فهرست مطالب

  • Volume:11 Issue:17, 2019
  • تاریخ انتشار: 1398/09/02
  • تعداد عناوین: 12
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  • Treatment of a Distillery Wastewater in a Bipolar-Mode Electrocoagulation System: Performance Evaluation and Kinetic Analysis
    Madhuri Damaraju, Ryuichi Muraki, Debraj Bhattacharyya*, Tarun kanti panda, kiran kumar kurilla Pages 1643-1652

    This work investigates the performance of a bipolar mode electro coagulation system with multiple electrodes. The objective is to remove recalcitrant total organic carbon (TOC) and total phosphorus (TP) from distillery wastewater. The design surface area to volume (S/V) ratio considered for the study was 76.5/m. The effects of the process variables, such as initial pH, retention time and current density, were evaluated on the performance of the reactor. The percentage removal of pollutants increased with an increase in current density and time. The treatment efficiency was found to be at near neutral pH. The results of the experiment revealed that the efficiencies of removing the pollutants were found to be 73% and 85% for TOC and TP, respectively. The reactions followed first-order kinetics for both TOC and TP removal from distillery wastewater. The mass transfer coefficient, K values were found to be higher at near neutral pH. The correlation between the current density and mass transfer coefficients for both the pollutants was deduced and the energy consumption was found to be 12 kWh/cu m

    Keywords: Bipolar mode electrocoagulation, Phosphorus, Reaction kinetics, Total organic carbon
  • Empirical Study on Pedestrian Signal Design and Compliance in the State of Qatar
    Mohamed Kharbeche, Wael K. M. Alhajyaseen, Mohammed Al Salem, Deepti Muley* Pages 1653-1666

    To ensure safe crossing manoeuvres at signalized crosswalks, the pedestrian delays and allocation of sufficient pedestrian green and flashing green times should be considered at design stage. The pedestrian signal settings in the State of Qatar were analyzed through empirical observations of eight crosswalks. Video recording technique was used to record the pedestrian movements and signal settings at selected crosswalks. The results indicated that excessive delays resulted in low compliance rates at all crosswalks and the signal phasing affected compliance rate. Moreover, the analysis of crossing speed indicated that the speed (1.2 m/s) currently specified by the Qatar Traffic Control Manual, 2015 for determining clearance time is sufficient for safe crossing. In addition, the results of speed analysis indicated that the gender, type of pedestrian signal display, and crosswalk length affect the crossing speed of pedestrians. A comparison of crossing times with the provided signal timings indicated that a lower pedestrian flashing green is provided at all sites, and excessively large buffer intervals are available. These results demonstrate the urgent need to modify signal settings to enable more opportunities for walking and legal crossings. It is recommended that pedestrian signals should be always activated based on the applied phasing plan without the need for pressing the push buttons. These push buttons can be used to recall early pedestrian green to reduce their waiting time. Furthermore, at major crossings, countdown timers showing time remaining for PG should be installed to improve compliance rates.

    Keywords: Signalized intersections, Pedestrian delay, Signal compliance, Clearance time, Crossing speed
  • Comparison of CFRP and GFRP Wraps on Reducing Seismic Damage of Deficient Reinforced Concrete Structures
    Son Quang Pham, Vui Van Cao* Pages 1667-1692

    The effectiveness of glass/carbon fibre reinforced polymer (GFRP/CFRP) wraps at plastic hinges has been confirmed; however, their respective effectiveness on reducing seismic damage of deficient reinforced concrete structures has hardly been compared. The current study aims at this comparison, providing some useful information to realise the better FRP for confinement retrofitting of reinforced concrete structures poorly confined due to deficient transverse reinforcement. Four- and eight-storey poorly confined reinforced concrete frames were selected to represent low- and mid-rise building structures, respectively. These deficient frames were then strengthened by CFRP/GFRP wraps via external confinement. Inelastic time history and cumulative damage analyses of the original, CFRP- and GFRP-retrofitted frames were performed. The damages of CFRP- and GFRP-retrofitted frames were compared with each other and with the damage of the original frame. The comparison results show that CFRP and GFRP wraps at plastic hinges substantially reduce damage. More importantly, GFRP wraps are more effective than CFRP wraps by reducing a higher amount of the cumulative damage index. The conclusions can help in deciding on the type of FRP to be used for confinement retrofitting of RC structures poorly confined due to deficient transverse reinforcement.

