Bus and Facilities Condition Assessment
Authors: Tomeh Osama , Brady Stephen , Skorupski Douglas
Published: April 2007

This assessment of the national bus situation involved on-site physical inspections of buses and related facilities at a representative sample of transit operators in the United States. In total, the current physical condition of 572 vehicles and 77 facilities at 31 different transit properties was evaluated. The primary goal of this assessment was to provide FTA with an accurate snapshot of the current physical condition of the nation’s bus fleets and related assets. A secondary goal was to develop improved statistical models of bus and facility decay to significantly improve modeling accuracy and the understanding of asset decay. The primary highlights of the assessment results are as follows: ( a) the condition of the nation’s bus fleet is poorer than expected; ( b) the bus life cycle is characterized by three vehicle decay regimes; ( c) vehicle decay rates vary widely across transit agencies; ( d) vehicle and facility condition is better for agencies pursuing preventive maintenance and poorer for agencies pursuing corrective maintenance; ( e) primary determinants of vehicle decay are high utilization rates, salt-related corrosion, and poor preventive maintenance; and ( f) bus facilities are in poorer condition than expected. On the basis of the condition assessment data decay curves for vehicles and facilities were reestimated.
"Second Train Coming" Warning Sign Demonstration Project
Authors: Khawani Vijay
Published: April 2007

Data collected to date for a demonstration project on the Los Angeles County Metropolitan Transportation Authority’s (LACMTA) Metro Blue Line (MBL) are presented. The project involves the installation of a train-activated sign to warn pedestrians when two or more trains are approaching a highway-rail intersection (HRI). The hazard associated with two trains approaching an HRI is particularly prevalent if the HRI is adjacent to a station. Typically, if pedestrians see a train berthed at a station that has activated warning devices downstream, in a haste to board the train, they fail to notice trains approaching from the opposite direction on adjacent tracks. This scenario has resulted in 14 accidents and 4 fatalities at LACMTA’s Vernon Avenue HRI since the start of MBL operations in 1990. A second train approaching the HRI can reasonably be assumed to be a major contributing factor in many of such train-pedestrian collisions. The process for selecting the demonstration site and warning sign is described. Also described are the sign’s detail, public information plan to educate and inform pedestrians about the sign, and method to evaluate sign effectiveness. Because the project is under way, final results on sign effectiveness cannot be presented, but data collected and projected final results are discussed.
Regional Intermodal Freight Transport Flows and Projections
Authors: Brander J. Robert G. , Wilson Frank R.
Published: April 2007

This study examined intermodal transport in the Province of New Brunswick in Canada’s Maritime Provinces. In 1998, the Policy Branch of the New Brunswick Department of Transportation commissioned the University of New Brunswick’s Transportation Group to conduct a study of intermodal freight transport in New Brunswick. The objective was to evaluate intermodal movements and provide the first provincial database on intermodal traffic, consisting of (a) traffic flowing through the province without an intermediate stop, (b) movements entirely within the province, and (c) movements with either a destination or an origin in the province. Data were collected from rail, truck, air, and marine centers. Transborder (between the United States and Canada) traffic was monitored, and a survey was conducted of shippers using either intermodal transport or potential users of the service. Issues that carriers and shippers had with existing intermodal services were solicited and evaluated. Growth trends for intermodal transport in the study area were developed using a most likely scenario. In developing the growth trends, the potential effects of recent and current events on growth were evaluated.
Ferries for Airport Drayage: Analysis of the San Francisco Bay Area
Authors: Bruzzone Anthony , Ballesteros Jon , Glover John
Published: April 2007

The San Francisco Bay Area’s intercity air transportation system can move transcontinental goods from airport to airport in less than 6 hours. However, congestion on the Bay Area’s regional highway system significantly increases the door-to-door travel time. This study shows that using water transit instead of trucks at peak periods in two primary air express markets would save shippers 20 to 50 min of travel time. The calculated additional cost for each min of savings is $0.003 to $0.01 per air express package. Using water transport for midday air cargo drayage increases costs over the air express component, but may be justified for logistical reasons. Constraints to implementation include environmental, jurisdictional, and labor issues.
Application of Dynamic Cone Penetrometer in Evaluation of Base and Subgrade Layers
Authors: Chen Dar-Hao , Wang Jian-Neng , Bilyeu John
Published: April 2007

