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RSS-feedMon, 06 Oct 2014 08:22:22 GMT2014-10-06T08:22:22ZAeroelastic Response of High-Rise Buildings
https://projekter.aau.dk/projekter/da/studentthesis/aeroelastic-response-of-highrise-buildings(56d38c05-06c3-4763-8a98-07ba6eb261d3).html
<div style='font-size: 9px;'><div class="rendering rendering_studentproject rendering_short rendering_studentproject_short"><div class="common_wrap_floats"><h2 class="title"><a rel="StudentProject" href="https://projekter.aau.dk/projekter/da/studentthesis/aeroelastic-response-of-highrise-buildings(56d38c05-06c3-4763-8a98-07ba6eb261d3).html" class="link"><span>Aeroelastic Response of High-Rise Buildings</span></a></h2><p class="relations persons">Anders Trondal Svendsen, Allan Michaelsen</p><p>Bygge- og anlægskonstruktion, Kandidat, (Kandidatuddannelse) 4. semester, 2008</p></div><p class="type"><span class="type_family">Studenteropgave<span class="type_family_sep">: </span></span><span class="type_classification">Speciale (inkl. HD afgangsprojekt)</span></p></div><div class="rendering rendering_studentproject rendering_detailsportal rendering_studentproject_detailsportal"><ul class="relations persons"><li>Anders Trondal Svendsen</li><li>Allan Michaelsen</li></ul><div class="textblock educations">4. semester, <a rel="Education" href="https://projekter.aau.dk/projekter/da/educations/bygge-og-anlaegskonstruktion-kandidat(de1daae1-63ab-4ecf-9eba-64618d87a271).html" class="link"><span>Bygge- og anlægskonstruktion, Kandidat</span></a> (Kandidatuddannelse)</div><div class="textblock abstract">The present report deals with the aeroelastic response of high-rise buildings. The
wind flow around an assumed square cylindrical high-rise building is modeled using
the commercial CFD-program Ansys CFX 11. To model the Fluid-Structure
Interaction (FSI) a FEM beam model is used to represent the structure while the
dynamic model is set up using a modal representation.
A method for generating 3D meshes suitable for exterior flow around a rectangular
cylindrical building is presented, with basis in an algorithm for generating
2D meshes using a hyperbolic grid generation scheme. Some simple mechanisms
to ensure a smoother mesh are presented as well. The difference between using
structured and unstructured meshes are analyzed, and it is concluded that use
of structured meshes is superior with respect to computation time.
An analysis is then performed to see, which methods for governing mesh stiffness
during mesh deformations in Ansys-CFX is best, and on basis of 2D analyses it
is concluded that the use of the reciprocal of the wall distance as stiffness parameter,
or use of the built-in function ’Increase Near Boundaries’ show superior
performance.
Due to limited availability of computational power in the project, analyses are
made determining the effects of using simulation settings that are less than ideal.
In these analyses it is shown that these delimitations show little influence on the
loads on the building in the streamwise direction, but that the loads in the cross
stream direction show strong dependency.
The effect of modeling the aeroelastic response of a high-rise building is determined,
by comparing the response of two different simulations, one where the
structure is allowed to move freely, and one where it is stationary. It is concluded
that there is an obvious difference between the two methods.