    Keywords: Retrofitting, CFRP, GFRP, Seismic damage, RC frame, Confinement
  • Substructure Responses of a Concrete Bridge with Different Deck-to-Pier Connections
    Fatemeh Shaker, Alireza Rahai* Pages 1683-1695

    This paper tried to analyze the effects of deck-to-pier connections on pier design forces of a number of typical bridges. To this end, the behavior of pier connection of several 3D concrete bridge models was studied under service loads. A parametric study is conducted to investigate the different bearing types and pier height effects. The responses of models, such as superstructure displacements, forces, and displacements of deck-to-pier connections, and column forces are presented. The analysis results revealed that an increase in pier height leads to a considerable rise in the pier displacements and a decrease in transferring forces in all types of connections, and the greatest increase was found in the single elastomeric-bearing line. Therefore, rigid connections have better performance compared to other cases in high piers. Moreover, evaluating the effect of deck-to-pier connection on the pier force distribution indicated that the double elastomeric-bearing line connection increases the rigidity and transferred moment in comparison to the single line to the pier. Thus, its restraint lies between rigid and single bearing line conditions, and it should be considered in column design and can be more effective in moderate pier height. It was also revealed that the bearing location has a significant effect on the connection stiffness and transferred forces to the pier and influences its behavior and design.

    Keywords: Bridge bearing, Rigid connection, Semi-rigid connection, Elastomeric bearing
  • Method for Construction, Maintenance, and Management of Rigid-Frame Bridges Using H-Shaped Steel Girders
    Mitsuhiko Tokuno, Saiji Fukada, Yoshiaki Nakai, Tuan Minh Ha* Pages 1697-1714

    This work outlines an actual case study performed on a rigid-frame bridge using H-shaped steel girders in the laboratory and introduces the process of construction, maintenance, and management of the proposed bridge structure in practical cases. A novel structural rigid connection was developed for H-shaped steel girders and reinforcing bars at the corner of the rigid-frame structure. Additionally, a full-size model of the reinforced concrete rigid-frame bridge with H-shaped steel girders was constructed and subjected to destructive loading tests to evaluate the structural integrity of the proposed rigid connection and to reveal the load-carrying capacity and failure mode of the bridge. As a result of the loading test, compression failure occurred on the upper surface of the concrete deck at midspan, whereas plasticization and breakage of the fixing nut did not occur in the vicinity of the fixing part. Therefore, the feasibility of the connection approach at the rigid corner was verified experimentally. In addition, the results of cost analysis showed that the rigid-frame bridge could potentially provide significant cost benefits compared to the other bridge structures considered in this study. Notably, regarding the total cost for a life cycle of 100 years, the overall cost of rigid-frame bridges was estimated to be approximately 0.49–0.58 of the total expenses for slab bridges. Finally, this work introduced a scheduled inspection procedure with new inspection items corresponding to the proposed bridges by utilizing visual observation in combination with other testing techniques.

    Keywords: Reinforced concrete rigid-frame bridge, H-shaped steel girder, Construction procedure, Scheduled inspection, Cost comparison
  • Analysis of Stakeholder Concerns at Different Times of Construction Projects Using Social Network Analysis (SNA)
    Ahad Nazari, Mohammadhossein Dadpour, Eghbal Shakeri* Pages 1715-1727

    Success in the projects will not be achieved without analyzing the key stakeholder concerns. Indeed, against such concerns will result in higher project costs. One of the most important steps in stakeholder management is paying attention to the stakeholders’ concerns and planning how to respond to them. Stakeholders and their concerns change with time throughout execution of projects. The purpose of this research was to identify and analyze stakeholders of road construction projects and their concerns using social network analysis (SNA) method. First, the stakeholders and their concerns were identified and evaluated. Next, using the Net Miner four network software, their concerns were analyzed and assessed at different times of their projects. Finally, the main challenges involving stakeholders were identified and classified in different groups and some strategies were proposed for responding to them. According to the obtained results, the lack of comprehensive environmental studies, the presence of adverse effects of the project performance on the environment and inaccurate estimates of cost, as well as completion time of the project were the major concerns of project stakeholders. In the initiation phase of every project, the challenges were more related to the environmental and political problems affecting the project. In the planning phase, concerns were more related to the selection of appropriate contractors and methods with their sufficient experiences and knowledge in various fields, such as environmental problems and project budgeting, etc. In the execution phase of the projects, foreign policy pressures and sanctions, high inflation, and qualities of observing and implementing the environmental rules and public discontent were among stakeholders’ key challenging concerns.

