KSCE Journal of Civil Engineering

The city of Scottsdale Arizona implemented the first fixed photo Speed Enforcement camera demonstration Program (SEP) on a US freeway in 2006. A comprehensive before-and-after analysis of the impact of the SEP on safety revealed significant reductions in crash frequency and severity, which indicates that the SEP is a promising countermeasure for improving safety. However, there is often a tradeoff between safety and mobility when safety investments are considered. As a result, identifying safety countermeasures that both improve safety and reduce Travel Time Variability (TTV) is a desirable goal for traffic safety engineers. This paper reports on the analysis of the mobility impacts of the SEP by simulating the traffic network with and without the SEP, calibrated to real world conditions. The simulation results show that the SEP decreased the TTV: the risk of unreliable travel was at least 23% higher in the ‘without SEP’ scenario than in the ‘with SEP’ scenario. In addition, the total Travel Time Savings (TTS) from the SEP was estimated to be at least ‘569 vehicle-hours/year.’ Consequently, the SEP is an efficient countermeasure not only for reducing crashes but also for improving mobility through TTS and reduced TTV. Keywordsphoto enforcement-travel time savings-safety-microscopic simulation

The occurrence of thirty-one selected Endocrine Disrupting Compounds (EDCs) and Pharmaceuticals and Personal Care Products (PPCPs) was analyzed in eleven major municipal Wastewater Treatment Plants (WWTPs) in Seoul, Korea over two consecutive days. The area was selected since there was a lack of information in the Seoul area on the suspected contamination of wastewater effluents by micropollutants. Discharge from those major WWTPs accounted for approximately 25% of the Han River flow where over 99% of drinking water is produced from surface waters in this area that has a population approximately 15 million inhabitants. Samples collected in WWTP effluents were analyzed by Liquid Chromatography with tandem Mass Spectrometry (LC-MS/MS) with Electrospray Ionization (ESI) and Atmospheric Pressure Chemical Ionization (APCI). Many target compounds were detected in the effluent samples (66%). Atenolol, iopromide, TCPP, TCEP, musk ketone, naproxen, DEET, carbamazepine, trimethoprim, sulfamethoxazole, and benzophenone were frequently detected in effluent samples with mean concentrations ranging from 98 to 663 ng/L (maximum = 230–1,700 ng/L). However, the steroid hormones (17 α-ethynylestradiol, progesterone, and testosterone), atrazine (herbicide), and octylphenol (surfactant) were not detected in all the samples. Results of this study can provide evidence that WWTP effluent is one of the major sources contaminating the Han River. Keywordswastewater treatment plant-endocrine disrupting compounds-pharmaceuticals-personal care products-wastewater

This paper describes numerical experiments of high resolution schemes applied to open-channel flow equations with discontinuities in the solution. The high resolution schemes tested are the second-order symmetric TVD scheme, the upwind TVD scheme, the upwind TVB scheme, the predictor-corrector TVD scheme, the second- and third-order ENO schemes, and the space time conservation method. The six schemes except the space time conservation method are the approximate Riemann solvers, so that they need entropy correction for the numerical solution of physical meaning. These methods are applied to 1D dam-break wave propagation over the horizontal and frictionless open-channel. The computed solutions are compared with the Stoker's solution and the solution from the first-order Roe's scheme. All schemes including the Roe's scheme are found to yield results which agree well with the analytical solution when the ratio of upstream to downstream depths is moderate such as 0.05. When the ratio is reduced to 0.0001, most schemes appear to be diffusive and to retard the shock front. It was found that the second-order upwind TVB scheme and the space time conservation scheme are very accurate but expensive regarding the computing time. The second-order ENO scheme and the second-order predictor-corrector TVD scheme appear to be moderately accurate and economical.

During the period 1994–2004, before the Mw 9.3 Sumatra-Andaman earthquake of 26 December 2004, Thailand was moving horizontally constantly eastward with an average rate of approximately 33.2±1.1 millimeters per year in ITRF2000. The magnitude of the horizontal strain rate was less than 30 nanostrain per year, which was considered small but significant. After the occurrence of the mega thrust earthquake, a horizontal movement to the southwest direction is evident at different rates all over the Thai region. Large co-seismic horizontal displacements were observed in the southern part of Thailand, while moderate and small displacements were seen in the central and northern parts of Thailand. The Royal Thai Survey Department (RTSD) carried out multiple Global Positioning System (GPS) field campaigns to monitor the post-seismic displacements. However, their efforts were complicated by the second mega thrust (Mw8.7) earthquake, which occurred at Nias, Sumatra on 28 March 2005. This study focuses on the use of GPS data, collected between 1994 and 2006, gathered from six GPS stations located at Phuket, Chumporn, Chonburi, Uthaitani, Srisaket and Lampang in Thailand and an additional station located in the northern part of Malaysia to derive changes in the strain rate. Here we find that today’s deformation in Thailand is dominated by SW-NE trending extension. This feature is in agreement with post-seismic relaxation occurring on the Sumatran trench. Keywordsstrain rate-GPS-Sumatra-Andaman earthquake-Nias earthquake-Thailand

The semi-active tuned liquid column damper (TLCD) system is investigated for control of coupled responses of 3D irregular buildings under seismic excitations. The TLCD system is a special type of tuned mass damper (TMD) system providing a performance similar to a TMD system but offers a number of practical advantages over the traditional TMD system. The equations of motion for the combined building and TLCD system are derived for multistory building structures with rigid floors and plan and elevation irregularities. Simulation results for control of two multistory moment-resisting space structures with vertical and plan irregularities show clearly that the semi-active TLCD control system reduces the responses of 3D irregular buildings subjected to earthquake ground motions efficiently.

