Architectural Engineering Commons^™

Long-Term Low Do Enriches And Shifts Nitrifier Community In Activated Sludge, Guoqiang Liu, Jianmin Wang

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

In the activated sludge process, reducing the operational dissolved oxygen (DO) concentration can improve oxygen transfer efficiency, thereby reducing energy use. The low DO, however, may result in incomplete nitrification. This research investigated the long-term effect of low DO on the nitrification performance of activated sludge. Results indicated that, for reactors with 10- and 40-day solids retention times (SRTs), complete nitrification was accomplished after a long-term operation with a DO of 0.37 and 0.16 mg/L, respectively. Under long-term low DO conditions, nitrite oxidizing bacteria (NOB) became a better oxygen competitor than ammonia oxidizing bacteria (AOB) and, as a result, no …

Pump Controller Design For Variable Primary Flow Configuration Systems, Yifan Shi

Durham School of Architectural Engineering and Construction: Dissertations, Theses, and Student Research

Pump systems are utilized widely in Heating, Ventilation and Air-Conditioning (HVAC) systems. There are mainly three configuration types: (1) the constant primary-only flow configuration, (2) the constant primary/variable secondary flow configuration, and (3) the variable primary-only flow configuration. This thesis focuses on finding the optimal control strategy for it and programming a controller for easy in-field usage.

In this thesis, the pump brake horse power (BHP) of the three pump configurations is simulated and compared using varying control methods. The best pump efficiency staging and DP reset control methods are implemented into the pump controller. A one month field experiment …

Vulnerability Of Progressive Collapse In Reinforced Concrete Flat-Plate Buildings, Jinrong Liu

College of Engineering: Graduate Celebration Programs

• Progressive collapse is the spread of initial local failure, causing partial or
  even total collapse of a building.
• Flat plate structure is widely used for office and residential buildings.
• There is a large inventory of older flat plate building without continuous slab bottom reinforcement through columns.
• Limited knowledge exists regarding the risk of disproportionate collapse in
  older flat-plates under sudden column removal during abnormal events.
• Reliable mechanical model is needed for structural evaluation.

Precast Concrete Insulated Wall Panel Corbels Without Thermal Bridging, Mohamed Elkady

Department of Construction Engineering and Management: Dissertations, Theses, and Student Research

The common practice in corbel design is to block out the insulation in order to provide a solid concrete area at the corbel location. This connection practice results in thermal bridging, which significantly reduces the energy performance of the panel. For example, the PCI Design Handbook indicates that the reduction in thermal resistance caused by a solid part with an area equal to 9% of the total panel surface area is as high as 42%. This paper presents a discussion of a new concept for corbel design of insulated wall panels with the thermal break totally preserved. Two different designs …

Multi-Objective Time-Cost Optimization Using Cobb-Douglas Production Function And Hybrid Genetic Algorithm, Zhigang Shen, Ashkan Hassani, Qian Shi

Durham School of Architectural Engineering and Construction: Faculty Publications

Existing research on construction time-cost tradeoff issues rarely explore the origin of the crashing cost. Crashing cost function was either assumed without much justification, or came from historical data of some real projects. As a result the conclusions of the papers can hardly be used to guide allocations of labor and equipment resources respectively. The authors believe Cobb-Douglas function provides a much-needed piece to modeling the cost functions in the construction time-cost tradeoff problem during the crashing process. We believe this new perspective fills a gap of existing time-cost tradeoff research by considering project duration, labor and equipment cost as …

Parameters Influencing Pressure During Pumping Of Self-Compacting Concrete, Dimitri Feys, Geert De Schutter, Ronny Verhoeven

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

The Main Difference between Conventional Vibrated Concrete (CVC) and Self-Compacting Concrete (SCC) is Observed in the Fresh State, as SCC Has a Significantly Lower Yield Stress. on the Other Hand, the Placement of SCC by Means of Pumping is Done with the Same Equipment and Following the Same Practical Guidelines Developed for CVC. It Can Be Questioned Whether the Flow Behavior in Pipes of SCC is Different and Whether the Developed Practical Guidelines Can Still Be Applied. This Paper Describes the Results of Full-Scale Pumping Tests Carried Out on Several SCC Mixtures. It Shows Primarily that the Slump or Yield …

Special Section On Natural Treatment Systems: More Than Just A Solution To Pollution, Joel Gerard Burken

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

No abstract provided.

