The correct answer is D. All of the above.
A horizontal stiffener is a plate that is welded or bolted to the web of a plate girder to provide additional support. It can help to prevent the web plate from buckling under shear or compression loads, and can also help to distribute the load more evenly across the web plate.
Shear buckling is a type of buckling that occurs when a plate is subjected to a shear load. The plate will buckle when the shear stress exceeds the critical shear stress. The critical shear stress is a function of the plate’s thickness, width, and length, as well as the material’s properties.
Compression buckling is a type of buckling that occurs when a plate is subjected to a compressive load. The plate will buckle when the compressive stress exceeds the critical compressive stress. The critical compressive stress is a function of the plate’s thickness, width, and length, as well as the material’s properties.
Yielding is a plastic deformation that occurs when a material is subjected to a load that exceeds its yield strength. The yield strength is the stress at which a material begins to deform plastically. Once a material has yielded, it will not return to its original shape when the load is removed.
Horizontal stiffeners can help to prevent all of these types of failure by providing additional support to the web plate.