This paper presents a Reynolds stress modeling of compound open-channel flows with vegetation on the floodplain. In the Reynolds stress model, we use the SSG model by Spezialeet al., for the pressure-strain correlation term, Mellor and Herring's model for the turbulent diffusion term, and Hanjalic and Launder's model for the dissipation term. In order to take into account the anisotropy of turbulence due to the free surface, the combination of Shir's model and Gibson and Launder's model is included in the pressure-strain correlation model. Model validations are carried out for the compound open-channel flows without vegetation. Then, the model is applied to the compound open-channel flows with vegetated floodplains. The mean flow and turbulence structures are simulated and the impact of vegetation on the floodplains is investigated.

The Southern Great Plains Hydrology experiment (SGP'97) was conducted on an area approximately 12 times larger than that of previous field experiments (e.g. Washita'92), and thus the statistical structure of soil moisture can be examined using large-scale remotely sensed images (40 km×250 km). Here, empirical scaling analysis was conducted to elucidate the link-ages between the spatial and temporal variability of soil moisture and the succession of wetting and drying cycles in the landscape. The results show that the soil moisture fields exhibit multiscaling behavior varying with the scales of observation and hydrometeorological conditions. During inter-storm periods the spatial evolution of soil moisture is closely associated with the spatial variability of soil permeability, and by vegetation after it reaches values near field-capacity. Topography appears to dominate the spatial structure of soil moisture during and immediately after storm events, while evapotranspiration increasingly dominates the evolution of soil moisture fields as the landscape dries. Specifically, the multiscaling behavior is consistent with the scaling behavior of soil hydraulic properties as described by soil texture parameters such as sand and clay percentage. Finally, a break in statistical symmetry (multiple scaling behavior) was identified, which separates the spatial and temporal evolution of the statistical structure of soil moisture fields for wavelengths below and above 10 km, the α- and β-scale ranges respectively.

AADT estimation for a new highway route has been performed depending on complicated procedures with diversified variables. However, regardless of types of estimation procedures and variables, errors between AADTs estimated and observed appear in most AADT estimation. They have been statistically expressed in terms of forecast error in percent (FEIP). The presented study is based on FEIP collection at freeway sections. It is found that by the province, there exist historical patterns of FEIPs, safety margins, and reliabilities of estimation. Based on this finding, this paper provides a way to distribute a uniform reliability of AADT estimation for a new highway route. Uniform reliability distribution over AADTs estimated in serial sections of a highway route is important because a uniform reliability of AADTs at the design level potentially guarantees to sustain a uniform level of service during the operation of a highway in serial sections of a highway route. Through the example study in the paper, it may be concluded that the introduction of the reliability concept and historical patterns of FEIPs may improve the AADT estimation in design of a new highway route over which overestimation or underestimation have prevailed.

Variable Message Signs (VMS) have become a new trend in roadway signs. These signs offer an increase in traffic safety by their ability to relay messages to motorists for warning of hazards ahead such as fog, traffic congestion, accidents, and lane closings. the geometry of these signs sometimes results in significant cyclic loading of the support structure due to wind gusts. This studypresents analytical and experimental investigations of bridge-type VMS structures. GTSTRUDL (2003) is used to perform space frame structural analyses of these welded tubular structures. This paper includes measurements from a static filed test and compariso ns between the measurements and the structural analyses results. Fatigue evaluations are performed based on the stress ranges fromfield measurements and structural analyses. According to this comparative study, the fatigue design loadings derived from AASHTOSpecifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals (2001) can be conservatively used to evaluate the fatigue life of the bridge-type VMS structures.

This paper presents the method and the results of investigations to determine the position vector of a static or moving vehicle using the Global Positioning System (GPS) in the absolute (point) positioning mode with and without selective availability. Starting from the basic positioning scheme with code observation, the most accurate positioning strategy using the phase is described. The main strategy for the highest accuracy absolute positioning is to estimate GPS satellite clock errors independently, thus obviating the between-station differencing. The GPS clock errors are estimated at 30-second intervals using International GPS Service (IGS) orbits and stations. The clock error estimates are then used in an absolute positioning algorithm to determine the coordinates without any other reference site. Static and kinematic GPS data at 1-second sampling rate were processed and compared with the known values and the corresponding DGPS solutions. For the static case, an IGS station was assumed as unknown and its coordinates were estimated. For the kinematic case, the aircraft survey observations were tested. The positions were compared with the corresponding DGPS solutions for each case. Since Selective Availability (SA) is now turned off, its effect on the clock estimation as well as on the position is compared and emphasized.

Riemann invariant manifolds (RIM) are used to evaluate the performance of absorbing boundary conditions (ABC) for numerical modeling of an unbounded acoustic waveguide. The evaluation is carried out by extracting, from the computed solution, spurious waves caused by the approximate nature of the ABC used. Unlike the traditional bicharacteristics method for multi-dimensional wave motion, use of RIMs leads to an equivalent one-dimensional problem involving invariants along characteristics. The clear physical meaning associated with the invariant allows for the estimation of the energy flux into the computational domain due to reflected waves from the ABC. Numerical examples demonstrate that the total energy carried by reflected waves that enter the computational domain becomes smaller as the unbounded domain is modeled more accurately, and thus can be used to evaluate the performance of the ABC.

