Browsing by Author "Emmett Sumner, Committee Member"

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3D Orthogonal Woven Glass Fiber Reinforced Polymeric Bridge Deck: Fabrication and Experimental Investigation
(2004-10-27) Norton, Taylor Montgomery; Sami Rizkalla, Committee Chair; Amir Mirmiran, Committee Co-Chair; Jack Lesko, Committee Member; Emmett Sumner, Committee Member
Rapid deterioration of civil infrastructure has created one of the major challenges facing the construction industry. In recent years, fiber reinforced polymers (FRP) have emerged as a potential solution to the tribulations associated with deficient bridge decks. The main objective of the proposed research is to adapt the 3-D orthogonal 3Weaving™ process to develop an innovative completely woven fiber reinforced polymeric bridge deck. The research accomplished fabricating a unique 3Weaving™ loom capable of weaving an E-glass preform which 'puffs out' into an open cell truss-like structure aimed to overcome each the weaknesses of its predecessors. The project succeeded in providing fiber reinforcement through the connection of the truss core components with the outer composite deck skins. The loom provided continuous fiber reinforcement through these top and bottom skins. And the innovative fiber architecture provided inplane fiber reinforcement in each of the structural components. Two 5' long by 15' wide deck preforms were produced: the first 1 ½ thick and the second 3' thick. In addition, a 2' long by 12' wide by 1 ½ thick non-truss composite deck was produced for comparison. The truss oriented decks utilized triangular cut shafts of Balsa as core inserts, and the non-truss deck maintained a rectangular block of Balsa core; each deck was infused with an epoxy resin; and concrete was cast atop. Each of the decks was tested for stiffness and strength in three-point bend. The stiffness tests comprised loading and unloading the deck in 2 kip increments up to 22 kips and using linear regression analysis to ascertain any degradation in stiffness. The strength tests consisted of loading the deck until failure. The testing exemplified the importance of the attachment of the core structural components to the outer composite deck skins and demonstrated a resistance of delamination of the core to the outer skins and the outer skins to themselves.
Behavior of Concrete Bridges Reinforced with High-Performance Steel Reinforcing Bars
(2007-05-09) Seliem, Hatem Mohamed; Paul Zia, Committee Member; Emmett Sumner, Committee Member; Ajaya Kumar Gupta, Committee Member; Sami Rizkalla, Committee Chair
High-performance (HP) steel reinforcing bars are characterized by their high tensile strength and enhanced corrosion resistance in comparison to conventional ASTM A 615 Grade 60 steel. Use of HP steel in concrete bridges could lead to potential savings by reducing the amount of steel required based on its higher strength characteristics and expanding the service life of bridges due to its enhanced corrosion resistance. A commercially available steel know Micro-Composite Multi-Structural Formable (MMFX) steel which is conforming to ASTM A 1035, was selected for this study because of its high tensile strength and enhanced corrosion resistance. Comprehensive experimental and analytical programs were carried out to evaluate the mechanical properties of the HP steel bars, its bond characteristics, and the behavior of concrete bridge decks reinforced with HP steel. Research findings showed that HP steel used in this study exhibited much higher tensile strength than that of conventional Grade 60. In addition, the HP steel bars had much lower corrosion rate than Grade 60 bars. Bending HP steel bars reduce its ultimate strength and strain by 6 and 70 percent, respectively. However, when HP steel bent bars are bonded to concrete they develop their full stress-strain capacity. Bond test results indicated that a stress level up to 90 ksi can be developed in #8 HP steel bars without the use of transverse reinforcement. The use of transverse reinforcement increases the bond strength of HP steel reinforcing bars, consequently reaching stress levels in the bars up to 150 ksi. When possible, it is recommended to use a minimum amount of transverse reinforcement to confine spliced bars to ensure ductile behavior and provide warning prior to failure. Direct replacement of Grade 60 with HP steel bars in bridge decks is a conservative approach. However, reducing the amount of HP steel by 33 percent does not impair the ultimate-load carrying capacity or alter the serviceability behavior of bridge decks. Under service load, the behavior of bridge decks is two-way flexural behavior. Increasing the applied load leads to development of internal membrane action, known as arching action. The presence of these forces significantly increases the ultimate load-carrying capacity of concrete bridge decks until failure typically occurs by punching shear due to the nature of the applied concentrated loads simulating truck wheel loads. Based on the study presented herein, design yield stress of 90 ksi is recommended for design of concrete bridge decks reinforced with HP steel reinforcing bars. However, the requirements of the AASHTO LRFD Bridge Design Specifications for maximum spacing of reinforcement shall be satisfied. Use of HP steel bars will expand the service life of concrete bridges due to its enhanced corrosion resistance.
Behavior of Concrete Members Containing Lightweight Synthetic Particles.
