A. James Clark School of 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 Reliability-Based Design Of Piping: Internal Pressure, Gravity, Earthquake, and Thermal Expansion(2007-08-09) Avrithi, Kleio; Ayyub, Bilal M.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Although reliability theory has offered the means for reasonably accounting for the design uncertainties of structural components, limited effort has been made to estimate and control the probability of failure for mechanical components, such as piping. The ASME B&PV Code, Section III, used today for the design of safety piping in nuclear plants is based on the traditional Allowable Stress Design (ASD) method. This dissertation can be considered as a primary step towards the reliability-based design of nuclear safety piping. Design equations are developed according to the Load and Resistance Factor Design (LRFD) method. The loads addressed are the sustained weight, internal pressure, and dynamic loading (e.g., earthquake). The dissertation provides load combinations, and a database of statistical information on basic variables (strength of steel, geometry, and loads). Uncertainties associated with selected ultimate strength prediction models -burst or yielding due to internal pressure and the ultimate bending moment capacity- are quantified for piping. The procedure is based on evaluation of experimental results cited in literature. Partial load and resistance factors are computed for the load combinations and for selected values of the target reliability index, β. Moreover, design examples demonstrate the procedure of the computations. A probabilistic-based method especially for Class 2 and 3 piping is proposed by considering only cycling moment loading (e.g., thermal expansion). Conclusions of the study and provided suggestions can be used for future research.