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3,108 full-text articles. Page 80 of 88.

Structural Topology Optimization: Moving Beyond Linear Elastic Design Objectives, James K. Guest, Reza Lotfi, Andrew T. Gaynor, Mehdi Jalalpour 2012 Johns Hopkins University

Structural Topology Optimization: Moving Beyond Linear Elastic Design Objectives, James K. Guest, Reza Lotfi, Andrew T. Gaynor, Mehdi Jalalpour

Civil and Environmental Engineering Faculty Publications

Topology optimization is a systematic, free-form approach to the design of structures. It simultaneously optimizes material quantities and system connectivity, enabling the discovery of new, high-performance structural concepts. While powerful, this design freedom has a tendency to produce solutions that are unrealizable or impractical from a structural engineering perspective. Examples include overly complex topologies that are expensive to construct and ultra-slender subsystems that may be overly susceptible to imperfections. This paper summarizes recent tools developed by the authors capable of mitigating these shortcomings through consideration of (1) constructability, (2) nonlinear mechanics, and (3) uncertainties.


Interfacing Building Response With Human Behavior Under Seismic Events, Z. Liu, Mehdi Jalalpour, C. Jacques, S. Szyniszewski, J. Mitrani-Reiser, James K. Guest, T. Igusa, B. W. Schafer 2012 Johns Hopkins University

Interfacing Building Response With Human Behavior Under Seismic Events, Z. Liu, Mehdi Jalalpour, C. Jacques, S. Szyniszewski, J. Mitrani-Reiser, James K. Guest, T. Igusa, B. W. Schafer

Civil and Environmental Engineering Faculty Publications

The goal of this paper is to model the interaction of humans with their built environment during and immediately following a natural disaster. The study uses finite element simulations to evaluate the response of buildings under input ground motions and agent-based dynamic modeling to model the subsequent evacuation of building occupants in the study area immediately following the seismic event. The structural model directly captures building damage and collapse, as well as floor accelerations and displacements to determine nonstructural damage, injuries and fatalities. The goal of this research is to make connections between building damage and occupant injuries, with geographic ...


North American Standard For Cold-Formed Steel Framing -- Nonstructural Members, 2011 Edition, American Iron and Steel Institute 2012 Missouri University of Science and Technology

North American Standard For Cold-Formed Steel Framing -- Nonstructural Members, 2011 Edition, American Iron And Steel Institute

AISI-Specifications for the Design of Cold-Formed Steel Structural Members

No abstract provided.


Performance Of Mechanical And Non-Mechanical Connections To Gfrp Components, Nnadozie N. Dike 2012 University of Central Florida

Performance Of Mechanical And Non-Mechanical Connections To Gfrp Components, Nnadozie N. Dike

Electronic Theses and Dissertations

There are presently many solutions to dealing with aging or deteriorated structures. Depending on the state of the structure, it may need to be completely over-hauled, demolished and replaced, or only specific components may need rehabilitation. In the case of bridges, rehabilitation and maintenance of the decks are critical needs for infrastructure management. Viable rehabilitation options include replacement of decks with aluminum extrusions, hybrid composite and sandwich systems, precast reinforced concrete systems, or the use of pultruded fiber-reinforced polymer (FRP) shapes. Previous research using pultruded glass fiber-reinforced polymer (GFRP) decks, focused on behaviour under various strength and serviceability loading conditions ...


Resilience Of Bridges Following Aftershocks, Diego Francisco Espinosa 2012 University of Central Florida

Resilience Of Bridges Following Aftershocks, Diego Francisco Espinosa

Electronic Theses and Dissertations

The ability to predict the reduction in capacity of a structure after an earthquake is vital in the process of assessing a structure after a main-shock or an after-shock. Main-shocks are normally followed by a few aftershocks in a short period of time. Researchers in the past have focused for the most part on the effects of main-shocks on buildings. Very little research has been performed on the ability to predict the reduction in capacity of bridges in aftershocks. This thesis focuses on providing a way of assessing the reduction in capacity for main-shocks as compared to aftershocks and the ...


