When bearing links are located at the bottom of the girder, and have nonzero stiffness in the longitudinal direction, this results in longitudinal force acting on a lever arm about the neutral axis of the section. This is kinematically correct behavior. Releasing the abutment bearing links in the longitudinal direction (U3) should produce zero moment at the abutments. For stability, ensure that the model has a longitudinal restraint, such as at one abutment or bent.

To avoid removing longitudinal restraint, set the bearing elevation to the neutral axis of the superstructure section. This de-couples longitudinal and bending behavior, though it may not be physically realistic.

See also

• Effect of insertion point on beam reactions test problem for additional information.