Engineering Commons^™

Hyperelastic Structural Fuses For Steel Buildings, Francys López

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Why to upgrade traditional systems?

The FEMA P-58-1 listed some of the limitations in present-generation procedures:

Questions regarding the accuracy and reliability of available analytical procedures in predicting actual building response.

“High” level of conservatism underlying the acceptance criteria.

Inability to reliably and economically apply performance-based procedures to the design of new buildings; and Lack of alternative ways of communicating performance to stakeholders that is more meaningful and useful for decision making purposes.

Performance based design (PBD) emerges as the methodology aiming to bridge this gap, raising the design level performance from life safety (traditional systems) to keep structures fully …

Impact-Resistant Behavior Of Reinforced Concrete Bridge Columns, Chen Fang

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

The damage caused by a vehicle collision on a pier column can be catastrophic for the functionality of a bridge, even a total collapse of the bridge. ❖ A vehicle collision and a subsequent vehicle blast cause more damages on the bridge. ❖ Limited researches have been conducted to investigate the behavior of the bridge subjected to the combined effect of vehicle collision and blast. ❖ It is necessary to analyze the responses of the bridge under the vehicle collision and blast and provide some design suggestions to strengthen the bridge.

Conclusions ❖ The finite element models including column, pile …

Optimizing Steel Railway Truss Bridge Health Monitoring, Ahmed Rageh, Daniel Linzell

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Problems - Steel Railway Trusses • Aging • Large system – bridge AND railway • Labor intensive condition eval • Reported conditions: Stringer-to-floor beam connections [Haghani 2012] Stringer flange clip angle cracks [Haghani 2012] Unequal eyebars stress distribution [DelGrego 2008] Displaced eyebar pins [DelGrego 2008

Problems – Condition Evaluation • Visual inspection: Prescribed frequency Costly Subjected to human interpretation • Sensors: Focused on a single bridge Extensive array Costly

Influence Of Skew And Nonlinear Deck On Elastic Versus Inelastic Distribution Behavior And Ultimate Capacity Of Steel Girder Bridges, Fayaz Sofi, Joshua Steelman

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Research Objectives

• Assessment of alternative load distribution methodologies for potential discrepancies that arise when evaluating distribution behavior of skewed steel girder bridges.

• Investigate the influence of skew and material nonlinearities (concrete cracking and steel yielding) on

• Load distribution behavior (elastic versus inelastic).

• System capacities (yielding and ultimate).

Summary and Conclusions • Influence of skew was examined on load distribution behavior, and nonlinear system-based capacities (yielding and ultimate) of composite steel girder bridges in presence of full material nonlinearities. In addition, assessment of two general definitions (beam-line and response fraction approaches) for quantifying load distribution behavior was …

Simulation As Supplementary Tool In Construction Management Education, Saeed Rokooei, James D. Goedert, Asregedew Woldesenbet

Department of Construction Engineering and Management: Faculty Publications

Many academic programs utilize simulation applications to supplement higher education, but there are only a few applications responding to the need in construction curricula, particularly with a focus on project management. Project management is an interdisciplinary area of study, crosscutting multiple fields including the construction, information technology, and business sectors. This paper presents the design, development, and test of a research project entitled Project-oriented Educational Research Fostering Excellence in Cyber-infrastructure Teaching (PERFECT). It investigates the effect of a construction project management simulation on construction management students’ engagement and perceptions at the University of Nebraska- Lincoln.

The goal of PERFECT was …

Investigating Students’ Perception Using Construction Management Simulations, Saeed Rokooei, James D. Goedert, Asregedew Woldesenbet

Department of Construction Engineering and Management: Faculty Publications

Today, construction programs are incorporating a wide variety of active learning methods in their curricula to improve student learning outcomes and induce a more knowledge retention rate. Simulations and educational games are one of the fast growing and effective active learning methods that have been implemented in many programs. However, there are few instances of such learning methods applied in construction programs and a limited number of research projects have been conducted to investigate short-term and long-term outcomes of these methods and applications. This paper presents construction students’ perceptions of tested simulations with regards to the features, knowledge gained, level …

Development Of A Test Level 3 Transition Between Guardrail And Portable Concrete Barriers, Robert W. Bielenberg, David Gutierrez, Ronald K. Faller, John D. Reid, Phil Tenhulzen

Department of Civil and Environmental Engineering: Faculty Publications

Road construction often requires that work zones be created and shielded by portable concrete barriers (PCBs) to protect workers and equipment from errant vehicles as well as to prevent motorists from striking other roadside hazards. For an existing W-beam guardrail system installed adjacent to the roadway and near the work zone, guardrail sections are removed so a PCB system can be placed. A study was done to develop a crashworthy transition between W-beam guardrail and PCB systems. Design concepts were developed and refined through computer simulation with LS-DYNA. Additionally, a study of critical impact points was conducted to determine impact …

