bluuebunny/crossref_metadata_2025 huggingface dataset:
Superstructure Flexibility and Disintegration of Reinforced Concrete Deck Slabs: An LRFD Perspective
Authors: Burke Martin P.
Published: April 2007

The new deflection criteria of the AASHTO load and resistance factor design (LRFD) bridge specifications are examined with respect to their potential impact on the serviceability and long-term integrity of decktype highway bridges. The examination suggests that if the intent of these new criteria is implemented, the effective service life of reinforced concrete deck slabs may in some areas of the country become considerably less than 250,000 h (30 years). Today, this is the age by which many deck slabs have disintegrated to the extent that they must be funded and programmed for replacement. On the basis of the examination, it is urged that long-term superstructure flexibility research on aging reinforced concrete deck slabs be accomplished so that specification changes and bridge characteristics can be based on known consequences. Otherwise, unwary transportation administrators who adopt LRFD recommendations and abandon live load deflection limitations may find themselves owners of defective bridges that may have to be replaced rather than just redecked.
Bridge Safety Monitoring Using: Coupled Current Device Images
Authors: Fu Gongkang , Moosa Adil G.
Published: April 2007

A new method of global diagnosis for bridge safety monitoring using high-resolution coupled current device (CCD) images is presented. Its advantages are as follows: ( a) no sensors need to be attached to the structure, ( b) no mathematical modeling is required (such as finite element methods), ( c) a probability-based diagnosis approach is used to deal with measurement noise associated with image data, and ( d) CCD cameras are affordable now and are expected to continue to drop in price, which will make this new technique workable for implementation. The new method was applied in the laboratory to a bridge structure model, as presented. Experimental results show that the method is able to identify stiffness losses as small as 3 percent for both their presence and their location. It is concluded that the proposed approach is promising for experimentation in the field.
Escape Adits for Tunnel Safety
Authors: Gonzalez Joseph , Pease Kent
Published: April 2007

The Upper Narrows Tunnel on Highway 160 in southern Colorado has been designed with a unique system of escape adits to provide for life safety in the event of emergencies in the tunnel. The use of adits provides for a higher level of safety in this application than would be provided by the more common ventilation system. A summary of the unique project conditions that facilitate such a system is presented, and the methods of analyses and results of calculations used during the design are reviewed.
Time-Dependent Deflection of Thermoplastic Pipes Under Deep Burial
Authors: Sargand Shad M. , Hazen Glenn A. , White Kevin , Moran Alan
Published: April 2007

Field performance data are presented on the time-dependent deflection of thermoplastic pipes tested at the Ohio Research Institute for Transportation and the Environment (ORITE) at Ohio University in Athens, Ohio. In fall 1999, ORITE began its study of 18 thermoplastic pipe products—12 HDPE (polyethylene) high-density and 6 PVC (polyvinylchloride)—ranging in diameter from 762 to 1524 mm and buried under either 6.1 m or 12.2 m of embankment fill. The installation conditions for these pipes were varied to study the effects of bedding thickness, backfill material type, and relative compaction on their structural performance. The pipes have been extensively monitored using a comprehensive set of sensors. Until this point, insufficient field data have been available for the development of design standards for thermoplastic pipes since previous tests were conducted over a short time period. Long-term tests are more reliable for calculating field performance since the structural response of plastic pipe is time dependent. The focus of the study described was the deflection performance of six of the thermoplastic pipes during burial and over the long term under actual field conditions. The six different thermoplastic pipes were located under 12.2 m of cover using either Ohio Department of Transportation (ODOT) 304 crushed limestone or ODOT 310 river sand materials for backfill. Each pipe was instrumented with displacement potentiometers measuring deflection in the vertical and horizontal directions as well as the circumferential shortening. The results from the study indicate that the deflections stabilized within 2 months from the completion of construction.
Computing Fastest Paths in Continuous-Time Dynamic Networks with Piecewise Linear Link Travel-Time Functions
Authors: Chabini Ismail
Published: April 2007

The problem of computing minimum-time paths from all nodes to one destination node, for all possible departure times, in continuous-time dynamic networks with piecewise linear link travel-time functions is considered. Two types of algorithms to solve this problem are presented: a continuous-time label-correcting algorithm and an algorithm that determines optimal minimum travel-time functions in decreasing order of departure times. The algorithms are valid in networks in which “first in, first out” holds and does not necessarily hold. Computer implementations of these algorithms were developed and are available. It is demonstrated that the algorithms have modest computational time and memory requirements. The decreasing order of time algorithm generally requires less running time than the label-correcting algorithm, which is comparatively easier to implement.
Calibration and Path Dynamics Issues in Microscopic Simulation for Advanced Traffic Management and Information Systems
Authors: Jayakrishnan R. , Oh Jun-Seok , Sahraoui Abd-El-Kader
Published: April 2007

