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Concrete

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Full-Text Articles in Architectural Engineering

Pumping Of Fresh Concrete: Insights And Challenges, Geert De Schutter, Dimitri Feys Jan 2016

Pumping Of Fresh Concrete: Insights And Challenges, Geert De Schutter, Dimitri Feys

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

Pumping of Fresh Concrete is of Utmost Importance for Concrete Practice. Required Pumping Pressures Are Typically Estimated based on Design Charts. However, with the Increased Use of Chemical Admixtures and the Development of More Flowable Concrete Mixtures, the Accuracy of Traditional Design Charts is Questioned. in Recent Years, Significant Progress Has Been Obtained in Understanding the Flow of the Material in the Pumping Pipe, Including the Behavior of the Lubrication Layer Near the Pipe Surface. in Comparison with Traditional Design Charts, This Results in More Reliable Pressure Predictions When Considering Very Fluid Concrete Types Like Self-Consolidating Concrete. Some Remaining Challenges …


Factors Affecting The Seismic Behavior Of Segmental Precast Bridge Columns, Haitham Dawood, Mohamed Elgawady, Joshua Hewes Dec 2014

Factors Affecting The Seismic Behavior Of Segmental Precast Bridge Columns, Haitham Dawood, Mohamed Elgawady, Joshua Hewes

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

This manuscript discusses the design parameters that potentially affect the lateral seismic response of segmental precast post-tensioned bridge piers. The piers consist of precast circular cross section segments stacked one on top of the other with concentric tendons passing through ducts made in the segments during casting. The bottommost segments of the piers were encased in steel tubes to enhance ductility and minimize damage. An FE model was used to investigate different design parameters and how they influence the lateral force — displacement response of the piers. Design parameters investigated included the initial post-tensioning stress as a percentage of the …


Effect Of Fly Ash Replacement Level On The Fracture Behavior Of Concrete, Mahdi Arezoumandi, Jeffery S. Volz Dec 2013

Effect Of Fly Ash Replacement Level On The Fracture Behavior Of Concrete, Mahdi Arezoumandi, 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. This study presents the results of an experimental investigation that evaluates effect of fly ash replacement level on the fracture energy of concrete. This study includes four mixes with 0%, 30%, 50%, and 70%fly ash as a cement replacement. This …


Compression Testing And Failure Modes Of Steel-Concrete Composite (Sc) Structures For Nuclear Containment, Patrick Michael Wanamaker, Amit H. Varma Oct 2013

Compression Testing And Failure Modes Of Steel-Concrete Composite (Sc) Structures For Nuclear Containment, Patrick Michael Wanamaker, Amit H. Varma

The Summer Undergraduate Research Fellowship (SURF) Symposium

Although being able to provide much cleaner power than burning coal and other fossil fuels, nuclear power plants are still a tough sell to the general public due to their history of being spontaneously dangerous. The containment structures surrounding these nuclear plants, however, can play a huge role in reducing the risks associated with them. Relatively new designs for these containment assemblies, known as SC (steel-concrete composite) structures, aim to increase the strength and durability of the containment facilities while keeping costs down. By varying the spacing between shear studs, the ratio of concrete to steel, and the ratio of …


Performance-Based Seismic Design Of Unbonded Precast Post-Tensioned Concrete Filled Gfrp Tube Piers, Haitham M. Dawood, Mohamed Elgawady Jan 2013

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 …


Behavior Of Segmental Precast Posttensioned Bridge Piers Under Lateral Loads, Haitham Dawood, Mohamed Elgawady, Joshua Hewes Sep 2012

Behavior Of Segmental Precast Posttensioned Bridge Piers Under Lateral Loads, Haitham Dawood, Mohamed Elgawady, Joshua Hewes

