Byungik Chang | University of New Haven (original) (raw)

Papers by Byungik Chang

Engineering Solid Mechanics, 2021

The incremental launching method (ILM) is an efficient method of bridge construction primarily su... more The incremental launching method (ILM) is an efficient method of bridge construction primarily suited for environmentally sensitive areas. However, during the bridge launching, there are significant contact stresses between the launching system and the steel bridge girders. These substantial contact stresses can cause damage both on, and just under, the girder surface. Although Hertz contact theory solutions may give an insight into the problem, the accuracy is uncertain due to the presence of complex geometries, loads, and material properties. The complicated structural systems need to rely on numerical modeling such as the finite element analysis which are not always available. The primary objective of this study is to estimate the relationship of the maximum contact stress between an I-girder and a roller using a nomogram. The nomogram is built based on a parametric study with various roller dimensions and loads by numerical modeling. The maximum contact stress from the nomogram ...

The Iowa DOT owns 233 high-mast lighting towers, ranging from 100 to 180 feet tall. These structu... more The Iowa DOT owns 233 high-mast lighting towers, ranging from 100 to 180 feet tall. These structures are typically located at the intersection of major highways and interstates and provide broad illumination to the traveling public. In 2000, a statewide inspection was conducted of the 193 towers in the inventory at that time. A 140-foot tower located near Sioux City collapsed in 2003 due to the development of a large fatigue crack at the welded connection at the base plate. Subsequently, cracks were found in 20 other towers. In all cases, the cracked structures were taken out of service. This paper will present forensic information about the collapsed and cracked towers and describe the instrumentation and long-term monitoring of Iowa towers. Preliminary findings of the monitoring will be included. The goal of the testing is to determine the types of vibration and stress ranges that the towers are experiencing. This testing will provide a better understanding of the ways the towers ...

The objective of the study presented in this report was to document the launch of the Iowa River ... more The objective of the study presented in this report was to document the launch of the Iowa River Bridge and to monitor and evaluate the structural performance of the bridge superstructure and substructure during the launch. The Iowa Department of Transportation used an incremental launching method, which is relatively unique for steel I-girder bridges, to construct the Iowa River Bridge over an environmentally sensitive river valley in central Iowa. The bridge was designed as two separate roadways consisting of four steel plate girders each that are approximately 11 ft deep and span approximately 301 ft each over five spans. The concrete bridge deck was not placed until after both roadways had been launched. One of the most significant monitoring and evaluation observations related to the superstructure was that the bottom flange (and associated web region) was subjected to extremely large stresses during the crossing of launch rollers. Regarding the substructure performance, the co...

This study examines usage paterns of educational websites that employ databases, wikis, andgenera... more This study examines usage paterns of educational websites that employ databases, wikis, andgeneral resources for information sharing and dissemination. To gather data about website usage, a quantitative survey was sent out to students and to the users of an existingeducational website. Additionaly, participantsprovided data on learning preferences and practices. Findings from the survey showthat users visit an education website for finding information and geting connected to a community. The survey resultsalso show that while communicating information should remain a toppriority, educational web sites wil need to adapt to an increasing desire for interpersonal communication within their own online communities.

2017 ASEE Annual Conference & Exposition Proceedings

Dr. Chang was also awarded his MBA degree from West Texas A&M University in 2012. His doctoral wo... more Dr. Chang was also awarded his MBA degree from West Texas A&M University in 2012. His doctoral work focused on addressing a critical need related to the unexpected failure of slender light poles. Prior research from his master's degree work at Iowa State University included design verification, behavior analysis, and nonlinear modeling of an incrementally launched bridge to obtain roller-girder contact stresses using the finite element method.

Sustainability, 2020

Ready-mix concrete is not always affordable because it is less economical for small projects. Thi... more Ready-mix concrete is not always affordable because it is less economical for small projects. This study shows an effort to introduce alternative home-produced concrete for small paving areas such as sidewalks, backyards, or fixing the existing concrete and discusses the economic evaluation of the alternative concrete for home purpose. The materials being used in this study are available locally or are easily purchased. The primary objective of the study is to analyze the compressive strength and conduct economic analysis of alternative home-produced concrete with different mix designs. Wood ash, fly ash, and recycled aggregate concretes are the alternative concrete types discussed in this study. Fly ash can replace Portland cement up to 30% without losing significant compressive strength of the concrete. Furthermore, fly ash is less expensive than Portland cement and can reduce the cost of concrete by saving approximately 15%. Wood ash can be used up to 25% in concrete without losi...

