Stiffeners are provided to transfer transverse concentrated compressive force on the flange into the web and are essential for desired performance of web panels. These are referred to as bearing stiffeners.
(1) is true.It is provided to support
(2) is true.Bearing stiffeners are required whenever concentrated loads, which could cause vertical buckling of web of the girder, are applied to either flange.
(3) is partially true. If the check indicates that the web may fail in bearing,then a bearing stiffener must be provided.The stiffener should be checked to ensure that it can carry the applied load less the capacity of the unstiffened web ( But this check is required only for intermediate stiffeners )