The dynamic cone penetrometer (DCP) is one of the lowest-cost alternatives for characterization of pavement layer qualities. In addition, it is fairly easy to collect and analyze data with the DCP. The DCP is not popular in the pavement engineering community, partly because of the lack of a solid correlation between DCP results and modulus values. More than 60 DCP tests have been conducted on two test pavements used for accelerated pavement testing to assess the validities of empirical equations proposed in previous literature to compute layer moduli from data obtained with the DCP. The effect of the test procedure on the DCP test values was studied, and the moduli obtained with the DCP were compared with those obtained by falling weight deflectometer (FWD)-multidepth deflectometer (MDD) and laboratory tests. It was found that the values obtained with the DCP are dependent on the test procedure, which affects the results by at least 10 percent. If there is an asphalt concrete layer, it is preferable to conduct DCP tests through a drilled hole. A sample size of 6 is recommended for routine characterization of base and subgrade layers, because this number would achieve 95 percent confidence and an error of estimate of less than 20 percent. The moduli obtained by using the DCP and the adopted equations yielded results compatible with those obtained from FWD-MDD tests. Those equations have been recommended to the Texas Department of Transportation for further evaluation and use in routine analysis. The laboratory-determined subgrade moduli were only slightly higher than those from DCP and FWD-MDD tests. No correction factor is required for the moduli backcalculated from FWD data to match the moduli obtained in the laboratory.
Simple Dynamic Backcalculation Procedure for Falling Weight Deflectometer Testing of Rigid Pavements
Authors: Chatti Karim , Kuk Kim Tae
Published: April 2007

A simple and direct method for backcalculation of the dynamic subgrade stiffness and damping coefficients from falling weight deflectometer (FWD) deflection basins is presented. The method can also be used to detect a stiff layer underneath the pavement system. The method consists first of decomposition of the transient deflection signal of each sensor into a series of harmonic motions by the fast Fourier transform algorithm. Then, for each frequency of interest, the real and imaginary components of the displaced volume underneath the slab are calculated from the complex deflection basin. The dynamic force-displacement relationship is decomposed into real and imaginary parts, leading to a simple system of equations that can easily be solved for the coefficient of the subgrade reaction ( k) and the radiation damping coefficient ( c). The method was verified by using FWD test data from six different sites in Michigan. In addition, the backcalculated k-values were compared with those obtained by the AASHTO-recommended (static) backcalculation method. The results obtained by the new procedure showed very good agreement and consistency with those obtained by the AASHTO method.
Effects of Measured Tire Contact Stresses on Near-Surface Rutting
Authors: Drakos Christos A. , Roque Reynaldo , Birgisson Bjorn
Published: April 2007

Instability rutting occurs within the top 50 mm (2 in.) of the asphalt concrete layer. This type of failure is attributed to the asphalt mixture properties and poses a considerable safety problem in terms of hydroplaning. A literature review has shown that several researchers have presented observations that attempt to explain near-surface rutting, but a clear and complete identification of the failure mechanism does not exist. Measured tire-pavement interface stresses were studied to determine the effects of tire structure, load, and inflation pressure on the tire-contact stress distribution. It was shown for the two tire types investigated, bias-ply and radial tires, that their loading patterns were different. Bias-ply and radial tires were modeled as input loads from actual tire-pavement stress data. The input loads were then analyzed with an elastic layer analysis program (BISAR) to predict the pavement’s response under the different loadings. The analytical evaluations performed illustrate the differences in stress distributions under the modeled tires within the top 63 mm (2.5 in.) of the pavement. The loading characteristics of radial truck tires appear to induce surface tension, which results in the loss of confinement. The combination of surface tension and high shear stresses that were predicted in the analysis might be a possible explanation of the mechanics of this mode of failure.
Assessing Variability of Surface Distress Surveys in Canadian Long-Term Pavement Performance Program
Authors: Goodman Stephen N.
Published: April 2007

In 1997 the Canadian Long-Term Pavement Performance (C-LTPP) project capitalized on an opportunity to have surface distress surveys completed twice at more than half of its test sections to provide some insight as to the variability between different raters. The major findings of that investigation are presented. Because only two distress surveys for each test section were available for comparison, traditional variance analysis techniques were not applicable. Instead, a technique involving an “agreement index,” also known as “Cohen’s weighted kappa statistic,” was used to directly compare the levels of agreement between the surveys. The kappa statistic considers the likelihood of chance agreement and also allows the introduction of penalty values for individual cases of disagreement. The analysis results indicated that the level of agreement based on crack type was very high; less agreement was observed for severity level. Agreement increased significantly with increased data aggregation, indicating that less variability will be present for network-level analyses than for project-level analyses. The effect of rater experience was also investigated, although no firm conclusions could be made with the available data. Recommended methods for reduction of the variability of future distress surveys included reduction of the number of severity levels from five to three, reduction of the number of individual agency raters, more frequent training of raters, and the use of rating teams. In general, the results of the C-LTPP project distress variability analysis were in agreement with previous studies, including the recent study completed by the U.S. LTPP program.
Verification of Network-Level Pavement Roughness Measurements
Authors: Ningyuan Li , Kazmierowski Thomas , Sharma Brij
Published: April 2007