This paper is a review of the scour conditions, and scour-estimation difficulties, associated with scour at abutments of bridges over rivers and streams. A recent survey of abutment-scour problems in the U.S., Korea, and abroad, shows that several scour conditions can occur, and that existing relationships for scour estimation, besides being inaccurate do not match the scour conditions. Moreover abutment scour is found to be primarily a concern for bridges over smaller rivers and streams than for larger rivers, because inadequate design and monitoring attention has been give to abutment scour at the many small bridges. This paper also discusses the difficulties confronting accurate estimation of abutment-scour depth. The difficulties, which include similitude aspects of laboratory experiments on scour at bridge abutments, complicate the development of reliable scour-estimation relationships. In a practical sense, the difficulties imply that design relationshipsfor scour-depth estimation inevitably have to be of approximate accuracy given the great variability of channel conditions at most abutments.

Laboratory models for fatigue cracking and permanent deformation growth are validated using the response and performance measured from asphalt pavements with different air void contents under the third scale Model Mobile Loading Simulator (MMLS3). The fatigue life prediction algorithm is developed based on a cumulative damage concept and the algorithm for permanent deformation prediction involves a sub-layering method, dividing a pavement layer into several artificial layers for analysis. These algorithms account for the effects of applied loading rate and temperature variation along the pavement depth. The difference in loading frequencies between the laboratory experiments and the MMLS3 test was taken care of using the time-temperature superposition principle with growing damage. The proposed methodology is found to be reasonable in predicting fatigue life and permanent deformation growth in the MMLS3 tests. It is found that the resulted alliance among the accelerated pavement test, laboratory test, and performance models could serve as a foundation for the successful estimation of pavements’ service life in the future.

This paper presents an experimental study on the durability of mortar specimens incorporating inorganic alkali-free accelerator (AFA) exposed to external sulfate attack. Visual examination, compressive strength, expansion and density of mortar specimens with or without AFA were monitored up to 360 days of exposure. Additionally, in order to identify the products formed by sulfate attack, mineralogical analysis based on x-ray diffraction (XRD) was also performed on paste samples. Test results confirmed that the mortar specimens with AFA suffered a serious deterioration by sulfate attack, especially in 10% sodium sulfate solution. Furthermore, XRD traces indicated that the formation of ettringite and/or thaumasite is primarily responsible for the sulfate deterioration of mortar specimens. Conclusively, it must be taken a special care when the shotcrete with AFA is applied under the sulfate-bearing environments.

The paper presents an algorithm for designing a layout of accelerometers for structural monitoring and damage detection. The maximum likelihood approach has been applied as a mathematical basis for the algorithm. Fisher information matrix is formulated in terms of mode shape sensitivity with respect to structural parameters. A scheme of an effective independence distribution vector has been applied to determine optimal locations of accelerometers. Singular value decomposition scheme has been applied to overcome the rank deficiency problem in the computed sensitivity matrix. The adequacy of the proposed algorithm has been examined by estimating structural parameters through a frequency-domain system identification. The identification results using the response data measured at the locations selected by the proposed algorithm are compared with those at arbitrary locations. In addition to the design of accelerometer layout for a structural monitoring of general purpose, the paper proposes another algorithm of layout design for damage detection with the assumption that some members critical for the structural safety are pre-determined. Damage possibility of each member computed from the static strain energy has been implemented as a weighting factor in the algorithm. Simulation studies have been carried out on a two-span multigirder bridge to examine the proposed algorithms.

The objective of this paper is to establish a statistical relationship correlating crash severity with weather, traffic maneuve rs, and specific roadway geometrics at four-legged signalized intersections in rural areas. In this paper, the probability of the levels of injury severity is examined by applying ordered probit regression models for all crash types, single-vehicle crashes, two-vehicle cras hes, and three or more-vehicle crashes. The study results suggest that in terms of crash severity for all crash records, more vehicl e presence of protected left lane, wider median widths, and higher traffic flows, and more driveways are associated with less injury severity of intersections. By the number of vehicles involved in crashes, the variable shows variations in the models and magni tudes of the estimates.

The construction industry has had a disproportionately high rate of accidents, for its size. Although improvements in construction worker safety have been achieved, the construction industry continues to lag behind most other industries with regard to safety. This study, which is one of several studies on accident prevention in the construction industry, identifies the effect of accidents and intends to increase employer and worker awareness of potential hazards in the workplace. In order to measure the effect of accidents, this study adopted a quantitative approach to measuring productivity loss from an accident in terms of a delay in utility trenching operations. The research finding indicates that the increasing rate of productivity loss following accidents is decreasing, although the probability of the occurrence of accidents is consistently increasing, which means that productivity is not lowered as much as the probability of the occurrence of an accident is increased. It is also notable that the backfill activity, which is one of three major activities comprising utility trenching operations, is most vulnerable to productive loss due both to the variations in the probability of the occurrence of accidents and to the extra durations, whereas the pipe installation activity is more sustainable than the other activities. Efforts to identify the effect of accidents on productivity, such as potential productivity loss, may help superintendents make more appropriate decisions regarding safety on-site, thereby balancing accident prevention with productivity.

Transportation externalities like air pollution, noise and others are acost or a benefit that arises from an economic transaction and that falls on people who do not participate in the transaction (Perkin, 2000). Among those externalities, noise has become such a pervasive factor in our life recently. Conventional economic feasibility analysis, however, does not account the costs of such externalities. The purpose of this paper is to address the issue of the economic feasibility analysis with accounting such externalities, focusing on traffic noise area. Based on TNM model cost along with conventional construction, right-of-way, and maintenance costs, a revised benefit/cost (B/C) analysis will be conducted for a hypothetical city called U-TOWN. By incorporating the noise cost, represented by the noise barrier cost, the revised B/C indicator can be obtained along with range of cost share by the addition of the noise barrier and the range of B/Cs thereof. This paper, more specifically, proposes the framework of how to incorporate noise element into the existing B/C analysis. It also includes the usage of TNM, noise level prediction method, and how to obtain the optimal design of noise barrier within TNM. If successfully conducted, the analysis framework set forth here in this paper can be further explored and the results may shed light on a new and better framework combining transportation and environmental modeling to better address the environmental aspects of transportation.