Response Surface Method Based On Radial Basis Functions For Modeling Large-Scale Structures In Model Updating, Linren Zhou, Guirong Yan, Jinping Ou

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

The Response Surface (RS) Method based on Radial Basis Functions (RBFs) is Proposed to Model the Input-Output System of Large-Scale Structures for Model Updating in This Article. as a Methodology Study, the Complicated Implicit Relationships between the Design Parameters and Response Characteristics of Cable-Stayed Bridges Are Employed in the Construction of an RS. the Key Issues for Application of the Proposed Method Are Discussed, Such as Selecting the Optimal Shape Parameters of RBFs, Generating Samples by using Design of Experiments, and Evaluating the RS Model. the RS Methods based on RBFs of Gaussian, Inverse Quadratic, Multiquadric, and Inverse Multiquadric Are …

Relationships Between Unoccupied Classroom Acoustical Conditions And Elementary Student Achievement Measured In Eastern Nebraska, Lauren M. Ronsse, Lily M. Wang

Durham School of Architectural Engineering and Construction: Faculty Publications

Building standards recommend maximum background noise levels (BNL) and reverberation times (RT) for unoccupied classrooms. However, existing research does not show a consistent correlation between these parameters and student achievement. Through in situ testing, this research seeks to determine what acoustical conditions should be attained in elementary schools for students to meet educational goals. Acoustical measurements were conducted in a Nebraska public school system and correlated to achievement scores from students in the surveyed classrooms. Unoccupied BNLs and RTs were gathered in 34 third and 33 fifth-grade classrooms. Additionally, binaural room impulse response measurements were gathered in a subset of …

Flexural And Shear Behavior Of Reinforced Concrete Members Strengthened With A Discrete Fiber-Reinforced Polyurea System, Courtney E. Greene, John J. Myers

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

Recent research has been conducted to evaluate the benefits provided by externally applied discrete fiber-reinforced polyurea (DFRP) coating systems. This coating was proposed to allow for ease of construction in repair-retrofit situations and to provide multihazard benefits, ranging from blast or impact fragmentation mitigation to seismic reinforcement and general strengthening. This phase of research investigated the flexural and shear reinforcement capabilities of the systems. Testing parameters included type of structural failure, polyurea, and fiber volume fraction. Additionally, the effects of the thickness of the composite system were considered. Concrete beam specimens were fabricated and coated per the designed test matrix …

The Bridge Newsletter Spring 2013, Missouri University Of Science And Technology

The Bridge Newsletter

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A Novel Approach To Detecting Breathing-Fatigue Cracks Based On Dynamic Characteristics, Guirong Yan, Alessandro De Stefano, Emiliano Matta, Ruoqiang Feng

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

During the Service Life of Structures, Breathing-Fatigue Cracks May Occur in Structural Members Due to Dynamic Loadings Acting on Them. These Fatigue Cracks, If Undetected, Might Lead to a Catastrophic Failure of the Whole Structural System. Although a Number of Approaches Have Been Proposed to Detect Breathing-Fatigue Cracks, Some of Them Appear Rather Sophisticated or Expensive (Requiring Complicated Equipment), and Others Suffer from a Lack of Sensitivity. in This Study, a Simple and Efficient Approach to Detecting Breathing-Fatigue Cracks is Developed based on Dynamic Characteristics of Breathing Cracks. First, Considering that Breathing Cracks Introduce Bilinearity into Structures, a Simple System …

A Comparative Study Of The Bond Strength Of Reinforcing Steel In High-Volume Fly Ash Concrete And Conventional Concrete, Mahdi Arezoumandi, Michael H. Wolfe, Jeffery S. Volz

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

The production of Portland cement-the key ingredient in concrete-generates a significant amount of carbon dioxide. However, due to its incredible versatility, availability, and relatively low cost, concrete is the most consumed manmade material on the planet. One method of reducing concrete's contribution to greenhouse gas emissions is the use of fly ash to replace a significant amount of the cement. An experimental investigation was conducted to compare the bond strength of reinforcing steel in high-volume fly ash concrete (HVFAC)-concrete with at least 50% of the cement replaced with fly ash-with conventional concrete (CC). This experimental program consisted of 12 pull-out …

