INVESTIGATION OF BOND STRENGTH AND WATERTIGHTNESS OF ASPHALT CONCRETE WEARING SURFACES FOR TIMBER BRIDGE DECKS

ype of Document Master's Thesis
Author Haramis, John Emmanuel II
Author's Email Address jharamis@vt.edu
URN etd-7597-22949
Title INVESTIGATION OF BOND STRENGTH AND WATERTIGHTNESS OF ASPHALT CONCRETE WEARING SURFACES FOR TIMBER BRIDGE DECKS
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
Dr. Richard E. Weyers Committee Chair
J. Daniel Dolan none
Joseph R. Loferski none
Keywords

* timber bridge decks
* asphalt overlays
* waterproof membranes
* watertightness
* bond strength
* glulam

Date of Defense 1997-04-21
Availability unrestricted
Abstract

Two different asphalt concrete systems were examined in this research study. The existing system, consistent with current timber bridge construction practice, uses a preformed waterproofing membrane placed on a preservative treated wood deck overlaid with a bituminous concrete wearing surface. The second system consists of a treated wood deck overlaid with a base course of bituminous concrete, a waterproofing membrane, and a bituminous concrete wearing surface.

The testing regime used in this research to evaluate watertightness and bond performance incorporated three parameters: three waterproofing membranes, two wood preservative treatments, and two environmental degradation conditions induced by temperature cycling in a moisture saturated condition. Control groups were evaluated for each study parameter and duplicate specimens were prepared and tested for each of the study parameters. A total of 160 specimens were constructed and tested.

Watertightness of each system was determined by measuring the electrical impedance across a test specimen perpendicular to the direction of bond orientation in the pavement. The bond strength between each material of the paving systems was assessed using a shear test apparatus designed and built for this study.

In addition to the laboratory constructed specimens, three drilled cores were taken from a bridge located on Creekside Drive in East Pennsboro Township, Pennsylvania. The deck was constructed using the new design proposed in this research and each core was tested for watertightness and bond strength.

Results of watertightness testing indicated that low temperature environments appear to be most detrimental to system integrity in both the existing and proposed paving system configurations examined in this research. In general, each membrane appeared to perform equally well in the proposed paving system configuration as well as with all of the wood preservative treatments used in the existing pavement system.

Bond strength between asphalt and wood with no membrane was observed to be nonexistent whether or not any preservative treatment was present. The placement of a membrane between these two layers did, however, result in a significant increase in bond strength because each membrane tested was able to adhere to the wood base better than the asphalt overlay. This gain is strength was significantly offset when petroleum solvent based preservative treatments were present in the wood substrate. Protectowrap M400 membrane performed slightly better than the other membranes when used with untreated wood, but all of the membranes performed equally when preservative treatments were present. The highest interlayer bond strengths (asphalt/asphalt or asphalt/wood) observed in this research occurred when asphalt concrete surface material was placed directly on top of asphalt concrete base material, however the addition of a membrane between the asphalt lifts consistently reduced this strength. The results of bond testing indicate that the proposed system will perform better in terms of shoving in the pavement overlay. Based on bond test results of cores taken from the Creekside Drive bridge, it appears that a shear strength greater than 25 psi after 200 low temperature exposure cycles will provide acceptable paving system performance in a low temperature (0-40�F) environment.

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Hydrodynamic and Water Quality Simulation of Fecal Coliforms in the Lower Appomattox River, Virginia

Type of Document Master's Thesis
Author Hammond, Andrew Jesse
URN etd-09222004-190559
Title Hydrodynamic and Water Quality Simulation of Fecal Coliforms in the Lower Appomattox River, Virginia
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
Dr. David F. Kibler Committee Chair
Dr. Daniel Gallagher Committee Member
Dr. G. V. Loganathan Committee Member
Keywords

* water quality modeling
* tidal estuary
* hydrodynamic modeling

Date of Defense 2004-09-09
Availability unrestricted
Abstract

The Virginia Department of Environmental Quality (VADEQ) under the direction of the United States Environmental Protection Agency (USEPA) has listed the lower Appomattox River as impaired because it violates current water quality standards for fecal coliforms. To advance the analytical process by which various scenarios for improving water quality within the estuary are examined, an array of computer-based hydrodynamic and water quality models were investigated. The Dynamic Estuary Model (DYNHYD5), developed by USEPA, was used to simulate hydrodynamics within the lower Appomattox River. The Water Quality Analysis Simulation Program (WASP6.1), also developed by USEPA, was employed to perform water quality simulations of fecal coliforms. Also, a detailed literature review examined DYNHYD5 and WASP6.1 model theory, computer-based model solution techniques, and background hydrodynamic theory.

DYNHYD5 sensitivity analysis showed that the model was most responsive to tidal heights (seaward boundary conditions) both upstream and downstream within the model network. Specific model parameters were varied during calibration until modeled water surface elevations converged on observed water surface elevations. A goodness-of-fit value of 0.749 was determined with linear regression analysis for model calibration. DYNHYD5 input parameter validation was performed with additional observations and a goodness-of-fit value of 0.829 was calculated.

Through sensitivity analysis, WASP6.1 proved to be most responsive to coliform loading rates in the downstream direction and boundary concentrations in the upstream direction. With these results, WASP6.1 input parameters were calibrated against observed fecal coliform concentrations. A goodness-of-fit value of 0.573 was determined with linear regression analysis for model calibration. WASP6.1 input parameter validation was performed with additional observations and a goodness-of-fit value of 0.0002 was calculated.

Model results suggest that hydrodynamic model calibration and validation can be improved with additional tidal height observations at the downstream seaward boundary. Similarly, water quality model calibration and validation can possibly be improved with the aid of detailed, time-variable coliform concentrations at the downstream seaward boundary. Therefore, it is recommended that a water quality sampling station and tidal stage recorder be installed at the confluence of the Appomattox and James Rivers to

provide for further testing of estuary hydrodynamic and water quality models.

