Bearing stiffeners in plate girders are provided at the end supports.

Explanation:
Plate girders are structural members commonly used in bridges and buildings to support heavy loads. They are made up of a web plate (which acts as the main load-carrying element) and two flange plates (which provide additional strength and stiffness).

Bearing stiffeners are vertical plates that are attached to the web plate at the points where the girder is supported. Their primary function is to provide additional support to the web plate and prevent local buckling or distortion of the girder at the end supports.

Here is why bearing stiffeners are provided at the end supports of plate girders:

1. Load Distribution: The end supports of a plate girder are subjected to high concentrated loads. Bearing stiffeners help distribute these loads evenly along the web plate, reducing localized stresses and minimizing the risk of failure.

2. Lateral Support: Plate girders are susceptible to lateral buckling, especially near the supports where the bending moment is high. Bearing stiffeners provide lateral support to the web plate, preventing buckling and maintaining the stability of the girder.

3. Shear Resistance: The end supports of a plate girder experience significant shear forces. Bearing stiffeners increase the shear capacity of the web plate by resisting the vertical shear forces and preventing shear failure.

4. Connection Stability: Bearing stiffeners also play a crucial role in maintaining the stability of the connections between the web plate and the flange plates. By providing additional stiffness to the web plate, they help prevent local distortions and ensure the integrity of the connections.

In summary, bearing stiffeners are essential components in plate girders, and they are provided at the end supports to enhance load distribution, provide lateral support, increase shear resistance, and maintain connection stability.