2017 Gulf Southwest Annual Regional Conference Proceedings

Students in the mechanical and civil engineering programs at West Texas A&M University are ex... more Students in the mechanical and civil engineering programs at West Texas A&M University are exposed to sustainability in a wide variety of required courses in thefreshman through senior level coursework. The projects in these courses are carefully selected to provide an in-depth understanding of sustainability through analytical and experimental studies. In thermal-fluid design, students were asked to build an environmentally friendly and energy efficient systemfor the distillation of wastewater produced in agricultural processing facilities in west Texas. The solar still was to be augmented with evacuated solar tubes collector to enhance the solar performance of the still and increase the daily production yield rate.West Texas is a dry land area with an annual rain fall of less than 20 inches per year. This project addresses the need set into effect by watermanagement practices for this region regarding water conservation, reuse and reclamation of wastewater to extend the life time of the Ogallala Aquifer, a major source for water irrigation.Due to having low investment and operation cost, students learned that solar distillation is a feasible system for use in semi-arid and arid regions where solar energy is abundantly available. Field tests show the augmentation of the still with evacuated solar tubes increased its production rate by 263%.The maximum daily production was 1.4 kg/m 2 day for the passive distillation system, and 3.6 kg/m 2 day for the active distillation system.

Journal of Wind Engineering and Industrial Aerodynamics, 2020

High mast light poles (HMLP) are used nationwide on major interstates and at local intersections ... more High mast light poles (HMLP) are used nationwide on major interstates and at local intersections for luminary purposes in the United States. The HMLPs are subjected to major oscillatory wind loading which may cause fatigue and earlier life expediency failure. From the concerns that HMLP failures would lead to pedestrian harm, extensive studies were performed to develop a standard model of behavior for high wind loads and vortex shedding that can be used for future design. Numerical modeling with the use of Computational Fluid Dynamics (CFD) is proposed to simulate the typical shape (dodecagonal cylinders) of the HMLPs and be validated with wind tunnel experiments. The k-ω based SAS-SST turbulence model will be used to handle the turbulence closure for the fully turbulent flow regime. The work done will look at validating static and dynamic force coefficients of a dodecagonal cylinder at different orientations. In addition, the lock-in behavior will be simulated to determine the applicability of modern CFD approaches to be able to perform the oscillatory behavior of a dodecagonal cylinder. Added mass cases also will be examined to determine the damping effects on an unsteady cylinder as additional in-depth study.

Journal of Performance of Constructed Facilities, 2020

AbstractDynamic messaging signs (DMS) are found in operation over freeways, expressways, and othe... more AbstractDynamic messaging signs (DMS) are found in operation over freeways, expressways, and other major intersections and provide information to travelers. If the DMS structure fails, then pedestr...

Renewable Energy, 2019

The primary objective of the project is to evaluate the benefits of wind and solar energy and det... more The primary objective of the project is to evaluate the benefits of wind and solar energy and determine economical investment sites for wind and solar energy in Texas with economic parameters including payback periods. A 50 kW wind turbine system and a 42 kW PV system were used to collect field data. Data analysis enabled yearly energy production and payback period of the two systems. The average payback period of a solar PV system was found to be within a range of 2-20 years because the large range of the payback period for PV systems were heavily influenced by incentives. This is in contrast to wind energy, where the most important factor was found to be wind resources of a region. Payback period for the installed wind system in Texas with federal tax credits was determined to be approximately 13 years.

Wind and Structures, 2014

ABSTRACT A major problem with high-mast light poles is the effects that wind vortex shedding can ... more ABSTRACT A major problem with high-mast light poles is the effects that wind vortex shedding can have on the pole itself because of the lock-in phenomenon. It is desired that the coefficients in the AASHTO Standard Specifications ( edition) for Structural Supports for Highway Signs, Luminaries, and Traffic Signals be analyzed and refined. This is for the belief that the span of the shapes of poles for which the coefficients are used is much too broad and a specific coefficient for each different shape is desired. The primary objective of this study is to develop wind vortex shedding coefficient for a multisided shape. To do that, an octagonal shape was used as the main focus since octagonal cross sectioned high-mast light poles are one of the most common shapes in service. For the needed data, many wind parameters, such as the static drag coefficient, the slope of aerodynamic lift coefficient, Strouhal number, the lock-in range of wind velocities producing vibrations, and variation of amplitude of vortex-induced vibration with Scruton number are needed. From wind tunnel experiments, aerodynamic parameters were obtained for an octagonal shape structure. Even though aerodynamic coefficients are known from past test results, they need to be refined by conducting further wind tunnel tests.