Two critical aspects related to microscopic simulation are discussed: a methodology for calibration and validation, and the integration of path dynamics modeling on large networks. These are among the most significant challenges in microscopic simulation for decision support and analysis in advanced traffic management and information systems. For calibration and validation, a distinction is made between conceptual and operational phases; the conceptual phase concerns the basic models such as car following and lane changing, and the operational phase is associated with the context of the study (origin-destination, parameters adjustments with respect to the network under study, etc.). Then a methodology is described that brings to microscopic simulation the type of capabilities for path processing and storage normally found only with macroscopic models, often because the network representation is less detailed for those. This is based on a hybrid simulation approach. An example of integrating the parallel microscopic simulation with the routing and behavior response simulation schemes, as in the dynamic network assignment simulation model for the advanced road telematics macroscopic model, is used to explain a candidate methodology to enhance microscopic models for evaluating information-routing schemes in advanced traffic management and information systems. Relevant problems faced by advanced traffic management and information systems modelers are raised that are worth further discussion; the intention is not to provide extensive results or even to answer all of the questions raised.
Parametric Evaluation for Route Guidance Systems with Analysis of Sustainable Driver Compliance
Authors: Oh Jun-Seok , Jayakrishnan R. , Chen Anthony , Yang Hai
Published: April 2007

A framework is developed to parametrically evaluate networks under user equilibrium route guidance (UERG) and system optimal route guidance (SORG), assuming that the unguided traffic is in stochastic user equilibrium. The framework can determine in what condition an advanced traveler information system performs well and which route guidance state performs better as the market penetration of guidance systems increases. Unlike other studies that assumed a fixed number of compliant drivers, this study explicitly considers compliance rate as an endogenous variable in a general parametric nonlinear programming framework. Under endogenously determined compliance rate, SORG may result in a higher total system cost than UERG because of a lower compliance rate, even though SORG aims to minimize total system cost. In contrast, even though UERG is generally preferable because of higher acceptance, it may result in increased total system cost under certain conditions. A simple network is used to illustrate the application of the framework and show that the performance of route guidance is highly dependent on the level of unguided drivers’ familiarity with the network. A significant part of the framework is the scheme to find “sustainable” compliance rates under assumed compliance function.
Computer Vision Detection System for Network Model Validation
Authors: MacCarley C. A. , Hemme Brian
Published: April 2007

A computer vision-based traffic detection system has been developed and tested that is capable of uniquely identifying vehicles in a traffic network from video images and later reidentifying them at other detection sites in the network. This capability may serve as the basis for deterministic validation of microscopic network flow models, origin-destination tables, and travel-time tables. The system is referred to as the video-based vehicle signature analysis and tracking system. With video cameras used as primary sensors, detection modules generate a numeric video signature vector (VSV) for each vehicle and transmit them to a central Internet-connected correlation computer via a public low-power wireless network. The correlation computer attempts to match vehicles, as represented by their VSVs, generated at successive detection sites to enable a sampled real-time microscopic flow representation of a freeway network. Test results indicate 93.6 percent accuracy in correctly reidentifying vehicles at successive sites. The tendency of the system to incorrectly match different vehicles at successive sites was measured at 0.0116 percent. Potential advantages are low cost in widespread deployment, simplicity and reliability of detection, minimal bandwidth and storage requirements for transmission of the VSV, and reasonable identification ability without violation of privacy rights. The primary disadvantages are the requirement to place video cameras above each traffic lane and video imaging limitations related to reliance on ambient illumination.
Transit Vehicle Arrival Prediction: Algorithm and Large-Scale Implementation
Authors: Dailey D. J. , Maclean S. D. , Cathey F. W. , Wall Z. R.
Published: April 2007

An algorithm is presented to predict transit vehicle arrival times up to 1 h in advance. It uses the time series of data from an automated vehicle location system, consisting of time and location pairs. These data are used with historical statistics in an optimal filtering framework to predict future arrivals. The algorithm is implemented for a large transit fleet in Seattle, Washington, and the prediction results for hundreds of locations are made widely available on the Web. An evaluation of the second busiest but most complex prediction site is presented to demonstrate the value of prediction over the use of schedules alone.
Evaluation with Traffic Assignment Under Demand Uncertainty
Authors: Waller S. Travis , Schofer Joseph L. , Ziliaskopoulos Athanasios K.
Published: April 2007