In 1997 the Ministry of Transportation of Ontario (MTO), Ontario, Canada, switched to international roughness index (IRI) measurements as an indicator of network-level pavement roughness within its pavement management system. Measurement of pavement roughness or ride quality in terms of IRI can be performed with different measuring devices. However, the individual measurements for the same pavement section may vary significantly because of the use of different measuring devices, different longitudinal profiles, and different measuring speeds. Recent evidence obtained by MTO indicates that the longitudinal profile measurements provided by different measuring devices contain systematic differences that range from 0.1 to 1.0 m/km. Such differences in IRIs cause significant concerns for agencies that contract out collection of network-level roughness measurements on a yearly basis. Through the process of verification and comparison of longitudinal profile measurements obtained with different profilers, MTO has gained insight into the functional relationships and factors that affect profile measurements in terms of precision and bias. The verification techniques used to obtain normalized, reproducible, and time-stable IRI measurements for IRIs supplied by different IRI providers are described. Preliminary findings and statistical analyses of IRI values measured on a verification circuit, which is composed of 12 sections with four different pavement types, are provided. In addition, the results of analyses of the various IRI measurements and their impacts on network-level pavement serviceability are discussed.
Measuring As-Constructed Smoothness of Portland Cement Concrete Pavements with Lightweight Profilometers
Authors: Akhter Mahmuda , Hossain Mustaque , Hancock Jeffrey , Boyer John , Parcells William J.
Published: April 2007

Several lightweight, noncontact profilometers (LWPs) are now available to measure profiles of newly constructed portland cement concrete pavements (PCCPs). As-constructed smoothness measurements were obtained with four LWPs and the California-type profilograph on four newly constructed PCCP sections in Kansas. The LWPs used were the Ames Engineering lightweight inertial surface analyzer (LISA); K. J. Law T6400; International Cybernetics Corporation (ICC) all-terrain vehicle (ATV); and Surface Systems and Instruments, Inc., LWPs. Smoothness measurements were also obtained with two high-speed profilers: South Dakota-type profilometer and K. J. Law T6600 profiler. Data were statistically analyzed by the analysis of variance and the least-squares means approaches. Profile index (PI) values for LWPs were statistically similar to those for the California-type profilograph, which, on average, reported lower PI values for most of the sections. The international roughness index (IRI) values reported by LISA, T6400, and ICC ATV profilers were statistically similar. The South Dakota-type profiler reported IRI values statistically similar to most reported by LWPs and the K. J. Law T6600 profiler. However, some significant differences were observed when the K. J. Law T6600 profiler and SSI LWP were compared. Variable coefficients of determination ( R2) were obtained by doing a linear regression analysis between the PIs obtained with LWPs and those obtained with the California-type profilograph. Correlation analyses were done with PI and IRI data for individual sections and all sections for a given profiler. The relationship between these smoothness statistics appeared to be both site specific and equipment dependent.
Characteristics of Cold Processed Asphalt Millings and Cement-Emulsion Mix
Authors: Issa Rita , Zaman Musharraf M. , Miller Gerald A. , Senkowski Lawrence J.
Published: April 2007

A study was conducted to characterize the behavior of cold recycled asphalt pavement (RAP) millings rejuvenated with high float emulsion and portland cement, producing a cement-emulsion mix. The main objectives were to investigate how the behavior of RAP mixes was affected by the addition of cement and to find the optimum emulsion and cement contents. Test samples were prepared with four different cement contents, three emulsion contents, and one free water content. It was concluded that Hveem stability values increased with cement content but decreased with emulsion content. The addition of portland cement affected the Hveem stability value of samples cured under soaked conditions more than those cured under dry conditions. Samples prepared with 2 percent emulsion had the highest gain in soaked stability because of the addition of cement. Overall it was concluded that a cold RAP mix containing a low percentage of cement would perform better than conventional cold RAP mixes.
Hydraulic Conductivity (Permeability) of Laboratory-Compacted Asphalt Mixtures
Authors: Kanitpong Kunnawee , Benson Craig H. , Bahia Hussain U.
Published: April 2007