Intermittency And Local Dissipation Scales Under Strong Mean Shear, Khandakar Niaz Morshed, Subhas Karan Venayagamoorthy, Lakshmi Prasad Dasi

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

We experimentally probe the local dissipation scale distribution Q(η) and temporal fluctuations of the turbulent kinetic energy dissipation rate ε in the strongly anisotropic flow past a backward facing step. A shift in Q(η) and corresponding reduction in the relative intermittency of ε is observed with increasing mean shear S. We offer physical arguments to elucidate the role of strong shear on the small-scale structure. A local mean-shear dissipation Reynolds number, ReS ≡ {ε}/(S²ν), is proposed that may define a family of universal small-scale structures of turbulence. © 2013 American Institute of Physics.

Performance-Based Engineering Framework For Earthquake And Fire Following Earthquake, Aerik Carlton

Dissertations, Master's Theses and Master's Reports - Open

The objective for this thesis is to outline a Performance-Based Engineering (PBE) framework to address the multiple hazards of Earthquake (EQ) and subsequent Fire Following Earthquake (FFE). Currently, fire codes for the United States are largely empirical and prescriptive in nature. The reliance on prescriptive requirements makes quantifying sustained damage due to fire difficult. Additionally, the empirical standards have resulted from individual member or individual assembly furnace testing, which have been shown to differ greatly from full structural system behavior. The very nature of fire behavior (ignition, growth, suppression, and spread) is fundamentally difficult to quantify due to the inherent …

Extension Of The Reiner-Riwlin Equation To Determine Modified Bingham Parameters Measured In Coaxial Cylinders Rheometers, Dimitri Feys, Jon E. Wallevik, Ammar Yahia, Kamal H. Khayat, Olafur H. Wallevik

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

The Determination of the Exact Rheological Properties, in Fundamental Units, of Cementitious Materials Has Become Gradually a Necessary Step in the Domain of Concrete Science. Several Types of Rheometers and their Corresponding Transformation Equations Are Described in the Literature. in This Paper, the Reiner-Riwlin Transformation Equation, Valid for Coaxial Cylinders Rheometers, is Developed for the Modified Bingham Model, which is an Extension of the Bingham Model with a Second Order Term in the Shear Rate. the Established Transformation is Shown to Be Compatible with the Reiner-Riwlin Equation for the Bingham and Herschel-Bulkley Models. its Validation is Further Proven by Means …

Effect Of High-Volume Fly Ash On Shear Strength Of Concrete Beams, Mahdi Arezoumandi, Jeffery Volz, John Myers

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

Every year concrete production exceeds 6.5 billion tons worldwide, nearly 1 ton for every man, woman, and child on the planet. In fact, concrete is used 10 times more than any other building material in the world, primarily because of its incredible versatility, availability, and relatively low cost. Unfortunately, the production of Portland cement - the key ingredient in concrete - generates approximately a pound of carbon dioxide for every pound of cement produced. One method of reducing concrete's carbon footprint is to replace a significant amount of the cement with fly ash, a by-product of coal-burning thermal power stations. …

Effect Of Moist Curing And Use Of Lightweight Sand On Characteristics Of High-Performance Concrete, Soo Duck Hwang, Kamal H. Khayat, Dalia Youssef

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

Factorial design approach was undertaken to determine the effect of initial moist-curing duration (0 and 6 days) on properties of high-performance concrete (HPC) made with different water-to-cementitious materials ratios (w/cm) of 0.30 and 0.40 and sand substitution rates with lightweight sand (LWS) of 0 and 30 %, by volume. Mechanical properties of HPC are shown to be mainly affected by w/cm and total shrinkage of concrete by the LWS replacement rate and initial moist-curing period. It should be noted that concrete made with 30 % LWS replacement that did not receive any moist-curing exhibited lower shrinkage than moist-cured concrete prepared …