Failure Analysis Of Impact-Damaged Metallic Poles Repaired With Fiber Reinforced Polymer Composites, Robert Arthur Slade 2012 University of Central Florida

Failure Analysis Of Impact-Damaged Metallic Poles Repaired With Fiber Reinforced Polymer Composites, Robert Arthur Slade

Electronic Theses and Dissertations

Metallic utility poles, light poles, and mast arms are intermittently damaged by vehicle collision. In many cases the vehicular impact does not cause immediate failure of the structure, but induces localized damage that may result in failure under extreme service loadings or can promote degradation and corrosion within the damaged region. Replacement of these poles is costly and often involves prolonged lane closures, service interruption, and temporary loss of functionality. Therefore, an in situ repair of these structures is required. This thesis examines the failure modes of damaged metallic poles reinforced with externally-bonded fiber reinforced polymer (FRP) composites. Several FRP ...


Flexural Behavior Of Laterally Damaged Full-Scale Bridge Girders Through The Use Of Carbon Fiber Reinforced Polymers (Cfrp), Nicholas James Alteri 2012 College of Computing, Construction and Engineering

Flexural Behavior Of Laterally Damaged Full-Scale Bridge Girders Through The Use Of Carbon Fiber Reinforced Polymers (Cfrp), Nicholas James Alteri

UNF Graduate Theses and Dissertations

ABSTRACT

The repair and strengthening of concrete bridge members with CFRP has become increasingly popular over recent years. However, significant research is still needed in order to develop more robust guidelines and specifications. The research project aims to assist with improving design prosedures for damaged concrete members with the use of CFRP.

This document summarizes the analysis and testing of full-scale 40’ foot long prestressed concrete (PSC) bridge girders exposed to simulated impact damage and repaired with carbon fiber reinforced polymers (CFRP) materials. A total of five AASHTO type II bridge girders fabricated in the 1960’s were taken from ...


An Empirical Study Of Particulate Matter Exposure For Transit Users At Bus Stop Shelters, Adam Moore 2012 Portland State University

An Empirical Study Of Particulate Matter Exposure For Transit Users At Bus Stop Shelters, Adam Moore

Dissertations and Theses

Congested traffic corridors in dense urban areas are key contributors to the degradation of urban air quality. While waiting at bus stops, transit patrons may be exposed to greater amounts of vehicle-based pollution, including particulate matter, due to their proximity to the roadway. Current guidelines for the location and design of bus stops do not take into account air quality or exposure considerations. This thesis provides a unique contribution to roadside air quality studies and presents an innovative method for the consideration of bus shelter placement. Exposure to roadside pollutants is estimated for transit riders waiting at three-sided bus stop ...


Developments In Performance Monitoring Of Concrete Exposed To Extreme Environments., W. J. McCarter, T. M. Chrisp, G. Starrs, A. Adamson, E. Owens, P. A. M. Basheer, S. V. Nanukuttan, S. Srinivasan, Niall Holmes 2011 Institute for Infrastructure and Environment, Edinburgh, Scotland.

Developments In Performance Monitoring Of Concrete Exposed To Extreme Environments., W. J. Mccarter, T. M. Chrisp, G. Starrs, A. Adamson, E. Owens, P. A. M. Basheer, S. V. Nanukuttan, S. Srinivasan, Niall Holmes

Articles

The performance of the surface zone of concrete is acknowledged as a major factor governing the rate of deterioration of reinforced concrete structures because it provides the only barrier to the ingress of water containing dissolved ionic species such as chlorides, which ultimately initiate corrosion of the reinforcement. In situ monitoring of cover-zone concrete is therefore critical in attempting to make realistic predictions as to the in-service performance of the structure. To this end, this paper presents developments in a remote interrogation system to allow for continuous, real-time monitoring of the cover-zone concrete from an office setting. Use is made ...


