Type of Document Master's Thesis Author Ely, Paul T. URN etd-1719959711591 Title Internal Damping Rates of Construction Cranes Degree Master of Science Department Civil Engineering Advisory Committee
Advisor Name Title Brandon, Thomas L. Lutz, James D. Beliveau, Yvan J. Committee Chair Keywords
Date of Defense 1997-05-27 Availability unrestricted Abstract
The conveyance of payloads by construction cranes
generates pendulations of the payload. This research
provides a critical design parameter for the development of
a device that aids in reduction of these pendulations.
Previous research developed a tuned mass damping
system, that effectively attenuated the energy of a
pendulating payload. In order to be effective the internal
damping rate of the tuned mass damper must be at least
twice that of the system to be damped. Prototypes of a
tuned mass damping system have achieved damping rates
between 6 and 12 %, making cranes with damping rates
below 3% attractive. This research indicates that the
internal damping rate of construction cranes is on the order
of one percent, suggesting that a tuned mass damping
system could be retrofitted to today's construction cranes.
This thesis is an investigation of the internal damping rates
of construction cranes. Three hydraulic and two lattice
boom cranes were tested. The motion of pendulating
payloads was modeled after a simple pendulum. The
internal damping rate was calculated using logarithmic
decrement technique. Light to medium duty cranes were
tested with loads similar to those used in duty cycle
operations. Damping tests were performed both
perpendicular and parallel to the mast of the crane. Values
were calculated from data extracted from videos of a
payload oscillating over a measurement scale.
A FMC Link Belt 25-ton hydraulic crane was tested at 6.4
% of capacity and displayed damping rates between 0.25
and 0.6 %. A 50-ton FMC Link Belt was tested at 10 %
of capacity and had damping rates of 0.18 % for both
tests. The third hydraulic crane was a 60-ton P&H
T-600XL. The test parallel to the mast was performed at 6
% of capacity having a damping rate of 0.22 %. The
test-performed perpendicular to the mast was at 3.5 % of
capacity with a damping rate of 0.65 %.
Two lattice boom cranes with capacities of 70 and 100
tons were tested. The 70-ton LIMA 778c's damping rates
were 0.06 and 1.3 percent. This test was performed at 15
% of capacity. The 100-ton Link Belt LS318 was tested at
6.8 % of capacity and had damping rates between 0.07
and 0.08 percent.
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