Architecture Commons^™

Hybrid Of Natural Element Method (Nem) With Genetic Algorithm (Ga) To Find Critical Slip Surface, Shahriar Shahrokhabadi, Vahid Khoshfahm, Hamed Nabizadeh Rafsanjani

Durham School of Architectural Engineering and Construction: Faculty Publications

One of the most important issues in geotechnical engineering is the slope stability analysis for determination of the factor of safety and the probable slip surface. Finite Element Method (FEM) is well suited for numerical study of advanced geotechnical problems. However, mesh requirements of FEM creates some difficulties for solution processing in certain problems. Recently, motivated by these limitations, several new Meshfree methods such as Natural Element Method (NEM) have been used to analyze engineering problems. This paper presents advantages of using NEM in 2D slope stability analysis and Genetic Algorithm (GA) optimization to determine the probable slip surface and …

Shallow Flat Soffit Precast Concrete Floor System, George Morcous, Maher Tadros

Durham School of Architectural Engineering and Construction: Faculty Publications

A precast concrete floor system that eliminates the need for column corbels and beam ledges while being very shallow. The main advantages of the present system include a span to-depth ratio of 30, a flat soffit, economy, consistency with prevailing erection techniques, and fire and corrosion protection. The present system consists of continuous precast columns, prestressed rectangular beams, hollow-core planks, and cast-in-place composite topping. Testing results have indicated that a 12 inch deep flat soffit precast floor system has adequate capacity to carry gravity loads (including 100 psf live load) in a 30 ft x 30 ft bay size. Testing …

The Influence Of National Culture On Effectiveness Of Safety Trainings During Postdisaster Reconstruction, Behzad Esmaeili, Kevin Grosskopf, Amy Javernick-Will

Durham School of Architectural Engineering and Construction: Faculty Publications

Non-English speaking workers constitute a disproportionately high number of workers involved in postdisaster reconstruction. Additionally, the rate of fatality among these workers is higher than the industry average. Research shows this population is more prone to unsafe behaviors in the working environment, conceivably because many of these workers are sent into the field prior to any formalized training. Recent studies show that the native culture of construction workers can impact risk-taking behavior. While numerous researchers have attempted to develop training materials for Hispanic workers, the number of studies that consider the impact of native culture on safety behavior is minimal. …

A Simple Method For Estimation Of Queue Length, S. P. Anusha, Lelitha Devi Vanajakshi, Anuj Sharma

Department of Civil and Environmental Engineering: Faculty Publications

Urban arterials are characterized by frequent intersections. Queue length and delay are the two primary measures of performance of intersection. These measures play a primary role in determining the arterial performance. This article presents a methodology to determine the number of vehicles in queue at a signalized intersection for under saturated traffic conditions. The results obtained were validated using actual values that are manually extracted. The root-mean-square error is of the range 1.3 vehicles for estimation of number of vehicles in queue. The various aspects that have to be considered in accurate estimation of performance measures are also discussed.

The Mayaarch3d Project: A 3d Webgis For Analyzing Ancient Architecture And Landscapes, Jennifer Von Schwerin, Heather Richards-Rissetto, Fabio Remondino, Giorgio Agugario, Gabrio Girardi

Department of Anthropology: Faculty Publications

There is a need in the humanities for a 3D WebGIS with analytical tools that allow researchers to analyze 3D models linked to spatially referenced data. Geographic Information Systems (GIS) allow for complex spatial analysis of 2.5D data. For example, they offer bird’s eye views of landscapes with extruded building footprints, but one cannot ‘get on the ground’ and interact with true 3D models from a pedestrian perspective. Meanwhile, 3D models and virtual environments visualize data in 3D space, but analytical tools are simple rotation or lighting effects. The MayaArch3D Project is developing a 3D WebGIS—called QueryArch3D—to allow these two …

Rating Low Levels Of Ambient Noise In Performing Arts Facilities, Lily M. Wang, Brent A. Kraay

Durham School of Architectural Engineering and Construction: Faculty Publications