Many of the traffic accidents on roads are a result of alignment defects in the roads. Therefore, it is very important to deter mine alignments, and correct the elements of the alignments that do not meet design requirements. This will insure that cars run on the roads safely. In order to determine the correct alignment of roads, a three-dimensional trajectory of the center line shall be acquired as data. Although there will be various methods, we can do that easily with GPS. Additionally, it is very convenient to use, because it acquires the same data for interpreting positions, as car navigation system. Although we can acquire data from a three-dimensional trajectory of a center line using GPS, it will be more accurate if it is based on a combination of GPS/GLONASS. Accordingly, in this study, the precision based on traditional design drawings was compared with the data acquired with the combination of GPS and GLONASS. We would like to propose an effective and useful approach to utilize the satellite road alignment system by evaluating the existing roads horizontal alignment.

Although construction productivity has received a great deal of attention from construction practitioners and researchers, few research efforts have specifically evaluated productivity in the context of the productivity management cycle. Consequently, there is still a lack of useful indicators for determining which items should be prioritized and improved upon in order to yield the highest benefits from productivity management. In an effort to address this issue, this study proposes the Productivity Achievement Ratio (PAR), which is a productivity evaluation indicator that will assist in the selection of the most appropriate management items for construction productivity enhancement. Using a multiple linear regression analysis, the process for calculating the PAR is developed, and the applicability of the proposed indicator is verified through a case study of steel erection work. The results of this study indicate that the PAR can aid construction practitioners in achieving more balanced and effective productivity management, even when management resources are limited. Keywordsproductivity-productivity management-reduction factor-productivity achievement ratio-regression analysis

This paper presents an Acoustic Emission (AE) characterization of damage accumulation and strength recovery in Asphalt Concrete (AC) mixture. A series of uniaxial tensile cyclic tests with and without rest period has been conducted on a 19 mm nominal maximum size of aggregate (NMSA) AC at 20°C. During the fatigue tests, key AE parameters including emission counts were acquired from two piezo-type sensors attached to the middle of a 150 mm high, 75 mm diameter cylindrical specimen. Test results indicate that accumulative AE energy and AE count may be used not only to assess the initiation and propagation of fatigue damage, but also to quantify the beneficial effect of rest period on the performance of AC. The frequency-amplitude analysis shows that crack formations coincide with the peaks of maximum AE amplitude (Amax) with higher frequencies, while healing is best described by Amax with lower frequencies during the rest periods. In addition, it is demonstrated that the Kaiser effect, the stress dependence of AE generation, does not hold for fatigue in AC.

The influence of temperature and Freeze-Thaw (FT) processes on the mechanical properties of frozen soils were investigated in the laboratory in order to give a better understanding of changes in engineering properties of frozen soils. The experimental data revealed a dependence of compressional and shear wave velocity of frozen soils on temperature, soil type and FT cycles. Compressional wave velocity showed a strong correlation to the unfrozen water content dependent on soil type, while shear wave velocity was mainly influenced by the ice content and the soil matrix. Compressional and shear wave velocity changed for samples subject to FT cycling, which appears to be caused by alterations in the soil structure. Elastic constants were calculated based on the wave propagation theory and compared to results from uniaxial compression tests. The dynamic elastic modulus, dynamic shear modulus and compressive strength increased with descending temperature. FT cycles reduced the compressive strength, and influenced the dynamic elastic constants. Poisson’s ratios of all tested soils not subject to FT cycling decreased upon a change in negative temperature; while the opposite trend was observed for soils influenced by FT cycles.

In this paper, we propose a system combining various methods for monitoring leakage of underground pipelines. The system uses a wireless connection for communications and uses acoustic emission effects to detect and locate leakages. The system is easily deployed, with a flexible configuration that requires less maintenance because a wireless connection is used. Moreover, the system is accurate, simple, and inexpensive, because it is based on acoustic emissions. Experiments determining the wireless connectivity of the proposed system are also presented. Keywordswireless sensor–monitoring system–underground–acoustic emission sensor–leakage monitoring

Polymer modification was widely used to improve the properties of construction materials. The concept of polymer modification for mortar and concrete was put forward 80 years ago. It was known that the use of polymers for modification can greatly improve the strength, adhesion, resilience, impermeability, chemical resistance and durability properties of mortars and concrete. In southern Vietnam, a tropical weather country, the environment was usually hot with high humidity. The durability of mortar or concrete coating was reduced over time in such a condition. This study examines the strength of polymer-modified mortars in high temperature and high humidity. Moreover, the results included the improvement of strength of acrylic emulsion polymer-modified mortar (PMM) by the addition of blast furnace slag. Fifteen percent cement was replaced with blast furnace slag (BFS) in a mix proportion in order to improve strength of PMM. The specimens were cured in cycles 50±2°C, RH 90±3%, for 5 hours and 20±2°C, RH 60±3 %, for 19 hours per day. The strength of PMM was measured at the age of 3, 7, 14, 21 and 28 days, 3 and 6 months and 1 year in a high temperature and high humidity cycles.

