In the transformation, the opening of the floor is normal. In the structure of the building, the floor can bear the vertical load on the upper part, and provide the lateral stiffness for the structure, coordinate the lateral deformation of the structure, and maintain the role of the whole work together. The floor has an important effect on the structure as a whole. Therefore, when opening holes, the consequences should be considered carefully.

The opening of the floor will cause more adverse effects

First, the opening of the floor will reduce the overall stiffness of the floor and reduce the integrity of the structure. The reduction of floor stiffness will affect the seismic performance of buildings. When the earthquake occurs, the floor will be subject to greater deformation.

On the other hand, the opening of the floor will not only produce stress concentration at the opening, but also weaken the bearing capacity of the floor surrounding the floor. When the load is increased, the loading capacity is easy to occur around the opening, resulting in the cracking and even destruction of the concrete. Therefore, when the floor is opened, the structure should be reinforced according to the actual situation.

Small slab opening retrofitting

When the opening of the floor is small, that is, the width of the hole perpendicular to the direction of the plate is not more than 300mm or the diameter of the hole is not more than 300mm, and the number of the cutting bar is not more than 5%, the treatment can not be done, but it is necessary to pay attention to the waterproofing and leakage prevention and avoid the corrosion of the steel bar.

When the above openings can not meet the actual needs and need to be further expanded, the width of the hole or the diameter of the hole in the hole is between 300mm-1000mm, or when the steel bar is cut off more than 20%, the reinforcement should be made according to the structure to compensate for the reinforcement. The compensatory reinforcement is around the hole, reinforced by sticking steel plate or pasting carbon fiber fabric(CFRP), and strengthening the bearing capacity of the opening by the equivalent of the cut bar. When the two methods are used, the negative bending moment area of the plate should be strengthened in the form of double-sided reinforcement in the upper and lower parts of the plate, and at the same time, the anchorage measures of the end should be ensured.

Big slab opening retrofitting

When the opening of the floor is further enlarged, the width of the hole or the diameter of the hole is greater than 1000mm, or the number of steel bars is more than 20%, as well as the large concentrated load in the hole and the cut off of the main rib of the prefabricated plate, the reinforcement effect only on the carbon fiber cloth or steel plate will be very limited. The force path should be changed to reduce the stress set. The negative effect on the force of the floor slab. In order to change the stress transfer, the new beam can be used to transfer the support at the entrance of the cave.