Previous studies have indicated that common indoor noise rating metrics, such as Noise Criteria NC and Room Criteria RC, do not best correlate to human perceptions of annoyance and distraction in typical office environments. Based on investigations conducted at the University of Nebraska using noise levels between 30 – 60 dBA, the author has proposed that an effective indoor noise rating method should begin with a rating of level (either dBA or sones), then an assessment of spectral quality, tones, and fluctuations. How well would such a system work at very low levels of ambient noise, though, as found in …

Quantifying The Just Noticeable Difference Of Reverberation Time With Band-Limited Noise Centered Around 1000 Hz Using A Transformed Up-Down Adaptive Method, Matthew G. Blevins, Adam T. Buck, Zhao Peng, Lily M. Wang

Durham School of Architectural Engineering and Construction: Faculty Publications

This study seeks to quantify the just noticeable difference (JND) of reverberation time (RT) using band-limited noise. ISO 3382-1 lists the JND of reverberation metrics at 5% based on work by Seraphim (1958). However, others have found the JND of RT to be higher from 6% to 39%. Many of these studies utilized band-limited stimuli, e.g. speech, music motifs and bandlimited noise. A previous study by the authors conducted on 30 subjects using white noise demonstrated a JND of RT at 22%. To further verify these results and investigate potential upward frequency masking, the present study was conducted following the …

Effects Of Background Noise Alternating Between Two Levels At Varying Time Intervals On Human Perception And Performance, Andrew Hathaway, Lily M. Wang

Durham School of Architectural Engineering and Construction: Faculty Publications

This research experiment aims to better quantify human perception and performance under increased background noise levels of varying intervals. Twenty-seven participants were tested over five 30 minute sessions where they were subjected to RC-29(H) and RC-47(RV) conditions created by broadband noise fluctuating on different time intervals. These intervals varied from two minutes to ten minutes, simulating the conditions of a noisy HVAC system turning on and off. The performance results of an arithmetic test dealing with short-term memory and a subjective questionnaire will be presented and compared to a similar test using broadband noise bursts and correlated to noise metrics …

Effects Of Reverberation And Noise On Speech Comprehension By Native And Non-Native English-Speaking Listeners, Zhao Peng, Lily M. Wang, Siu Kit Lau, Adam M. Steinbach

Durham School of Architectural Engineering and Construction: Faculty Publications

Previous studies have demonstrated the negative impact of adverse signal-to-noise-ratios on non-native English-speaking listeners' performance on speech recognition using recall tasks, as well as implied that comprehension skills were more impaired than recognition skills under reverberation and noise. The authors have themselves previously conducted a pilot study on three native and three non-native Englishspeaking listeners to examine the effects of reverberation and noise using speech comprehension tasks. Those results suggested that speech comprehension performance is worse under longer reverberation times (RT), and that a longer RT is more detrimental to speech comprehension by non-native listeners than native listeners. This paper …

Precast/Prestressed Concrete Truss-Girder For Roof Applications, Peter S. Samir

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

Steel trusses are the most popular system for supporting long span roofs in commercial buildings, such as warehouses and aircraft hangars. There are several advantages of steel trusses, such as lightweight, ease of handling and erection, and geometric flexibility. However, they have some drawbacks, such as high material and maintenance cost, and low fire resistance. In this paper, a precast concrete truss is proposed as an alternative to steel trusses for spans up to 160 ft. without intermediate supports. The proposed design is easy to produce and has lower construction and maintenance costs than steel trusses. The proposed design is …

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

Durham School of Architectural Engineering and Construction: Dissertations, Thesis, 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 …

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 …

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 …

Geospatial Virtual Heritage: A Gesture-Based 3d Gis To Engage The Public With Ancient Maya Archaeology, Heather Richards-Rissetto, Jim Robertsson, Jennifer Von Schwerin, Giorgio Agugario, Fabio Remondino, Gabrio Girardi

