First of all, these boards should be reinforced once, and then an additional rib is added, so it is called additional. Additional reinforcement is the reinforcement added in the middle of the laid reinforcement after the reinforcement not marked with the word "additional" is prepared.

According to article 2 of point 1, there is no additional reinforcement available for the reinforcement on the plate bearing surface; These slabs with additional reinforcement should be equipped with foundation reinforcement first, and then with additional reinforcement. The figure does not explain how to match the foundation reinforcement, but it is omitted for the sake of clear design.

meaning

Double-layer bidirectional total * * * is a two-layer steel mesh.

Cast-in-place slab reinforcement, which is two-way.

Double-layer, because the board has a certain thickness, so use a layer of steel bar at the top of the board and a layer of steel bar at the bottom of the board, which is double-layer.

Two-way, that is, the reinforcement of bottom reinforcement and gluten in both vertical and horizontal directions, that is, the reinforcement is arranged in the X and Y directions of the bottom plate and the panel, and each layer of reinforcement is in both vertical and horizontal directions.