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.)--Lehigh University, 2006. / Includes vita. Includes bibliographical references (leaves 360-363).

The purpose of the research reported here was to determine if single angles can be used for chord and web members in lightweight steel open web rafters, and if so to determine what effect the single angles have on the design of the rafter's members. A computer model was constructed to determine the effects of a unsymetric cross section coupled with eccentric loadings of the members on out-or-plane displacements, and bending moments and stresses in the chord and web members. This computer model modeled the eccentricities and unsymetric section properties of the single angles. A study of the effect of out-or-plane bracing on the bending moments and stresses was also conducted. Finally various web configurations (angle web members on the same side, alternating, and opposite) were studied to determine their effect on moments in the web and chord members, along with their effect on out-or-plane displacements. A preliminary design procedure for chord and web members using the new AISC ""Specification For Allowable Stress Design of Single Angle Members" is presented. Finally suggestions on out-of-plane bracing and connections are made. / Master of Science

No description available.

Thesis (Ph. D.)--University of Alabama at Birmingham, 2008. / Title from PDF title page (viewed Jan. 28, 2010). Additional advisors: Michael Anderson, Fouad Fouad, Wilbur Hitchcock, Virginia Sisiopiku. Includes bibliographical references (p. 203-208).

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.

Curved and skewed I-girder bridges exhibit torsional displacements of the individual girders and of the overall bridge cross-section under dead loads. As a result, the girder webs can be plumb in only one configuration. If the structure is built such that the webs are plumb in the ideal no-load position, they generally cannot be plumb under the action of the structure's steel or total dead load; hence, twisting of the girders is unavoidable under dead loads. The deflected geometry resulting from these torsional displacements can impact the fit-up of the members, the erection requirements (crane positions and capacities, the number of temporary supports, tie down requirements, etc.), the bearing cost and type, and the overall strength of the structure. Furthermore, significant layover may be visually objectionable, particularly at piers and abutments. If the torsional deflections are large enough, then the cross-frames are typically detailed to compensate for them, either partially or fully. As specified in Article C6.7.2 of the AASHTO LRFD Specifications, different types of cross-frame detailing methods are used to achieve theoretically plumb webs under the no-load, steel dead load, or total dead load conditions. Each of the cross-frame detailing methods has ramifications on the behavior and constructability of a bridge. Currently, there is much confusion and divergence of opinion in the bridge industry regarding the stage at which steel I girder webs should be ideally plumb and the consequences of out-of-plumbness at other stages. Furthermore, concerns are often raised about potential fit-up problems during steel erection as well as the control of the final deck geometry (e.g., cross-slopes and joint alignment). These influences and ramifications of cross-frame detailing need to be investigated and explained so that resulting field problems leading to needless construction delays and legal claims can be avoided. This dissertation addresses the influence of cross-frame detailing on curved and/or skewed steel I girder bridges during steel erection and concrete deck placement by conducting comprehensive analytical studies. Procedures to determine the lack-of-fit forces due to dead load fit (DLF) detailing are developed to assess the impact of different types of cross-frame detailing. The studies include benchmarking of refined analytical models against selected full scale experimental tests and field measurements. These analytical models are then utilized to study a variety of practical combinations and permutations of bridge parameters pertaining to horizontal curvature and skew effects. This research develops and clarifies procedures and provides new knowledge with respect to the impact of cross-frame detailing methods on: 1) constructed bridge geometries, 2) cross-frame forces, 3) girder stresses, 4) system strengths, 5) potential uplift at bearings, and 6) fit-up during erection. These developments provide the basis for the development of refined guidelines for: 1) practices to alleviate fit-up difficulties during erection, 2) selection of cross-frame detailing methods as a function of I-girder bridge geometry characteristics, and 3) procedures to calculate the locked-in forces due to DLF cross-frame detailing.