An enhanced truss model is presented in the present study. The model is theoretically based on the well-known relationship between shear and the rate of change of bending moment in a reinforced concrete beam subjected to combined shear and moment loads. The new model shows that a new perspective on the shear resistance can be gained by considering the variation of the internal arm length along the span. And the shear resistance mechanism is resolved into three independent base components; arch action, truss action and membrane action. The compatibility of deformation associated to the two actions is indirectly taken into account by employing an empirical factor. Then the base equation of V=dM/dx is numerically formulated so as to clarify the physical basis of the behavior related to beams under combined action of flexure and shear. Keywordsarch action-beams-reinforced concrete-truss model-shear strength

The ability to re-sequence activities is a critical task for project planners for effective project control. When re-sequencing activities, planners need to determine the role and “status” of activities (i.e., whether activities can or cannot be delayed), which they infer based on the rationale between activity sequences. The current CPM framework only distinguishes activities with respect to their time-criticality and represents sequencing rationale using precedence relationships. Thus, CPM-based schedules make it difficult for planners to modify existing schedules to evaluate and generate sequencing alternatives. These limitations has been addressed by formalizing a constraint ontology and classification mechanism. The constraint ontology allows explicit representation of the rationale for activity sequences in CPM-based schedules, while the classification mechanism leverages the ontology to automate the inference of the role and status of activities. These formalizations were implemented in a prototype system called “Constraint-loaded CPM” (CLCPM). With this tool, users can keep track of the different types of rationale for activity sequencing logic, and discern which activities to delay to expedite milestone or bottleneck activities. Thus, the formalizations provide planners with the information they need to easily and quickly evaluate and generate sequencing alternatives.

Developments and applications of structural health monitoring (SHM) systems have become active particularily for long-span bridges in Korea. They are composed of sensors, data acquisition system, data transmission system, information processing, damage assessment, and information management. In this paper, current status of research and application activities on SHM systems for civil infra-structures in Korea are briefly introduced by 4 parts: (1) current status of bridge monitoring systems on existing and newly constructed bridges, (2) research and development activities on smart sensors such as optical fiber sensors and piezo-electric sensors, (3) structural damage detection methods using measured data, and (4) a test road project for verification and enhancement of the pavement design procedures by the Korea Highway Corporation. Finally the R&D activities of a newly established Smart Infra-Structure Technology Center at Korea Advanced Institute of Science and Technology are also briefly described.

Uncertainty is inherent in the construction projects. Appropriately determining a project schedule under uncertainty is one of the most important factors for a contractor’s success in a project. However, when the likelihood of incurring risk events and the riskassociated consequences are uncertain, contractors often face difficulties in estimating project duration. While the Critical Path Method (CPM) has been widely used in scheduling a project, it has been frequently criticized because it assumes an activity’s duration deterministic without reflecting uncertainty involved in a project schedule. The Program Evaluation and Review Technique (PERT) and the Monte Carlo Simulation (MCS) technique have been used to reinforce the shortcomings of the CPM through applying probabilistic analysis approach. They, however, still impose a problem of identifying probabilities under the circumstances where schedule variables cannot be defined as probabilistic nature. The main objective of this paper is to present an alternative schedule risk quantification method based on the fuzzy set theory for estimating a risk-associated activity’s duration. A hypothetical case study is prepared to show how the proposed method can be put into practice. Interviews with industry experts are also held to verify the usability as well as to identify the pros and cons of the method. Keywordsschedule risk-fuzzy set-PERT (Program Evaluation and Review Technique)-MCS (Monte Carlo Simulation)-CPM (Critical Path Method)-fuzzy mean

A few recent studies have shown the benefits of optimizing time-of-day break points at a coordinated actuated traffic signal control system. Even though these studies considered transition costs between break points in the performance evaluations, they did not explicitly consider transition costs during the optimization. Obviously this is because the microscopic simulation run time to explicitly account for such transition costs during the optimization is quite expensive. This study presents an enhanced procedure for determining time-of-day break points for coordinated actuated traffic signal systems with explicit consideration of transition costs using a genetic algorithm. The enhanced procedure was implemented using a hypothetical network consisting of four signalized intersections and the results indicated that the enhanced procedure outperformed the previously developed greedy search-based method. A quick investigation of the transition costs indicated that the impacts of transitions were negligible for those break points optimized by the proposed approach. Keywordstraffic-traffic signal control-coordinated actuated signal-time-of-day operations-genetic algorithm-transition costs

This paper presents the development and evaluation of a procedure for determining optimal break points for time-of-day based coordinated actuated traffic signal operations. The proposed procedure uses a feature vector of optimal cycle length per time interval instead of traffic volume itself. Initial break points determined by the proposed feature vector are used in the greedy search algorithm to obtain optimal break points. By using the greedy search algorithm the number of evaluations in the search are dramatically reduced when compared to an exhaustive search or other common heuristic search methods such as a genetic algorithm. The proposed procedure was evaluated using a hypothetical network consisting of four signalized intersections and the results indicated that the proposed procedure effectively improved the performance of the coordinated actuated signal control. In addition, sensitivity analyses results on randomly varying demand conditions up to ±20% and randomly increased demand conditions up to 30% indicated that the newly developed break points were robust for such varying demand fluctuations.

