A, brick masonry wall hole
The bearing system of brick-concrete structure is clay solid brick, and the opening of the wall weakens the existing structural stiffness and local bearing capacity of the wall. Therefore, for this type of opening, it is necessary to calculate the overall impact of opening on the structure from the aspects of bearing capacity and earthquake resistance, and strictly control the number, size and location of opening. The damage of brick-concrete structure is loose damage, which takes a short time and is difficult to remedy. If the hole is too large, it will bring irreversible damage to the building.
Second, the hole reinforcement method
The new era is pregnant with new technologies, and the building renovation and reinforcement industry is booming in today's society. There are many ways to strengthen the wall by opening holes, and the main ideas are replacement method and reinforcement method. Accordingly, the national standards, specifications and atlas were promulgated in order to better guide the reinforcement design and construction. Now, describe the way to make holes in the wall.
2. 1 hole of brick masonry wall
Mainly refer to the national standard atlas 15G6 1 1 brick-concrete structure reinforcement and repair and related specifications. According to the size of holes, they can be divided into small holes (< 600), general holes (600 ~ 1 200), large holes (1 200 ~ 2000) and super-large holes (> 2000). The following are expressed separately.
1) pinhole (< 600).
This kind of hole is mainly used for equipment pipeline opening or temporary opening for maintenance. Because brick masonry itself is made by horse teeth, the bite force between them is acceptable. For this type of hole, it is best to choose the lower part of the ring beam, so that the ring beam can bear part of the upper load, without causing structural hidden dangers or damage, and the impact on earthquake resistance is almost negligible. Therefore, in the construction of the above-mentioned hole, try to cut statically along the brick joints to prevent the original structure from being more damaged due to improper cutting methods. If you can't open a hole in the lower part of the ring beam, you should also choose it near the ring beam. If a hole is opened at the lower end of the wall, from the safety point of view, steel bars should be embedded in the mortar joint of the upper wall of the hole, and each side exceeds the hole by 200. The embedded steel bars should be sealed with cement.
2) General hole (600 ~ 1200).
This type of hole is usually a doorway or passage, which is the most common situation to connect closed spaces with each other. According to the requirements of the specification atlas, this kind of hole needs to temporarily support the floor or superstructure before opening, and the reinforcement method adopts angle steel to close the hole. The specific method is as follows:
a)。 Chisel away the plastering layer of masonry wall and control it to damage the wall as little as possible;
B) According to the selected angle steel size, remove the mortar from the horizontal mortar joint at the upper part of the hole similar to the angle steel size, blow off the ash powder, and add cement mortar mixed with glue to ensure that the mortar fills the mortar joint and is 3 ~ 5 mm higher than the mortar joint, and immediately embed and compact the cut angle steel;
C) construct the angle steel on the other side of the wall according to the same process, and let it stand for not less than 24h.
D) drill holes on the angle steel with a drilling machine, and connect the angle steel on both sides with ordinary bolts, with no less than two bolts, and the spacing is not more than 500mm.
E) Dismantle the local masonry at the mouth of the cave, and then connect the lower end of the original angle steel with batten welding. After the completion of the construction of the upper part of the hole, observe the settlement and cracking of the upper wall of the hole. If it is normal, the hole can be excavated in a large area;
f)。 Remove the temporary support and seal the wall around the hole with cement mortar. If necessary, reinforce the hole edges on both sides of the hole in this way. Make sure that the angle steel exceeds 200mm on each side of the hole. If the number of openings is small, there is no need for seismic checking calculation; If the number of openings is large, the seismic and bearing capacity of the whole structural model should be checked; In the case of insufficient earthquake resistance and bearing capacity, methods to increase the stiffness of the wall should be considered, such as opening holes in the wall surface to strengthen or adding structural columns.
3) Big hole (1200 ~ 2000).
This type of hole is generally used to connect two closed rooms to form a large space with a wider view, which is also a common way. According to the requirements of the specification atlas, this kind of hole should temporarily support the floor or superstructure before opening, and the reinforcement method is to add reinforced concrete joists along the lower edge of the hole. The specific method is as follows:
a)。 Chisel away the plastering layer of masonry wall and control it to damage the wall as little as possible;
B) Pay-off the joist size calculated according to the upper load at the door opening position, and make the steel brace with the same height as the beam, which can be round steel or I-beam, and then place the steel brace at the concrete joist position by partially punching holes to support the load from the upper wall;
C) All steel supports of the wall shall be constructed according to the same process, with the spacing not more than 500 mm and the hanging time not more than 24 hours;
D) Remove the wall at the joist by static cutting method, and cut along the mortar joint as far as possible, with both ends of the joist beyond the hole not less than 200 mm. After cutting, clean up the dust and sundries, place joist reinforcement and formwork support, and bury the steel support directly into the joist without taking it out;
E) When pouring joist concrete, it is best to use fine stone concrete or grouting material. When the strength reaches 70% of the design strength, dismantle the formwork and check the pouring quality. If there is any pouring problem, re-pouring should be considered, and secondary repair pouring is not allowed;
F) Remove the wall at the entrance statically and seal the wall around the entrance with cement mortar. If necessary, the side of the entrance can be reinforced by this method to ensure that the joist reinforcement is anchored in the floor or beam. This kind of hole belongs to the big hole with clear seismic code, and it needs bearing capacity and seismic checking calculation. If the seismic capacity and bearing capacity are insufficient, we should consider ways to increase the stiffness of the wall, such as opening holes in the wall surface to strengthen it or adding structural columns.
4) Super-large hole (> 2000).
This kind of hole basically belongs to the demolition of facade wall, so it is generally recommended to consider it at the top floor of the house, and it is not recommended to open a hole at the bottom floor. The method of opening the hole is the same as the above-mentioned big hole, except that the joist must calculate the load and replace it. This type of hole will inevitably have a great impact on earthquake resistance, and improper reinforcement will easily lead to structural safety problems, so we need to be cautious.
Third, the conclusion
Coupled with the hole in the wall, some houses have better use value and commercial value, and of course they have brought great harm to the building itself. In principle, it is not recommended to open holes in existing structures, especially large holes and oversized holes. Many engineering accidents are caused by the random opening of holes in old buildings, which leads to the collapse of the whole building. We must be careful when encountering such problems.
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