A flexible-wall permeameter was used to study the hydraulic conductivity (also referred to as “permeability”) of asphalt mixtures commonly used in Wisconsin. Effects of saturation, hydraulic gradient, and sidewall leakage were studied to determine an appropriate testing procedure. The test procedure was then used to study how mixture design variables affect hydraulic conductivity. Four aggregate gradations were tested to develop relationships between hydraulic conductivity and volumetric properties. Two mixtures were also compacted to different heights (ranging from 37.5 mm to 110.0 mm) to evaluate how lift thickness affects hydraulic conductivity. Results of the tests indicate that back-pressure saturation can be used to ensure that specimens are saturated and that the saturated hydraulic conductivity is measured. Sidewall leakage was eliminated by using bentonite clay as a sealing agent. The hydraulic gradient was selected on the basis of a parametric experiment showing how the gradient affects hydraulic conductivity. Tests on the various mixtures showed that a power-law relationship exists between air voids content and hydraulic conductivity, but the hydraulic conductivity also depends on the gradation. Lift thickness also appears to be important, with lower hydraulic conductivity obtained from greater lift thickness at a given air void content. The results show that hydraulic conductivity cannot be controlled only by limiting air voids and that a hydraulic conductivity test is necessary for a mixture design that includes hydraulic conductivity as a criterion.
Development of Void Pathway Test for Investigating Void Interconnectivity in Compacted Hot-Mix Asphalt Concrete
Authors: Hall Kevin D. , Ng Hooi G.
Published: April 2007

In response to reports of moisture “weeping” out of hot-mix asphalt concrete (HMAC) pavements, research was initiated on the permeability of coarse-graded Superpave mixes. Tests using a falling-head permeameter yielded inconsistencies in the relationship between air voids and permeability. It was hypothesized that the inconsistencies related to the inability of the permeability device and procedures to account for a compacted specimen’s void characteristics: void size, arrangement, and interconnectivity. A testing apparatus and methodology, the void pathway test (VPT) was developed to describe such void characteristics. The VPT forces air (under pressure) through a HMAC specimen; a soap solution painted on specimen surfaces creates bubbles at exit points for the air flow. Void pathways and characteristics are related to the number and size of bubbles mapped on specimen surfaces. Results from 43 HMAC specimens indicated that significantly more void openings occur on perimeter surfaces than on cross-sectional surfaces. The majority of perimeter openings occurred within 25 mm of the cross-sectional surface through which air was input. No discernable pattern was evident in the number, arrangement, or interconnectivity of voids mapped on cross-sectional surfaces of a specimen. The results suggest that void pathways are not relatively straight and vertical but convoluted and that most tend toward the perimeter of a compacted specimen. These findings could significantly effect permeability testing using falling-head permeameters by challenging the basic assumptions relating to the flow necessary for using Darcy’s law to calculate permeability.
Evaluation of Laboratory-Measured Crack Growth Rate for Asphalt Mixtures
Authors: Zhang Zhiwang , Roque Reynaldo , Birgisson Bjorn
Published: April 2007

A clear understanding of the cracking mechanisms of asphalt mixtures is needed to identify the most rational approach to analyzing its cracking behavior. Asphalt mixture properties were determined for eight asphalt mixtures of known cracking performance. Crack growth rates were measured in the laboratory for each mixture using the method developed by Roque et al. The crack growth rates were evaluated to determine ( a) the validity of the test results, ( b) the relationship if any between laboratory crack growth rates and field performance, ( c) the relationship between the measured crack growth rates and other mixture properties, and ( d) the validity of Paris law of crack propagation for evaluating asphalt mixture performance in the field. Through this evaluation, it was found that Paris law does not appear to incorporate all aspects involved in the mechanism of cracking of asphalt mixtures subjected to generalized loading conditions, such as those encountered in pavements in the field. Therefore, a concept appears to be warranted involving the use of fracture energy as a failure criterion for the initiation and propagation of cracks. This concept may explain both laboratory-measured crack growth rates and field cracking performance.
Field Aging Effects on Fatigue of Asphalt Concrete and Asphalt-Rubber Concrete
Authors: Raad Lutfi , Saboundjian Steve , Minassian George
Published: April 2007