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

Abstract a segmental precast posttensioned (SPPT) bridge pier is an economic recentering structural system. Understanding the seismic behavior of a SPPT system is an important step toward its application in high seismic zones. This paper presents a detailed three-dimensional finite-element (FE) model that was developed using the ABAQUS platform. a brief description and discussion of cyclic tests on eight large-scale SPPT piers is also presented. Four of the piers were constructed and tested to a predefined degree of damage. Then, these piers were retrofitted and retested. the FE models developed and presented in this paper predicted the backbone curves of …


High-Volume Fly Ash Concrete For Sustainable Construction, Jeffery S. Volz Jun 2012

High-Volume Fly Ash Concrete For Sustainable Construction, Jeffery S. Volz

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

With worldwide production of fly ash approaching 800 million tons annually, increasing the amount of fly ash used in concrete will remove more material from the solid waste stream and reduce the amount ending up in landfills. However, most specifications limit the amount of cement replacement with fly ash to less than 25 or 30%. Concrete with fly ash replacement levels of at least 50% - referred to as high-volume fly ash (HVFA) concrete - offers a potential green solution. the following study investigated the structural performance of HVFA concrete compared to conventional Portland-cement concrete. Specifically, the research examined both …


Structural Performance Of Reinforced Concrete Flat Plat Buildings Subjected To Fire, Sara Jean George May 2012

Structural Performance Of Reinforced Concrete Flat Plat Buildings Subjected To Fire, Sara Jean George

UNLV Theses, Dissertations, Professional Papers, and Capstones

Reinforced concrete structures are typically considered to have inherent resistance to fire. However, several concrete structures around the world have experienced partial or total collapse under fire. Reinforced concrete flat-plate is a type of structural system widely used for office and residential buildings. Flat plate construction is prone to punching shear failure at slab-column connections which may lead to a catastrophic progressive collapse. The slabs of flat-plates generally have very thin concrete cover leaving steel reinforcement more sensitive to thermal loads. Little is known in the engineering community about the structural performance of flat-plate structures subjected to fire. Through a …


Accelerated Construction For Pedestrian Bridges: A Comparison Between High Strength Concrete (Hsc) And High-Strength Self Consolidating Concrete (Hs-Scc), John J. Myers, Kurt Bloch Sep 2011

Accelerated Construction For Pedestrian Bridges: A Comparison Between High Strength Concrete (Hsc) And High-Strength Self Consolidating Concrete (Hs-Scc), John J. Myers, Kurt Bloch

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

High-strength concrete (HSC) and glass fiber reinforced polymer (GFRP) bars are materials utilized in bridge construction to lower cost, reduce construction time, and increase service life of bridge structures. Recently, high-strength self-consolidating concrete (HS-SCC), a highly flowable concrete that does not require vibration, has been developed as a viable alternative to HSC for use in situations with congested steel or a need for rapid construction. Coupling HS-SCC with GFRP bars could create durable structures built rapidly. Several performance related issues remain to be investigated such as the behavior of prestress loss, shear, creep, shrinkage, thermal gradients, mechanical property development, time …


Evaluation Of Time Independent Rheological Models Applicable To Fresh Self-Compacting Concrete, Dimitri Feys, Ronny Verhoeven, Geert De Schutter Jan 2007

Evaluation Of Time Independent Rheological Models Applicable To Fresh Self-Compacting Concrete, Dimitri Feys, Ronny Verhoeven, Geert De Schutter

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

Self-Compacting Concrete is a New Type of Concrete Which is More Liquid Compared to Traditional Concrete and Which Does Not Need Any Form of External Compaction. as a Result, This Type of Concrete is Suitable for a New Placing Technique: Pumping SCC from the Bottom in the Formwork and Letting It Rise in the Formwork Due to the Applied Pressure. in Order to Understand the Phenomena Occurring during Pumping Operations, the Rheological Properties of SCC Must Be Investigated and Controlled. Tests Have Been Performed with Two Different Rheometers, Which Are Described in This Paper. for the Tattersall MIk-II Rheometer, a …