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Three-Dimensional Analysis of Geogrid Reinforcement used in a Pile-Supported Embankment

Type of Document Master's Thesis
Author Halvordson, Kyle Arthur
URN etd-12142007-105941
Title Three-Dimensional Analysis of Geogrid Reinforcement used in a Pile-Supported Embankment
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
Raymond H. Plaut Committee Chair
Elisa D. Sotelino Committee Member
George M. Filz Committee Member
Keywords

* Cable Net
* Geosynthetic Reinforcement
* Geogrid
* Minimization of Energy

Date of Defense 2007-12-03
Availability unrestricted
Abstract

Pile-supported geogrid-reinforced embankments are an exciting new foundation system that is utilized when sites are limited by a soft soil or clay. In this system, an embankment is supported by a bridging layer, consisting of granular fill and one or multiple layers of geogrid reinforcement. The bridging layer transfers the load to piles that have been driven into the soft soil or clay. The load from the embankment induces large deformations in the geogrid reinforcement, causing tensile forces in the ribs of the geogrid. Many of the current methods used to design geogrid reinforcement for this system simplify the approach by assuming that the reinforcement has a parabolic deformed shape. The purpose of this thesis is to thoroughly examine the behavior of the geogrid in a pile-supported embankment system, in an effort to determine the accuracy of the parabolic deformed shape, and identify the most important parameters that affect reinforcement design.

The geogrid was analyzed using a three-dimensional model that included a cable net to represent the geogrid and linear springs to represent the soil underneath the geogrid. A larger pressure was applied to the geogrid regions that are directly above the pile caps so that arching effects could be considered, and the stiffness of the springs on top of the pile were stiffer to account for the thin layer of soil between the geogrid and the pile cap. A Mathematica algorithm was used to solve this model using the minimization of energy method.

The results were compared to another model of this system that used a membrane to represent the geosynthetic reinforcement. Additionally, the maximum strain was compared to the strain obtained from a geosynthetic reinforcement design formula. A parametric study was performed using the Mathematica algorithm by varying the pile width, embankment pressure applied to the soil, embankment pressure applied to the pile, stiffness of the soil, stiffness of the soil on top of the pile, stiffness of the geogrid, geogrid orientation, rotational stiffness of the geogrid, and the layers of geogrid reinforcement.

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Strength and Performance of Fiber-Reinforced Concrete Composite Slabs

Type of Document Master's Thesis
Author Guirola, Marcela Renee
URN etd-10192001-141348
Title Strength and Performance of Fiber-Reinforced Concrete Composite Slabs
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
Dr. Carin Roberts-Wollmann Committee Chair
Dr. W. Samuel Easterling Committee Co-Chair
Dr. Richard Weyers Committee Member
Keywords

* composite beams and joists
* composite slabs
* push-out tests
* fiber-reinforced concrete
* shear connectors

Date of Defense 2001-10-18
Availability unrestricted
Abstract

The purpose of this research is to evaluate and compare the influence of four types of secondary reinforcement on various component strengths related to composite slabs. These components include the composite slab strength under uniform load, the strength of two types of shear connectors used with composite beams and joists, composite slab strength due to a concentrated load, and the flexural toughness and first-crack strength of fiber-reinforced concrete using ASTM C1018 (1998) standard test. The performance of the specimens reinforced with fibers are compared with that of the specimens reinforced with welded-wire fabric (WWF), with the purpose of determining if fiber-reinforced concrete can be used as an alternative to WWF

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Integrating a Regional Planning Model (TRANSIMS) With an Operational Model (CORSIM)

Type of Document Master's Thesis
Author Gu, Yahong
URN etd-02202004-160557
Title Integrating a Regional Planning Model (TRANSIMS) With an Operational Model (CORSIM)
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
Antoine G. Hobeika Committee Chair
Antonio A. Trani Committee Member
Sam C. Tignor Committee Member
Keywords

* Evacuation
* TRANSIMS
* CORSIM
* Sub area focusing
* Transportation planning
* Traffic operation

Date of Defense 2004-02-09
Availability unrestricted
Abstract

TRANSIMS is a disaggregate, behavioral, regional transportation planning package developed by Los Alamos National Laboratory (LANL) under funding from US DOT, EPA, and Department of Energy. It is an integrated system of travel forecasting models designed to give transportation planners accurate, complete information on traffic impacts, congestion, and pollution by simulating on a second-by-second basis the movements of every person and every vehicle through the transportation network of a large metropolitan area. This regional microsimulation approach provides a better assessment of the performance of a large network than the current link performance functions utilized in the current planning procedures. On the other hand, their microsimulation approach on a regional scale requires a lot of data that may not be readily available, and utilize a low fidelity microsimulation in order to make it operational. Some agencies may be interested in performing a more detailed investigation of traffic patterns within a sub area, such as the downtown area. The author implemented a subarea focusing methodology within TRANSIMS and also developed an interface that allows the investigator to use a high-fidelity, small-size network efficient traffic operational software package – CORSIM to perform sub area traffic operational analysis with demand and network extracted from applications of TRANSIMS. This methodology will allow TRANSIMS to take advantage of higher fidelity models for sub-network analysis and allow CORSIM to use planning inputs such as individual 24 hour travel activities and trip chains. An evacuation model is also built and applied to Virginia Tech main campus, Blacksburg, VA to evaluate this sub area focusing methodology.