Use Of Vacuum For The Stabilization Of Dry Sand Slopes, B. Bate, Limin Zhang

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

Vacuum is proposed as a means for rescuing soil slopes showing signs of impending failure. Two aspects associated with the proposed method were studied: namely, the theory of airflow through dry soils and the effectiveness of vacuum for enhancing the stability of soil slopes. A model test device was developed, and two series of tests were carried out using this device. One was a series of tests on pore-air pressure distributions in dry sand slopes, and the second series involved dry sand slope stability tests. The results revealed that a vacuum (negative pore-air pressure) even as small as 20.4 kPa …

Spacecraft Module Hole Size And Crack Length Prediction Following A Penetrating Debris Particle Impact, Joel E. Williamsen, William P. Schonberg, Hilary J. Evans

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

The process used to calculate and reduce the consequences of meteoroid and orbital debris (MOD) penetrations and their link to catastrophic failure has evolved over time. As the threat of the orbital debris population increased in the 1980s and early 1990s, NASA developed a tool to determine the probability of no catastrophic failure, or PNCF, for the space station and to assess possible changes in station design and/or operations to improve that survivability percentage. PNCF is directly related to the PNP, or probability of no penetration, as calculated by Bumper, the code used by NASA to perform MOD risk assessments. …

Effect Of Fly Ash On The Shear Strength Of Concrete Beams Without Shear Reinforcement, Mahdi Arezoumandi, Jeffery S. Volz, Carlos A. Ortega

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

The following paper presents the results of an experimental investigation of the shear strength of full-scale reinforced concrete beams constructed with both high-volume fly ash concrete (HVFAC)-concrete with at least 50% of the cement replaced with fly ash-and conventional concrete (CC). This study includes two HVFAC mixes and one CC mix. The two HVFAC mixes are identical except for the amount of Class C fly ash replacement of cement, with one mix replacing 50% of the cement with fly ash and the other replacing 70 %. The test matrix included 18 beams-six for each concrete type-with three different longitudinal reinforcement …

Hypervelocity Impact Testing Of Multiwall Targets Using Multiple Simultaneously Launched Projectiles, William P. Schonberg, Steve Evans, Michael D. Bjorkman

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

Multiwall shield designs for spacecraft have been studied extensively in the last four decades as a means of reducing the perforation threat of the near-Earth particulate environment over equivalent single-wall structures. The performance of an impact shield is typically characterized by its ballistic limit equation, which is obtained through high-speed impact tests that typically use spherical projectiles fired in light gas guns. Traditional firings employ only one projectile per launch package. However, some facilities have taken to launching multiple projectiles of different sizes in a single launch package. In light of the significant role played by a ballistic limit equation …

Plants As Bio-Indicators Of Subsurface Conditions: Impact Of Groundwater Level On Btex Concentrations In Trees, Jordan Wilson, Rachel Bartz, Matt Limmer, Joel Gerard Burken

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

Numerous Studies Have Demonstrated Trees' Ability to Extract and Translocate Moderately Hydrophobic Contaminants, and Sampling Trees for Compounds Such as BTEX Can Help Delineate Plumes in the Field. However, When BTEX is Detected in the Groundwater, Detection in Nearby Trees is Not as Reliable an Indicator of Subsurface Contamination as Other Compounds Such as Chlorinated Solvents. Aerobic Rhizospheric and Bulk Soil Degradation is a Potential Explanation for the Observed Variability of BTEX in Trees as Compared to Groundwater Concentrations. the Goal of This Study Was to Determine the Effect of Groundwater Level on BTEX Concentrations in Tree Tissue. the Central …

Some Insights For The Prediction Of Near-Wall Turbulence, Farid Karimpour, Subhas K. Venayagamoorthy

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

In this paper, we revisit the eddy viscosity formulation to highlight a number of important issues that have direct implications for the prediction of near-wall turbulence. For steady wall-bounded turbulent flows, we make the equilibrium assumption between rates of production (P) and dissipation (ε) of turbulent kinetic energy (κ) in the near-wall region to propose that the eddy viscosity should be given by vt ε/S², where S is the mean shear rate. We then argue that the appropriate velocity scale is given by (STL)-1/2 k^1/2 where TL = k ε is the turbulence (decay) time scale. The …

