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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Horizontal Stiffness of Wood Diaphragms

Bott, James Wescott 19 May 2005 (has links)
An experimental investigation was conducted to study the stiffness of wood diaphragms. Currently there is no method to calculate wood diaphragm stiffness that can reliably account for all of the various framing configurations. Diaphragm stiffness is important in the design of wood framed structures to calculate the predicted deflection and thereby determine if a diaphragm may be classified as rigid or flexible. This classification controls the method by which load is transferred from the diaphragm to the supporting structure below. Multiple nondestructive experimental tests were performed on six full-scale wood diaphragms of varying sizes, aspect ratios, and load-orientations. Each test of each specimen involved a different combination of construction parameters. The construction parameters investigated were blocking, foam adhesive, presence of designated chord members, corner and center sheathing openings, and presence of walls on top of the diaphragm. The experimental results are analyzed and compared in terms of equivalent viscous damping, global stiffness, shear stiffness, and flexural stiffness in order to evaluate the characteristics of each construction parameter and combinations thereof. Recommendations are presented at the end of this study as to the next steps toward development of an empirical method for calculating wood diaphragm stiffness. / Master of Science
2

Design of One-Story Hollow Structural Section (HSS) Columns Subjected to Large Seismic Drift

Kong, Hye-Eun 24 September 2019 (has links)
During an earthquake, columns in a one-story building must support vertical gravity loads while undergoing large lateral drifts associated with deflections of the vertical seismic force resisting system and deflections of the flexible roof diaphragm. Analyzing the behavior of these gravity columns is complex since not only is there an interaction between compression and bending, but also the boundary conditions are not perfectly pinned or fixed. In this research, the behavior of steel columns that are square hollow structural sections (HSS) is investigated for stability using three design methods: elastic design, plastic hinge design, and pinned base design. First, for elastic design, the compression and flexural strength of the HSS columns are calculated according to the AISC specifications, and the story drift ratio that causes the interaction equation to be violated for varying axial force demands is examined. Then, a simplified design procedure is proposed; this procedure includes a modified interaction equation applicable to HSS column design based on a parameter, Pnh/Mn, and a set of design charts are provided. Second, a plastic hinge design is grounded in the concept that a stable plastic hinge makes the column continue to resist the gravity load while undergoing large drifts. Based on the available test data and the analytical results from finite element models, three limits on the width to thickness ratios are developed for steel square HSS columns. Lastly, for pinned base design, the detailing of a column base connection is schematically described. Using FE modeling, it is shown that it is possible to create rotational stiffness below a limit such that negligible moment develops at the column base. All the design methods are demonstrated with a design example / Master of Science / One-story buildings are one of the most economical types of structures built for industrial, commercial, or recreational use. During an earthquake, columns in a one-story building must support vertical gravity loads while undergoing large lateral displacements, referred to as story drift. Vertical loads cause compression forces, and lateral drifts produce bending moments. The interaction between these forces makes it more complex to analyze the behavior of these gravity columns. Moreover, since the column base is not perfectly fixed to the ground, there are many boundary conditions applicable to the column base depending on the fixity condition. For these reasons, the design for columns subjected to lateral drifts while supporting axial compressive forces has been a growing interest of researchers in the field. However, many researchers have focused more on wide-flange section (I-shape) steel columns rather than on tube section columns, known as hollow structural section (HSS) steel columns. In this research, the behavior of steel square tube section columns is investigated for stability using three design methods: elastic design, plastic hinge design, and pinned base design. First, for elastic design, the compression and flexural strength of the HSS columns are calculated according to current code equations, and the story drift that causes failure for varying axial force demands is examined. Then, a simplified design procedure is proposed including design charts. Second, a plastic hinge design is grounded in the concept that controlled yielding at the column base makes the column continue to resist the gravity load while undergoing large drifts. Based on the available test data and results from computational models, three limits on the width to thickness ratios of the tubes are developed. Lastly, for pinned base design, concepts for detailing a column base connection with negligible bending resistance is schematically described. Using a computational model, it is shown that the column base can be detailed to be sufficiently flexible to allow rotation. All the design methods are demonstrated with a design example.

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