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Energy-Based Evaluation and Remediation of Liquefiable Soils

Type of Document Dissertation
Author Green, Russell A.
Author's Email Address rugreen@vt.edu
URN etd-08132001-170900
Title Energy-Based Evaluation and Remediation of Liquefiable Soils
Degree PhD
Department Civil Engineering
Advisory Committee
Advisor Name Title
James K. Mitchell Committee Chair
J.R. Martin Committee Member
M. Gutierrez Committee Member
M.P. Singh Committee Member
S.F. Obermeier Committee Member
T. Kuppusamy Committee Member
Keywords

* Remediation
* Ground Improvement
* Liquefaction
* Energy
* Earthquake
* Densification

Date of Defense 2001-08-06
Availability unrestricted
Abstract

Energy-Based Evaluation and Remediation of Liquefiable Soils

Russell A. Green

Dr. James K. Mitchell, Chair

Charles E. Via, Jr. Department of Civil and Environmental Engineering

ABSTRACT

Remedial ground densification is commonly used to reduce the liquefaction susceptibility of loose, saturated sand deposits, wherein controlled liquefaction is typically induced as the first step in the densification process. Assuming that the extent of induced liquefaction is approximately equal to the extent of ground densification, the purpose of this research is to assess the feasibility of using earthquake liquefaction data in remedial ground densification design via energy-based concepts.

The energy dissipated by frictional mechanisms during the relative movement of sand grains is hypothesized to be directly related to the ability of a soil to resist liquefaction (i.e., Capacity). This hypothesis is supported by energy-based pore pressure generation models, which functionally relate dissipated energy to residual excess pore pressures. Assuming a linearized hysteretic model, a �simplified� expression is derived for computing the energy dissipated in the soil during an earthquake (i.e., Demand). Using this expression, the cumulative energy dissipated per unit volume of soil and normalized by the initial mean effective confining stress (i.e., normalized energy demand: NED) is calculated for 126 earthquake case histories for which the occurrence or non-occurrence of liquefaction is known. By plotting the computed NED values as a function of their corresponding SPT penetration resistance, a correlation between the normalized energy capacity of the soil (NEC) and SPT penetration resistance is established by the boundary giving a reasonable separation of the liquefaction / no liquefaction data points. NEC is the cumulative energy dissipated per unit volume of soil up to initial liquefaction, normalized by the initial mean effective confining stress, and the NEC correlation with SPT penetration resistance is referred to as the Capacity curve.

Because the motions induced during earthquake shaking and remedial ground densification significantly differ in amplitude, duration, and frequency content, the dependency of the derived Capacity curve on the nature of the loading needs to be established. Towards this end, the calibration parameters for energy-based pore pressure generation models are examined for their dependence on the amplitude of the applied loading. The premise being that if the relationship between dissipated energy and pore pressure generation is independent of the amplitude of loading, then the energy required to generate excess pore pressures equal to the initial effective confining stress should also be independent of the load amplitude. However, no conclusive statement could be made from results of this review. Next, first order numerical models are developed for computing the spatial distribution of the energy dissipated in the soil during treatment using the vibratory probe method, deep dynamic compaction, and explosive compaction. In conjunction with the earthquake-derived Capacity curves, the models are used to predict the spatial extent of induced liquefaction during soil treatment and compared with the predicted spatial extent of improvement using empirical expressions and guidelines. Although the proposed numerical models require further validation, the predicted extent of liquefaction and improvement are in very good agreement, thus giving credence to the feasibility of using the Capacity curve for remedial ground densification design.

Although further work is required to develop energy-based remedial densification design procedures, the potential benefits of such procedures are as follows. By using the Capacity curve, the minimum dissipated energy required for successful treatment of the soil can be determined. Because there are physical limits on the magnitude of the energy that can be imparted by a given technique, such an approach may lead to improved feasibility assessments and initial designs of the densification programs.

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Verification of Mechanistic-Empirical Pavement Deterioration Models Based on Field Evaluation of In-Service Pavements

Type of Document Master's Thesis
Author Gramajo, Carlos Rafael
URN etd-05262005-201211
Title Verification of Mechanistic-Empirical Pavement Deterioration Models Based on Field Evaluation of In-Service Pavements
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
Dr. Gerardo Flinstch Committee Chair
Dr. Amara Loulizi Committee Member
Dr. Imad Al-Qadi Committee Member
Keywords

* backcalculation
* pavement evaluation
* pavement structural capacity
* mechanistic-empirical design
* pavement distresses
* performance prediction

Date of Defense 2005-05-23
Availability unrestricted
Abstract

This thesis focused on using a detailed structural evaluation of seven (three flexible and four composite) high performance in-service pavements designated as high-priority routes to verify the applicability of the Mechanistic Empirical (M-E) models to high performance pavements in the Commonwealth of Virginia. The structural evaluation included: determination of layer thicknesses (from cores, GPR and historical data), pavement condition assessment based on visual survey, estimation of layer moduli from FWD analysis as well as material characterization. One of the main objectives of this study was to utilize the results from the backcalculated moduli in order to predict the performance of this group of pavement structures using the M-E Design Guide Software. This allowed a quick verification of the performance prediction models used by comparing their outcome with the current condition.

The in-depth structural evaluation of the three flexible and four composite pavements showed that all the sites are structurally sound. The investigation also confirmed that the use of GPR to determine layer thicknesses and the comparison with a minimum number of cores is a helpful tool for pavement structural evaluation. Despite some difficulties performing the backcalculation analysis for complex structures, the obtained results were considered reasonable and were useful in estimating the current structural adequacy of the evaluated structures.

The comparison of the measured distresses with those predicted by the M-E Design Guide software showed poor agreement. In general, the predicted distresses were higher than the distresses actually measured. However, there was not enough evidence to determine whether this is due to errors in the prediction models or software, or because of the use of defaults material properties, specially for the AC layers. It must be noted that although an in-depth field evaluation was performed, only Level 3 data was available for many of the input parameters. The results suggest that significant calibration and validation will be required before implementation of the M-E Design Guide.

