1. Top Slab

The top edge of the box section is referred to as the deck, which is the primary working part bearing positive and negative bending moments. It must not only meet the requirements of the transverse bending moment of the bridge deck but also provide a sufficiently large bearing area in reinforced concrete bridges; in pre-stressed concrete bridges, it must also satisfy the requirements for the arrangement of longitudinal prestressed steel tendons.

2. In mining engineering, the roof refers to the strata located a certain distance above the coal seam. The strata or coal seam underground is solid. The weight of the upper strata presses down on the lower strata, maintaining a state of balance. At this point, the rock mass does not deform or move. After we excavate a tunnel in the coal seam or strata, the roof strata above the tunnel will fall downwards, and the weight of this roof strata will press on the sides of the tunnel. This roof strata is known as the roof.