Thesis (M.S.)--University of Alabama at Birmingham, 2008. / Additional advisors: James Davidson, Jason Kirby, Talat Salama. Description based on contents viewed Feb. 11, 2009; title from PDF t.p. Includes bibliographical references (p. 97-99).

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains xv, 141 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 139-141).

Thesis (M.C.E.)--University of Delaware, 2006. / Principal faculty advisor: Dennis R. Mertz, Dept. of Civil and Environmental Engineering. Includes bibliographical references.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (site viewed on Oct. 6, 2006). PDF text:xxiii, 306 p. : ill. ; 15.42Mb. UMI publication number: AAT 3213328. Includes bibliographical references. Also available in microfilm, microfiche and paper format.

Gusset plate connections are commonly used in steel truss bridges to connect individual members together at a node. Many of these bridges are classified as non-load-path-redundant bridges, meaning a failure of a single truss member or connection could lead to collapse. Current gusset plated design philosophy is based upon experimental work from simplified, small-scale connections which are seldom representative of bridge connections. This makes development of a refined methodology for conducting high-fidelity strength capacity evaluations for existing bridge connections a highly desirable goal. The primary goal of this research effort is to develop an analytical model capable of evaluating gusset plate stresses and ultimate strength limit states. A connection-level gusset connection model was developed in parallel with an experimental testing program at Oregon State University. Data was collected on elastic stress distributions and ultimate buckling capacity. The analytical model compared different bolt modeling techniques on their effectiveness in predicting buckling loads and stress distributions. Analytical tensile capacity was compared to the current bridge gusset plate design equations for block shear. Results from the elastic stress analysis showed no significant differences between the bolt modeling techniques examined, and moderate correlation between analytical and experimental values. Results from the analytical model predicted experimental buckling capacity within 10% for most of the bolt modeling techniques examined. Tensile capacity was within 7% of the calculated tensile nominal capacity for all bolt modeling techniques examined. A preliminary parametric study was conducted to investigate the effects of member flexural stiffness and length on gusset plate buckling capacity, and showed an increase in member length or decrease in member flexural stiffness resulted in diminished gusset plate buckling capacity.

In recent years there has been a constant search for better and more economical structures in the field of structural engineering. Within the past ten to twenty years this search has resulted in the introduction of two new structural systems: prestressed concrete and composite design. Each of these new construction methods has advantages and limitations. A new idea of combining these two structural systems into one could result in more economical structures particularly suited for long span bridges. The slab-and-stringer bridge is one of the most common types in highway construction. Such a bridge is composed of two principal load-carrying elements: the steel beams which transfer the loads in the direction along the bridge axis, and the concrete slab which distributes the loads in the transverse direction to the steel beams. If some appropriate mechanical device is used to connect the steel beams end concrete slab together, the concrete slab can act as a cover plate for the beams and assist the beams in carrying the load in the longitudinal direction. Such a structure is known as a Conventional Composite Structure. If such a structure is prestressed with high-strength steel cables, it acquires additional qualities. The principle of prestressing in steel structures is not used to overcome tensile deficiencies of the material, as ls the case for concrete, but to build opposing stresses into members in order to counteract the stresses caused by external forces. When favorable residual stresses have been induced in such structures they will be capable of carrying greater loads than their conventional counterpart. It is the objective of this thesis: (1) to investigate the physical properties of the materials used in prestressed composite structures, (2) to discuss the methods for construction, (3) to develop a usable design technique for simply supported and continuous beams, (4) to discuss the layout of prestressing cables in continuous prestressed composite beams, (5) to show the use of equations for selecting the steel beam cf the prestressed composite structure, and (6) to illustrate the design of prestressed composite structures with typical problems. / Master of Science

The construction of horizontally curved bridges with skewed supports requires careful consideration. These types of bridges exhibit three-dimensional response characteristics that are not commonly seen in straight bridges with normal supports. As a result, engineers may face difficulties during the construction, when the components of the bridge do not fit together or the final geometry of the structure does not correspond to that intended by the designer. These complications can lead to problems that compromise the serviceability aspects of the bridge and in some cases, its structural integrity. The three dimensional response that curved and skewed bridges exhibit is directly influenced by the bracing system used to configure the structure. In I-girder bridges, cross-frames are provided to integrate the structure, transforming the individual girders into a structural system that can support larger loads than when the girders work separately. In general, they facilitate the construction of the structure. However, they can also induce undesired collateral effects that can be a detriment to the performance of the system. These effects must be considered in the design of a curved and skewed bridge because, in some cases, they can modify substantially its response. This research is focused on understanding how the bracing system affects the performance of curved and skewed I-girder bridges, as well as, the ability of the approximate analysis methods to capture the structural behavior. In this research, techniques that can be implemented in the creation of 2D-grid models are developed to overcome the limitations of this analysis method. In addition, efficient cross-frame arrangements that mitigate the collateral effects of skew are developed. These mitigation schemes reduce the undesired cross-frame forces and flange lateral bending stresses associated with the transverse stiffness of the structure, while ensuring that the bracing system still performs its intended functions.

