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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.
11

The effects of cutouts in joists on the vibrational response of wood floors

Stiess, Timothy Stephen 09 May 2009 (has links)
This thesis presents the effects of cutouts in joists on the dynamic performance of wood floors. Ten floors and four-floor joist types were used to evaluate the vibrational response of wood floors with and without cutouts in the joists. Each floor was also subjected to different boundary conditions and imposed load during the evaluation. Two types of tests were performed on the floors, a free vibration test and a drop weight test. Data collected from these tests were used to determine several dynamic variables. These variables are the peak displacement, peak acceleration, resonant frequencies, separation of resonant frequencies, root-mean-squared (RMS) acceleration, log-decrement damping ratio, and modal damping ratios. Included in the thesis are the results of a static test (load sharing) performed on the floors with and without cutouts in the joists. / Master of Science
12

Predicting the strength of notched wood beams

Zalph, Barry Louis January 1989 (has links)
A simple expression using a critical fillet hoop stress (CFHS) model was derived to predict the capacity of a simply supported wood beam with a notch on the tension face between the supports. The derivation used the hypothesis that cracking initiates when the hoop stress tangent to the free surface of a round-cornered notch exceeds a critical value. This critical value is characteristic to the material. Finite element modeling was used to explore the effects of a broad range of notch geometries, notch locations, beam sizes, loading configurations, and material elastic properties on fillet hoop stress. The analyses assumed homogeneous, orthotropic, linear elastic behavior, and used a hybrid element to provide accurate results in the region of high stress gradients. Simplified, closed form expressions to predict maximum hoop stress were developed from the numerical results. Notched beam tests included nine wood materials, encompassing hardwoods and softwoods in both green and kiln-dried conditions. A broad array of notch geometries was tested. A theoretical framework related the experimental failure loads with the calculated maximum fillet hoop stress values. The dependence of failure loads on notch geometry, location, and loading condition was described well by the predictive expression derived from the finite element modeling. The CFHS model can be applied to sharp-cornered notches when an appropriate effective fillet radius is substituted into the strength equation. Preliminary test results showed the effective fillet radius to be material dependent; theoretical analysis suggested a beam depth dependence as well. The notched beam strength equation utilizes a single material constant which can be experimentally determined from tests of beams with a single notch geometry. The notched beam strength parameter, κ, was found to be strongly related to specific gravity and cross-grain tensile strength. The regression equation from this work can be used to estimate κ for solid wood materials outside of this study. CFHS results compared favorably with those of earlier models shown to be accurate over a more limited set of cases. In addition to its broad applicability, the CFHS method benefits from its reliance on only one, easily determined, material parameter and avoids the need for directional fracture toughness and elastic parameter data which are very difficult to obtain. / Ph. D.
13

Strain-deflection relationships of freely vibrating wood beams

Minor, Ray Carl January 1966 (has links)
Several researchers engaged in family housing have recently become concerned about the vibrational behavior of residential floors. This concern resulted in a need for methods of sensing floor vibrations. Some investigators have sensed floor vibrations with electric resistance strain gauges bonded to the underside of the floor joists. These experiments using strain gages as vibration sensing devices resulted in a need to be able to determine the vibration amplitude (or deflection) from strain vibration data. The objectives of this project were to theoretically and experimentally determine the relationship between midspan flexural strain and midspan deflection of freely vibrating wood beams with various end conditions. Theoretical strain-deflection relationships of freely vibrating wood beams with pinned-end and fixed-end conditions were derived from vibration theory. Free vibration tests on three wood beams with pinned-ends and fixed-ends gave results which were in agreement with theory. The theoretical relationship between the end rigidity and natural frequency of beams with semi-rigid end connections was derived. Vibration tests performed on wood beams with semi-rigid end connections produced frequency-rigidity results which agreed with theory within five percent. The semi-rigid end connections were achieved by using a torsion bar on each end designed so that the beam would have a static behavior midway between pinned-end conditions and fixed-end conditions. However, it was found both theoretically and experimentally that these torsion bars resulted in a dynamic behavior (strain-deflection ratio and frequency) much closer to pinned-end conditions than to fixed-end conditions. It was established that the strain-deflection relationship of freely vibrating wood beams can be predicted from vibration theory if the rigidity of the end connections is known. / Master of Science
14