International Journal of Green Energy, 2017

Experimental studies were conducted on a single basin active solar distillation system augmented ... more Experimental studies were conducted on a single basin active solar distillation system augmented with a solar collector using evacuated solar tubes. Tests were conducted over several days under the climatic conditions of West Texas to evaluate the effect evacuated solar tubes have on the daily distillate yield rate. To investigate the feasibility of the solar tubes, passive and active solar stills were studied. Solar stills with and without exterior insulation were also examined. The maximum daily production was 1.4 L/m 2 /day for the passive distillation system, and 3.6 L/m 2 /day for the active distillation system using evacuated solar tubes. The tests showed the augmentation of the still with evacuated solar tubes increased its production rate by 263%. Also, for the same average water temperature in the basin, an insulated basin produced a higher amount of distillate compared to an un-insulated basin. The peak in the thermal efficiency of the active and passive systems was about 19%.

Renewable Energy, 2016

Compared to the national average residential retail electricity price, Connecticut (CT) had the 4... more Compared to the national average residential retail electricity price, Connecticut (CT) had the 4 th highest electricity price in the country with 19.23 cents/kWh in September 2015, nearly 50% higher than the national average for price of electricity. This study aims to assess the economic feasibility of the solar PV systems at the campus under realistic constraints, by analyzing actual data from the solar array on campus. The project focused on the economic feasibility of solar PV systems on campus with physical, spatial, and practical constraints that result in a project to deviate from theoretical (estimated) values. To achieve that, the prediction of the PV power generation from the building was developed and compared with the actual (measured) data. The average payback period of a campus-wide PV system was calculated as primarily 11 years, within a range of 8-12 years, and was estimated to reduce overall building operating expenses by $250,000, or 8%. The economic parameters such as NPV and IRR also validated the investment worthiness. The results of the study could be used to analyze or further develop feasibility studies of PV systems at other universities in Connecticut and neighboring states that share similar climatic characteristics and economic factors.

This report evaluates TxDOT criteria for the superheavy loads that trigger bridge analyses to det... more This report evaluates TxDOT criteria for the superheavy loads that trigger bridge analyses to determine whether the criteria adequately protects Texas bridges. Researchers used solid modeling calibrated with a bridge test of a 3-span continuous steel girder unit of SH 159. The bridge testing measured girder end rotations with tilt loggers and load position using a sub-foot accuracy GPS. Solid modeling was done with ANSYS 12. The calibrated model was used to conduct a parametric study. Axle distribution factors of 0.28 and 0.45 were experimentally determined for interior and exterior girders respectively. Results of the parametric study showed that the Texas superheavy load criteria are valid for this bridge type. A study of service life extension showed that operational stress level loads applied as little as 5 percent of time to a particular structure will have a significant effect on the lifetime of the structure, and that the number of fatigue load-cycles per truck cannot be assumed to be one. A graphical version of the bridge review trigger (load-length curve with existing allowances and restrictions) might serve TxDOT and heavy-haul carriers better than does the gross vehicle weight triggers. Data collected long term of load frequency and load level from a relevant bridge would help TxDOT determine what effects stress level variations have on the life of Texas bridges.

Wind Tunnels and Experimental Fluid Dynamics Research, 2011

The incremental launching method is one of the unique methods being considered for bridge constru... more The incremental launching method is one of the unique methods being considered for bridge construction. Incremental launching is accomplished by assembling segments of the bridge girders behind an abutment, joining them together, and pushing the assembled segments on support bearings to their permanent position. During bridge launching there are significant forces that can develop between the launching system and the girders. For example, high contact stresses can be created in the area where the launch rollers and the lower surface of the bottom flange of a steep bridge girder come into contact. The analysis of contact-stress problems is not typically possible with closed-form solutions because of the complicated geometries, loadings, and material properties. This paper discusses the recommendations for developing a nonlinear finite-element model for analyzing the contact-stresses scenarios within the context of the Iowa River Bridge launch.