Performance-Based Seismic Design Of Unbonded Precast Post-Tensioned Concrete Filled Gfrp Tube Piers, Haitham M. Dawood, Mohamed Elgawady

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

This paper presents a seismic design procedure for self-centering precast post-tensioned bridge piers. The piers presented in this manuscript consisted of concrete filled fiber reinforced polymer (FRP) tubes. A large set of 84 piers with different design parameters were analyzed using finite element models. The backbone curve of each pier was developed and bilinearized. The idealized backbone curves were used to develop a set of empirical equations that were able to reproduce the bilinearized backbone curve of a given pier. Different performance criteria have been proposed for the system according to the intensity and the frequency of occurrence of a …

An Experimental Study On Shear Strength Of Chemically-Based Self-Consolidating Concrete, Mahdi Arezoumandi, Jeffery S. Volz

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

An experimental investigation was conducted to compare the shear strength of full-scale beams constructed with chemically based, self-consolidating concrete (SCC) with conventional concrete (CC). This experimental program consisted of 16 rectangular beams (12 without shear reinforcing and 4 with shear reinforcing in the form of stirrups), 8 beams for each mix design. Additionally, three different longitudinal reinforcement ratios were evaluated within the test matrix. The beam specimens were tested under a simply supported four-point condition. The experimental shear strengths of the beams were compared with both the shear provisions of selected standards (U.S., Australia, Canada, Europe, and Japan) and a …

Effect Of Fly Ash On Growth Of Mustard And Corn, Cailie Carlile, Snehalata Nadiger, Joel Gerard Burken

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

Fly Ash is Generated as a By-Product of Coal Combustion and Contains Many Nutrients, Such as Ca, K, Na, Mg, and S, as Well as Toxic Metals Such as As, B, Cd, Cr, Hg, and Pb. for This Project, the Goal is to Optimize a Phytoremediation Technique to Stabilize the Toxic Metals and Produce Biomass Which Could Have Benefit for Example as Biofuel. the Hypothesis Was that Different Amendments Would Improve the Water Holding Properties of the Ash and Reduce Metals Availability and Toxicity. Flyash Was Combined with Leaf Mulch (1%, 3%, 5%, 10%, 20%), Wood Mulch (1%, 3%, 5%, …

Scale Of Fluctuation Of Geotechnical Parameters Estimated From Cptu And Laboratory Test Data, Site Onyejekwe, Louis Ge

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

For a complete probabilistic characterization of a geotechnical parameter, its mean, variance, and the scale of fluctuation have to be known. While the mean and variance can be easily determined, determination of the scale of fluctuation is a little more complex. Knowledge of the scale of fluctuation is important in reliability-based design as it is used in implementing spatial averaging and computing the variance-reduction factor. Published values of scale of fluctuation of geotechnical parameters are based on widely sourced data and hence may not be most appropriate for local situations. Based on 11 CPTu soundings and laboratory test results of …

Probability Of Failure For Slopes With Sensitivity Analysis, Michelle Deng, Ronaldo Luna

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

The significance of random variables on the probability of failure of slopes is generally evaluated by changing a different set of values for each variable and repeating the approach several times to conclude a trend. This method is very straightforward but requires time and computational resources; and it is inefficient especially when the number of random variables is large. This paper presents an analysis approach in which the sensitivity analysis is introduced to quantify the influence of the random variables on the probability of failure for slopes. In this study, the factor of safety of the slope was determined using …

Appropriate Viscous Damping For Nonlinear Time-History Analysis Of Base-Isolated Reinforced Concrete Buildings, Deepak R. Pant, Anil C. Wijeyewickrema, Mohamed A. Elgawady

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

SUMMARY: There is no consensus at the present time regarding an appropriate approach to model viscous damping in nonlinear time-history analysis of base-isolated buildings because of uncertainties associated with quantification of energy dissipation. Therefore, in this study, the effects of modeling viscous damping on the response of base-isolated reinforced concrete buildings subjected to earthquake ground motions are investigated. The test results of a reduced-scale three-story building previously tested on a shaking table are compared with three-dimensional finite element simulation results. The study is primarily focused on nonlinear direct-integration time-history analysis, where many different approaches of modeling viscous damping, developed within …