Department of Anthropology: Faculty Publications

This paper presents our research to develop a gesture-based 3D GIS system to engage the public in cultural heritage. It compares two types of interaction—device-based vs. natural interaction— and summarizes the beta-testing results of a 3D GIS tool for archaeology, called QueryArch3D, in which participants used device-based interaction (i.e. mouse and keyboard). It follows with a description of the gesture-based system—that we developed in response to these beta-tests. The system uses QueryArch3D and Microsoft’s Kinect to enable people use body movements (in lieu of keyboard or mouse) to navigate a virtual reality landscape, query 3D objects, and call up photos, …

Elec 2110: Elements Of Electrical Engineering—A Peer Review Of Teaching Project Benchmark Portfolio, Mahmoud Alahmad

UNL Faculty Course Portfolios

I have been teaching this class for the last five years. As an introductory course to electrical engineering, there is a lot of material that needs to be covered. All the material is important and relevant, and I try to go in-depth in each topic area. This approach has resulted in overwhelming the students and made them struggle with the course content, application and utilization. As I consider this course for the peer review, I am evaluating the depth of each topic and the opportunity to adjust the approach and method used to introduce new concepts and at the same …

Binaural Room Impulse Response Database Acquired From A Variable Acoustics Classroom, Zhao Peng, Siu Kit Lau, Lily M. Wang, Sean Browne, Kenneth P. Roy

Durham School of Architectural Engineering and Construction: Faculty Publications

Room measurements were conducted in a variable acoustics classroom mockup space (epod) at Armstrong World Industries in Lancaster, Pennsylvania, USA. Binaural room impulse responses were measured in the epod using a head and torso simulator. Five reverberation time (RT) scenarios were achieved with various combinations of absorptive wall panels and acoustical ceiling tile. These provided a range of mid-frequency RTs from 0.4 to 1.1 seconds. Three of the five RT scenarios were achieved using two different material configurations to also consider material location effects. For each of the eight material configurations, two student-teacher orientations were tested. One orientation had all …

Acoustic Tweets And Blogs: Using Social Media In An Undergraduate Acoustics Course, Lily M. Wang

Durham School of Architectural Engineering and Construction: Faculty Publications

Each fall, the author teaches an undergraduate architectural acoustics course to around 40 third-year architectural engineering students at the University of Nebraska. Beginning in 2011, a social media component was introduced to explore the use of this technology and how it may supplement the students' learning experience. Students were given an opportunity to receive extra credit by using Twitter and/or blogging about course material using a set hashtag (#AE3300) or through the course website. Results were positive, and the author will discuss pros and cons that she has experienced in adding this social media component. Suggestions for future implementations and …

Effects Of Reverberation And Noise On Speech Comprehension By Native And Non-Native English-Speaking Listeners, Z. Ellen Peng, Lily M. Wang, Siu-Kit Lau, Adam M. Steinbach

Durham School of Architectural Engineering and Construction: Faculty Publications

Previous studies have demonstrated the negative impact of adverse signal-to-noise-ratios on non-native English-speaking listeners' performance on speech recognition using recall tasks, as well as implied that comprehension skills were more impaired than recognition skills under reverberation and noise. The authors have themselves previously conducted a pilot study on three native and three non-native Englishspeaking listeners to examine the effects of reverberation and noise using speech comprehension tasks. Those results suggested that speech comprehension performance is worse under longer reverberation times (RT), and that a longer RT is more detrimental to speech comprehension by non-native listeners than native listeners. This paper …

Lifecycle Energy Consumption Prediction Of Residential Buildings By Incorporating Longitudinal Uncertainties, Endong Wang, Zhigang Shen

Durham School of Architectural Engineering and Construction: Faculty Publications

Accurate prediction of buildings’ lifecycle energy consumption is a critical part in lifecycle assessment of residential buildings. Longitudinal variations in building conditions, weather conditions and building’s service life can cause significant deviation of the prediction from the real lifecycle energy consumption. The objective is to improve the accuracy of lifecycle energy consumption prediction by properly modelling the longitudinal variations in residential energy consumption model using Markov chain based stochastic approach. A stochastic Markov model considering longitudinal uncertainties in building condition, degree days, and service life is developed: 1) Building’s service life is estimated through Markov deterioration curve derived from actual …