A study was undertaken to investigate the influence of field aging on the fatigue performance of asphalt concrete and asphalt-rubber concrete. Two California mixes were investigated: conventional asphalt concrete dense graded (CAC-DG) and asphalt-rubber hot-mix gap graded (ARHM-GG). Laboratory fatigue tests were conducted on beam specimens obtained from a 10-year-old pavement section in southern California. Both stiffness and fatigue were determined using controlled-strain fatigue beam tests performed at 22°C and -2°C. Results were compared with published data for the original (unaged) materials. Stiffness and fatigue data were also used in pavement analysis to assess the influence of aging on predicted fatigue performance. Results indicate that field aging reduced the beam fatigue resistance of CAC-DG and, to a lesser extent, ARHM-GG. Aging effects on beam fatigue life were more severe at -2°C than at 22°C. The influence of aging on predicted pavement fatigue life depends not only on the stiffness of the mix and its fatigue properties but also on the stiffness or layer moduli of the pavement components. For new pavement construction and overlaid pavement sections, longer fatigue life predictions were obtained for ARHM-GG than CAC-DG for both aged and unaged conditions. Aging of CAC-DG could be detrimental to pavement fatigue. In comparison, aging of ARHM-GG showed increased fatigue life performance.
Comparison of Four Brands of Superpave Gyratory Compactors
Authors: Hinrichsen John
Published: April 2007

Four different brands of gyratory compactors were chosen for an experiment to determine if the devices would produce comparable results. For this experiment, a Troxler model 4140, a Test Quip Brovold gyratory, a Pine model AFGC 125X, and an Interlaken model 1 were used. The four brands of gyratory compactors were compared on four different plantproduced Superpave mixtures. Three of the four mixtures were coarse graded (below the restricted zone); the other was fine graded (above the restricted zone). All the gyratory compactors were calibrated according to the manufacturers’ recommendations. Testing was randomized to reduce bias. A comparison of the results indicates that distinct differences exist among the devices. The same trend was observed for all four mixtures; however, the magnitude of the differences was mix dependent. The coarse mixtures showed greater differences than the fine mixture. Under the conditions of this experiment, the Interlaken produced lower densities than the other devices.
Repair and Strengthening of Concrete Structures Through Application of Corrective Posttensioning Forces with Shape Memory Alloys
Authors: Soroushian Parviz , Ostowari Ken , Nossoni Ali , Chowdhury Habibur
Published: April 2007

Shape memory alloys recover deformations induced at lower temperatures after being heated above a transformation temperature; restraint of this shape recovery generates relatively large stresses. These stresses are used to transfer corrective forces to structural systems for strengthening and repair. For this purpose, shape memory rods are pre-elongated, anchored to the structure, and subjected to electrical resistance heating to transfer corrective forces to the structure. The project used iron-based shape memory alloys of relatively low cost; the alloy composition was selected to yield relatively high and stable levels of restrained-shape recovery stresses. Laboratory tests verified the ability of pre-elongated rods anchored onto damaged structural systems to restore structural integrity through application of corrective forces. Subsequent damaging effects could also be overcome by electrical resistance reheating of rods. A reinforced concrete bridge structure with beams lacking sufficient shear strength at longitudinal bar cutoff locations was selected for field demonstration of the technology. A design methodology was developed and verified through laboratory tests simulating conditions of the selected bridge structure. Subsequently, a detailed design was developed and the approach was implemented under field conditions. Application of corrective (posttensioning) forces to structural systems using shape memory steel provides an efficient, rapid, and convenient approach for repair and strengthening of damaged or deficient structures. The relatively large recoverable strains of shape memory alloys help reduce losses of posttensioning forces. The approach suits application to diverse structures for corrective and strengthening effects.
Retrofitting to Correct Uplift of Curved Girder Bridge Through: Field Testing and Analysis
Authors: Alampalli Sreenivas , Morreale Thomas A.
Published: April 2007

The Ramp C bridge at the New York State Thruway interchange with I-287 and New York State Route 17 in Rockland County near the New Jersey state line is a continuous four-span bridge with a reverse horizontal curve alignment. It consists of five steel girders with radial abutments and skewed pier supports (61 degrees). During construction immediately after the girders were erected and the counterweights were poured, at low temperatures, an unanticipated girder uplift occurred at one corner of an end span. Physical testing and analysis were undertaken to investigate this occurrence and to estimate the uplift forces. The data were used to design a tie-down system to correct the uplift problem and thus avoid delays in opening the bridge to traffic.
Field Studies of Strengthened Timber Railroad Bridge
Authors: Gutkowski Richard M. , Shigidi Abdalla M. T. , Tran An Vinh , Peterson Michael L.
Published: April 2007