Invasive Species Impacts On Infrastructure, Invasive Species Advisory Committee

National Invasive Species Council

Executive Summary

Invasive species represent one of the most significant threats to ecosystems, human and animal health, infrastructure, the economy, and cultural resources. Because potentially invasive, non-native species typically enter the United States through ports of entry in urban environments, some of the first observable impacts may be to infrastructure, yet little is known about the economic costs associated with these impacts to the “built” environment. In addition, federal agencies currently lack the authority necessary to effectively prevent, eradicate, and control invasive species that impact the human-built environment. This lack of authority prevents rapid response to some of the most …

Experimental Modal Analysis And Seismic Mitigation Of Statue-Pedestal Systems, Christine E. Wittich, Tara C. Hutchinson

Department of Civil and Environmental Engineering: Faculty Publications

The seismic protection of cultural heritage, particularly statues, is a critical issue due to its high cultural significance, difficulty to repair or replace artifacts, and observed poor behavior during past earthquakes. Recent research has explored analysis techniques and methodologies for predicting the seismic response of statues; however, these studies typically assume the statue to be either freestanding or rigidly attached. The seismic response of statues with these different boundary conditions varies widely and therefore accurate characterization is critical. While modern mounting techniques aim to rigidly attach a statue to the floor or to a pedestal, the degree of rigidity of …

Predicting Construction Labor Productivity With Bayesian Belief Networks, Ayoub Hazrati

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

Construction labor productivity plays an important role in labor intensive projects. Therefore, increasing construction labor productivity is a vital task to decrease a project’s cost (time). The primary goal of this research is to investigate the feasibility of developing a comprehensive causal model that can predict construction labor productivity for various project’s situations, such as existence of “Adverse Weather,” “Changes,” “Working Overtime,” etc., while considering uncertainty. It is found that Bayesian Belief Networks (BBNs) is the best approach that can model causal relationships among different factors while considering uncertainty, simultaneously.

Developing a BBNs model requires to extract its structure and, …

Case Study Of Quantifying Energy Loss Through Ceiling-Attic Recessed Lighting Fixtures Through 3d Numerical Simulation, Ri Na, Shengmao Lin, Zhigang Shen, Linxia Gu

Durham School of Architectural Engineering and Construction: Faculty Publications

Air leakage through improperly installed recessed lighting fixtures has been identified as a common issue causing extra energy consumption of residential buildings. However, little quantitative study was found in this area. In this paper, a preliminary evaluation of the magnitude of such energy loss was conducted by numerical simulations using 3 dimensional transient computational fluid dynamics (CFD) model. A typical layout of recessed lighting fixtures was used in this case study with boundary conditions in four different seasons, which were obtained from past measured roof/attic temperature data sets. The results of the numerical simulations indicate that leakage of recessed lighting …

Ae 2250: Construction Graphics And Design—A Peer Review Of Teaching Project Benchmark Portfolio, Asregedew Woldesenbet

UNL Faculty Course Portfolios

This course portfolio designs and documents AE 2250 (Construction Design and Graphics) course that is taught in Spring 2016 at UNL's College of Engineering under the Durham School of Architectural Engineering and Construction program. The course is intended to introduce BIM (Building Information Modeling) to architectural engineering, construction engineering, construction management and civil engineering students ranging from freshman to juniors. This course portfolio documents the challenges associated with delivering this course, tailors the course objectives, activities and tracking measures to meet the course objectives throughout the semester. This portfolio uses quantitative and qualitative measures to track student performances and learning …

Expedient Airfield Runway Repair Using Folded Fiberglass Mat, Christopher Y. Tuan, Willaim C. Dass

Department of Civil and Environmental Engineering: Faculty Publications

For expedient airfield runway repair, the US Air Force has developed a folded fiberglass mat to cover craters repaired with a well-compacted granular base material. The objective of this study was to evaluate the adequacy of using polymer plugs to anchor the mat to a repaired asphalt pavement for heavy aircraft operations. The effort consisted of materials testing, field experiments and analytical modeling. An 89,800-kg (198,000-pound) load cart having the footprint of a single C-5 main gear was pulled on a mat with wheels locked to simulate full braking forces. Anchor bushings were instrumented to measure anchor loads. A simplified …

Subjective Perception Of Varying Reflection Densities In Room Impulse Responses, Hyun Hong