(2010-07-30) Hosny, Amr; Sami Rizkalla, Committee Chair; Paul Zia, Committee Member; Rudolf Seracino, Committee Member; Emmett Sumner, Committee Member
Behavior of High Performance Steel as Shear Reinforcement for Concrete Beams
(2007-07-05) Sumpter, Matthew Scott; Paul Zia, Committee Member; Abhinav Gupta, Committee Member; Emmett Sumner, Committee Member; Sami Rizkalla, Committee Chair
The objective of this research is to study the feasibility of using high performance steel as shear reinforcement for concrete beams. High performance steel is characterized by enhanced corrosion resistance and higher strength in comparison to conventional Grade 60 steel reinforcement. Advantages of using higher strength steel include the ability to design for longer span lengths and/or reducing the amount of material needed for design. This could greatly reduce the overall costs of construction for future structures. Nine reinforced concrete beams were constructed using No. 9 longitudinal bars and No. 3 bars for the stirrups. The main variables considered in the study are the stirrup spacing and the type of reinforcing steel material. Testing was performed using a single concentrated load positioned closer to one end of the beam, which allowed for two tests per beam. Research findings indicate that using MMFX stirrups increases the overall shear strength and enhances serviceability by distributing cracks and reducing crack width. Pairing high performance longitudinal and transverse reinforcement shows an optimum design in terms of strength gain and reduction in crack width. Enhanced serviceability behavior can be attributed to the better bond characteristics of MMFX steel in comparison to conventional Grade 60 steel. Test results suggest that combining high performance steel with high strength concrete could lead to a better utilization of the materials. Analysis shows that the ACI 318-05, CSA, and AASHTO LRFD design codes can conservatively be used for the design of high performance steel up to a yield strength of 80 ksi. Detailed analysis using the Modified Compression Field Theory can be used to accurately predict the behavior of the beams.
Experimental Testing of Unreinforced Masonry Walls Strengthened with Orthogonal Near-Surface Mounted CFRP Subjected to Out-of-Plane Loading
(2009-08-05) Wylie, John Curtis; Rudolf Seracino, Committee Chair; Emmett Sumner, Committee Member; Mervyn Kowalsky, Committee Member
Unreinforced masonry (URM) structures comprise a considerable proportion of the building stock worldwide. However, these structures generally do not behave well under extreme wind or earthquake loading. As part of on-going research, methods of repairing or strengthening URM walls subject to out-of-plane loading using fiber-reinforced polymers (FRP) are being investigated. For several reasons, one method showing particular promise is the use of near-surface mounted (NSM) Carbon FRP strips. Research to-date has made significant progress in quantifying the fundamental behavior of the bonded FRP-to-masonry interface and the behavior of URM walls repaired with vertical FRP strips subject to out-of-plane loading. This thesis presents the experimental results of five large-scale clay brick masonry walls strengthened using NSM CFRP strips and loaded out-of-plane statically to failure using an airbag system. Vertical and Horizontal NSM configurations were tested separately as well as orthogonal grid configurations constructed using two different techniques. The experimentally observed failure mechanisms are described in detail for each wall.
GA-Based Optimization of Steel Moment Frames: A Case Study
(2006-03-07) Hall, Brian Scott; Emmett Sumner, Committee Member; John Baugh, Committee Member; Abhinav Gupta, Committee Chair
Moment resisting frames are utilized in steel construction in order to provide overall stability and to withstand lateral forces related to wind and earthquake loadings. While the industry focuses on producing more economical moment frames by optimizing for the weight of steel, it should be noted that because of present trends the labor cost associated with rigid moment connection fabrication governs the total cost of these frames. Therefore, the objective of this case study is to discover alternative ways of producing more cost-effective moment frames without compromising overall stability. This is achieved by considering both the cost of steel and the cost of connections within the design process. In order to reduce cost, rigid connections within the frame are replaced with standard pinned connections, and member sizes are increased where needed, a method unlike the current least-weight design approach. Optimization techniques are developed in order to identify the most advantageous locations of the remaining moment connections. A Genetic Algorithm, interfaced with a Java-based frame analysis program, is utilized to produce these optimal solutions. At the present time, the consideration of connection-related costs is crucial in determining the most cost effective moment frames. By developing an optimization technique that considers both the number of moment connections and the total weight of the frame, the least weight optimal solution can be improved upon drastically, with an almost 50% reduction in the total cost and an approximately 60% increase in total weight. The unorthodox connection arrangements produced are important, as they provide alternative designs that, while functional, are not currently explored by those in practice.
Lateral Flange Bending in Heavily Skewed Steel Bridges.
(2010-11-03) Morera, Francisco; James Nau, Committee Chair; Sami Rizkalla, Committee Member; Rudolf Seracino, Committee Member; Emmett Sumner, Committee Member
Two-Way Behavior and Fatigue Performance of 3-D GFRP Sandwich Panels
(2009-07-16) Taylor, Elliott; Emmett Sumner, Committee Member; Sami Rizkalla, Committee Chair; Vernon Matzen, Committee Member
This research presents the two-way bending and fatigue behavior of an innovative 3-D glass fiber reinforced polymer (GFRP) pultruded sandwich panel. The panels consist of two GFRP face sheets separated by a foam core with through thickness GFRP fiber insertions to achieve the composite action between the top and bottom layers of the panel. The panels tested under two-way bending include six different configurations to consider the effect of number of skin plies, fiber insertion patterns, panel thicknesses, and the foam type. All panels were simply supported at the four edges, loaded by a single concentrated load at mid span, and tested subjected to a quasi-static loading condition up to failure. The parameters under consideration for testing the two-way panels were also used in a one way configuration under two fatigue loading condition. The fatigue test consists of three point flexural loading configuration in which the panel is subjected to cyclic loading for a minimum of 600,000 cycles or up to failure. The research also presents the finite element analysis (FEA) which was used to describe the behavior of the 3-D GFRP sandwich panel under the effect of the applied load used in the experimental program. The effect of the various parameters including: the aspect ratio, thickness, number of skin plies, skin strength, and insertion density were considered. The experimental results were used to calibrate the analysis and produce design guidelines for practitioners. The proposed design guidelines can be used for design of the panels for various applications such as truck trailer elements, temporary mats, and pedestrian bridge decks.