Comprehensive field testing had been done previously on a typical three-span, open-deck timber deck railroad bridge. The test program was done in cooperation with the Transportation Technology Center, Inc., of the Association of American Railroads. The bridge was subjected to static and moving train loads as well as controlled actuator ramp loading. The bridge was later stiffened by the addition of a stringer to each chord. The bridge was retested after the stiffening using moving train loads. Results of this field study are reported, and comparisons of the response of the bridge before and after the stiffening are made. The efficiency of the stiffening was between 82 and 97 percent.
Ultrasonic Inspection of Glued Laminated Timber Fabricated with Defects
Authors: Emerson Robert , Pollock David , McLean David , Fridley Kenneth , Ross Robert , Pellerin Roy
Published: April 2007

FHWA set up a validation test to compare the effectiveness of various nondestructive inspection techniques for detecting artificial defects in glued laminated (glulam) members. The validation test consisted of a glulam beam fabricated with artificial defects known to FHWA personnel but not originally known to the scientists performing the validation tests. Ultrasonic inspection was effective in identifying voids within the glulam beam. The glulam was inspected across the width and through the depth. The inspections from each direction were combined to accurately detect and locate artificial voids in three dimensions. Wave travel time allowed identification of some of the voids, but signal amplitude parameters, such as root-mean-square voltage and peak voltage, provided more precise location of the voids. The three-dimensional image provided valuable insight into the internal condition of the glulam. However, through-thewidth inspection was able to locate voids in two dimensions along the length and depth of the glulam. For a field inspection, two-dimensional location of decay would provide sufficient information for judgments to be made on the future of the inspected specimen.
Virtual Reality Images to Aid Public Involvement in Appearance of Roads and Bridges
Authors: Wallsgrove Jon , Barlow Richard
Published: April 2007

The U.K. Highways Agency has completed a research project on the feasibility of using virtual reality technology to help communicate information about proposed new roads and bridges to the public and to encourage their involvement in the design and appearance of roads and bridges. Bridge aspects primarily are considered. In the past there was a tendency to consult the public in two stages. Initially they were consulted conceptually about the route, with little information about the detail of any major structures. Then a few years later they would be shown an artist’s perspective of the bridge, often out of context, and road layout plans of the detailed route. A physical model emphasized psychologically that it was probably too late to change very much. This type of consultation neither contributed to the elegance of the bridge nor particularly encouraged local support for the project. Using virtual reality, the visual effect of a road or bridge in the specific location can be demonstrated at the very earliest stage. Later, with high-quality images, the local community as well as the designers can make real choices between viable structural options and can see the effect of different materials and colors in the real context. The result will be more beautiful bridges that, because of public involvement and support, will be built sooner and without public objection. The Highways Agency is in the process of trying out this new approach.
Performance in Lieu of Prescription in Bridge Design: Changi Airport Mezzanine Bridge, Singapore
Authors: Roche Mark
Published: April 2007

As part of the current expansion to Changi Airport and the Mass Rapid Transit lines in Singapore, a unique bridge is to be incorporated within the new tunnel linking Terminals 2 and 3. The unusual physical circumstances and the aim to create an environment compatible with the intrigue and character of Singapore suited the adoption of a record-reaching 140-m low arch span for the centerpiece footbridge. With 200 m of shimmering glass cladding, the bridge will be an intimate part of the airport experience, though its in-service behavior and intricate frequency characteristics remain to be proved. These characteristics are similar to those of the recently completed London Millennium Bridge, the in-service behavior of which was unacceptable to the public. To determine the behavior of the Changi bridge during service and in ultimate conditions, it was found that performance as opposed to prescriptive design criteria was fundamental, in particular, its structural behavior under fire loading.
Least Expected Time Hyperpaths in Stochastic, Time-Varying Multimodal Networks
Authors: Opasanon Sathaporn , Miller-Hooks Elise
Published: April 2007