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A GPS-IPW Based Methodology for Forecasting Heavy Rain Events

Type of Document Master's Thesis
Author Gorugantula, Srikanth VL
Author's Email Address svenkata@vt.edu, sgorugantula@gky.com
URN etd-12302002-114005
Title A GPS-IPW Based Methodology for Forecasting Heavy Rain Events
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
G.V.Loganathan Committee Chair
Tamim Younos Committee Member
Vinod K Lohani Committee Member
Keywords

* radiosode
* statistical analysis
* GOES satellite

Date of Defense 2002-12-06
Availability unrestricted
Abstract

The mountainous western Virginia is the source of the headwater streams for the New, the Roanoke, and the James rivers. The region is prone to flash flooding, typically the result of localized precipitation. Fortunately, within the region, there is an efficient system of instruments for real-time data gathering with IFLOWS (Integrated Flood Observing and Warning System) gages, WSR-88D Doppler radar, and high precision GPS (Global Positioning System) receiver. The focus of this research is to combine the measurements from these various sensors in an algorithmic framework to determine the flash flood magnitude. It has been found that the trend in the GPS signals serves as a precursor for rain events with a lead-time of 30 minutes to 2 hours. The methodology proposed herein takes advantage of this lead-time as the trigger to initiate alert related calculations. It is shown here that the sum of the rates of change of total cloud water, water vapor contents and logarithmic profiles of partial pressure of dry air and temperature in an atmospheric column is equal to the rain rate. The total water content is measurable as the profiles of integrated precipitable water (IPW) from the GPS, the vertically integrated liquid (VIL) from the radar (representing different phases of the atmospheric water) and the pressure and temperature profiles are available. An example problem is presented illustrating the involving the calculations.

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Development of an extended hyperbolic model for concrete-to-soil interfaces

Type of Document Dissertation
Author Gomez, Jesus Emilio
Author's Email Address jgomez@vt.edu
URN etd-07242000-15060006
Title Development of an extended hyperbolic model for concrete-to-soil interfaces
Degree PhD
Department Civil Engineering
Advisory Committee
Advisor Name Title
George M. Filz Committee Chair
J. Michael Duncan Committee Member
James R. Martin Committee Member
Rakesh K. Kapania Committee Member
Thomas L. Brandon Committee Member
Keywords

* data normalization
* hyperbolic parameter
* concrete
* yield surface
* staged shear
* interface model
* hydrocompression
* interface testing
* sand
* unloading-reloading
* backfill inundation
* interface element
* yielding

Date of Defense 2000-07-19
Availability unrestricted
Abstract

Development of an Extended Hyperbolic Model for Concrete-to-Soil Interfaces

by

Jes�s E. G�mez

Dr. George M. Filz, Chairman

Via Department of Civil Engineering

ABSTRACT

Placement and compaction of the backfill behind an earth retaining wall may induce a vertical shear force at the soil-to-wall interface. This vertical shear force, or downdrag, is beneficial for the stability of the structure. A significant reduction in construction costs may result if the downdrag is accounted for during design. This potential reduction in costs is particularly interesting in the case of U.S. Army Corps of Engineers lock walls.

A simplified procedure is available in the literature for estimating the downdrag force developed at the wall-backfill interface during backfilling of a retaining wall. However, finite element analyses of typical U.S. Army Corps of Engineers lock walls have shown that the magnitude of the downdrag force may decrease during operation of the lock with a rise in the water table in the backfill. They have also shown that pre- and post-construction stress paths followed by interface elements often involve simultaneous changes in shear and normal stresses and unloading-reloading. The hyperbolic formulation for interfaces (Clough and Duncan 1971) is accurate for modeling the interface response in the primary loading stage under constant normal stress. However, it has not been extended to model simultaneous changes in shear and normal stresses or unloading-reloading of the interface.

The purpose of this research was to develop an interface model capable of giving accurate predictions of the interface response under field loading conditions, and to implement this model in a finite element program. In order to develop the necessary experimental data, a series of tests were performed on interfaces between concrete and two different types of sand. The tests included initial loading, staged shear, unloading-reloading, and shearing along complex stress paths.

An extended hyperbolic model for interfaces was developed based on the results of the tests. The model is based on Clough and Duncan (1971) hyperbolic formulation, which has been extended to model the interface response to a variety of stress paths. Comparisons between model calculations and tests results showed that the model provides accurate estimates of the response of interfaces along complex stress paths. The extended hyperbolic model was implemented in the finite element program SOILSTRUCT-ALPHA, used by the U.S. Army Corps of Engineers for analyses of lock walls.

A pilot-scale test was performed in the Instrumented Retaining Wall (IRW) at Virginia Tech that simulated construction and operation of a lock wall. SOILSTRUCT-ALPHA analyses of the IRW provided accurate estimates of the downdrag magnitude throughout inundation of the backfill. It is concluded that the extended hyperbolic model as implemented in SOILSTRUCT-ALPHA is adequate for routine analyses of lock walls.