Análise de vigas de madeira pregadas com seção composta I / Analysis of nailed timber built-up I beams

Góes, Jorge Luís Nunes de 09 April 2002 (has links)
As vigas compostas pregadas possuem vasta aplicação como material estrutural, desde vigas para instalações residenciais e industriais até longarinas de pontes de pequenos vãos, apresentando como principais vantagens o baixo custo e a facilidade de execução, não exigindo mão-de-obra qualificada. Este trabalho tem como objetivo o estudo teórico e experimental de vigas de madeira com seção composta I formadas por peças de madeira serrada e solidarizadas por pregos. São apresentados os critérios das normas EUROCODE 5, DIN1052 e NBR 7190, bem como a teoria a respeito do assunto. É avaliado o procedimento de cálculo da NBR 7190, em comparação com o EUROCODE 5, sendo realizada verificação experimental dos critérios destas normas, por meio de ensaios de flexão em protótipos de vigas compostas em escala natural. Os resultados obtidos demonstram que o modelo do EUROCODE 5 é o mais indicado para estimar a rigidez efetiva, tensões normais e de cisalhamento como também a força nos conectores / The built-up I beams are widely employed as structural elements, from residential and industrial facilities, to girders for bridges of small span. The fact that they do not demand skilled workmanship, the low cost and easiness of construction are their main advantages. This research aims at the theoretical and experimental analysis of built-up I beams, made of sawn elements nailed jointed. The EUROCODE 5, DIN 1052 and NBR 7190 criteria as well as the basic theory are presented. The design procedure adopted by NBR 7190 is compared to the EUROCODE 5 one. Experimental evaluation of these criteria is made subjecting built-up beam prototype to bending tests. The results should that the EUROCODE criteria is the most recommended for estimate the effective rigidity, normal and shear stresses as well as the load on a fastener
15

Evaluation of remediation techniques for circular holes in the webs of wood I-joists

Polocoser, Tiberiu 12 June 2012 (has links)
The objective of this project was to evaluate methods to remediate a wood I-joist with a single, circular hole in the web while leaving utilities in place. The methods were experimentally evaluated with a full-scale bending test using four equally spaced point loads. There were three depths of joists with varying flange widths and two span lengths (4.88 m & 2.44 m). Failure modes for the long span joists without holes were in the flanges in either tension, compression or lateral buckling; but once a hole was introduced the majority were classified as shear failures. Effectiveness of the remediation was evaluated based on three criteria: strength, stiffness, and ease of installation/cost. The OSB collar patch was effective for 8 out of the 12 series tested. A maximum reduction of load from a joist with no hole to one with a hole was 49% for the long span and 58% for the short span. The OSB collar was not as effective in returning stiffness to the joists, but was easier to install and less expensive than the LSL patch. / Graduation date: 2013
16

Análise de vigas de madeira pregadas com seção composta I / Analysis of nailed timber built-up I beams

Jorge Luís Nunes de Góes 09 April 2002 (has links)
As vigas compostas pregadas possuem vasta aplicação como material estrutural, desde vigas para instalações residenciais e industriais até longarinas de pontes de pequenos vãos, apresentando como principais vantagens o baixo custo e a facilidade de execução, não exigindo mão-de-obra qualificada. Este trabalho tem como objetivo o estudo teórico e experimental de vigas de madeira com seção composta I formadas por peças de madeira serrada e solidarizadas por pregos. São apresentados os critérios das normas EUROCODE 5, DIN1052 e NBR 7190, bem como a teoria a respeito do assunto. É avaliado o procedimento de cálculo da NBR 7190, em comparação com o EUROCODE 5, sendo realizada verificação experimental dos critérios destas normas, por meio de ensaios de flexão em protótipos de vigas compostas em escala natural. Os resultados obtidos demonstram que o modelo do EUROCODE 5 é o mais indicado para estimar a rigidez efetiva, tensões normais e de cisalhamento como também a força nos conectores / The built-up I beams are widely employed as structural elements, from residential and industrial facilities, to girders for bridges of small span. The fact that they do not demand skilled workmanship, the low cost and easiness of construction are their main advantages. This research aims at the theoretical and experimental analysis of built-up I beams, made of sawn elements nailed jointed. The EUROCODE 5, DIN 1052 and NBR 7190 criteria as well as the basic theory are presented. The design procedure adopted by NBR 7190 is compared to the EUROCODE 5 one. Experimental evaluation of these criteria is made subjecting built-up beam prototype to bending tests. The results should that the EUROCODE criteria is the most recommended for estimate the effective rigidity, normal and shear stresses as well as the load on a fastener
17