    Keywords: Stakeholder concern, Social network analysis, Key stakeholder, Road project, Project phase
  • Application of Falling Weight Deflectometer (FWD) Data and Energy Ratio (ER) Approach for Cracking Performance Evaluation of Asphalt Pavements
    ongsuk Park, Sanghyun Chun*, Sangyoung Han Pages 1729-1737

    This study primarily focuses on evaluating the falling weight deflectometer (FWD) time history data for use in relative cracking assessment of asphalt pavements. Eight field project sections with a similar pavement structure were selected for evaluation; they include sections with and without the evidence of cracks. FWD tests were conducted for all selected field sections at a similar temperature to obtain load–deflection time history data. The results of the FWD-dissipated energy were further compared with the results of the energy ratio (ER), which is a well-known performance-based fracture property previously introduced for the cracking performance evaluation of asphalt mixtures. Pavement structures with the existence of cracks showed significantly greater FWD-dissipated energy and maximum deflection indicating a relatively higher rate of deterioration and/or damage for the pavement systems. Additionally, a proportional relationship identified between rate of change in normalized ER and FWD-dissipated energy confirmed that the FWD time history data was able to effectively differentiate pavement structures with and without the existence of cracks. Comparative results between the FWD-dissipated energy and the ER further support the validity of application of FWD-dissipated energy and the maximum deflection as a reliable material and/or pavement structural response indicator that can be used for cracking performance evaluation of asphalt pavements.

    Keywords: Cracking performance, Pavement damage, Energy ratio, Falling weight deflectometer, Asphalt pavement
  • Performance Comparison of Various Chicane Types: A Driving Simulator Study
    Metin Mutlu Aydin*, authorBanihan Gunay, Kadir Akgol Pages 1735-1765

    Urban streets are becoming noisy, less safe and unattractive places due to high traffic volumes and vehicular speeds. Especially, high speeds causes many problems such as traffic accidents, noise, etc. To prevent these problems and negative effects of speeding, traffic calming measures have been widely used in many developed countries. In this study, the effectiveness of ten most common chicane types on speed limit compliance were examined by comparing and ranking chicanes according to their performance. For this purpose, a “Safety Index” was developed and an Ordinary Least Square Regression analysis was performed to identify safest chicane types for undivided two-lane and divided four-lane roads by using various parameters. Additionally, statistical tests were conducted to determine the most important driver characteristics of drivers before and inside the chicanes. For the analyses, all necessary data were obtained from the driving tests of 106 volunteers using a driving simulator. For the simulation scenarios, Akdeniz University’s (Antalya/Turkey) campus roads were selected as a case area. The results showed that Chicane Types 2 (CT-2) and 7 (CT-7) have the highest Safety Index values (0.69 and 0.98) and they were found to be the most proper CTs for the undivided and divided roads, respectively. From the statistical tests, it was also found that education level, gender and driving license duration were found to be the statistically significant parameters on speed choice for the most proper chicane types. Additionally, it was concluded that the most important driver characteristics are determined as age (has a negative effect) and gender (to be male has a positive effect) of drivers before and inside the chicanes. All these findings show that the investigation of different CTs has a great potential to reduce speeds and ensure safety in urban minor roads to limit vehicle speeds.

    Keywords: Chicane, Driving simulator, Safety, Speed reduction, Traffic calming
  • Economic Analysis of Crack Treatment Methods Using HDM-III Modeling
    Moon Sup Lee, Mithil Mazumder, Hyun Hwan Kim, Soon Jae Lee* Pages 1739-1751

    Crack sealing treatment includes the use of a router to create a reservoir on the intended cracks, whereas crack filling is given without any modification to the crack wall. With sealing treatment the pavement can have longer service period because of its good adhesion and cohesion performance. However, the initial cost of sealing is higher due to the use of extra material, equipment and labor. As a result, the aim of this study is to investigate the long-term cost-effectiveness in between these two treatment techniques in Texas and to observe if the longer service period can compensate the higher initial cost of sealing treatment. For this purpose, the initial cost inputs have been identified and a highway design and maintenance standard model (HDM-III) used to evaluate the most cost-effective pavement maintenance between crack sealing and filling treatment over a 25-year analysis period. Agency, capital and net present value have been calculated by using HDM-III based upon average daily traffic (ADT), altitude and road length. The results of this study indicated that (1) crack sealing is more cost-effective pavement maintenance compared to crack filling over a long period of time; (2) agency cost can be reduced by 15% and 14% based on ADT and road length analysis, respectively, by implementing crack sealing treatment; (3) capital cost in terms of ADT and road length with crack sealing maintenance can be saved by 24% and 19%, respectively; (4) the net present value with crack sealing treatment after a 25-year analysis period is higher for ADT and road length compared to crack filling by 18% and 19%, respectively; (5) the cost-effective resealing interval years of 5 years is proposed when the unit cost of routing increased by 25%.