The impact of demand uncertainty on the evaluation of network improvements when using traffic assignment is addressed. Theoretical results indicate that the expected value of the performance of the traffic system is not necessarily equivalent to the performance of the system at the expected value of demand, and therefore the expected demand cannot be used with disregard of the variance in demand forecasts. Using expected demand tends to overestimate performance of the network and could lead to erroneous choice of improvements. Alternative possibilities for dealing with this problem are explored, including an approach in which the demand is inflated. This yield benefits not only in terms of selecting improvements with lower expected total system travel time but also significant reductions in the variance associated with this measure. Demand inflation should take place after a budget has been set, so that decisions resulting from inflation do not dictate that more infrastructure be built but that different improvements be selected. Furthermore, numerical examples indicate that there is a significant probability that the deterministic traffic assignment procedure will incorrectly rank improvement policies. This poses a serious concern for decisions based on this procedure, so potential actions are discussed to address the problem.
Estimation of Origin-Destination Demand for Dynamic Assignment with Simultaneous Route and Departure Time Choice
Authors: Van der Zijpp N. J. , Lindveld C. D. R.
Published: April 2007

As congestion results not only in the dispersion of origin-destination (O-D) demand across multiple routes but also in peak spreading, use of dynamic traffic assignment models as a means of predicting the impact of a new infrastructure should take into account departure time choice in addition to route choice. Departure time choice may be modeled simultaneously with route choice. In such a model, each traveler has a preferred departure and arrival time, deviation from which results in a certain disutility. Departure time choice can be viewed as route choice in a suitably defined hypernetwork. The combination of departure time choice and route choice in a single framework is called the dynamic user optimum departure time and route choice (DUO-D&R) assignment. When the DUO assignment needs a dynamic O-D matrix with fixed departure times, the DUO-D&R assignment needs a dynamic O-D matrix with preferred departure times. This matrix is called the preferred departure time O-D (pOD) matrix. A method is proposed for estimating the pOD demand matrix that reflects preferred instead of realized departure times. To carry out this estimation, the DUO-D&R problem is formulated and solved. The schedule delay function and the departure choice model are assumed to be known. The possible advantage of the DUO-D&R assignment over DUO assignment is demonstrated through numerical experiments that correspond to scenarios in which infrastructure is expanded and travel demand is subject to uniform growth.
Modeling of Nonlinear Stochastic Dynamic Traffic Flow
Authors: Jou Yow-Jen , Lo Shih-Ching
Published: April 2007

Most dynamic flow models are developed under deterministic assumptions or simple linear models. Although these models can describe dynamic phenomena, they cannot adapt a variance of the real world. However, in the developing trend of intelligent transportation systems, operators have to understand and accurately predict traffic flow to predict, evaluate, and manage the performance of present and future systems. Thus, a model capable of describing variant traffic phenomena, which encompasses both nonlinearity and stochasticity, is necessary. This study formulates nonlinear stochastic dynamic traffic flow models based on conventional macroscopic models; the nonlinear terms are decomposed by polynomials to reduce the complexity of the models. Then, the Itô equation is introduced to convert the deterministic model to a stochastic one. Also considered here is the traffic flow model with a diffusion effect.
Accelerating Strategies and Computational Studies of the Frank–Wolfe Algorithm for the Traffic Assignment Problem
Authors: Lee Der-Horng , Nie Yu
Published: April 2007

An accelerating strategy to the well-known Frank-Wolfe algorithm for solution of the traffic assignment problem (TAP) is presented here. The Frank-Wolfe algorithm has been widely accepted and recognized by transportation researchers and practitioners as a state-of-the-practice solution method for TAP. With abundant numerical examples, the proposed accelerating strategy was compared with other accelerating methods, such as the parallel tangent technique, Fukushima direction, and Weintraub step size. The computational results successfully indicate that this new strategy is capable of obtaining highly accurate solutions with relatively moderate central processing unit time consumed. The computational results also indicate that the performance of this accelerating strategy is better than state-of-the-art algorithms, such as the restricted simplicial decomposition algorithm and the gradient projection algorithm. The proposed accelerating strategy is easy to implement and suitable for obtaining accurate solutions to TAP because of its economical memory requirement and stable performance, even when large and congested networks are considered.
Stochastic Dynamic Network Design Problem
Authors: Waller S. Travis , Ziliaskopoulos Athanasios K.
Published: April 2007

The continuous network design problem that occurs when the origindestination time-dependent demands are random variables with known probability distributions is described. A chance-constraint and two-stage linear programming formulation are introduced based on a system optimum dynamic traffic assignment model that propagates traffic according to the cell transmission model. The introduced approaches are limited to continuous link improvements and do not provide for new link additions. The chance-constrained model is tested on an example network that resembles a freeway corridor to demonstrate the simplicity and applicability of the approach. Initial results suggest that planning for an inflated demand may produce benefits in terms of system performance and reduced variance.
Assessing Financial Feasibility of a Build–Operate–Transfer Project Under Uncertain Demand
Authors: Chen Anthony , Subprasom Kitti , Chootinan Piya
Published: April 2007

