Civil & Environmental Engineering
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Item LATERAL LOAD PATTERNS FOR THE CONCEPTUAL SEISMIC DESIGN OF MOMENT-RESISTING FRAME STRUCTURES(2007-11-27) Park, Kyungha; Medina, Ricardo A.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This study deals with the development of lateral load patterns for the conceptual seismic design of moment-resisting frame structures. The proposed lateral load patterns are based on inelastic behavior and are a fundamental component of a proposed seismic design methodology to limit the extent of structural damage in the system and distribute this damage uniformly along the height. These load patterns are expected to provide a uniform distribution of story ductility ratios when compared to the distributions obtained with moment-resisting frames designed based on the code-compliant design lateral load patterns. The implementation of the aforementioned methodology would not only distribute damage along the height of the frame, but also help avoid undesirable dynamic responses that occur once structural damage is concentrated in one or in a few stories, e.g., story drift amplifications caused by P-delta effects. The family of structural models used in this study is composed of six to eighteen-story moment resisting frame structures with fundamental periods of vibration that vary from 0.6 s. to 3.0 s. On the input side, two basic types of ground motions are used: far-field and near-field ground motions. The proposed design lateral load patterns are a function of the fundamental period of the structural system, the target level of inelastic behavior (or damage), the total height of structures, and the frequency content of the ground motions.Item Corrosion Resistance of Weathering Steels(2004-08-30) Park, Kyungha; Albrecht, Pedro; Fu, Chung C.; Amde, Amde M.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)To reduce both the initial and the maintenance painting costs, engineers in many states have increasingly been designing bridges made of bare, exposed weathering steel. However, after many years of experience, engineers are concerned about the long-term performance of weathering steel bridges. Nevertheless, as with all new materials, much research has been conducted to find solutions for atmospheric corrosion to enhance the successful application of weathering steel to bridges for more economic and environmental benefits Numerous representative data show the corrosion behavior not only of weathering steel, but also copper steel, and carbon steel under localized microenvironment conditions investigated by many researchers: angle of exposure, orientation, shelter, continuously moist conditions, industrial pollutants, deicing salts, galvanic corrosion, pitting and crevices. The results and discussions demonstrate that uncoated weathering steels should not be exposed in the following conditions: marine or heavily industrial environment, high rainfall or humidity conditions, sheltered conditions, and some other bad design conditions. Therefore, for proper bridge design, the micro-environment as well as the macro-environment should be considered with caution and a study of previous experience by a corrosion engineer as a significant factor in preventing further corrosion.