Development of three-dimensional finite element software for curved plate girder and tub girder bridges during construction

Because of its ability to be easily shaped, steel is an attractive material for curved girders. Plate girder and tub girder bridges, for example, are often the preferred solution for direct connectors in highway networks. This flexibility in fabrication, however, presents challenges for structural engineers because of the difficulties associated with accounting for combined bending and torsion with curved geometry. The potential presence of skewed supports is a further source of complexity. In fact, no commercial structural engineering program currently addresses the evaluation of plate girder and tub girder bridges while modeling them to the full extent of their three-dimensional configuration. Most engineers, for example, use a two-dimensional bridge representation, which is often accurate for typical design of a complete bridge but may also be unconservative in many cases. The few programs that allow a full three-dimensional representation require extensive knowledge of finite element theory as well as significant time to model any complex structure. This dissertation presents the assumptions, methodology and calculations involved in the programming of a new structural engineering program designed to assess the behavior and stability or curved plate girder and tub girder bridges during erection or deck placement. It then illustrates the capabilities of the program for various structural systems subjected to a variety of loads, from self-weight to wind and temperature loads. In addition to a linear elastic analysis, multiple types of analysis are offered to the engineer: a geometrically nonlinear analysis provides a more accurate behavior for flexible systems, a linearized buckling analysis yields an upper bound evaluation of the stability of the structure, while a modal dynamic analysis estimates the free vibration modes of that structure.Civil, Architectural, and Environmental Engineerin

Partial Depth Precast Concrete Deck Panels on Curved Bridges: Finite Element Analytical Model of PCPs

Report on partial depth precast concrete deck panels on curved bridges

Applications of Partial Depth Precast Concrete Deck Panels on Horizontally Curved Steel and Concrete Bridges

0-6816Horizontally curved bridges are commonly used for direct connectors at highway intersections as well as other applications. The majority of curved bridges utilize continuous steel curved I-girder or tub girder systems. In recent years, isolated applications of spliced prestressed concrete U-beams have been successfully used for curved bridge applications in Colorado and are currently being considered for use in Texas bridges. One of the most critical construction stages from a stability perspective is placement of the wet concrete deck at which point the girders must support the full construction load of the system until the deck stiffens and acts compositely. Bridges with a curved geometry experience significant torsional forces and require a substantial amount of bracing to control deformation during construction. Bracing in the form of cross frames for steel I-girder systems, top lateral trusses for steel tub girder systems, and lid slabs for concrete U-beams are provided to improve the girder behavior. While partial depth precast concrete panels (PCPs) are commonly used as stay-in-place formwork for straight bridges, the panels are not currently permitted on horizontally curved girder systems in Texas. TxDOT would like to extend the use of PCPs to bridges with curved girders. This report focuses on the stability of PCPs that rest on polystyrene bedding strips. The project studied the behavior for PCPs with and without a positive connection to steel girders and also considered the behavior of the current TxDOT reinforcing details for PCPs with concrete U-beam systems. The experimental portion of this study consists of large-scale PCP shear tests and large-scale combined bending and torsion tests on both a twin steel I-girder system and on a single steel tub girder. The PCP shear tests were used to develop a simple and effective connection between the PCPs and the girder, as well as to empirically determine the in-plane stiffness and strength of the PCP/connection system. The large-scale girder tests were used to investigate the performance of PCPs and their connection to a system that simulates the load experienced in a realistic construction situation. Also, parametric finite element modeling of the PCPs and the curved girder systems were performed and validated with the results from the experimental tests. The finite element models were used to develop an understanding of the fundamental behavior of the steel girder systems in combination with the PCP systems. In addition to focusing on connection methods to the PCPs, guidelines were also developed for cases where the panels can be used on horizontally curved girder systems without a positive connection to the girders

Contrasting styles of (U)HP rock exhumation along the Cenozoic Adria-Europe plate boundary (Western Alps, Calabria, Corsica)

Since the first discovery of ultrahigh pressure (UHP) rocks 30 years ago in the Western Alps, the mechanisms for exhumation of (U)HP terranes worldwide are still debated. In the western Mediterranean, the presently accepted model of synconvergent exhumation (e.g., the channel-flow model) is in conflict with parts of the geologic record. We synthesize regional geologic data and present alternative exhumation mechanisms that consider the role of divergence within subduction zones. These mechanisms, i.e., (i) the motion of the upper plate away from the trench and (ii) the rollback of the lower plate, are discussed in detail with particular reference to the Cenozoic Adria-Europe plate boundary, and along three different transects (Western Alps, Calabria-Sardinia, and Corsica-Northern Apennines). In the Western Alps, (U)HP rocks were exhumed from the greatest depth at the rear of the accretionary wedge during motion of the upper plate away from the trench. Exhumation was extremely fast, and associated with very low geothermal gradients. In Calabria, HP rocks were exhumed from shallower depths and at lower rates during rollback of the Adriatic plate, with repeated exhumation pulses progressively younging toward the foreland. Both mechanisms were active to create boundary divergence along the Corsica-Northern Apennines transect, where European southeastward subduction was progressively replaced along strike by Adriatic northwestward subduction. The tectonic scenario depicted for the Western Alps trench during Eocene exhumation of (U)HP rocks correlates well with present-day eastern Papua New Guinea, which is presented as a modern analog of the Paleogene Adria-Europe plate boundary

A new porous material based on cenospheres

This thesis deals with the mechanical and physical investigations on a newly discovered porous material based on fly ash cenospheres. The process used to fabricate the material along with the physical properties of the material is first described. Under uniaxial compression, it is observed that the material exhibits a long load plateau that is typical of energy absorbing materials such as thin-walled metallic honeycombs. In tension, the material fractures similar to most traditional brittle materials such as glass and ceramics. As a result, several uniaxial compression and tension tests are performed on different samples to evaluate the influence of the different chemicals, the curing time, and the mass density on the 'plateau' strength. However, in addition to its low processing costs, the new material presents important properties that are desirable for discrete materials such as homogeneity and isotropy. Although its insulating properties were not quantified, it appears that the material can be used as an excellent heat barrier. Finally, metallic tubes as well as bamboo poles reinforced with the new material are tested to investigate the effectiveness of the reinforcement, showing highly improved structural performance.M.S.Committee Chair: Dr. Mulalo Doyoyo; Committee Member: Dr. Arash Yavari; Committee Member: Dr. Kenneth M. Wil

Applications of Partial Depth Precast Concrete Deck Panels on Horizontally Curved Steel And Concrete Bridges

Report examining the possibilities offered by spliced prestressed concrete U-beams used in Colorado for Texas bridge applications