The financial feasibility of the build—operate—transfer (BOT) approach, which is being used increasingly by governments in their drive to privatize major public transportation projects, is discussed. A simulation-optimization framework is developed as an assessment tool to evaluate the financial feasibility of BOT projects. It embeds an efficient network optimization solver in a stochastic simulation framework to assess the investment risk of BOT projects under uncertain traffic forecasts. The network optimization solver determines the traffic volumes that will patronize both the BOT links and free links, and the stochastic simulation creates the uncertain traffic forecasts. The simulation-optimization procedure is used to conduct an experiment to estimate the expected profit and its associated probability of making a certain desired profit. These profit forecasts and their probability will help the authorities or the private sector to properly and systematically evaluate BOT investment projects. A case study of the superhighway project of the Pearl River delta in China is used to illustrate the application of the assessment tool developed.
Demand Matrix Adjustment for Multimodal Freight Networks
Authors: Crainic Teodor Gabriel , Dufour Gina , Florian Michael , Larin Diane , Leve Zvi
Published: April 2007

The problem of adjusting freight demand matrices to observed flows for multimodal, multicommodity transportation planning is addressed. A model is introduced, and an algorithm is described to solve the corresponding bilevel optimization problem. The algorithm is efficiently implemented by using strategic transportation analysis, an interactivegraphic transportation planning package designed for national and regional strategic analysis and planning of multimode, multiproduct freight transportation. Data from an actual application are used to characterize the performance of the proposed methodology. In conclusion, a number of generalizations and promising developments are presented.
Analytical Dynamic Network Loading Problem: Formulation, Solution Algorithms, and Computer Implementations
Authors: Chabini Ismail
Published: April 2007

The dynamic network loading problem is considered. This problem is at the heart of analytical approaches to dynamic traffic assignment models. Given path flow rate and link travel time functions, the dynamic network loading problem consists of determining time-dependent network flow conditions, such as link travel times, total number of vehicles on links, and link inflow and outflow rates. The dynamic network loading problem is formulated as a continuous-time system of nonlinear equations expressing link dynamics, flow conservation, flow propagation, and boundary constraints. A discrete-time version of the continuoustime model is developed to design solution algorithms. Two solution algorithms are developed and implemented efficiently. Techniques are described that were designed to reduce memory usage and computation times of these solution algorithms. Computational results with a realworld traffic network emanating from the Amsterdam A10 beltway, containing 300 nodes, 1,500 paths, 1,000 origin-destination pairs, and 2 h of analysis period indicate that the developed computer implementations can solve the network loading problem in 2 min when a small discretization interval of 3.5 s is used.
Bitwise Algorithm for Fastest Paths in Time-Dependent Networks
Authors: Chabini Ismail , Yadappanavar Vinay
Published: April 2007

An algorithm operating on a new and compact representation of link exit times to solve the one-to-all fastest path problem in dynamic networks is presented. The new space-efficient representation that exploits the first-in, first-out property of link travel times in dynamic networks is developed. The algorithm is described, and its working on a simple network is presented. The algorithm directly operates on bit streams of data representing time-dependent link travel times and performs logical operations on 0 and 1 bits only. Computational results are presented for large dynamic networks. The ideas behind the development of this algorithm are extendable to the development of algorithms operating at the bit level to solve other variants of dynamic shortest path problems and other dynamic network flow problems. These developments then open new research possibilities in the development of solution algorithms for dynamic network problems.
Advances in Discrete-Time Dynamic Data Representation with Applications to Intelligent Transportation Systems
Authors: Chabini Ismail , Yadappanavar Vinay
Published: April 2007

Efficient storage, processing, and communication of dynamic data are at the heart of intelligent transportation systems (ITS) applications. The speed of communication and processing as well as the storage space required by such data depend on the method used for its representation. ITS applications typically involve dynamic data that are discrete and require fast computation and communication speeds to support real-time operations. An efficient representation method is presented, which is called the bit-stream representation, for discrete-time dynamic data. Its positive impacts are presented by developing efficient representations for storage and communication of travel times in dynamic transportation networks. It is shown theoretically that this representation method typically leads to an L/2-fold gain in both storage space and communication speed compared with methods that represent discretetime dynamic data using L-bits to store an integer. The proposed representation holds the potential to develop new faster algorithms that would directly operate on dynamic data represented as bit streams.
Laterally Loaded Drilled Shafts Embedded in Soft Rock
Authors: Hwan Cho Kook , Clark Shane C. , Keaney Brian D. , Gabr Mohammed A. , Borden Roy H.
Published: April 2007