    Keywords: HDM-III, Routing, Crack sealing, Crack filling, Life cycle cost
  • Seismic Responses of a Bridge Pier Isolated by High Damping Rubber Bearing: Effect of Rheology Modeling
    A. K. M. T. A. Khan, M. A. R. Bhuiyan*, S. B. Ali Pages 1767-1783

    This study is aimed at evaluating seismic responses of a bridge pier isolated by high damping rubber bearing (HDRBs), subjected to intra-plate and inter-plate earthquake ground motion records. In this regard, a conventional bilinear model and two elasto-visco-plasticity-based rheology models (the original rheology model [36] and an improved rheology model proposed in the current study) of HDRBs have been utilized in this study. In the first part of the paper, the adequacy of the two elasto-visco-plasticity-based rheology models has been checked in predicting the mechanical behaviour of the HDRBs, subjected to sinusoidal loadings. The numerical results of the HDRBs have shown that the improved rheology model can predict the mechanical behaviour of the bearings in a quite better way in comparison to the original rheology model, particularly at higher shear strain levels of the bearings. In the second part, seismic response analysis of a 3-DOF bridge superstructure–pier–foundation (s–p–f) system has been evaluated. In the end, nonlinear dynamic analysis using a standard direct time integration approach has been carried out. The seismic responses of the s–p–f system considered in the current study are the pier and deck displacements, the shear force of the bridge pier, the shear strain of the bearing and the total hysteretic energy of the bearings. The analytical results have shown that the rheology modeling of HDRBs has a significant effect on seismic responses of bridge pier.

    Keywords: Rheology model, High damping rubber bearing, Base isolation, Soil–structure interaction, Nonlinear dynamic analysis
  • Seismic Reliability Analysis of RC Frames Rehabilitated by Glass Fiber-Reinforced Polymers
    Mansour Bagheri*, Azadeh Chahkandi, Hashem Jahangir Pages 1785-1797

    Optimum length of glass fiber-reinforced polymers (GFRP), as an advantageous type of composites, on the retrofitted columns of RC frames is obtained in this study by conducting seismic reliability analyses. To achieve this goal, maximum reliability index with different FRP lengths of columns of a six-story RC frame was calculated to find the optimal length for FRP-retrofitted columns. The seismic behavior of structure after verification was assessed by nonlinear time history analysis with OpenSees finite element software. Three scaled far-field earthquake records were selected for nonlinear time history analysis. The reliability analysis was performed by first-order reliability method and Monte Carlo simulation in RT software. The optimal length of FRP was obtained on the results of reliability analysis. The findings of the study showed that increased FRP material quantities do not affect the retrofitted reliability index. The findings of the study showed that increased FRP material quantities do not affect the retrofitted reliability index. The convergence of Monte Carlo simulation occurred after a variety of iterations and, consequently, was alternated with the first-order reliability analysis which has very short run time and is lower error methodology. Moreover, in all cases of reinforcement and analyses, the compressive strength of the concrete is extremely important.

    Keywords: Seismic reliability, RC frame, Nonlinear time history analysis, FRP jacketing region
  • Composite Strips with U-Shaped CFRP Wrap Anchor Systems for Strengthening Reinforced Concrete Beams
    Catreen S. Marji, Rami H. Haddad* Pages 1799-1811

    The contribution of carbon fiber reinforced polymer (CFRP) wrap as an anchorage system of CFRP plates, used for flexural strengthening, is investigated. Eighteen concrete beams (100 × 150 × 1400 mm3) were cast and cured for 28 days before strengthening with both CFRP plates (1.2 × 50 mm2) and anchorage-used, U-shaped CFRP wraps. These were adhered on the top of the CFRP plates at different longitudinal and transverse extensions. The mechanical response of the concrete beams was examined under four-point loading including measurements of load versus deflection, bond stress versus slippage and strain in CFRP plates. Crack formation and failure modes were also monitored and characterized. End anchorage regimes, using 300-mm-long U-shaped segmented CFRP wraps, impart the best improvement to load capacity, rigidity, and toughness (up to 80, 57, and 40%, respectively) without harming tangibly ductility in terms of deflection at failure. Anchorage cases involving attaching continuous single or double layers of U-shaped CFRP wrap on the top of CFRP plates impart lower but tangible overall improvements in mechanical performance of CFRP-strengthened beams. A simple empirical model is developed to predict ultimate strain in CFRP plate based on present results before examining using available literature data. Moreover, the efficiency of the present technique is compared to that present in literature.

    Keywords: Beams, Composite materials, Bond, CFRP wrap anchorage, Strain in CFRP, Failure patterns