Development of a Nonlinear Bearing for Large Movable Structures

It is not uncommon for large movable structures such as retractable roofs on stadiums to employ linear bearings which allow lateral horizontal movement that will reduce the demand on the structure - in essence creating the roller support of the classic pin-roller simply supported beam. In designing various retractable roofs in the past, Geiger Engineers has sought to improve on the typical linear bearing. Dr. Keith MacBain, one of Geiger's principals, has now developed a nonlinear bearing that will provide the desired translational movement while also allowing for rotation. With the combination of translation and rotation, the structural designer gains a greater ability to tailor the bearing's response. Dr. MacBain and Geiger currently have a patent pending on their nonlinear bearing.

At right are snapshots of the animations illustrating various types of motion achievable with the nonlinear bearing. The motions that may be selected are described relative to the lower-left of the truss (point A). As this point moves to the left, it rotates clockwise for an in-phase motion; counter-clockwise for an out-of-phase motion. Tuned motion shows a general motion however in this case, the radii are selected to accommodate the displacement and rotation of point A with no rotation of the lower portion (and no associated horizontal reaction).