The current design criterion for laterally loaded drilled shafts embedded in weathered Piedmont rock profiles requires a challenging effort on the part of the engineer. A substantial cost saving could be realized, while maintaining an acceptable and safe performance, if a rational method were developed for the analysis and design of drilled shafts in such a profile. In a current research project, the primary objective is to develop and validate a procedure for design and analysis of laterally loaded drilled shafts embedded in the Piedmont weathered rock profiles. A major component of this research is a field-testing program. Presented are the results of the first in a series of several lateral load tests performed on two drilled shafts 0.762 m (30 in.) in diameter embedded in Piedmont weathered rock. These shafts were instrumented with inclinometers and strain gauges. Field data obtained from the instrumented shafts were used to develop P-y curves. Field testing also encompassed the use of a borehole dilatometer to establish correlations between the rock strength and deformation parameters and potential P-y curves. A comparison is made between backcalculated P-y curves, P-y curves predicted by using Reese’s method, and P-y curves from the rock dilatometer. Loaddeformation results are presented and discussed for all methods used.
Field Installation of an Earth Pressure Cell
Authors: Theroux Brent , Labuz Joseph F. , Dai Shongtao
Published: April 2007

An earth pressure cell (EPC) is a device designed to provide an estimate of normal stress in soil. The practice of designing and manufacturing stress-measurement devices revolves around the study of the interaction between the measuring device and the host material. However, distribution of normal stress is not necessarily uniform across a given surface. Consequently, output from an EPC may be different under soil-loading conditions than under fluid pressure. In addition, depending on the design, as the cell deflects, an arching-type phenomenon may develop. A study was conducted to devise a scheme for calibration of EPCs and to recommend a procedure for field installation. A new testing device was designed to permit the application of uniaxial soil pressure to the EPC by using various types of soil and load configurations. Sensitivities computed from soil calibrations varied from those determined from fluid calibrations by as much as 30 percent. A field installation procedure was developed from model tests. In the laboratory, a thin-walled steel cylinder with a geotextile bottom was filled with uniform silica sand in a medium-dense state, and the EPC was placed within the sand. The entire apparatus (EPC, cylinder, and sand) was carried into the field and installed in the desired locations. The steel cylinder was then removed, leaving the cell, sand, and geotextile behind. Preliminary field data indicate that the soil calibration and placement procedure provide reasonably accurate measurements of the change in vertical stress.
Monitoring the Effects of a Deep Excavation on Two Adjacent Office Buildings
Authors: Edgers Lewis , Henige Richard , Weinmann Thomas L. , Wiesner Kenneth B.
Published: April 2007

Described are the instrumentation systems that were developed to monitor the effects of excavations for the Boston Central Artery–Third Harbor Tunnel (CA/T) project on two adjacent modern, high-rise office buildings. These are the Federal Reserve Bank of Boston (FRB) and the One Financial Center (OFC) buildings. The CA/T work adjacent to the FRB and OFC buildings consists of a multilane cut-and-cover highway tunnel extending to a maximum excavation depth of more than 33.55 m (110 ft) below the ground surface and more than 21.35 m (70 ft) below the foundation levels of both buildings. Because even small excavationinduced ground movements may have large effects on modern buildings, the FRB and OFC were extensively instrumented to monitor and help control the effects of the CA/T excavation on these buildings. A comprehensive array of instrumentation was installed to measure excavationinduced movements and stresses in the FRB and OFC buildings. The CA/T instrumentation specification describes threshold and limiting values for all the FRB and OFC instruments, which may trigger responses ranging from more frequent readings to modifications of construction procedures and, in the extreme, to implementation of a specified contingency plan. Presented are typical data and how the data were used to control the adjacent construction process.
Instrumentation and Construction Performance Monitoring for I-15 Reconstruction Project in Salt Lake City, Utah
Authors: Bartlett Steven , Monley Greg , Soderborg Andrew , Palmer Andrew
Published: April 2007

The I-15 reconstruction project in Salt Lake City, Utah, involves the widening and rebuilding of 27 km of urban Interstate on alluvial and lacustrine deposits. In some locales, these soils have low shear strength and require up to 2 to 3 years to complete primary consolidation settlement. The aggressive 4-year construction schedule required much of the embankment and foundation work to be completed in the first 12 to 18 months, including the time required to complete primary settlement. To meet these rigorous schedule constraints, the geotechnical construction made extensive use of prefabricated vertical drains, ground modification, staged embankment construction, lightweight fill, mechanically stabilized earth walls, and pile foundations. Also, because of rigid time constraints, initial foundation treatments and embankment construction proceeded as parallel activities with the geotechnical design. Instrumentation and construction performance monitoring played a vital role in affirming initial design assumptions and developing a better understanding of strength, deformation, and consolidation characteristics of the foundation soils. Discussed are the instrumentation program and how performance monitoring was implemented to control construction processes and improve the geotechnical design.
Class-A Prediction of Construction Defects in Drilled Shafts
Authors: Iskander Magued , Roy Douglas , Ealy Carl , Kelley Shawn
Published: April 2007