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An Evaluation of Assignment Algorithms and Post-Pro cessing Techniques for Travel Demand Forecast Models

Type of Document Master's Thesis
Author Goldfarb, Daniel Scott
Author's Email Address dgoldfar@vt.edu
URN etd-04052003-152157
Title An Evaluation of Assignment Algorithms and Post-Pro cessing Techniques for Travel Demand Forecast Models
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
John Collura Committee Chair
Antonie Hobeika Committee Member
Sam Tignor Committee Member
Keywords

* Post-Processing
* Travel Demand Forecast

Date of Defense 2003-04-01
Availability unrestricted
Abstract

An Evaluation of Assignment Algorithms and Post-Processing Techniques for Travel Demand Forecast Models

Daniel S. Goldfarb

(ABSTRACT)

The purpose of this research project was to evaluate the techniques outlined in the National Cooperative Highway Research Program Technical Report 255 Highway Traffic Data for Urbanized Area Project Planning and Design (NCHRP-255), published in 1982 by the Transportation Research Board. This evaluation was accomplished by using a regional travel demand forecast model calibrated and validated for the year 1990 and developing a highway forecast for the year 2000. The forecasted volumes along the Capital Beltway (I-495/I-95) portion located in the State of Maryland were compared to observed count data for that same year. A series of statistical measures were used to quantitatively evaluate the benefits of the techniques documented in NCHRP-255.

The primary research objectives were:

· To critically evaluate the ability of a regional travel demand forecast model to accurately forecast freeway corridor volumes by comparing link forecast volumes to the actual count data.

· To evaluate and determine the significance of post-processing techniques as outlined in NCHRP-255.

The most important lesson learned from this research is that although it was originally written in 1982, NCHRP-255 is still a very valuable resources for supplementing travel demand forecast model output. The “raw” model output is not reliable enough to be used directly for highway design, operational analysis, nor alternative or economic evaluations. The travel demand forecast model is a tool that is just part of the forecasting process. It is not a turn-key operation, and travel demand forecasts cannot be done without the application of engineering judgment.

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Analysis of Pressurized Arch-Shells

Type of Document Master's Thesis
Author Goh, Julian Kok Seng
URN etd-110298-213557
Title Analysis of Pressurized Arch-Shells
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
Raymond H. Plaut Committee Chair
Rakesh K Kapania Committee Member
Siegfried M. Holzer Committee Member
Keywords

* shell
* arch
* Rayleigh-Ritz method
* wind load
* structural analysis
* snow load

Date of Defense 1998-11-19
Availability unrestricted
Abstract

A pressurized arch-shell structural component made of flexible material is considered.

The component is inflated with high internal pressure. The behavior of similar types

of structures, such as a pair of leaning pressurized arches and pressurized arch-supported

membrane shelters, has been investigated in the past. More recently, several types of

pressurized structures have been incorporated as part of the framework for a variety of

structural systems. Particularly, the U.S. Army has been investigating the use of large

lightweight and transportable pressurized arch-shell structures to be used as maintenance

shelters for vehicles, helicopters, and airplanes.

The formulated equations using thin shell theory are applied to a pressurized arch-shell

component. A numerical investigation based on the Rayleigh-Ritz method is utilized to

determine the behavior of arch-shells under various types of loading. The types of loading

include a uniformly distributed vertical load representing snow, a wind load, and a

horizontal side load distributed along the arc length. Deflections, stress resultants, and

moments at various locations are computed for two types of shapes: circular and non-circular

arch-shells.

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A NUMERICAL INVESTIGATION OF THE SEISMIC RESPONSE OF THE AGGREGATE PIER FOUNDATION SYSTEM

Type of Document Master's Thesis
Author Girsang, Christian Hariady
URN etd-12212001-133242
Title A NUMERICAL INVESTIGATION OF THE SEISMIC RESPONSE OF THE AGGREGATE PIER FOUNDATION SYSTEM
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
Dr. Marte S. Gutierrez Committee Chair
Dr. James K. Mitchell Committee Member
Dr. James R. Martin Committee Member
Keywords

* liquefaction
* aggregate pier
* ground improvement
* numerical modeling
* earthquake
* mitigation

Date of Defense 2001-12-20
Availability unrestricted
Abstract

The response of an aggregate pier foundation system during seismic loading was investigated. The factors and phenomena governing the performance of the aggregate pier and the improved ground were identified and clarified. The key factors affecting the performance of the aggregate pier include soil density, stiffness modulus, and drainage capacity. The improved ground is influenced by soil stratification, soil properties, pore pressure dissipation, and earthquake time history.

Comprehensive numerical modeling using FLAC were performed. The focus of the study in this research was divided into three parts: the studies of the ground acceleration, the excess pore water pressure ratio and the shear stress in soil matrix generated during seismic loading. Two earthquake time histories scaled to different peak acceleration were used in the numerical modeling: the 1989 Loma Prieta earthquake (pga = 0.45g) and the 1988 Saguenay earthquake (pga = 0.05g).

The main results of the simulation showed the following effects of aggregate pier on liquefiable soil deposits: 1) The aggregate pier amplifies the peak horizontal acceleration on the ground surface (amax), 2) The aggregate pier reduces the liquefaction potential up to depth where it is installed, 3) Pore pressures are generally lower for soils reinforced with aggregate pier than unreinforced soils except for very strong earthquake, 4) The maximum shear stresses in soil are much smaller for reinforced soils than unreinforced soils.

The excess pore water pressure ratio and the shear stress in the soil matrix calculated by FLAC were generally lower than those predicted by available procedures.

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INTEGRATING GEOSPATIAL TECHNOLOGIES INTO THE PROPERTY MANAGEMENT PROCESS OF THE TRANSPORTATION RIGHT-OF-WAY

Type of Document Master's Thesis
Author Ghanta, Neelima
Author's Email Address neelimag@vt.edu
URN etd-02192007-105015
Title INTEGRATING GEOSPATIAL TECHNOLOGIES INTO THE PROPERTY MANAGEMENT PROCESS OF THE TRANSPORTATION RIGHT-OF-WAY
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
Dr. Kathleen L. Hancock Committee Chair
Dr. Gerardo W. Flintsch Committee Member
Dr. Pamela M. Murray-Tuite Committee Member
Keywords

* geographic information systems (GIS)
* enterprise architect
* unified modeling language (UML)
* property management
* right-of-way (ROW)
* department of transportation (DOT)