Transportation Research Record: Journal of the Transportation Research Board, 2014

ABSTRACT Dynamic message signs are increasingly used on freeways, expressways, and major arterial... more ABSTRACT Dynamic message signs are increasingly used on freeways, expressways, and major arterials to manage traffic flow better by providing accurate and timely information to drivers. Overhead truss structures that allow for wide displays across multiple travel lanes are typically used to support those signs. Recently, cracks at welded toes in these structures have been identified in multiple states. The AASHTO standard specification defines the loads to be considered during design as wind load, dead load, live load, and ice load, and fatigue design for wind galloping, vortex shedding, natural wind gust, and truck-induced gust. Notably missing from this list is any consideration for thermal loads. Although the number of thermal cycles is relatively low, the temperature variations are relatively large. Should these large temperature ranges result in large stresses, the potential for fatigue failures to initiate, principally from thermal variations, exists. The objectives of this study were to investigate the influence of thermal- and wind-induced loads on bridge-type overhead truss support structures and to provide a resource aimed at improving current design specifications for thermal design. To provide a solid baseline for this work, field monitoring of several overhead trusses was conducted. The evaluation of the collected data was important for understanding the structural behavior and for the advancement of any future code provisions. In addition, finite element modeling was conducted to further study strain and stress magnitudes, which were compared with the field monitoring data. The fatigue life of the truss structures was also estimated on the basis of AASHTO specifications and the numerical modeling results.

Journal of Performance of Constructed Facilities

The number of permits for superheavy loads crossing Texas bridges has steadily increased over the... more The number of permits for superheavy loads crossing Texas bridges has steadily increased over the years, and, compared with several other states, the criteria that establish superheavy-load status is generous. The result is that many Texas bridges experience routine, high-stress loads that cause accelerated deterioration. In this study, bridge load and rating factors and the validity of the criteria for establishing superheavy load status are evaluated. The primary objective of this study was to evaluate Texas Superheavy load criteria for bridges. To accomplish this, field tests for the response behavior of a bridge subjected to overweight vehicles and parametric study using finite element analysis were utilized to extract bridge criteria triggers. The field calibrated solid model and related parametric study show that the Texas superheavy load criteria are valid for the study bridge type. Bridge rating, using the distribution factors determined in the study, show that the bridge has much reserve capacity, even with short 230 kip and longer 311 kip superheavy loads applied. The parametric study using finite element modeling shows that the criteria adequately protect this bridge type. Because the criteria are based on TxDOT’s prior permitting, a graphical version of the criteria might serve TxDOT and carriers better than does the gross vehicle weight limits alone. Data collected long term of frequency and load level from a relevant bridge would help TxDOT determine what effects stress level variations have on the life of Texas bridges.

2015 ASEE Annual Conference and Exposition Proceedings

at Birmingham (UAB) and the director of the Transportation program. She holds a B.S. degree in Ci... more at Birmingham (UAB) and the director of the Transportation program. She holds a B.S. degree in Civil Engineering from Aristotelian University in Greece, and M.S. and Ph.D. degrees in Civil Engineering from the University of Illinois at Chicago. Her teaching and research focus on traffic operations and safety, sustainable transportation, and traffic simulation and modeling. She has served as the principal investigator in 80 projects and authored/co-authored over a 160 technical papers.

Journal of Performance of Constructed Facilities, 2015

AbstractThe number of permits for superheavy loads crossing Texas bridges has steadily increased ... more AbstractThe number of permits for superheavy loads crossing Texas bridges has steadily increased over the years, and compared with several other states, the criteria that establish superheavy-load status are generous. The result is that many Texas bridges experience high-stress loads that cause accelerated deterioration. In this study, bridge load and rating factors and the validity of the criteria for establishing superheavy-load status are evaluated. The primary objective of this study was to evaluate Texas superheavy-load criteria for bridges. To accomplish this, field tests for the response behavior of a bridge subjected to overweight vehicles and a parametric study using finite element analysis were utilized to extract bridge criteria triggers. The field-verified solid model and related parametric study show that the Texas superheavy-load criteria are valid for the study bridge type. Load ratings computed using the distribution factors determined in this study show that the evaluated bridge has much ...