Groundwater flow and contaminant transport simulations require the determination of various hydro geological parameters such as transmissivity, aquifer thickness, seepage velocity, dispersibility etc. Due to the complex behavior of Groundwater flow and contaminant transport simulations, reliable measurement of the parameters involved is often not possible while performing groundwater system simulations. Hence a methodology is developed in this study wherein a neural-fuzzy model based on an Adaptive Neuro Fuzzy Inference System (ANFIS) is integrated with the particle swarm optimization to estimate the uncertainties in output parameters due to imprecision in input parameters. The Particle Swarm Optimization (PSO) technique is used to find a global optimal solution to a groundwater flow and contaminant transport problem. This is achieved by incorporating the Adaptive Neuro Fuzzy Inference System (ANFIS) to evaluate the objective function within the PSO framework. Later, the ANFIS-PSO algorithm is applied to four problems taking a) a single imprecise parameter for radial flow to a well, b) two imprecise parameters for one dimensional solute transport in steady uniform flow, c) three imprecise parameters for a two-dimensional heterogeneous steady flow problem and finally d) four imprecise parameters for the problem of two-dimensional solute transport. The results show that with the ANFIS-PSO algorithm, the computational burden is reduced considerably when compared to the commonly used vertex method. KeywordsAdaptive Neuro Fuzzy Inference System-ground water flow-contaminant modeling-uncertainty-particle swarm optimization

In this paper, we examine the modeling process of traffic conditions that drivers learn such as travel time through longterm learning behavior under a nonstationary traffic environment. We found that rational expectations formation about the route travel time can be expressed by the adaptive expectations model when the travel time changes in accordance with a nonstationary process which consists of permanent shock and transient shock. We found that the adaptive parameter of the model converges to a fixed value corresponding to the route conditions. Furthermore, when the traffic environment follows stationary processes, the expectations of the traffic agent are congruent with the rational expectations. In other words, rational expectations formation can be regarded as a special case of the expectation formation model that is proposed in this research. The paper is concluded by illustrating some numerical examples.

In this paper, an uncertainty analysis framework for uncertainty analysis of velocity measurements from Acoustic Doppler Current Profiler (ADCP) having four transducers was developed, based on the American Institute of Aeronautics and Astronautics (AIAA) uncertainty analysis standard. In the developed framework, the data reduction equation for computing velocity with the raw ADCP measurements was established from a given common algorithm that has been used in various conventional ADCP post-processing software. The proposed framework was formulated in terms of mathematical expressions that entail the sensitivity coefficients documenting propagation of the uncertainties from the fundamental sources into the ADCP velocity. KeywordsAcoustic-Doppler Current Profilers-uncertainty analysis-sensitivity analysis-data reduction equation

Effects of admixture type and dosage have been investigated in the scope of this study. The influence of incorporation of chemical admixtures at different dosages on the development of pore structure of cement mortars has also been investigated. A delay on the development rate of strength by incorporation of chemical admixtures at early ages has been determined. The highest strength values were obtained for the cement mortars prepared by naphthalene sulphonate based chemical admixture. The strength values of specimens prepared with overdosage were lower than those of control specimens. Therefore, setting time and flow values were investigated related to admixture dosage and type. Increase in dosage of admixtures results in an increase of setting time and flow values. The pore structure development was given by time and dosage. Maximum pore area ratio values are determined for cement mortars prepared with overdosage. Pore area ratio values decrease by time, as compressive strength values increase. Keywordsadmixtures–microstructure–strength–pore area ratio–SEM–image analysis

The purpose of this study is to elucidate the adsorption, desorption and movement of napropamide in soils, that have been mainly used in farmland. Experiments were carried out with the adsorption and desorption tests on various shaking time, temperature, pH and the content of organic matter, and column test, in order to understand the movement characteristics of napropamide. As results, the isothermal adsorption characteristics of napropamide were well fitted with the Freundlich rather than with the Langmuir equation. When the content of organic matter in soil exceeded 2.0%, the adsorption rate of napropamide depended on the content of organic matter. However, in case the content of organic matter was below 2.0%, the content of clay became a determiner. Adsorption and desorption was little affected by pH. Though the adsorption was affected by soil temperature, desorption was little. The slope of adsorption curve was in the order of sandy loam>loam>silty clay. But a lot of napropamide was desorbed from the silty clay soil, even though its movement was slower than other two soils.

With the increase of the number of construction projects on soft ground due to the growth of regional industry, various construction problems related to soft soil behavior have also been reported. Especially, foundation piles of abutments and/or buildings which were constructed on soft ground have suffered from a great deal of stability problems due to excessive displacement accompanied by the lateral flow of soft ground. Although many researchers have studied this problem, it is still difficult to assess the mechanism of lateral flow quantitatively. Furthermore, a reliable design method for the judgment of lateral flow occurrence is not established yet. In this study, an advanced pattern recognition theory — i.e., the support vector machine (SVM) theory — was applied to develop a soft computing model for the judgment of lateral flow occurrence based on real data compiled from Korea and Japan. Predicted results from SVM models were compared with those from the conventional empirical methods. It has been found that the proposed SVM pattern recognition model can predict lateral flow occurrence practically and more accurately than the conventional empirical methods. Keywordslateral displacement-soft soil-support vector machine (SVM)

The driver route choice problem under real-time information provision is characterized by subjectively interpreted and/or linguistically expressed data in addition to quantitative inputs. In previous work, the authors propose a hybrid probabilistic-possibilistic model which treats qualitative and quantitative data simultaneously in a single framework. This paper presents experimental insights on the performance of the hybrid model based on extensive simulation analysis under potential real-world scenarios. It performs sensitivity analyses on the associated driver behavior model parameters, and investigates the model’s ability to capture dynamic qualitative phenomena under information provision. The results highlight the flexibility of the hybrid model in addressing a broad range of driver behavior characteristics and network conditions. They also suggest that the hybrid model can capture the evolution of the driver behavior characteristics over time and the influence of the randomness in network conditions on route choice behavior. Keywordshybrid probabilistic-possibilistic model-route choice-driver behavior dynamics-information provision

Real-time traffic data play a significant role for the provision of real-time traveler information and the development of other ITS (Intelligent Transport Systems) system. For instance, the steady real-time data can be used for incident detection system and dynamic route guidance. Many public transportation agencies or private information service providers are currently or will be providing the road traffic information. The basic form of traffic information would be traffic congestion status, incident, construction area, and the optimum path based on current traffic status. The systems deployed are now evolving with scanty traffic sources that are available. In spite of such poor infrastructure situation, we are trying to derive the link travel times by using whatever information sources available. Currently, the available sources are fixed traffic detectors, CCTVs, and probe vehicles that are running for dispatching and/or for solely collecting the link travel times. The purpose of this paper is to apply the framework of fuzzy operator logic to present methodological aspects of data conversion of each traffic sources and data fusion design by using those traffic data sources, and to implement the fusion mechanism in a typical traffic information center.