Date of Defense 2007-02-05
Availability unrestricted
Abstract

Property Management, one functional area within Right-of-Way offices in state transportation agencies, is responsible for managing the property acquired for highway projects. These activities are data and document intensive and efficiency for performing them would be improved through the implementation of an information management system. Because of the geospatial nature of many of these activities, geographic information systems (GIS) would increase the effectiveness of this system. A literature review and survey were conducted to understand the current state of practice for the use of GIS and information management systems in Property Management. There is no identified comprehensive system that covers all Property Management activities. An initial step in developing a geospatially-enabled enterprise-level information management system, a logical model was developed. This included developing the business process diagram, business process models, and use case models based on the principles of systems engineering using the Computer Aided Software (CASE) Enterprise Architecture. Activities that would benefit from a geospatial component have been identified and included in the models. The developed models have been validated by working with PennDOT staff. The resulting model serves as a standard template for state transportation agencies and helps conceptualize the advantages of integration and interaction with other systems, and geospatial enablement prior to investment in an information management system.

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STABILIZATION OF SOFT CLAY SUBGRADES IN VIRGINIA – PHASE I LABORATORY STUDY

Type of Document Master's Thesis
Author Geiman, Christopher Matthew
Author's Email Address cgeiman@vt.edu
URN etd-05102005-152711
Title STABILIZATION OF SOFT CLAY SUBGRADES IN VIRGINIA – PHASE I LABORATORY STUDY
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
George M. Filz Committee Chair
Raymond H. Plaut Committee Member
Thomas L. Brandon Committee Member
Keywords

* lime
* soil stabilization
* polymers
* cement

Date of Defense 2005-05-10
Availability unrestricted
Abstract

Many pavement subgrades in Virginia consist of wet, highly plastic clay or other troublesome soils. Such soils can be treated with traditional lime and cement stabilization methods. Alternatives, including lignosulfonates and polymers, are available, but their performance record is mixed and solid engineering data is lacking, which prevents reliable design. The goal of this research was to screen a suite of traditional and non-traditional stabilizers against three Virginia soils that have caused problems during construction or resulted in poor performance in service. The selected stabilizers were: quicklime, hydrated lime, pelletized lime, cement, lignosulfonate, synthetic polymer, magnesium chloride, and a proprietary cementitious stabilizer. A laboratory procedure was developed and applied to three Virginia soils obtained from Northern Virginia, Staunton, and Lynchburg.

Key findings from the research include that (1) traditional lime and cement stabilizers were far more effective than liquid stabilizers (lignosulfonate, synthetic polymer, and magnesium chloride) in increasing strength, (2) the liquid stabilizers were ineffective on soils with high moisture content, (3) the proprietary cementitious stabilizer was more effective in increasing strength than lime for all cases tested, but not was not as effective as the cement stabilizer, (4) quicklime and hydrated lime increased workability of the soils although they did not produce strengths comparable to cement, (5) the strength of soils stabilized with cement and the proprietary cementitious stabilizer can be estimated based on the water-amendment ratio of the mixture, and (6) the strength of soils stabilized with lime can be estimated based on a combination of plasticity index and water-amendment ratio of the mixture.

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Effects of a Flexible Foundation on the Response of a Timber Shear Wall

Type of Document Master's Thesis
Author Gates, Joseph Dwayne
Author's Email Address Jogates2@mail.vt.edu
URN etd-11197-105248
Title Effects of a Flexible Foundation on the Response of a Timber Shear Wall
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
Maurice White Committee Chair
Dr. Dan Dolan Committee Member
Dr. Siegfried Holzer Committee Member
Keywords

* Joist Stiffness
* Flexible Foundations
* Shear Walls

Date of Defense 1997-09-12
Availability unrestricted
Abstract

A parametric study was performed to determine the effect of flexible foundations on the response of timber shear walls. Timber shear walls, which typically consist of structural-use panels, such as plywood or oriented strand board (OSB), attached to a frame made from dimension lumber with dowel-type fasteners such as nails, provide resistance to lateral loading for many low-rise structures in North America. Research performed on shear walls has assumed that a wall is supported by a relatively stiff foundation, such as a concrete block wall, along the entire length of the wall. However, walls are sometimes supported by a relatively flexible foundation, such as a floor joist, which would alter the stiffness, and therefore the response of the wall. Research on flexible foundations is limited at best, and there is a string need to examine the behavior of shear walls on flexible foundations.

The study consisted of creating a shear wall numerical model, varying the conditions at the foundation of the model, and analyzing the model when subjected to both monotonic and dynamic loading for each foundation. The system modeled corresponded to a 2.4 m (8 ft) high by 3.7 m (12 ft) long shear wall supported by and parallel to a 7.3 m (24 ft) long joist with hold-downs at each chord of the wall. The joist was supported at each end, with one chord of the wall at an end of the joist and the other chord located at the center of the joist. Eleven joist cross-sections, with sizes determined based on deflection criteria ranging from L/180 to L/720, and a rigid base were included in the study, along with three different hold-down bolt sizes, for a total of thirty-six different foundations. The wall model was analyzed using WALSEIZ1, which is a modified version of the finite element program WALSEIZ (White and Dolan, 1995). Maximum displacements, internal forces, and maximum load were recorded when the model was subjected to monotonic loading, while the maximum displacements and base shear were recorded when the model was subjected to dynamic loading. Results from the study were examined to determine if modifications to the current design practices should be considered.