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

Reverberation time (RT) is a metric commonly used to describe room acoustic conditions, but different rooms which have the same reverberation time can have different reflection densities. Much less is known about how humans perceive different reflection densities and how sensitive humans are to changes in reflection density. Previous investigations in the existing literature have studied the upper limit of distinguishable reflection density using artificial impulse responses, but not with more realistic impulse responses simulated in room acoustic software or measured from real rooms. The aim of this dissertation is to investigate methods for quantifying reflection density from measured impulse …

Evaluate Students’ Learning Effectiveness Of Hvac System Using 3d Game Animation, Lalitha Devi Nandam

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

An important skill required for students in Construction Engineering and Architecture is to understand what the major components are and how the whole system and its components function. Students typically learn to understand HVAC equipment by reviewing two-dimensional (2D) CAD drawings, images and site visits. With latest developments in 3D game engines for facilitating interactive learning, it is now possible for students to experience three-dimensional (3D) environments of HVAC systems. While this technology is still at an early stage in learning application, it has the potential to significantly enhance the capability of students to study, comprehend and gain experience designing …

Airborne Infection In Healthcare Environments: Implications To Hospital Corridor Design, Ehsan Mousavi

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

Several studies have linked nosocomial transmission airborne diseases to airflow in healthcare settings. Quasi-experimental methods are developed to observe the aerodynamic transport behavior of synthetic respiratory particles in corridors of a hospital. Computational models, validated by experimental results, are then developed to explore the spatial relationships of supply-exhaust air ventilation in patient corridors. The aim of this study is to determine optimal HVAC design strategies to contain and remove airborne contaminants in healthcare environments.

In addition to occupant comfort, hospital HVAC systems are designed to provide ventilation and directional airflow to contain, dilute and remove contaminants including airborne disease. Of …

Estimation Of Optimal Productivity In Labor-Intensive Construction Operations, Krishna Prasad Kisi

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

In an attempt to evaluate the efficiency of labor-intensive construction operations, project managers typically compare actual with historical productivity for equivalent operations. However, this approach toward examining productivity only provides a relative benchmark for efficiency and may lead to the characterization of operations as objectively efficient when in reality such operations might simply be comparably efficient.

Optimal productivity is the highest sustainable productivity achievable under good management and typical field conditions. Optimal productivity is useful in the determination of the absolute efficiency of construction operations because an accurate estimate of optimal labor productivity allows for the comparison of actual vs. …

A Framework For Estimating Labor Productivity Frontiers, Nirajan Mani

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

The efficiency of construction operations is typically determined by comparing actual versus historical productivity. This practice is accurate if historical data reflects optimal values. Otherwise, this comparison is a gauge of relative rather than absolute efficiency. Therefore, in order to determine absolute efficiency, one must compare actual versus optimal productivity. Optimal productivity is the highest sustainable productivity level achievable under “good management” and “typical field conditions,” while the productivity frontier is the theoretical maximum achievable under “perfect conditions.”

The productivity frontier is an abstraction useful in the estimation of optimal productivity of construction operations. This research contributes to the body …

Assessing Gait And Postural Stability Of Construction Workers Using Wearable Wireless Sensor Networks, Houtan Jebelli

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

Falling accidents are a leading cause of fatal and nonfatal injuries in the construction industry. This fact demonstrates the need for a comprehensive fall-risk analysis that incorporates the effects of construction workers’ physiological characteristics. In this context, the objective of the thesis is to investigate and validate the usefulness of the gait- and postural-stability metrics in assessing construction workers’ fall risks. Diverse metrics that assess the capability to keep the body balanced and maintain coordination of body segments during locomotion (gait stability) and stationary postures (postural stability) have been introduced and used in clinical applications. However, their usefulness in the …

Using Simulated Virtual Interactivity In Construction Education, Saeed Rokooei, James D. Goedert

Department of Construction Engineering and Management: Faculty Publications

This paper briefly illustrates the design procedure, implementation and findings of a three year research project. Virtual Interactive Construction Education (VICE) is a project-based pedagogical model that uses a simulated environment to alter traditional subject-based lectures into virtual project-based interactive learning methods in construction education. For this purpose, the context of construction engineering and management curricula were aggregated into six construction project prototypes. VICE-Bridge is the first of these six prototypes that exposes players to experiential problem solving activities toward achieving a goal situation (construct the bridge) from an initial situation (start of construction). It was designed for students with …

Evaluating The Impact Of Bridge Deck Removal Method On The Performance Of Precast/Prestressed Concrete I-Girders, Shaddi Assad

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

Wide flange precast/prestressed concrete I-girders have been widely used by several State Departments of Transportation (DOTs) in the last two decades. These girders have many advantages over standard AASHTO I-girders. Their wide and thick bottom flange accommodates a large number of prestressing strands and their wide and thin top flange provides a shorter deck span, reduced girder weight, greater stability in construction, and adequate platform for workers. Despite these advantages, the wide and thin top flange might be disadvantageous when it comes to deck removal, as it is more susceptible to damage. Therefore there is a need to investigate the …