The primary focus of this research was an assessment of the external carbon source (RCS5, RCS15, and TPA5) as environmentally friendly, alternative of the carbon sources in the denitrification process. These alternative carbon sources (RCS5, RCS15, and TPA5) demonstrated the same grade of biodegradability and denitrification rate. The nitrogen removal efficiencies of RCS5, RCS15, and TPA5 in field application test were 77.4%, 58.7%, and 62.4%, respectively. The application of the alternative carbon sources (RCS5, RCS15, and TPA5) to sewage from K, N and S-STP facilities reduced the cost of an alternative carbon source more than 55.4% when compared with methanol application. Keywordsadvanced sewage treatment-denitrification-external carbon source-methanol-nitrification

In the finite element(FE) analysis of prestressed concrete shell structures, several automatic generation schemes have been proposed to accommodate the geometry-related inputs of tendons especially for large FE models. The previously proposed algorithms established well basic procedures of the automatic generation. However, some deficiencies are found in those studies and there are some crude sub-algorithms which can decrease the speed of the procedure. The purpose of this study is, therefore, to propose some efficient methods which can improve the capability of the existing automatic generation algorithm in prestressed concrete shell structures. The efficient techniques are proposed here to accelerate the generation procedure and overcome the singular cases. The parametric representations of each shell element and a tendon, which are obtained by interpolating the given points, are used to develop the proposed algorithm. A numerical example is presented to verify the effectiveness of the proposed scheme. The proposed algorithm allows faster and more effective generation of tendon geometries for the efficient FE analysis of prestressed concrete shell structures.

Differential Quadrature Method (DQM) to integrate the one-dimensional Advection-diffusion Equation (ADE) is presented. This method was applied to two examples and the results were compared with the performance of the Explicit Finite Difference Method (EFDM) and Implicit Finite Differences Method (IFDM). Based on the comparison with the exact solution, and both the explicit and implicit finite difference solutions, it was concluded that the DQM provides similar results but less grid points; besides the results are converged quickly. A numerical comparison for a case in which the exact solution is known, DQM gives closer results to the exact values than EFDM and IFDM.

Artificial intelligence is the area of computer science focusing on creating machines that can engage on behaviors that humans consider intelligent. In the past few years, the applications of artificial intelligence methods have attracted the attention of many investigators. Many artificial intelligence methods have been applied in various areas of civil and environmental engineering. The aim of this study is to develop models to estimate oxygen transfer efficiency in nappe, transition and skimming flow regimes over stepped cascades. For this aim, genetic expression programming, a new member of genetic computing techniques, is used. It is similar, but not equivalent to genetic algorithms, nor genetic programming. For nappe, transition and skimming flow regimes, three models are constructed using the experimental data. The test results indicate that for the model equations obtained, the correlation coefficients are very high and the minimum square error values are less than 0.0033. So, genetic expression programming approach can be successfully used in stepped cascades to predict the oxygen transfer efficiency. Keywordsartificial intelligence genetic expression programming–stepped cascade–oxygen transfer efficiency

Stepped chutes that are commonly used for gabion weirs, river training, irrigation channels, and storm waterways have become popular in recent years mainly due to the intrinsic low-cost and the speed of construction. Stepped chutes are used also for in-stream re-aeration and in water treatment plants to enhance the air-water transfer of atmospheric gases and of volatile organic components. In a stepped chute, the provision of steps can produce significant energy dissipation. This paper seeks the effect of energy dissipation over stepped chutes on aeration efficiency. It is observed from the results that aeration efficiency increases with increasing energyloss ratio. There is higher energy dissipation in nappe flows than skimming flow situations and nappe flow regime lead to greater aeration efficiency than skimming flow regime. Moreover, regression equations are obtained relating aeration efficiency to stepped chute slope and energy-loss ratio. For this aim, genetic expression programming, a recently developed artificial intelligence technique, is used. The model equations obtained have high correlation coefficients and low minimum square error values. Keywordsaeration efficiency–energy dissipation–oxygen transfer–stepped chute

Two dimensional tsunami waves induced by submerged or aerial/sub-aerial rigid slider with and without sudden stop are simulated in time domain by using fully-nonlinear NWT (numerical wave tank) technique. Special attentions are paid on the maximum free-surface depression/rise and the resultant run-up near shoreline to assess relevant potential hazard. The fully-nonlinear results are compared with linear results. The free-surface deformation and run-up increase with mass height and sliding velocity and the growth rate can be better predicted by using the nonlinear simulation. The cases with or without sudden stop are next compared. The maximum free-surface rise/fall as well as shoreline run-up significantly increases in the case of sudden stop due to additional transient waves generated by the impact-like change of motion. The aerial/sub-aerial cases are also compared with submerged/underwater cases. Through a series of parametric investigations, it is clearly seen that the potential tsunami risk of aerial/sub-aerial land slide is much higher than that of submerged underwater land slide.