The results of a blind Class-A prediction symposium of construction defects in drilled shafts are presented. Six drilled shafts were constructed at the National Geotechnical Experimentation Site in Amherst, Massachusetts. Several types of defects were integrated into the shafts, including necking, voids, caving, and soft bottoms. Seven organizations participated in a blind defect prediction symposium and used a variety of nondestructive testing techniques, including down-hole techniques, such as cross-hole sonic logging, single-hole sonic logging, and cross-hole tomography, and surface techniques, such as pulse echo and sonic mobility. Most participants found defects that were larger than 10 percent of the cross-sectional area. However, false positives and an inability to locate smaller defects and multiple defects in the same shaft were encountered.
Seismic Behavior of Micropiles: Used as Foundation Support Elements: Three-Dimensional Finite Element Analysis
Authors: Shahrour Isam , Sadek Marwan , Ousta Rami
Published: April 2007

Presented is a three-dimensional finite element analysis of the seismic behavior of micropiles used in engineering applications, such as construction in earthquake areas, and seismic retrofitting of structure foundation and retaining systems. It is composed of two parts. The first is concerned with analysis of the seismic behavior of a single micropile supporting a superstructure; results obtained with three-dimensional finite element modeling are compared to those obtained from a simplified model based on the Winkler approach. The second part includes a study of the seismic behavior of groups of micropiles. Numerical simulations are conducted to study the variation of the group effect with the variation of micropile spacing, number of micropiles, and the position of the micropile in the group. Analysis of results of numerical simulations shows that the presence of the superstructure induces significant inertial effect, which causes a high increase in the bending moment in the upper part of micropiles; the inertial effect depends mainly on the loading frequency with respect to the fundamental frequency of the soil layer and that of the superstructure. A group effect is observed in groups of micropiles connected by a rigid cap. The group effect depends mainly on micropile spacing, number of micropiles, and position of micropiles in the group. Results show an increase in moment at the head of micropiles with the increase of the micropile spacing (presence of inertial effect) and a concentration of seismic loading on corner micropiles.
Strain Wedge Model Hybrid Analysis of Laterally Loaded Pile Group
Authors: Pilling Patrick , Ashour Mohamed , Norris Gary
Published: April 2007

A simple hybrid method with which to characterize the response of flexible pile groups to lateral loading is presented. The reduction in the capacity of an isolated pile is calculated on the basis of the interference among piles in the group by using the strain wedge model technique. This technique characterizes structure response to lateral loading by determining the resistance provided by a three-dimensional passive wedge of soil that develops in front of the pile, and it relates the one-dimensional beam on an elastic foundation analysis to a three-dimensional soil-pile interaction response. The response of individual piles in a group (i.e., the resistance of the surrounding soil) is influenced by the interference among the soil passive wedges in front of the piles and is related to the pile-head response of the isolated pile.
Failure of Geotextile-Reinforced Vertical Soil Walls with Marginal Backfill
Authors: Suah Peter G. , Goodings Deborah J.
Published: April 2007

Twenty-seven physical models of geotextile-reinforced vertical walls with a range of backfill soils were tested to failure in the geotechnical centrifuge. The models were used to assess the effect on wall stability of the properties of the backfill, which ranged from clay through sand, with combinations of the two in varying ratios. The effects of the reinforcement length and of reinforcement overlap on stability also were assessed. Geotextile-reinforced clay backfill retaining wall models reached an equivalent full-scale height as great as 17.7 m for the wall geometries, clay, and geotextile used in these models. None of the models failed by geotextile pull-out, which typically is assumed to be the controlling mode of failure in walls with clay backfill and is perceived as a primary disadvantage to using such marginal soil as backfill. Development of failure was different for clay backfill walls than for backfill walls with clay-sand mixes, in large part because of prefailure deformations that were heavily influenced by the backfill properties. These deformations also played a very significant role in failure. Wall failure by sliding could be predicted adequately by using simple limit equilibrium analysis if realistic soil strength parameters were used in those analyses.
Use of Discrete Event Simulation to Design Geocomposite Membrane Installation
Authors: Wanamakok Phuwanai , Martinez Julio C. , Al-Qadi Imad L. , Wilkes John A.
Published: April 2007

Geosynthetics are incorporated into flexible pavement systems to improve their performance. However, geosynthetics must be installed properly to produce good results. The application of discrete-event simulation to design and analyze the installation of geocomposite membranes in flexible pavements is discussed. Data collected from two test sections at the Smart Road project in Blacksburg, Virginia, were used for modeling and analysis. Stroboscope was used as the simulation engine. The process used in the development of simulation models is discussed. A number of installation alternatives were studied and simulated to examine their practicality and to investigate their productivity, resource utilization, and unit cost.
Cycling to Work in Phoenix: Route Choice, Travel Behavior, and Commuter Characteristics
Authors: Howard Charlene , Burns Elizabeth K.
Published: April 2007

