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University of Arkansas, Fayetteville

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Articles 421 - 434 of 434

Full-Text Articles in Civil and Environmental Engineering

Laboratory Evaluation Of Dynamic Characterization Methods For Rapid Condition Assessment Of Bridges, Jason Kyle Herrman Aug 2011

Laboratory Evaluation Of Dynamic Characterization Methods For Rapid Condition Assessment Of Bridges, Jason Kyle Herrman

Graduate Theses and Dissertations

The objective of this thesis was to devise and refine Structural Health Monitoring methods and the associated quantitative characterization methods with the specific goal of enabling rapid and reliable safety evaluations of bridges following natural or manmade hazards. Presently, the safety and serviceability of these transportation infrastructure assets for use in emergency response and recovery operations are evaluated through on-site visual inspections of individual structures by teams of specially trained engineers or technicians; a process that is manpower-intensive, subjective, and slow. Specifically, the researcher was able to identify and evaluate strategies and procedures for using dynamic testing methods to rapidly …

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Two Dimensional Modeling Of Wind Effects On A Bridge Section Using Finite Difference Method, Jessica Carreiro May 2011

Two Dimensional Modeling Of Wind Effects On A Bridge Section Using Finite Difference Method, Jessica Carreiro

Civil Engineering Undergraduate Honors Theses

Wind effects on long span bridges are a major concern for bridge design. Wind acts as a dynamic load on the bridge deck causing the bridge to react in ways not accounted for in static load design. Attention to these effects increased tremendously after famous bridge collapses, such as the Tacoma Narrows Bridge in 1940. Due to this collapse and others, engineers were made painfully aware that wind phenomena, such as flutter and vortex shedding, can cause major structural damage if not considered in the design process. The solution for many years since has been to conduct wind tunnel tests …

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Effects Of Piston Uplift, Piston Friction, And Machine Deflection In Reduced Triaxial Extension Testing, Morgan Race May 2011

Effects Of Piston Uplift, Piston Friction, And Machine Deflection In Reduced Triaxial Extension Testing, Morgan Race

Civil Engineering Undergraduate Honors Theses

A series of Reduced Triaxial Extension (RTE) tests were conducted on dummy (brass) and null (water) samples to determine the effects of (corrections required for) piston uplift, piston friction and system compliance associated with RTE tests. During the consolidation stage of RTE tests, the sample may be consolidated in isotropic or anisotropic stress conditions. During the shearing stage of an RTE test, the sample is unloaded in the axial direction by decreasing the deviator stress while the radial stress remains constant. Ten (10) tests were conducted on a brass "dummy" sample. The device was assembled in the same manner as …

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Hot Mix Asphalt Longitudinal Joint Evaluation, Annette Porter May 2009

Hot Mix Asphalt Longitudinal Joint Evaluation, Annette Porter

Civil Engineering Undergraduate Honors Theses

Longitudinal joints are the portion of the road where two lanes meet and are formed because the lanes are paved at different times. Longitudinal joints tend to be the weakest portion of the roadway, and yet few regulations exist to control their quality. Currently, Arkansas specifications for asphalt pavement do not include any requirements for the measurement of joint quality. The purpose of this research project is to determine the most effective method for evaluating longitudinal joints in hot-mix asphalt (HMA) pavements. Most of the literature concerning longitudinal joints focuses on density as the determining factor of quality because density …

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Developing Subgrade Inputs For Mechanistic-Empirical Pavement Design, Meagan Berlau May 2008

Developing Subgrade Inputs For Mechanistic-Empirical Pavement Design, Meagan Berlau

Computer Science and Computer Engineering Undergraduate Honors Theses

The Resilient Modulus (MR) of a subgrade soil is an essential input into the flexible pavement design models contained in the American Association of State Highway and Transportation Official’s new pavement design guide, the MechanisticEmpirical Pavement Design Guide (MEPDG). For most inputs required for pavement design, there are three levels of input that can be used within the MEPDG system. Level One requires the engineer to enter a value for subgrade Resilient Modulus based on the results of Resilient Modulus tests conducted in the laboratory. Level Two allows the user to input values for other soil property tests including California …

