1,720,992 research outputs found
Predictive testing for heat induced spalling of concrete tunnels – The influence of mechanical loading
Full text linkThis paper describes Phase II of a project being undertaken to develop a predictive test method to investigate heat-induced explosive spalling of concrete, with a specific focus on concrete used in tunneling applications (but obviously applicable to other applications). The test method seeks to allow careful control of the thermal and mechanical transient conditions influencing the occurrence of heat-induced concrete spalling, thus enabling convenient, representative, repeatable, and comparable testing to be carried out on various concrete mixes under various potentially relevant conditions.Phase I of the project focused on establishing suitable thermal exposures to use for testing based on the thermal exposures which a sample would be exposed to during a standard furnace test (cellulosic or modified hydrocarbon) in the Promethee testing facility at CERIB in France. The work described in this paper deals with establishing suitable mechanical loading conditions for a spalling test, the focus in the current work is to enable provision of a representative test for precast segmental concrete tunnel linings (as opposed to sprayed or cut-and-cover tunnel linings). With small adaptations the spalling test method could be adjusted to suit other applications. This paper focuses on the motivation for developing the testing method and outlines the testing to be carried out. Tests are currently underway, and the full suite of results will be presented at the conference
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Learning from Disaster: Moment Resisting Frame Design after the Northridge and Hyogoken-Nanbu Earthquakes
No full textCharacterizing Soil-Foundation-Structure Interaction Using Experimental Data From A Test Structure
No full textMost of what is currently known about soil-structure interaction (SSI) is based on theoretical models. Since SSI can lead to seismically unsafe designs, as demonstrated by the devastating damage caused by soil amplification during the 1985 Mexico City Earthquake and the 1989 Loma Prieta Earthquake, it is important that these theoretical models be validated by field data. The primary objective of this research is to use experimental data from a well instrumented test structure to characterize the effects of SSI. The soil-foundation-structure-interaction (SFSI) test structure at the Garner Valley field site, operated by the Network for Earthquake Engineering Simulation (NEES) at the University of California Santa Barbara (UCSB), is designed to specifically study SSI.
Using data collected from three years of nightly forced vibration tests, the effects of SSI were evaluated using parametric system identification procedures. An average period lengthening and foundation damping of 1.28 and 1.57% were found, respectively. These results are higher than predicted by the theoretical model of Veletsos and Nair (1975). Non-parametric system identification procedures were also used to confirm the fundamental mode of the structure. Both the parametric and non-parametric analyses showed a first mode frequency of about 5.7 Hz for the SFSI test structure.
The effects of environmental conditions on structural response were also investigated. This is important for the structural health monitoring since environmental effects could mask damage and interfere with detection. A definite positive correlation between temperature and the first mode of the structure was found. A less definite but observable relationship was found between the water level in the soil and the first mode. In general, as the water level approaches the surface, the frequency decreases
A Structural Optimization of Félix Candela¿s Chapel of St. Vincent de Paul in Coyoacán, Mexico City
No full textFélix Candela gained fame as a builder of thin shell concrete structures, and
many of his creations are examples of structural art. Using the most sophisticated
optimization procedures, we sought to perform a structural optimization of his
chapel of St. Vincent de Paul in Coyoacán, Mexico City. In this investigation, we
define the optimal design as the one that minimizes tension and deflection in the
structure and reduces the overall materials needed for construction. The variables
that we examined were the thickness of the shell (different uniform thicknesses, as
well as a systematically determined distributed thickness) and the shell geometry.
We also studied the structure both with and without a concrete edge beam.
The results of this study show that Candela¿s design could have been
improved slightly with some small changes in geometry, but overall, the structure
performs very well as built. In our trials without the edge beam, the optimal
thickness distribution thickens the edges first, suggesting that the edge beam is a
crucial component of the shell. In our trials with the edge beam, the distributed
thickness results are not optimal because they require significantly more concrete
than what was used in the built structure.
Lastly, the methods that we employed in this investigation provide for easy
manipulation of structural models and relatively simple optimization. Therefore,
they may prove useful for designers in creating new thin shell concrete structures in
the future
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Roof Design Proposals with Ethylene Tetrafluoroethylene: Enclosing Princeton University Stadium with a Material of the Future
No full textPrinceton University needs more indoor training space. Adding a roof to the
existing Princeton Stadium would provide Princeton with the indoor training space it
needs and would give Princeton a stadium that could be used under all weather
conditions. After considering retractable, seasonal, and permanent roofs, I decide to
design a permanent roof covering for the Princeton Stadium. The permanent covering
will include a large, transparent section made of ETFE.
A tough, plastic polymer, ETFE is an emerging material that is replacing glass
because it is lightweight, translucent, eco-friendly, flexible, and cost-effective. ETFE
roofs can incorporate multiple layers of foil in an inflatable cushion system or can be a
single-skin system stretched into panels or supported by a cable net.
In this thesis I include: my motivation for designing a roof for the Princeton
Stadium, my inspirations for design, a chapter on ETFE, preliminary design proposals for
the Princeton Stadium roof, and a comparison of the designs examined with respect to
their efficiency, economy, and elegance
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