Weathering steel has been a primary construction material for bridges in the United States. Notches caused by corrosion are observed on the flange of steel I-beams. These notches reduce the cross section area of the structure and are threats to bridge safety. A606-04 Type 4 cold rolled weathering steel samples were studied in this thesis to understand the effect of notches that caused by corrosion. Weathering steel samples were in the shape of plates, which simulated flange of I-beams. The plate samples were notched across their surfaces by applying electrical current through an electrochemical circuit composed of an anode, a cathode and electrolyte. Sixteen samples were notched and cut into appropriate shape for fatigue testing. S-N (Stress-Number of cycles to failure) diagram established from fatigue data indicated that the fatigue strength decreased below AASHTO category B. Weibull analysis was also performed to understand the reliability distribution. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

Civil engineers are presently faced with the challenge of strengthening and repairing many existing structures to assure or increase their structural safety. The reasons for this include changes in the use of structures, and increased traffic loads on bridges. In Iraq, for example, several highway bridges needed to accommodate increased axle load during the transportation of huge turbines for electricity generating stations. The requirement for structural strengthening and repair methods is, however, driven by the worldwide need to ensure the safety and sustainability of our aging infrastructure which is deteriorating at a rate faster than it can be renovated. The ever increasing damage caused by environmental effects and the corrosion of steel and deterioration of concrete, reduce structural safety and lead to disruption for the users, which can have serious economic consequences. In a plate girder bridge, the plate girders are typically I-beams made up from separate structural steel plates (rather than rolled as a single cross-section), which are welded or, in older bridges, bolted or riveted together to form the vertical web and horizontal flanges of the beam. The two primary functions of the web plate in a plate girder are to maintain a relative distance between the top and bottom flanges and to resist the induced shear stresses. In most practical ranges of plate girder bridges’ spans, the induced shear stresses are relatively low compared to the bending stresses in the flanges induced by flexure. As a result the web plate is generally chosen to be much thinner than the flanges. The web panel consequently buckles at a relatively low shear force. For steel girder structures dominated by cyclic loading, as is the case with repeated vehicle axle loads on bridges, this can lead to the so-called ‘breathing’ phenomenon; an out-of-plane buckling displacement that can induce high secondary bending stresses at the welded plate boundaries. In the current work, a novel FRP strengthening technique using bonded shapes is applied to resist these out of plane deformations, and hence reduce the breathing stresses, and improve the fatigue life of the plate girder which is very different to the majority of applications of FRP strengthening that exploit the FRP for its direct tensile strength and stiffness. The objective of the current experimental programme is to strengthen thinwalled steel girders against web shear buckling using a corrugated CFRP or GFRP panel bonded externally along the compression diagonal of the web plate. The programme was divided into three main phases, including: (1) the development of a new preformed corrugated FRP panel, and (2, 3) testing its performance in two main experimental series. The initial series involved tests on 13 steel plates strengthened with the proposed preformed corrugated FRP panel and subjected to in-plane shear loading using a specially manufactured “picture-frame” arrangement designed to induce the appropriate boundary conditions and stresses in the web plates. This initial test series investigated the performance of different forms of strengthening under static load, in preparation for another series of cyclic tests to investigate their fatigue performance. The test variables included FRP type (CFRP or GFRP), form of FRP (closed or open section), number of FRP layers, and orientation of GFRP fibres used to produce the FRP panel. In the second series, six specimens were manufactured to simulate the end panel of a plate girder. These were strengthened with the optimized FRP panel from the initial series and tested for shear buckling under repeated cyclic loading with a stress range 40-80% of the static ultimate capacity. A considerable increase in the stiffness of the strengthened specimens is evident in the observed reductions of the maximum out-of-plane displacement. The stiffness of the strengthened specimens is assessed to be increased by a factor ranging between 3 to 9 times the stiffness of the corresponding unstrengthened specimen, depending upon the type of the FRP panel used and the aspect ratio of the tested specimens. The breathing phenomena is also significantly reduced, consequently the surface, membrane and secondary bending stresses are reduced. The 45° strengthening scheme succeeded the best both in reducing the breathing stresses and increasing the ultimate shear capacity of the specimen by 88%. Fatigue analyses indicated that the proposed strengthening technique is able to considerably elongate the life expectancy of the strengthened plate girders by a factor ranging between 2.5 and 7 depending on the applied cyclic load amplitude. In addition, the proposed strengthening technique did not show any debonding or delamination under both static and cyclic loading which makes it a good candidate for strengthening thin-walled structural members, especially, when ductility is a concern. In fact, the proposed strengthening technique succeeded in improving the energy absorption capacity of the strengthened specimens by a factor ranging between 1.5 and 2.5 times the corresponding control specimen which means that the ductile failure type associated with shear buckling of steel plate girders is not only maintained, but it was improved as well. This type of ductile failure is not common in other types of FRP strengthening techniques. Finally, a geometrical and material non-linear finite element model is presented both for the steel and composite sections which showed very good correlation with test results and was capable of predicting both the strength and deformational behaviour of the tested specimens. This numerical model is used for a parametric study to support the proposed design method.