Developing A Restorable Wetland Index For Rainwater Basin Wetlands In South-Central Nebraska: A Multi-Criteria Spatial Analysis, Zhenghong Tang, Xu Li, Nan Zhao, Ruopu Li, F. Edwin Harvey

Community and Regional Planning Program: Faculty Scholarly and Creative Activity

It is always challenging for decision makers to prioritize wetland conservation programs at the landscape scale. This study employed a GIS-based multi-criteria spatial decision support tool that identified locations with the highest restoration potential for wetland conservation programs in the Rainwater Basin in south-central Nebraska. Five indicators were considered to assess wetland restoration potential: (1) Vegetation characteristics; (2) Soil characteristics; (3) Water volume released from hydrological modification of agricultural irrigation pits; (4) Topographical depression status; and (5) Habitat condition. The results suggested 192 (1.6% of the total) hydric soil footprints as the highest prioritized locations for future wetland restoration programs. …

Investigating Self-Cooling Effects Of Ventilated Attics Under Different Roof And Ambient Temperatures In Summer, Zhigang Shen, Shimin Wang

Durham School of Architectural Engineering and Construction: Faculty Publications

An unsteady computational fluid dynamics model is employed to simulate summer-time buoyancy-driven turbulent ventilation in gable-roof attics of residential buildings. The energy performance of vented attics is assessed by comparing their performance to sealed attics with the same geometry and insulation configurations. The simulated boundary conditions of the roof-top temperature ranging between 295.15 K and 345.15 K, coupled with an ambient temperature ranging between 295.15 K and 315.15 K, resemble the summer attic conditions with effects of solar irradiance on the roofs. Simulation results indicate that both the vented and sealed attics are dominated by thermal stratification. The cooling load …

Effects Of Acoustic Environments On Speech Comprehension By Native-English-Speaking Listeners, Zhao Peng, Lily M. Wang, Siu Kit Lau

Durham School of Architectural Engineering and Construction: Faculty Publications

This study investigates the effects of acoustic conditions on speech comprehension, rather than speech intelligibility as often reported in existing literature. Sets of 15-minute-long listening comprehension tests were developed based on the format of the Test of English for International Communication (TOEIC). Each test set includes four types of tasks: matching aural phrases to photographs, selecting appropriate responses to aural questions, and answering questions after listening to conversations (between two talkers) and talks (single talker). Within the Nebraska acoustics test chamber, native-English-speaking participants are asked to perform these tests under 15 acoustic conditions, from combinations of three background noise levels …

A Composite Structural Steel And Prestressed Concrete Beam For Building Floor Systems, Nathan Dewit

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

Precast prestressed concrete beams, such as rectangular and inverted tee beam, currently used in residential and commercial buildings are deep, heavy, and limited to span-to-depth ratios of 15. The research proposes a composite structural steel and prestressed concrete beam that is shallow, light, easy to produce and erect, and able to achieve a span-to-depth ratio of 24. The proposed beam is designed to be used with precast columns, hollow-core planks, and a cast-in-place topping to create a moment-resisting floor system that minimizes the need for shear walls. The goal of this system is to eliminate as many of the limitations …

Assessing Impermeable Surface Area Impacts On Modeling: Implications For The Combined Sewer Overflow Long Term Control Plan In Omaha, Nebraska, Andrew D. Szatko

Community and Regional Planning Program: Professional Projects

The report looks at assessing the accuracy of estimating impervious surface areas (ISAs) by zoning code, the method utilized by the City of Omaha, Nebraska. A 101 acre subcatchment had all ISAs manually digitized and compared the actual with the estimated value. The subcatchment was then modeled with 10 percent decreases of ISAs to establish the relationship with peak flow rates and total volume in the combined sewer service area. The results show a significant relationship between the two that may provide insights into a new approach to manage CSO events with the integration of green infrastructure.

