Wind-induced dynamic responses of structures with outrigger systems

A multi-degree of freedom lumped mass model with rotational springs was built to investigate the influence of outrigger system on the natural periods and mode shapes of a structure. The presence of outrigger system was found to significantly stiffen the structure, reducing the natural periods and distorting the mode shapes. The influences of outrigger system on the modal properties of a structure vary with the change of its number, locations and rotational stiffness. Wind-induced along-wind and across-wind responses of structures with and without outrigger system were analyzed, compared and discussed. It was found that the outrigger system can effectively decrease the along-wind responses (peak displacements and accelerations) and its influence is the most significant when it's located at the middle of the structural height. For across-wind responses, the outrigger system(s) could help with the prevention of vortex-induced resonance, if its location(s) is(are) appropriately chosen, by shifting the natural periods of the original structure without outrigger away from the frequency of vortex shedding. Two methodologies were proposed for the design of outrigger systems in two different scenarios, one with the number and locations of outrigger(s) preset and the other not. For the first scenario, the corresponding methodology is a checking process and for the second, it is a designing process. Both methodologies are aimed at preventing vortex-induced resonance and minimizing along-wind peak displacements and accelerations, satisfying related human comfort criteria for motions and lateral drifts requirements.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Civil and Environmental Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2015

Author dc:creator

• Wu, Xiaoxiao, M. Eng Massachusetts Institute of Technology

Advisor dc:contributor.advisor

• Pierre Ghisbain.

• Civil and Environmental Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/99621

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/99621