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Diffuser Operations at Spring Hollow Reservoir

Type of Document Master's Thesis
Author Gantzer, Paul Anthony
Author's Email Address pgantzer@vt.edu
URN etd-05212002-163729
Title Diffuser Operations at Spring Hollow Reservoir
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
John Little Committee Chair
Dan Gallagher Committee Member
Randy Dymond Committee Member
Keywords

* Oxygenation
* Thermocline
* Diffuser
* Hypolimnion
* Aeration

Date of Defense 2002-05-09
Availability unrestricted
Abstract

Stratification is a natural occurrence in deep lakes and reservoirs. This phenomenon results in two distinct layers, the warmer, less dense epilimnion on top and the colder, denser, hypolimnion on the bottom. The epilimnion remains saturated with dissolved oxygen (DO) from mass transfer with the atmosphere, while the hypolimnion continues to undergo oxygen-depleting processes. During seasons of high oxygen demand the hypolimnion often becomes anoxic and results in the release of compounds, such as Iron, Manganese, Hydrogen Sulfide, and Phosphorous from the sediment. Iron, Manganese, and Hydrogen Sulfide can require addition Chlorine for water treatment plants, thus increasing cost and the potential production of DBP’s, while the release of phosphorous results in algal blooms the following year. Spring Hollow Reservoir, located in Roanoke County, Virginia is a deep reservoir that undergoes stratification during the summer months. During 1997 Roanoke County purchased a bubble-plume diffuser from Tennessee Valley Authority (TVA) to oxygenate the hypolimnion to maintain long-term water quality. Spring Hollow currently operates the diffuser, with compressed air, during late summer months when DO levels in the hypolimnion reach approximately 4 mg/L. Observations during oxygenation have identified changing DO addition rates during diffuser operation and changing DO depletion rates following termination of oxygenation. Future research should focus on developing a quantitative understanding of the changing rates as they are related to diffuser induced oxygen demand.

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Passive Site Remediation for Mitigation of Liquefaction Risk

Abstract

Passive site remediation is a new concept proposed for non-disruptive mitigation of liquefaction risk at developed sites susceptible to liquefaction. It is based on the concept of slow injection of stabilizing materials at the edge of a site and delivery of the stabilizer to the target location using the natural groundwater flow. The purpose of this research was to establish the feasibility of passive site remediation through identification of stabilizing materials, a study of how to design or adapt groundwater flow patterns to deliver the stabilizers to the right place at the right time, and an evaluation of potential time requirements and costs.

Stabilizer candidates need to have long, controllable gel times and low viscosities so they can flow into a liquefiable formation slowly over a long period of time. Colloidal silica is a potential stabilizer for passive site remediation because at low concentrations it has a low viscosity and a wide range of controllable gel times of up to about 100 days.

Loose Monterey No. 0/30 sand samples (Dr = 22%) treated with colloidal silica grout were tested under cyclic triaxial loading to investigate the influence of colloidal silica grout on the deformation properties. Distinctly different deformation properties were observed between grouted and ungrouted samples. Untreated samples developed very little axial strain after only a few cycles and prior to the onset of liquefaction. Once liquefaction was triggered, large strains occurred rapidly and the samples collapsed within a few additional cycles. In contrast, grouted sand samples experienced very little strain during cyclic loading. What strain accumulated did so uniformly throughout loading and the samples remained intact after cyclic loading. In general, samples stabilized with 20 weight percent colloidal silica experienced very little (less than two percent) strain during cyclic loading. Sands stabilized with 10 weight percent colloidal silica tolerated cyclic loading well, but experienced slightly more (up to eight percent) strain. Treatment with colloidal silica grout significantly increased the deformation resistance of loose sand to cyclic loading.

Groundwater and solute transport modeling were done using the codes MODFLOW, MODPATH, and MT3DMS. A "numerical experiment" was done to determine the ranges of hydraulic conductivity and hydraulic gradient where passive site remediation might be feasible. For a treatment are of 200 feet by 200 feet, a stabilizer travel time of 100 days, and a single line of low-head (less than three feet) injection wells, it was found that passive site remediation could be feasible in formations with hydraulic conductivity values of 0.05 cm/s or more and hydraulic gradients of 0.005 and above. Extraction wells will increase the speed of delivery and help control the down gradient extent of stabilizer movement. The results of solute transport modeling indicate that dispersion will play a large role in determining the concentration of stabilizer that will be required to deliver an adequate concentration at the down gradient edge. Consequently, thorough characterization of the hydraulic conductivity throughout the formation will be necessary for successful design and implementation of passive site remediation.

The cost of passive site remediation is expected to be competitive with other methods of chemical grouting, i.e. in the range of $60 to $180 per cubic meter of treated soil, depending on the concentration of colloidal silica used.



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Experiments and Analysis of Water-filled Tubes Used as Temporary Flood Barriers

Type of Document Master's Thesis
Author Freeman, Marcos
Author's Email Address mafreem3@vt.edu
URN etd-05062002-150824
Title Experiments and Analysis of Water-filled Tubes Used as Temporary Flood Barriers
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
Dr. George M. Filz Committee Co-Chair
Dr. Raymond H. Plaut Committee Co-Chair
Dr. Thomas E. Cousins Committee Member
Keywords

* inflatable tubes
* flood fighting
* geotubes
* flood control
* geosynthetic material
* flood barrier
* two-dimensional analysis

Date of Defense 2002-04-26
Availability unrestricted
Abstract

Geosynthetic tubes filled with water are considered. The tubes can be used in applications to resist rising floodwaters. They can also be used to form breakwaters and protect shores from erosion. This thesis considers single and stacked tubes resting on a rigid and deformable foundation resisting rising hydrostatic headwater.

Experiments were carried out to determine the behavior of a three-tube stacked configuration resting on a sand foundation. This study was a continuation of previous work on unstacked tubes. Many tests were performed to determine the deformation and stability of the system. A geosynthetic drain was placed beneath the tubes to prevent piping. The objective was to cause failure of the system in a sliding manner and formulate a hypothesis according to the placement of the drain beneath the tubes. In order to cause a sliding failure, a strapping system was developed to try and prevent the tubes from rolling.