The adaptive multimodal least expected time (AMLET) algorithm is presented for determining the adaptive least expected time (LET) hyperpaths from all origins to a specified destination for all departure times in a period of interest in stochastic, time-varying multimodal networks, when the “fastest” path can be appropriately selected depending on the arrival time at each node en route. Mode transfer delays are incorporated into the algorithm to represent waiting times required in transferring modes, such as between driving and boarding a transit vehicle. Both mode transfer delays and arc travel times may be stochastic and time varying. By considering stochastic, time-varying networks, the proposed algorithm can more realistically represent conditions in transportation networks than can exist in deterministic approaches. The resulting solutions provide not only the adaptive LET hyperpaths but also the travel mode to choose from along each path segment for completing a trip. Travelers are not restricted to traveling on only one path and one mode found to be best before they depart from the origin. Instead, they can choose their paths and travel modes en route in accordance to the knowledge of their arrival time at intermediate nodes. Hence, the solution is a set of hyperpaths instead of a single path to the destination. The AMLET algorithm is tested on a real-world transportation network, with several possible traffic scenarios to illustrate the nature of the solution paths.
Effects of Minor Anomalies on Axial Capacity of Drilled Shafts
Authors: Tabsh Sami W. , O’Neill Michael W.
Published: April 2007

Because of their visually unexposed locations and method of construction, drilled shafts often are constructed with minor anomalies, consisting mainly of small voids, mispositioned rebar cages, and corroded rebars. Anomalies can occur even with acceptable quality controls; hence, their existence must be incorporated into the design process. Laboratory tests were used on scaled reinforced concrete shafts in axial compression to quantify the extent of loss in compressive capacity caused by the presence of various anomalies and to investigate the amount of loss in stiffness and effect of confinement on the ductility and stiffness of model shafts with anomalies. Considered variables included the shape and length of the void, spiral spacing, rebar corrosion, and steel cage offset. Analysis of the test results showed that the presence of a void within the cross section affects both the compressive strength and the ductility of a shaft. The effect on the ductility, however, is more critical, particularly when the void extends inside the core of the shaft. Corrosion of the longitudinal rebars through a void significantly reduces the strength and ductility. However, slight cage offsets that are within the tolerance of the construction specifications have only a minor effect on the structural performance. The results of the laboratory tests will be used in future papers, along with further laboratory tests, field observations, and simulations, to derive and recommend rational structural resistance factors for drilled shafts that will be separate from those for structural columns.
Lizzi’s Structural System Retrofit with Reticulated Internal Reinforcement Method
Authors: Mason James A. , Bruce Donald A.
Published: April 2007

The internal reinforcement method (IRM) was developed by Fernando Lizzi in the early 1950s. It is a complete structural system reinforcement method used to retrofit nonreinforced masonry and stone structures and any associated foundation systems. The general design principles of the foundation retrofit are similar to the principles used in the structure retrofit, for placement and engagement of reinforcement. The IRM technology integrates the complete structure, the foundation and bridge or building, into a continuously reinforced seismic-resistant system. The Three Arches Bridge is the only three-span bridge in Venice today. Built in the 17th century, this simple pedestrian bridge was constructed of nonreinforced clay brick masonry with spread footings bearing on the canal floor. Over time, the differential settlement caused localized distress to the overall structure. It was in such a state of disrepair that it was scheduled for demolition in the early 1960s. Lizzi was named to design and construct the historic preservation and structural retrofit of the complete structure. This was accomplished with reticulated internal structural stitching and reticulated micropiles. This structure is a case study of use of the IRM for static and seismic retrofit. The geometric simplicity of the bridge and the clarity of purpose and execution of the reticulated internal stitching and micropiles provide an example of technology that exemplifies the IRM method of integrated complete system static and seismic retrofit.
Repeatability and Reliability of the Tube Suction Test
Authors: Spencer Guthrie W. , Ellis Peter M. , Scullion Tom
Published: April 2007

The tube suction test (TST) was developed in a cooperative effort between the Finnish National Road Administration and the Texas Transportation Institute for assessing the moisture susceptibility of granular base materials. The moisture-susceptibility ranking is based on the mean surface dielectric value of compacted specimens after a 10-day capillary soak in the laboratory. The factors that influence moisture susceptibility are discussed, and the use of dielectric measurements in the TST is explained. The TST protocol is given. The repeatability of the test is then evaluated at three different dielectric values, and statistical techniques are employed to enable estimation of the number of replicate samples required in the TST to achieve specified levels of tolerance and reliability. On the basis of the promising results of the test, the Texas Department of Transportation will begin implementation of the TST statewide during 2001.
Performance of Geocomposite Membrane as Pavement Moisture Barrier
Authors: Elseifi Mostafa A. , Al-Qadi Imad L. , Loulizi Amara , Wilkes John
Published: April 2007