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Kinetics Determination Of Soybean Oil Transesterification In The Design Of A Continuous Biodiesel Production Process, Irwin Jacob, Ed Clausen, Danielle Julie Carrier May 2008

Kinetics Determination Of Soybean Oil Transesterification In The Design Of A Continuous Biodiesel Production Process, Irwin Jacob, Ed Clausen, Danielle Julie Carrier

Biological and Agricultural Engineering Undergraduate Honors Theses

One-step batch transesterification consisting of three stepwise reversible reactions of pure soybean oil with methanol was conducted at two different mixing speeds (600 and 300 rpm) to produce soybean oil fatty acid methyl esters (biodiesel). In both batch reactions, sodium methoxide (1.09 wt% based on soybean oil) was used as the catalyst, the reaction temperature was 60oC, and the methanol-to-oil molar ratio was 6:1. The objectives were to determine and/or investigate: 1) the mechanism and order of the reaction, 2) the reaction rate constants, 3) the effect of changes in mixing intensity on the reaction rate, 4) the comparison of …

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A Comparison Of Nondestructive Testing Backcalculation Techniques For Rigid And Flexible Pavements, Trenton Ellis May 2008

A Comparison Of Nondestructive Testing Backcalculation Techniques For Rigid And Flexible Pavements, Trenton Ellis

Civil Engineering Undergraduate Honors Theses

In designing new pavements, engineers rely on many different measures to characterize the average traffic, climate and soil conditions of the region. Of those, soil conditions are the most elusive, but are also the most crucial for designing a pavement of proper thickness and stiffness. This problem is compounded when the design is for an overlay instead of a new pavement. For overlay designs, engineers require a quantitative characterization of the strength of the existing pavement as well as the underlying soil. Especially for new Mechanistic-Empirical design procedures, direct measures and/or estimates of pavement stiffness are essential inputs. A variety …

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The Development Of Regional Regression Equations For Flood Flow Estimates Of Ungauged Streams In The State Of Arkansas, Stephen Mccall Dec 2007

The Development Of Regional Regression Equations For Flood Flow Estimates Of Ungauged Streams In The State Of Arkansas, Stephen Mccall

Civil Engineering Undergraduate Honors Theses

The objective of this project is to improve the accuracy of the peak streamflow frequency estimates in ungauged streams by using a regionalization approach and the Bulletin 17B method of flood flow analysis. The entire state will be considered one region and the final results will be compared to previous studies done in the state. The data used will be the most up-to-date available from the USGS gauging stations around the state. This includes data from gauging stations that had less than 10 years of data when the last such study was conducted by Hodge & Tasker (1995). The data …

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Validation Of Adaptive Aeroelastic Finite Element Program For Two Dimensional Flow Past A Suspension Bridge Girder Section Using Unstructured Grids., Shanique Murray Dec 2007

Validation Of Adaptive Aeroelastic Finite Element Program For Two Dimensional Flow Past A Suspension Bridge Girder Section Using Unstructured Grids., Shanique Murray

Civil Engineering Undergraduate Honors Theses

The flow around suspension bridge decks was traditionally investigated using wind tunnel experiments. Computer modeling, an alternative to wind tunnel testing is now being used to simulate the wind flow around a bridge cross section. This alternative is less expensive and takes less time compared to wind tunnel experiments. The motion of flow around a bridge deck is described by a set of partial differential equations called Navier-Stokes (N-S) equations. Flow features such as velocity, pressure and vorticity are predicted by solving these equations. These flow features are then used to compute flow parameters such as aerodynamic drag, lift and …