Development Of Self-Stressing System For Bridge Application With Emphasis On Precast Panel Deck System, Marcelo Ferreira da Silva 2011 University of Nebraska-Lincoln

Development Of Self-Stressing System For Bridge Application With Emphasis On Precast Panel Deck System, Marcelo Ferreira Da Silva

Civil Engineering Theses, Dissertations, and Student Research

Steel girder bridges often utilize continuity over the pier to reduce interior forces on the spans. In continuous structures with composite concrete decks, the location of maximum negative bending moment is over the interior supports. This moment produces tensile stresses in the concrete deck and compressive stress in the bottom flanges of the girders. The tensile stress in the deck leads to cracking which allow intrusion of moisture and road salt, causing corrosion of the reinforcement and supporting girders. Continued maintenance is required to forestall the deterioration; however, replacement of the deck is eventually required.

To overcome this problem, a ...


Development Of A Design Procedure For Concrete Traffic Barrier Attachments To Bridge Decks Utilizing Epoxy Concrete Anchors, Benjamin J. Dickey 2011 University of Nebraska-Lincoln

Development Of A Design Procedure For Concrete Traffic Barrier Attachments To Bridge Decks Utilizing Epoxy Concrete Anchors, Benjamin J. Dickey

Civil Engineering Theses, Dissertations, and Student Research

A guide for the design of epoxy anchors for the use in concrete traffic barriers was developed in this study. A series of dynamic bogie tests and static tests was conducted on single and double anchors. The dynamic increase factor for the noted anchors was determined to be 1.06. Protective epoxy coatings for the anchors was observed to contribute to a 9 percent decrease in anchorage strength. The effects of anchors located in close proximity to each other was also investigated. Calibration factors were developed to apply recommended changes to the ACI code for use in bridge rail anchorages ...


Expanding The Length Of Jointless Bridges By Providing Rotational Capacity Over The Pile Head, Ardalan Sherafati 2011 University of Nebraska-Lincoln

Expanding The Length Of Jointless Bridges By Providing Rotational Capacity Over The Pile Head, Ardalan Sherafati

Civil Engineering Theses, Dissertations, and Student Research

Jointless bridges have been in service for more than 50 years. Since no expansion joint is utilized in these structures, they have longer service life, reduced maintenance and construction costs, improved riding quality, and added redundancy. Because of integrity of the superstructure with the substructure, the thermal movements as well as other longitudinal movements are transferred to substructure. These lateral movements can induce relatively large forces and moments in the substructure elements including the abutment and the piles. Typically, flexible foundations which include single row of piles are preferred in jointless bridges to reduce the stiffness of the system against ...


Performance Specification For Tennessee Bridge Decks, Brian Ray Buchanan 2011 University of Tennessee, Knoxville

Performance Specification For Tennessee Bridge Decks, Brian Ray Buchanan

Masters Theses

In today’s world of ever increasing demand on a weakening infrastructure, concentration is being firmly placed on increasing the sustainability of that infrastructure. Tennessee’s bridges and the concrete decks, on which the public travels, require a large part of the state’s infrastructure spending. Research has shown the current durability standards of Tennessee’s bridge decks could be significantly improved which would both increase service life and reduce maintenance costs of these structures. This research concentrates on greatly increasing the lifespan of these bridge decks, throughout the state, through an improved construction specification which will encourage the increased ...


Wim Based Load Models For Bridge Serviceability Limit States, Przemyslaw Rakoczy 2011 University of Nebraska-Lincoln

Wim Based Load Models For Bridge Serviceability Limit States, Przemyslaw Rakoczy

Civil Engineering Theses, Dissertations, and Student Research

The safety of aging bridge inventory is one of the main concerns of the state and federal agencies. Therefore, there is a need to quantify the safety margin of existing infrastructure and new design bridges. The Serviceability Limit States, i.e. fatigue, requires additional statistical parameters and not only the maximum values but also load spectra, i.e. frequency of occurrence of loads. The maximum values are needed for shorter time periods, such as day, week, month or year. Load spectra as well as material resistance are random variables. To quantify the safety margin of existing and future bridges load ...


Application Of Gis In Seismic Risk Assessment For The City Of Kelowna, Md. Nurul Alam 2011 University of British Columbia, Okanagan, Canada

Application Of Gis In Seismic Risk Assessment For The City Of Kelowna, Md. Nurul Alam

Md. Nurul Alam

No abstract provided.


