What structural feature assists in preventing a floor from shearing off at the columns?

The correct answer is drop panels. Drop panels are structural features that can be incorporated into concrete slabs to enhance their strength and reduce the tendency to shear off at the columns. By thickening the slab around the column, drop panels help to better distribute loads, enhance stability, and provide additional resistance to shear forces that could otherwise cause a failure in the connection between the floor and the columns.

In buildings, the connection between floors and columns is critical for maintaining overall structural integrity during loads, particularly lateral loads from wind or seismic activity. Drop panels, by enhancing the moment capacity of the slab at these connections, effectively improve the overall structural performance, helping to prevent failure at critical points.

Other structural features mentioned, such as reinforced beams, cross bracing, or shear walls, serve their respective purposes in enhancing overall structural stability and load-bearing capacity but are not specifically designed to prevent shearing at column connections in the same direct manner as drop panels do. Reinforced beams provide strength during bending, cross bracing helps with lateral stability, and shear walls are essential for resisting lateral loads, yet none specifically focus on the connection between floors and columns like drop panels.