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Computer Modeling Of Tornado Forces On A Cubic Building Using Large Eddy Simulation, R. Panneer Selvam, Paul C. Millett Jan 2003

Computer Modeling Of Tornado Forces On A Cubic Building Using Large Eddy Simulation, R. Panneer Selvam, Paul C. Millett

Journal of the Arkansas Academy of Science

A tornado changes its wind speed and direction rapidly; therefore, it is difficult to study the effects of a tornado on buildings in a wind tunnel. The status of the tornado-structure interaction and various models of the tornado wind field found in literature are surveyed. Three dimensional computer modeling work using the turbulence model based on large eddy simulation is presented. The effect of a tornado on a cubic building is considered for this study. The Navier-Stokes (NS) equations are approximated by the finite difference method and solved by an implicit procedure. The force coefficients are plotted in time to …

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Field Interpretation Of Latitude And Longitude In Arkansas: A Portable Coordinate Projection, William R. Teague Jan 2000

Field Interpretation Of Latitude And Longitude In Arkansas: A Portable Coordinate Projection, William R. Teague

Journal of the Arkansas Academy of Science

Two- and three-dimensional coordinate systems are fundamental to most quantitative mapping applications. The Geodetic, Universal Transverse Mercator (UTM),and State Plane systems have traditional roles in various science, surveying, and government agency engineering applications. The coordinates of three-dimensional Geodetic system are latitude, longitude, and height above ellipsoid (HAE).Because of its ability to cope with the intrinsically three dimensional character of the earth's surface, the Geodetic system is capable of supporting precise relative positioning and very high accuracy computations of distance between any two positions on or near the earth's surface. The two-dimensional UTMand State Plane systems are extremely useful for the …

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Construction Resource Allocation Using A Genetic Algorithm, Siripong Malasri, Jennifer R. Martin Jan 1995

Construction Resource Allocation Using A Genetic Algorithm, Siripong Malasri, Jennifer R. Martin

Journal of the Arkansas Academy of Science

A proper allocation of limited resources (men, machines, materials, and money) is critical in a construction project. Traditionally, resource allocation problems have been solved using methods in operations research (OR), such as mathematical programming. In recent years, genetic algorithms (GA) have emerged as an effective optimization methodology. One major advantage of the GA approach over the OR approach is that the GA approach is universal for various types of optimization problems, unlike the OR approach which varies depending on the types of problems at hand. This paper shows an application of GA to a resource allocation problem in the construction …

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Concrete Beam Design Optimization With Genetic Algorithms, Siripong Malasri, D. A. Halijan, M. L. Keough Jan 1994

Concrete Beam Design Optimization With Genetic Algorithms, Siripong Malasri, D. A. Halijan, M. L. Keough

Journal of the Arkansas Academy of Science

This paper demonstrates an application of the natural selection process to the design of structural members. Reinforced concrete beam design is used as the example to show how various chromosomes representing a design solution can be formulated. Fitter chromosomes (or better solutions) have a better chance of being selected for cross over; this in turn creates better generations. Random mutation is used to enhance the diversity of the population. The evolution progresses through several generations, and the best solution is then used in the design. The method gives reasonable results, but sometimes a local (as opposed to the global) optimized …

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Automation Of The Continuous Coagulation Monitor, Dee Mitchell, James J. Oskowis Jan 1974

Automation Of The Continuous Coagulation Monitor, Dee Mitchell, James J. Oskowis

Arkansas Water Resources Center Technical Reports

The development of automation in the past 50 years has paralleled the accelerating growth of today’s vast technological society. Automatic control systems are indispensable extensions of man's brain that enable him to monitor and regulate his complex environment. The principles of automatic control have a wide range of applications and interests in virtually every scientific field. The need for automatic control systems in vital applications of environmental engineering is both real and urgent. Extensive pollution has resulted in unavoidable water re-use and in the inevitable establishment of stringent effluent standards. Both water and wastewater treatment processes have necessarily become more …

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