1. Double-layer bidirectional reinforcement: it means that the reinforcement at the top of the slab and the reinforcement at the bottom of the slab are disconnected separately within the slab or between multiple slabs, as shown in the figure:
2. Double-layer bidirectional pull-through reinforcement: it means that the reinforcement at the top of the plate and the reinforcement at the bottom of the plate are pulled through separately, and there is no disconnection between the plates, as shown in the figure:
Extended data
When the elevation of the slab top and the reinforcement area are the same, the two-way reinforcement at the slab top can be pulled through; When the elevation and reinforcement area of the bottom of the slab are the same, the two-way reinforcement at the bottom of the slab can be pulled through.
When the elevation, thickness and reinforcement area of the top and bottom of the slab are equal, the two-way reinforcement of the top and bottom of the slab can be pulled through, that is, the double-layer two-way pull-through setting.
When the top elevation, bottom elevation and thickness of the slab are the same, but the reinforcement area is different, double-layer two-way reinforcement can also be pulled, but reinforcement should be added at the location with large local reinforcement area to meet the stress requirements.
In the building structure, for some special parts of the floor, in order to better stress, heat preservation, heat insulation and waterproof functions, it is necessary to pull through the floor and steel bars in both directions. For example, the steel bars of the roof panel are pulled in two directions to ensure the waterproof, thermal insulation and thermal insulation performance of the roof panel. In order to ensure the better mechanical properties of the structure, the floor reinforcement in the weak connection part of the structure is set by double-layer bidirectional pull-through.
Atlas of National Building Standard Design16g1011Drawing Rules and Structural Details of Overall Representation of Construction Drawings of Concrete Structures-Cast-in-place Concrete Frames, Shear Walls, Beams and Slabs, published by China Planning Publishing House, pp. 39-44.