Comparative Study Of Base-Isolated And Fixed-Base Buildings Using A Damage/Cost Approach, Martin Lashgari

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

High performance base-isolated buildings are designed with a higher level of safety than the conventional fixed-base buildings under the current codes. As a sustainable development, these buildings have considerably lower social and economic impacts in a major event. The main factor limiting the extensive use of such systems is the higher initial construction costs. The cost estimations based on only initial investment may have concluded misleading results as the performance of those systems in earthquakes are different. Therefore, an evaluation considering initial costs and future repair costs due to damages from earthquakes gives a better scope for selection of an …

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 …

Automatic Object Recognition And Registration Of Dynamic Heavy Equipment Using A Hybrid Ladar System, Mengmeng Gai

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

It has been a challenging subject to recognize dynamic objects from a scattered work environment because large and complex 3D site data obtained by a laser scanner makes it difficult to process itself in real or near real time. This thesis introduces a model-based automatic object recognition and registration framework, Projection-Recognition-Projection (PRP), to assist heavy equipment operators in rapidly perceiving 3D working environment at dynamic construction sites. In this study, a digital camera and a hybrid laser scanner were used to rapidly recognize and register dynamic target objects in a 3D space by separating target object’s point cloud data from …

Dynamic Vulnerability Assessment Of Highway And Railway Bridges, Mehdi Mohseni

Department of Civil and Environmental Engineering: Dissertations, Theses, and Student Research

Dynamic loads can cause severe damage to bridges, and lead to malfunction of transportation networks. A comprehensive understanding of the nature of the dynamic loads and the structural response of bridges can prevent undesired failures while keeping the cost-safety balance. Dissimilar to the static behavior, the dynamic response of bridges depends on several structural parameters such as material properties, damping and mode shapes. Furthermore, dynamic load characteristics can significantly change the structural response. In most cases, complexity and involvement of numerous parameters require the designer to investigate the bridge response via a massive numerical study.

This dissertation targets three main …

In-Plane Shear Resistance Of Sustainable Structural Walls With Large Openings, Matija Radovic

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

Shear walls are primary structural systems that support building against lateral loads (tornadoes and hurricanes). Even though concrete shear walls are the most efficient lateral resisting system, they are rarely used in a residential construction. The reasons for why contractors do not use concrete walls in residential construction were due to higher construction cost and slower construction paces. This study proposes building and testing residential concrete structural wall system that is energy efficient, cost competitive and structurally safe.

In order to decrease environmental impact of the residential construction process, this study proposed implementing sustainability concept while building residential structures. The …

Applications Of Cobb-Douglas Production Function In Construction Time-Cost Analysis, Ashkan Hassani

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

Cobb-Douglas Production Function was widely used in economics and productivity studies across many sectors. The function’s quantitative modeling of resource inputs and production outputs is appealing to the research domain of construction management. In this thesis we explored this function’s application in construction schedule crashing and project risk analysis related to duration of construction projects. Existing research on construction time-cost tradeoff issues rarely explore the origin of the crashing cost which is defined as the cost needed to shorten the project to the desired duration. In the existing literature crashing cost function was either assumed without much justification, or came …

An Analysis Of The Impacts Of Temperature Segregation On Hot Mix Asphalt, Thaddaeus A. Bode

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

This research was conducted to produce a more realistic picture of how variables are created and dealt with during hot mix asphalt (HMA) paving construction. Several paving projects across the State of Nebraska have been visited where sensing devices were used to test how the selected variables contribute to temperature differentials. These variables include density, moisture content within the asphalt, material surface temperature, internal temperature, wind speed, haul time, and equipment type. Areas of high temperature differentials are identified using an infrared camera whose usefulness was initially confirmed with a penetrating thermometer. A non-nuclear density device was also used to …

Efficient Prestressed Concrete-Steel Composite Girder For Medium-Span Bridges, Yaohua Deng

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

In this dissertation, a new Prestressed Concrete-Steel Composite (PCSC) girder system is introduced. The PCSC girder is composed of a lightweight W-shape steel section with shear studs on its top and bottom flanges to achieve composite action with the pretensioned concrete bottom flange and the cast-in-place concrete deck. The PCSC girder is lightweight, economical, durable and easy to fabricate. To prove its feasibility and potential, this study is to investigate design and fabrication issues associated with the PCSC girder. A service design procedure is proposed using Age-adjusted Elasticity Modulus Method (AEMM) to evaluate the time-dependent stresses and strains in the …