Wind-Induced Dynamics of Large Observation Wheel
We served as the structural dynamics analysis consultants for a Large Observation Wheel project. Two large tuned-mass dampers are incorporated into the A-frame supports to provide wind-induced structural load mitigation under storm conditions and improved comfort for the occupants under normal operating-wind conditions. As the dynamics consultant, we provided input to the TMD specification and motion predictions of the Wheel and the TMDs.
Vortex-Induced Resonant Excitation of a Circular Cylindrical Tower
An aerospace test facility was experiencing what they thought was vortex-induced motion of a 150-foot tall circular tower and requested a concept design for a tuned-mass damper to provide base bending moment mitigation. We analyzed force pin data recorded during two of the events provided by the client and reviewed historical weather conditions for those days. Our analysis confirmed that wind speeds and air temperatures were consistent with turbulent vortex street formation and produced a vortex shedding frequency that matched the fundamental resonance frequency of the tower. We developed a concept design for a tuned-mass damper that would reduce the base bending moment by about 90%.
Structural Dynamics Analyses:
Modal Analysis - Provides the mode shapes and corresponding resonance frequencies for the structure and is used in the forced-response analyses.
Frequency Response Analysis - A form of forced-response analysis where the excitation is harmonic (single frequency) and the structure responds linearly. This analysis is used to determine the steady-state response at any location to harmonic excitation. Useful for assessing the structural response to vortex shedding (wind-induced excitation), mechanical system excitation (e.g., a pump), and provides insight into worst-case response to pedestrian-induced vibration.
Random Vibration Analysis - A form of forced-response analysis where the excitation is characterized in the form of a power spectrum and the structural response is linear. This analysis is used to assess the response caused by turbulent air/fluid-induced vibration and ground-borne vibration.
Shock Response Analysis - A form of forced-response analysis where the excitation is characterized in the form of a shock spectrum. The structural response is linear. This analysis primarily is used to assess structural response to earthquakes. The American Society of Civil Engineers (ASCE) defines earthquake shock spectra for any location in the United States. Seismic design parameters can be obtained from the USGS.
Transient Dynamic Analysis - The most general, but computation-intensive form of forced-response structural dynamics analysis, but it is the only analysis capable of capturing nonlinear structural response characteristics (e.g., material yielding and local failure) and the presence of discrete fluid viscous dampers (e.g., in tuned-mass dampers). Shock response spectra can be synthesized into equivalent ground motion time series to assess the response of any structure to any earthquake design requirement.
Seismic Analysis - Seismic analysis may be performed as a Shock Response Analysis or a Transient Dynamic Analysis, depending upon the nature of the structure being analyzed.
We provide specialized structural dynamics analysis and consulting services for other structural engineering firms, aerospace engineering companies, and mechanical system design companies that do not have in-house structural dynamics expertise. Examples of our services include:
Structural dynamics analysis and performance assessment of flexible structures (observation wheel, roller coaster, tall buildings)
Development of performance specifications performance assessment for structures with tuned-mass dampers
Vortex-induced vibration assessment of towers
Seismic- and wave-induced motion analysis of industrial facilities with fluid-filled vessels and offshore platforms
Structural dynamics analysis of mechanical and pipe systems
Special-purpose dynamics analyses of aerospace facilities and vehicles
Blast dynamics response of mission-critical structures
Contact Dr. James Lamb at 214.412.8388 or via email at jlamb@age-se.com
For more information please call Dr. Jay Lamb at (214) 520-7202.