State Dependent Properties Of Rail Pads, Sakdirat Kaewunruen, Alexander Remennikov 2011 RailCorp

State Dependent Properties Of Rail Pads, Sakdirat Kaewunruen, Alexander Remennikov

Alex Remennikov

Rail pad is one of the main components in ballasted railway track systems. It is inserted between the rail and the sleeper to attenuate dynamic wheel/rail interaction forces, preventing the underlying railway track components from excessive stresses. Generally, the dynamic design of tracks relies on the available data, which are mostly focused on the structural condition at a specific toe load. Recent findings show that track irregularities could significantly amplify the loads on railway tracks. This phenomenon gives rise to a concern that the rail pads may experience higher deterioration rate than anticipated in the past. On this ground ...


Relationship Between Impact Energy And Fracture Toughness Of Prestressed Concrete Railway Sleepers, Sakdirat Kaewunruen, Alexander Remennikov 2011 RailCorp

Relationship Between Impact Energy And Fracture Toughness Of Prestressed Concrete Railway Sleepers, Sakdirat Kaewunruen, Alexander Remennikov

Alex Remennikov

The prestressed concrete sleepers (or railroad ties), which are installed in railway track systems as the crosstie beam support, are designed to carry and transfer the wheel loads from the rails to the ground. It is well known that railway tracks are subject to impact loading conditions, which are attributable to the train operations with either wheel or rail abnormalities such as flat wheels, dipped rails, etc. These loads are of very high magnitude but short duration. In addition, there exists the potential of repeated load experience during the design life of prestressed concrete sleepers. Prestressed concrete has played a ...


Dynamic Design Guidelines For Prestressed Concrete Sleepers, Alexander Remennikov, Martin H. Murray, Sakdirat Kaewunruen 2011 University of Wollongong

Dynamic Design Guidelines For Prestressed Concrete Sleepers, Alexander Remennikov, Martin H. Murray, Sakdirat Kaewunruen

Alex Remennikov

Current design philosophy, outlined in AS 1085.14, is based on the analysis of permissible stresses resulting from quasi-static wheel loads and essentially the static response of concrete sleepers. In general, cracking can incur when the bottom fibre stress is larger than tensile strength of concrete. Premature cracking of prestressed concrete sleepers has been detected in railway tracks. The major cause of cracking is the infrequent but high-magnitude wheel loads produced by a small percentage of “out-of-round” wheels or railhead surface defects, which are crudely accounted for in AS 1085.14 by a single load factor. Based on the current ...


Dynamic Properties Of Railway Track And Its Components : A State-Of-The-Art Review, Sakdirat Kaewunruen, Alexander Remennikov 2011 Austrak Pty Ltd

Dynamic Properties Of Railway Track And Its Components : A State-Of-The-Art Review, Sakdirat Kaewunruen, Alexander Remennikov

Alex Remennikov

Recent findings indicate one of major causes of damages, which is attributed to the resonant behaviours, in a railway track and its components. Basically, when a railway track is excited to generalised dynamic loading, the railway track deforms and then vibrates for certain duration. Dynamic responses of the railway track and its components are the key to evaluate the structural capacity of railway track and its components. If a dynamic loading resonates the railway track’s dynamic responses, its components tend to have the significant damage from excessive dynamic stresses. For example, a rail vibration could lead to defects in ...


Seismic Microzonation Of Great Toronto Area And Influence Of Building Resonances On Measured Soil Responses, Dimitar Genchev Mihaylov 2011 The University of Western Ontario

Seismic Microzonation Of Great Toronto Area And Influence Of Building Resonances On Measured Soil Responses, Dimitar Genchev Mihaylov

Electronic Thesis and Dissertation Repository

A pilot seismic microzonation of the Greater Toronto Area (GTA) is used to establish the conditions and limitations of geophysical methods for site response investigations in city conditions. Maps of fundamental soil resonant frequencies, amplifications at these frequencies and interpolated average shear wave velocity of top 30 m of soil profile (VS- 30) used in soil classification were compared to the maps of drift thickness and surficial geology for the GTA. The non-applicability of the interpolated VS-30 map for site classification between measured test points is indicated. It is also shown that the soil response cannot be estimated properly using ...


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