Rotational Inertial Devices used for Passive Protection

The use of supplementary rotational masses in passive protection devices for civil structures has been proposed recently and is one of the key current topics of research for the group. These devices convert translational motion into the localized rotational motion of a portion of the device. This translation to rotation conversion can be physically realized with a number of mechanisms including the ball screw mechanism and the rack and pinion mechanism. One of the most important benefit of these rotational devices is that they are able to produce a large effective mass by using a relatively small rotational physical mass; therefore, these devices potentially need a small physical mass to be effective. The use of these devices is currently being investigated in grounded configurations and ungrounded configurations, such as incorporation into a modified tuned mass damper.

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Nonlinear Energy Sinks

Nonlinear energy sinks (NESs) are a type of passive mass damper utilizing essential nonlinear stiffness elements, generally with a cubic relationship between displacement and their restoring force. The essentially nonlinear restoring force provided by these elements allows the NES to interact with any mode of the primary structure to which the NES is attached and participate in targeted energy transfer (TET), the broadband transfer of energy from the primary structure to the NES where it can be rapidly dissipated. Additionally, this nonlinear restoring force allows the linear modes of the primary structure to become coupled and energy to be transferred from the lower modes of vibration to the higher modes where it is dissipated at a faster rate. Research is ongoing within the group studying the use of NESs to mitigate vibration in civil structures caused by both extreme loads and service level loads.

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Laser Metrology for Accelerated Steel Bridge Girder Fabrication

The group is currently studying the use of a laser metrology technique in the production of splice connections for steel bridge girders. With this technique, plate girders are created with steel plates that already have holes in them for splice plate connections. Once the girders are prepared, the locations of the splice connection holes is determined using a laser tracker. These hole locations are used to design and manufacture custom splice plates for this connections. The primary benefit of this new method is that time consuming match drilling of girder splice connections is replaced with automated drilling methods.

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