This paper deals with the environmentally assisted cracking behavior of high strength cable wires of a suspension bridge, expos ed to marine environments. The main objective is to determine the safety of a bridge system locally and globally. To evaluate the safety of a suspension bridge, an ultimate limit state for the local cracking in cable wires and service limit states for global respo nses of the bridge system are considered. In an ultimate limit state, the reliability of time-dependent and crack length-dependent Environmentally Assisted Cracking (EAC) of a cable wire has been calculated. Global system responses have been evaluated by a FEM program, which were used for the safety evaluation of service limit states. Due to the diffusion of hydrogen atoms affected by the gradient of hydrostatic stress, the section of cable wire will fail immediately when the ratio of EAC in a cable wire is la rger than 60percent. However, the global responses show ignorable differences in the considered analysis. Suggestions for the found problems are discussed.

In the gauging station which tidal current effects are dominant, the reliable measuring methods are needed. In this study, the stage height difference is considered to derive the rating curve and the index velocity is considered to derive the mean velocity equation which discharge results from these equations are compared with the measured discharge collected in the Samrangjin station where tidal current effects are dominant. A robust minimum covariance determinant method, one of the nonlinear multi-regression methods, is applied to derive regression equations for the rating curve and mean velocity equation using 39 measurements collected at Samrangjin gauging station. The new rating curves allow superior in predicting discharge more precisely in tidily affected river as compared to existing equation. The discharge estimated using the mean velocity from the index velocity is in best agreement with the measured discharge data.

Operational data from nine dairy wastewater plants (DWTPs) in Wisconsin were collected and analyzed to determine reasons for poor enhanced biological phosphorus removal (EBPR) efficiency. Several factors affecting EBPR performances in dairy were identified. Since many dairies operate five days a week, DWTPs suffer low F/M ratios during off-days, leading to sludge bulking and unstable EBPR efficiency. The most pronounced factor affecting EBPR performance was uneven organic loading caused by lack of an equalization tank or too a small volume to alleviate the fluctuation in flow and organic loading. The other factor was imbalance of nutrients, especially nitrogen. The other factors include sudden change of pH in a matter of hours and higher temperature (> 30°C) in the summer. The high temperature was thought to shift microbial population and thus lead to the loss of EBPR capability. Unexpected discharge of cleaning solution was another problem causing poor EBPR and COD removal efficiencies. Laboratory-scale tests confirmed the effects of the COD/P ratio (organic loading) and pH on EBPR efficiency. Microscopic examination showed the presence of tetrad-arranged coccoid cells, called G-bacteria in five out of nine DWTPs. Rhodocyclus-related PAOs were also detected from Fluorescent in situ hybridization (FISH) analysis.

In this study, a time-dependent agent-based taxi simulation model was developed. Modeling of taxi system is a complex task because it is dependent on the spatiotemporal pattern of passenger demand. However, the role of taxi as a public transport cannot be under-estimated in the urban area. Not only as a paratransit for the elder and disabled but also as a public transport for complementing the mass transit systems such as subways and arterial buses, a taxi conveys huge number of passengers every day. In this context, a practical modeling method for a taxi system was developed based on equilibrium philosophy and an agent-based simulation framework. In this study, the authors developed a simulation framework for the evaluation of taxi service for enhancing the quality of urban taxi transportation system. The developed model was tested with various passenger travel patterns, and a meaningful policy-related issue for improving the service performance of a taxi system was found for dealing with an asymmetric demand pattern. Keywordsagent-based model-taxi simulation-first-in-first-out violation function-asymmetric passenger travel demand

Replacement of scarcely available natural sand with fly ash has economical and environmental advantages. However due to lack of knowledge people avoid using fly ash at construction sites, which is increasing area under land bank. The paper presents the results of experimental investigation, which indicated about 20% increase in the compressive strength and about 15% increase in flexural strength of concrete by the inclusion of fly ash as a partial replacement of sand as compared to control concrete. Sand was replaced by fly ash by Maximum density method and Minimum voids method. Addition of 0.5% super plasticizer could achieve about 30% increase in the compressive strength and about 20% increase in flexural strength of concrete by the inclusion of fly ash as a partial replacement of sand as compared to control concrete. Results indicated increase in workability for all the cases over control concrete. Concrete with fly ash was also found to be about 25% economical when cost per N/mm2 was compared. Based on experimental results correlations are developed to predict Compressive Strength, Flexural strength, cost per N/mm2, Slump and Dry Density for percentage sand replacement with fly ash. Keywordsfly ash-compressive strength-flexural strength-flow-density

The emergy methodology was used to evaluate aggregate supply from marine sand extraction at an offshore site in the exclusive economic zone in the South Sea of Korea for use in the construction of the Pusan New Port. The marine sand from the offshore site had an emergy yield of 2.87 E22 sej, with 97.5% from the offshore sediments and 2.5% from the economy. The emergy yield ratio of the marine sand extraction was 40.7, implying that the process contributed a net benefit to the Korean society beyond the economic inputs required for it. The environmental loading ratio of the sand production was, however, very high at 3,422, indicating the great environmental stress of the extraction process to the marine ecosystem. The emergy sustainability index, therefore, was very low at 0.012. This study revealed that the marine sand extraction could be a viable option in terms of yield, but measures to reduce environmental impacts of the extraction are needed to increase the sustainability of the process. Further emergy evaluations on other aggregate production alternatives are required to provide better insight in determining policy priorities regarding the aggregate supply for the construction sector of Korea. Keywordsaggregate supply–emergy evaluation–marine sand–Pusan New Port