Load and resistance factor design for wood structures

Penketgorn, Thiwa January 1985 (has links)
Uncertainties in engineering design exist due to the random nature of loads and materials, lack of knowledge, and imperfect modelling of design parameters. Conventional design methods based on deterministic procedures do not always yield designs having consistent safety. In recent years considerable research has been conducted in the use of probability theory for modelling uncertainties in engineering designs and several probabilistic design formats have been developed. Probability based design methods provide a unified procedure applicable to all construction materials, all loads, and all types of uncertainties. Code committees are currently working on the development of the new design codes for various construction materials such as steel, concrete, and wood based on probabilistic concepts. The objective of this study is to study a probability based design format for wood members. Reliability analysis of wood structural elements such as beams, columns, and beam-columns is conducted, and the risk level is measured by the reliability or safety index, β. Wood members subjected to dead plus live load and dead plus snow load combinations are considered. After conducting a reliability analysis of current designs, a target reliability index is selected. The reliability index is then used in conjunction with the predetermined load factors and load combinations to determine resistance factors. Finally, a design format is proposed for Load and Resistance Factor Design for wood structures. / M.S.
18

A computer program for the tentative selection of structural members

Rightmier, Lonnie J. 20 November 2012 (has links)
The subject of this project is the development of a computer program that assists in the preliminary selection of wooden beams for residential scale buildings. It is a useful project because the program is intended to assist the architectural designer; it does not provide comprehensive engineering. With this purpose in mind, the intention is to simplify the process of sizing wooden members, to generate graphic visualization, and to make clear the analytic and decision making process incorporated in the program's construction. The user is presumed to be a designer or architectural student. Efforts towards the design of the program have been aimed at making the software effective for designers and students. This project deals with such issues as logical sequence or flow, decision points, and conceptual organization of display screens for the purpose of focusing the users attention on vital information. / Master of Architecture
19

Stress analysis of a glued timber beam

Williams, Walter Ray, January 2009 (has links)
Thesis (M.S.)--Mississippi State University. Department of Aerospace Engineering. / Title from title screen. Includes bibliographical references.
20

Galerie letecké techniky a tradic letectví na letišti Medlánky v Brně / Gallery aviation technology and traditions of aviation at the airport Medlánky in Brno

Blahová, Dagmar January 2016 (has links)
This thesis describes design gallery of aviation technology and traditions at the airport in Brno Part of my thesis is focused on urban solution of area layout its interconnections with near districts “Komín“ and “Medlánky“. There is new pedestrian, cycling paths, operational and logistic roads inside the complex layout. This design supposed to keep the two existing historic hangars and demolishing remaining buildings with subsequent completion of necessary objects. Priority and the main idea is to keep compositional and visual axis to ensure visual contact with all airport operational parts to ease of orientation. According to this principle is mass and platform solved with object “gallery”. This object in addition to the exhibition space is also used for administration and operation department of the gallery. In separate part there is ensured catering in form of restaurant with associated technical, operational and sanitary facilities. The gallery is designed to visually and physically separate section used by pilots and airport vehicles from visitors to avoid dangerous situation. Other buildings I have designed in my project are “the clubhouse”, airport administration, emergency accommodation, social activity space mainly designed for aircraft-model pilots and the air traffic control tower. These objects creates border between premises restricted for aero club and visitors.

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