Through a survey of expert cyclists, the relationship between the actual routes cyclists traveled and existing street conditions was documented, and bicycle commuters of the Phoenix metropolitan area were profiled. Data were collected on individual commuting routes between home and work. Additional data collected include age and gender characteristics. Frequency analysis in a geographic information system compared the number of common street segments among actual and alternative routes to determine cyclists’ use of existing street facilities. Findings are reported for actual routes compared with shortest distance, shortest time, and safest route alternatives on street facilities between the same origin and destination. Spatial analysis identified local gaps in arterial street bicycle facilities at municipal boundaries. These findings include evidence that cyclists adjust their routes to use current street bicycle facilities, and suggest that policy makers should concentrate on linking bicycle facilities across jurisdictions.
Relating Severity of Pedestrian Injury to Impact Speed in Vehicle-Pedestrian Crashes: Simple Threshold Model
Authors: Davis Gary A.
Published: April 2007

An ordered, discrete outcome model that relates the severity of injury suffered by a struck pedestrian to the speed of the striking vehicle is derived and then fit to previously published data. Particular care is taken to account for covariate measurement error and for the fact that the data were collected using an outcome-based, or retrospective, sampling plan. The results show similar patterns for children (ages 0–14) and adults (ages 15–59), but for elderly pedestrians (ages 60+) the injuries produced in crashes that involved lower impact speeds tended to be more severe than for the other two groups. Use of the model is illustrated by applying it to two reconstructed vehicle-pedestrian crashes to determine the likely severity of the injury had the driver adhered to a speed limit. Some implications for speed limits on residential streets are also pointed out.
Pedestrian Visibility Under Automobile Low-Beam Headlight Illumination: With and Without Headlight Covers
Authors: Schnell Thomas , Aktan Fuat , McGehee Daniel V. , Dvorak Mike , Hunt Jill , Reyes Abimael , Sorak Deanna
Published: April 2007

Pedestrians and bicyclists are the most vulnerable of all participants in traffic. Their safety at night should be a priority for headlamp designers, rule-making agencies, and consumers alike. A disturbing trend—the use of very dark aftermarket headlamp covers on vehicle headlamps—is emerging. This trend is observed primarily in sports cars owned by young drivers. These dark headlamp covers, often referred to as blackouts, serve no real purpose other than that of supposedly enhancing vehicle appearance. For a driver using such headlamp covers at night, it may appear as though the overall visibility is not much affected. However, this perception is misleading and wrong, as will be clearly demonstrated. The objective was to quantify the detrimental effects dark headlamp covers have on pedestrian visibility. To do so, detection distances were obtained in the field using 15 observers who were approaching stationary pedestrian mockups. The independent variables were pedestrian size (child, adult), diffuse clothing reflectance (dark, light), and illumination (with and without headlamp covers). Clothing reflectance turned out to have the strongest effect on the detection distance, closely followed by the factor of illumination. The conclusions that can be drawn from the work presented are simple. Nighttime pedestrians should not wear dark clothing, instead they should wear white or reflective clothing, and motorists should not drive with dark headlamp covers at night.
Hybrid Simulated Annealing and Case-Based Reasoning Approach for Computationally Intensive Transportation Problems: Rationale and Design Issues
Authors: Sadek Adel W.
Published: April 2007

A hybrid artificial intelligence approach based on combining simulated annealing (SA) and case-based reasoning (CBR) is presented. The approach is designed to allow for solving complex, time-critical optimization problems, examples of which lie at the heart of several intelligent transportation systems applications. According to this hybrid approach, the system, when faced with a new problem, first accesses the case base and attempts to locate a sufficiently similar case. If such a case can be located, the solution of the CBR-retrieved case is directly reused. If not, the SA algorithm is used to solve the problem, with the solution of the CBR-retrieved case serving as a starting point for the search algorithm. The rationale behind the approach is discussed, and its major design issues are analyzed. A case study is then presented to illustrate how the approach could be designed and to demonstrate its advantages. Results indicate that combining SA and CBR offers an efficient approach to solving complex, time-critical optimization problems. The results also indicate that SA, used in conjunction with CBR, should be started from a very low temperature to take advantage of the fact that the CBR-retrieved solution is close to the optimum.
Use of the National Architecture to Develop an Intelligent Transportation Systems Strategic Plan: Case Study for a Medium-Sized Area
Authors: Sadek Adel W. , Chamberlin Robert , Keating Peter R.
Published: April 2007