An Adaptive Utility Interactive Photovoltaic System Based On A Flexible Switch Matrix To Optimize Performance In Real-Time, Mahmoud Alahmad, Mohamed Amer Chaaban, Siu Kit Lau, Jonathan Shi, Jill Neal

Durham School of Architectural Engineering and Construction: Faculty Publications

Reconfigurable architectures are of great interest to system designers to improve the system’s operation and efficiency. In this paper, we propose an adaptive utility interactive photovoltaic (PV) system based on a novel Flexible Switch array Matrix topology. This proposed system maximizes the generated power in real-time in response to operational conditions such as shading, soiling, mismatches, and module failure among others. The proposed system is a compromise in the utilization of power conditioning equipment to maximize energy capture and system efficiency. Simulation results demonstrate an average 13% improvement in efficiency when compared with the central inverter topology performance. A prototype …

Application Of Drum-Buffer-Rope Methodology In Scheduling Of Healthcare System, Arefeh Mohammadi, Emmanuel S. Eneyo

Durham School of Architectural Engineering and Construction: Faculty Publications

Theory of constraints (TOC) is a management philosophy that seeks to increase throughput (efficiency or performance) of the system by identifying those processes that are constraining the system bottlenecks. There have been very few profound studies of TOC in health care systems. In order to fill this gap, this study was conducted to determine how healthcare systems are utilizing components of TOC to schedule operations and what results are being obtained. This is done by using a patient flow model for a radiotherapy section of a hospital. The drum-buffer-rope (DBR) was used as the methodology for scheduling this flow. Successful …

A Directionally Tunable But Frequency-Invariant Beamformer On An Acoustic Velocity-Sensor Triad To Enhance Speech Perception, Yue Ivan Wu, Kainam Thomas Wong, Xin Yuan, Siu-Kit Lau, Shiu-Keung Tang

Durham School of Architectural Engineering and Construction: Faculty Publications

Herein investigated are computationally simple microphone-array beamformers that are independent of the frequency-spectra of all signals, all interference, and all noises. These beamformers allow the listener to tune the desired azimuth-elevation “look direction.” No prior information is needed of the interference. These beamformers deploy a physically compact triad of three collocated but orthogonally oriented velocity sensors. These proposed schemes’ efficacy is verified by a jury test, using simulated data constructed with Mandarin Chinese (a.k.a. Putonghua) speech samples. For example, a desired speech signal, originally at a very adverse signal-to-interference-and-noise power ratio (SINR) of -30 dB, may be processed to become …

Effects Of Inclusion Shapes Within Rigid Porous Materials On Acoustic Performance, Hyun Hong, Siu-Kit Lau

Durham School of Architectural Engineering and Construction: Faculty Publications

The present study investigates the influence of various shapes of inclusions having same volume embedded in a porous rigid material. Previous studies showed improvement of the broadband sound absorption with particular shapes of inclusions. However, different volumes of the inclusions have been considered; therefore, the bulk densities are not the same for comparison. The present study extends the investigations of inclusions in porous materials with same volume (or bulk density) to eliminate the influence by the change of bulk density. The effects of shape will be discussed. Finite element modeling will be used for this study. Total four different shapes: …

Effects Of Roof Pitch On Air Flow And Heating Load Of Sealed And Vented Attics For Gable-Roof Residential Buildings, Shimin Wang, Zhigang Shen

Durham School of Architectural Engineering and Construction: Faculty Publications

Pitch value is an important consideration in residential gable roof design and construction. However, how roof pitch, coupled with air flows in attic space, affects the energy performance of building attics has been barely investigated. In this paper, a 2D unsteady computational fluid dynamics (CFD) model is employed to investigate the effects of roof pitch on air flow and heating load of both sealed and vented attics for gable-roof residential buildings. The simulation results show that air flow in the sealed attics is steady and asymmetric, while that in the vented attics is a combination of an essentially symmetric base …