With the advance in electromagnetic techniques, measuring and monitoring the moisture content in pavement systems appears feasible, and the contribution of geosynthetics to the drainage system can be verified. To investigate the performance of a geocomposite membrane (a lowmodulus polyvinyl chloride layer sandwiched between two nonwoven geotextiles), two sections at the Virginia Smart Road were instrumented and constructed to quantify the effectiveness of the geocomposite membrane as a moisture barrier and as a strain energy absorber. All layers were instrumented for stress and strain measurements as well as for environmental effects (temperature, frost, and moisture). The moisture variation in the subbase aggregate layer over different precipitations was continuously monitored by using time domain reflectometry (TDR). Ground penetrating radar (GPR) was used periodically to monitor water movement in the pavement sections. Results of the GPR surveys indicated that use of a geocomposite membrane underneath a drainage layer forms a water barrier, preventing the saturation of underlying layers and facilitating the lateral drain of water. Results of TDR moisture sensors validated the effectiveness of the geocomposite membrane in abating water infiltration into the subbase layer even in the event of heavy rain.
Rational Basis for Evaluation and Design of Pavement Drainage Layers
Authors: Fwa T. F. , Tan S. A. , Guwe Y. K.
Published: April 2007

A pavement drainage layer must have enough drainage capacity (that is, good drainage properties and adequate layer thickness) to discharge infiltrated water within a specified time, and it must be able to maintain sufficient drainage capacity throughout the entire design service life of the pavement (that is, have good anticlogging properties). A rational analytical engineering procedure for the evaluation and design of pavement drainage layers is lacking. Central to this problem is the need for a practical method with which to measure the fundamental drainage properties of the drainage layer materials and a suitable procedure with which to evaluate the clogging potential of the materials. Flow devices that measure empirical drainage or flow indices could not be used for mechanistic design of pavement drainage layers. An approach was adopted that is based on a falling-head apparatus similar in structure to conventional constant-head permeability test devices. Two procedures are proposed to meet the need for a rational design of pavement drainage layers based on engineering principles: ( a) the use of an expedient laboratory falling-head test to determine the permeability of drainage materials; this enables the geometric design (layer thickness and cross slope) of a drainage layer to be performed on the basis of drainage capacity consideration; and ( b) a laboratory clogging test to assess the clogging potential of the proposed material and thickness. A design framework is recommended to integrate the structural and drainage design of pavement drainage layers.
Examining the Effects of Reinforcement in U.S. Forest Service Deep-Patch Landslide Repair Technique: Full-Scale Model Tests
Authors: Wu Jonathan T. H. , Helwany Sam M. B.
Published: April 2007

A study was undertaken to investigate the effectiveness of the geosynthetic reinforcement in a skin-flow landslide repair method, known as the U.S. Forest Service deep-patch technique. A test apparatus, which can model a full-scale patched slope in the plane stain configuration, was devised and manufactured for the study. The test apparatus allows the behavior of the patched slope to be investigated in well-controlled test conditions. The base panel of the test apparatus contains a section that can be lowered gradually to simulate progressive failure underneath the patched slope subsequent to the repair work. Two tests, one with layers of geosynthetic reinforcement incorporated into the patched slope and one without any reinforcement, were conducted under otherwise identical conditions. Both tests were instrumented to monitor their behavior as the movable section of the base panel was being lowered. The effectiveness of the geosynthetic reinforcement, in terms of its potential for alleviating subsequent failures and its effects on the response of a patched slope during a subsequent failure, is discussed.
Method of Improving Pedestrian Safety Proactively with Geographic Information Systems: Example from a College Campus
Authors: Schneider Robert J. , Khattak Asad J. , Zegeer Charles V.
Published: April 2007

A method of combining two information bases with the aid of geographic information systems to identify locations where pedestrian crash problems exist or may exist in the near future is described. The first information base is a set of police crash reports. Locations and attributes obtained from these reports are used to identify clusters of pedestrian crashes in an area so that sites can be evaluated for safety improvements. Geographic analysis of crash types, severity, pedestrian age, and other factors may also be conducted with these data. The second information base is a set of pedestrian and driver perception surveys. Data from this survey are used to identify locations that may have a high potential for crashes even though none or few have been reported recently. Integrating the two information bases may allow transportation planners and engineers to focus on sites with the greatest potential for pedestrian improvements and ultimately prevent more crashes, injuries, and fatalities. The proactive data integration technique developed in this study was applied to pedestrian safety problems on a college campus, aiding the process of planning and implementing various countermeasures related to education, enforcement, and engineering. Note that more than 17 million people (more than 6 percent of the population) in the United States are associated with college campuses. The method can also be applied to bicycle or other special types of crashes in other geographic areas such as cities, commercial zones, and neighborhoods.