A single tube at rest, filled with water but with no external hydrostatic pressure, was considered for analysis first. The tube rested on a rigid foundation and was assumed to be infinitely long. The friction between the tube and the foundation was neglected, and the bending stiffness of the tube was assumed to be negligible. The tube material was assumed to be inextensible. Mathematica was used to solve the system of equations and compute the unknowns. Excel was used to plot the data and observe the behavior of the tubes.

An analysis was also performed on a single tube with an apron attached, resting on a rigid foundation. The apron was attached on the rising headwater side to increase stability. The assumptions for the tube at rest were also applied in this analysis. Two cases were derived and analyzed: a case where the internal hydrostatic pressure remains constant, and a case where the cross-sectional area remains constant. For the second case, the internal pressure changes as the floodwater level rises.

The results from this study demonstrated that water-filled tubes, stacked or with an apron attached, can be an effective alternative method to sandbags in resisting floodwaters.

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Contemporary Network Theory: Concepts and Implications for Transportation Asset Management

Type of Document Master's Thesis
Author Fonseca, Andrea Esperanza
Author's Email Address andreafm@vt.edu
URN etd-06122007-121744
Title Contemporary Network Theory: Concepts and Implications for Transportation Asset Management
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
Dr. Gerardo W. Flintsch Committee Chair
Elisa Sotelino-Ph.D Committee Member
Michael Garvin-Ph.D. Committee Member
Keywords

* Transportation Infrastructure; Asset Management; N

Date of Defense 2007-05-29
Availability unrestricted
Abstract

This thesis proposes a novel working paradigm for transportation infrastructure asset management by viewing the transportation networks as key components (or nodes) of a broader network of resources, which includes infrastructure linked with society’s ecological, social, and economic systems. An extensive review of network science literature suggested that to understand the behavior of a complex network is imperative to characterize its topology. Consequently, this thesis focused on developing a framework to characterize the topology of the transportation infrastructure systems, and understanding how the unveiling topology can be used for supporting transportation asset management decisions.

The proposed methodology determines whether the transportation infrastructure networks can be modeled as scale-free or exponential networks, using a framework for characterizing the agents of the network, their direct and indirect interactions among each other, and their importance as elements of a complex network, and utilizes these data to support transportation asset management. The methodology consist of seven steps: (1) define the networks of interest; (2) identify their intrinsic components; (3) visualize the identified networks using GIS maps; (4) identify direct and indirect interactions through superposition of the networks; (5) represent the relationship between the nodes and their linkages by frequency diagrams in order to determine the intrinsic topology of the network; (6) illustrate (graphically) the overall transportation infrastructure with the help of GIS; and (7) analyze the TINs from the decision-maker point of view, identifying the elements that are more relevant or need more attention on the network.

The procedure is then implemented in a small network in a localized area (Town of Blacksburg, Virginia) to show its practicality, and recommendations for further development and mathematical modeling in order to allow its implementation in larger networks are provided. Based on frequency analysis of the nodes and their connectivity, it was concluded that the transportation infrastructure networks in the case study behave as exponential networks. The study showed that the links determine how the infrastructure network grows and that problems like congestion can be addressed by analyzing other factors related with topology, such as speed, unit size, and lane width. The proposed methodology was found to be useful as an asset management tool. Finally, a list of findings and recommendations for further research are presented as opportunities to enhance the management of transportation infrastructure networks.

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AN EXPERIMENTAL INVESTIGATION OF STRUCTURAL COMPOSITE LUMBER LOADED BY A DOWEL IN PERPENDICULAR TO GRAIN ORIENTATION AT YIELD AND CAPACITY

Type of Document Master's Thesis
Author Finkenbinder, David Edward
Author's Email Address davidfink@vt.edu
URN etd-09142007-121840
Title AN EXPERIMENTAL INVESTIGATION OF STRUCTURAL COMPOSITE LUMBER LOADED BY A DOWEL IN PERPENDICULAR TO GRAIN ORIENTATION AT YIELD AND CAPACITY
Degree Master of Science
Department Civil Engineering
Advisory Committee
Advisor Name Title
Dr. Daniel P. Hindman Committee Co-Chair
Dr. W. Samuel Easterling Committee Co-Chair
Dr. Joseph R. Loferski Committee Member
Dr. Surot Thangjitham Committee Member
Keywords

* Parallel Strand Lumber
* Laminated Veneer Lumber
* Capacity
* Monotonic Loading
* Wood Connections

Date of Defense 2007-09-04
Availability unrestricted
Abstract

The research summarized by this thesis was comprised of an experimental analysis of beams loaded perpendicular to grain at midspan by a bolted double-shear laterally-loaded connection. Connection specimens were loaded monotonically until capacity was reached. Variables of consideration included the loaded edge distance of the connection main member, the span:depth ratio of the main member, and the main member material. Southern pine machine-stress-rated (MSR) lumber, laminated veneer lumber (LVL), and parallel strand lumber (PSL) were the three material types included in the program.

Experimental results were compared with theoretical predictions from three models: the yield theory-based general dowel equations, which are currently the standard for laterally-loaded connection design in the U.S., and two models based upon fracture mechanics. All material property inputs required by the three models, were measured in the experimental program of this research and used to produce theoretical predictions. Comparisons were also made with respect to design values in the form of calculated factors of safety, over-strengths, and design factors of safety.

Test results and observed trends are provided for all connection and material property tests. Notable trends included failure by splitting for all connections at low loaded edge distances, and variable span:depth ratios generally having a negligible effect on both connection and model performance. In most cases, the general dowel equations were more accurate than the two fracture models, however it should be noted that all three models over-predicted connection capacity at low loaded edge distances.

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