Finally the aeroelastic load response of a high-rise building are obtained by use
of flutter derivatives, and it is shown that this method gives qualitatively good
results, and seems applicable to use on high-rise buildings. The response is found
using the two first eigenmodes only, and the effects of including more eigenmodes
is not analyzed.</div><table class="properties"><tbody><tr><th scope="row">Sprog</th><td>Engelsk</td></tr><tr class="udgivelsesdato"><th scope="row">Udgivelsesdato</th><td><span class="date">2008</span></td></tr><tr><th scope="row">Antal sider</th><td>254</td></tr><tr><th scope="row">Udgivende institution</th><td>Aalborg Universitet</td></tr></tbody></table></div></div>Wed, 11 Jun 2008 12:22:07 GMThttps://projekter.aau.dk/projekter/da/studentthesis/aeroelastic-response-of-highrise-buildings(56d38c05-06c3-4763-8a98-07ba6eb261d3).html2008-06-11T12:22:07ZInvestigation on Long-Span Suspension Bridges
https://projekter.aau.dk/projekter/da/studentthesis/investigation-on-longspan-suspension-bridges(fb12a52d-4272-4c26-a7f3-f8965c8643f9).html
<div style='font-size: 9px;'><div class="rendering rendering_studentproject rendering_short rendering_studentproject_short"><div class="common_wrap_floats"><h2 class="title"><a rel="StudentProject" href="https://projekter.aau.dk/projekter/da/studentthesis/investigation-on-longspan-suspension-bridges(fb12a52d-4272-4c26-a7f3-f8965c8643f9).html" class="link"><span>Investigation on Long-Span Suspension Bridges: The Great Belt East Bridge</span></a></h2><p class="relations persons">Kenneth Simonsen, Robert Stevens</p><p>Bygge- og anlægskonstruktion, Kandidat, (Kandidatuddannelse) 4. semester, 2008</p></div><p class="type"><span class="type_family">Studenteropgave<span class="type_family_sep">: </span></span><span class="type_classification">Speciale (inkl. HD afgangsprojekt)</span></p></div><div class="rendering rendering_studentproject rendering_detailsportal rendering_studentproject_detailsportal"><ul class="relations persons"><li>Kenneth Simonsen</li><li>Robert Stevens</li></ul><div class="textblock educations">4. semester, <a rel="Education" href="https://projekter.aau.dk/projekter/da/educations/bygge-og-anlaegskonstruktion-kandidat(de1daae1-63ab-4ecf-9eba-64618d87a271).html" class="link"><span>Bygge- og anlægskonstruktion, Kandidat</span></a> (Kandidatuddannelse)</div><div class="textblock abstract">In this rapport, the aeroelastic phenomenon, flutter is investigated for the Great Belt East Bridge.
The bridge is examined at two different stages during construction: when only 15% of the bridge
deck is mounted and when the bridge is fully erected. A numerical approach, CFD, is used for both
stages.
According to the well-known Scanlan theory, the aerodynamic loads are described by a set of aerodynamic parameters, which can be derived by use of different approaches. These aerodynamic derivatives are found by a two dimensional analysis of the cross section of the bridge, by a forced
oscillation test. The derivatives are used in determination of the critical flutter wind velocity for the fully erected bridge. The purpose of this 2d-test is to validate the CFD as a mean of computing critical flutter wind velocities. The resulting critical flutter wind velocity of 71.9 m/s found, is not far
from the velocity found in wind tunnel tests, of 70 m/s to 74 m/s.
For the investigation of the bridge during erection, two three dimensional analysis are performed. A forced vibration test is performed in a similar way as for the two dimensional case. In this analysis the fluid is allowed to flow around the free end of the bridge, introducing some end effects. The structural behavior of the bridge during construction shows that the lowest vertical eigenfrequency is very close to the lowest torsional eigenfrequency. This implies that the critical flutter wind velocity should be somewhat lower for the bridge during construction. This velocity is found at 47.6 m/s. Wind tunnel tests of this construction stage show a critical flutter wind velocity of 43.3 m/s.
The rapport further investigates the possibility of using a fully coupled fluid-structure interaction when determining critical flutter wind velocities. A two degree of freedom system is used to determine the motion of the bridge deck, which is assumed rigid. A first order backward Euler integration scheme is applied in Ansys 11 when prescribing the movements of the system. The mesh of the fluid domain is very coarse, in order to reduce the computation time. The simulations have been run, but with some difficulties with respect to damping. The test show a critical flutter
wind velocity of approximately 20 m/s to 25 m/s which is far lower than the wind tunnel tests. The test
is, however described in the report, as the method gives a very good visual and physical understanding of the aeroelastic phenomenon.</div><table class="properties"><tbody><tr><th scope="row">Sprog</th><td>Engelsk</td></tr><tr class="udgivelsesdato"><th scope="row">Udgivelsesdato</th><td><span class="date">2008</span></td></tr><tr><th scope="row">Udgivende institution</th><td>Aalborg Universitet</td></tr></tbody></table></div></div>Tue, 10 Jun 2008 21:28:08 GMThttps://projekter.aau.dk/projekter/da/studentthesis/investigation-on-longspan-suspension-bridges(fb12a52d-4272-4c26-a7f3-f8965c8643f9).html2008-06-10T21:28:08Z