A case study of use of the national architecture to develop an intelligent transportation system (ITS) strategic deployment plan for Chittenden County, Vermont, an area with a population of 140,000, is presented. Because the study was conducted after a mature version of the national architecture had been completed, every effort was made to take full advantage of the national architecture documents in developing the plan. This helped reduce significantly the amount of effort needed to complete the plan, while ensuring the interoperability of the systems to be deployed. In developing the plan, the most recent version of the ITS planning process, which is based on the “market package” concept, was followed. A quantitative, systematic procedure was used to screen and prioritize the market packages. A regional ITS architecture was then developed, and the selected packages were developed into a list of recommended projects for the region. The study clearly demonstrates the value of the national architecture. The architecture provided guidance in formulating an ITS vision for the region, formed the basis on which ITS packages were selected, and dramatically reduced the amount of effort needed to develop the regional architecture. The architecture’s market packages are shown to be applicable to medium-sized areas; however, they need to be implemented at a smaller scale than in larger metropolitan areas.
Implementing Adaptive Driving Systems for Intelligent Vehicles by Using Neuro-Fuzzy Networks
Authors: Lin Y. T. , Wang F.-Y. , Mirchandani P. B. , Wu Long , Wang Z. X. , Yeo Chris , Do Michael
Published: April 2007

The application of supervised learning to train an intelligent vehicle with a neuro-fuzzy controller to mimic the driving behavior of a human driver is discussed. An initial fuzzy control system for vehicle driving was set up on the basis of general human driving experiences, and its control rules were modified to fit the driving behavior of an individual driver. This provides an effective mechanism to construct driving control systems with personality for automated intelligent vehicles.
Michigan’s Approach to a Statewide Investigation of Materials-Related Distress in Concrete Pavements
Authors: Van Dam Thomas J. , Buch Neeraj J. , Hanson Karl F. , Hiller Jacob E. , Sutter Lawrence L. , Muethel Robert
Published: April 2007

An approach is described that is used to identify to what degree Michigan’s concrete pavements are affected by materials-related distress (MRD) and to determine what distress mechanisms are at work. The approach taken includes a network-level visual assessment and detailed visual inspections, field sampling, and laboratory analyses on 14 selected projects to determine the distress mechanisms. It is concluded that although the majority of Michigan’s concrete pavements are unaffected by MRD, a significant percentage of the concrete pavement network have distress manifestations consistent with the occurrence of MRD. These manifestations included staining in the vicinity of joints and cracks, D-cracking, joint-crack deterioration, progressive map cracking with exudate, scaling, and corrosion of embedded steel. Each pavement section was visually assessed and then tested using a falling weight deflectometer. Field air permeability measurements were also made, and core samples were removed from the pavement to be analyzed in the laboratory. It was found that the presence of MRD affected both the mechanical and the microstructural properties of the pavement concrete. Further, the laboratory analysis determined that a number of MRD types are at work in some of Michigan’s concrete pavements, including aggregate freeze-thaw deterioration, corrosion of embedded steel, and alkali-silica reactivity. This work also found that dedolomization of certain carbonate aggregates and sulfate attack may pose a problem. With this knowledge, the Michigan Department of Transportation is better able to address the cause of distress when selecting repair options and to prevent MRD from affecting future concrete pavements.
Application of the Deformation Mapping Technique to Assess Deterioration in Cement-Based Materials
Authors: Chen Jeffrey J. , Rothstein David , Thomas Jeffrey J. , Jennings Hamlin M.
Published: April 2007

A revealing fact concerning the sophistication of modern concrete durability research is that, for the most part, structures still are categorized as sufficiently intact, irreparably damaged, or usually somewhere subjectively in between. Standard compression tests may indicate loss of serviceability in the advanced stages of deterioration when macroscopic damage is clearly visible and when future repair is inevitable. If there were a way, however, to quantify the progression of early microscopic damage before macroscopic damage occurs, structures conceivably could be identified for which early repair or isolation could provide costefficient alternatives to removal and replacement. With this goal in mind, the image analysis–based deformation mapping technique (DMT) becomes an attractive candidate for a quantitative forensic tool. DMT is a two-dimensional image correlation technique that determines microscopic deformations by computing the relative pixel displacements between an initial and a deformed image. The unique ability of DMT to translate these displacements into principal deformations allows for more accurate quantification of heterogeneous deformation at the microscopic scale, where the central deforming axis is not necessarily coincident with the loading axis. In the current study, the time progression of microstructural changes is shown in a mature ordinary portland cement paste dried at −30 percent relative humidity. Also, DMT illustrates the ability to quantify early microstructural changes by comparing the mechanical deformation response of a sound mortar and a mortar pre-exposed for 7 days in a saturated Na2SO4 solution. Isolation of the deformations specific to the paste phase of the mortars was obtained from a combined gray-scale thresholding–DMT procedure, from which high deformation concentrations could be visualized at the paste-aggregate interface of the sulfate-exposed specimen.