In steel structure plants, the most common components are steel columns and steel beams, which are a large part of the support and bearing, and the composition of the structure is an important component. The first component of steel structure plant is to be able to select different data to establish and form different data. The natural functions and quality of different data also have certain differences. It can also create different types of plants, such as multi-storey steel structure plant, light steel structure plant, brick concrete structure plant, etc. Only by controlling the quality of related components can the installation quality of all structures be improved.
1. Unloading method of steel structure column
When it is necessary to reinforce or replace new columns under unloading, the method of "joist and column replacement" shall be adopted. When only the upper column needs to be reinforced, the roof truss can be supported by crane beam bridge to unload the column. When the lower column needs to be reinforced or the process needs to cut off the lower column, a permanent joist can be set under the crane beam to share the load of the upper column (including the load of the crane beam) on the adjacent column (it is necessary to check the adjacent column and reinforce it, but also check the foundation). When selecting this method, it should be considered that after the joist is used to replace the lower column, the joist will have a certain deflection, forcing the original roof truss to sink, which may damage the connection nodes of the components connected to the roof truss. For this purpose, temporary load can be added on the joist in advance to make the joist have a pre deflection. The order of choosing this method is to strengthen adjacent columns, weld joists and adjacent columns, and add temporary loads Weld joists and center columns, remove temporary loads, and reinforce or cut off lower columns.
2. Reinforcement method of steel structure and steel column
The section of reinforced column in the reinforcement of steel structure workshop. Generally, steel plate or section steel is used to strengthen the section of reinforced column, welding bolts or high-strength bolts are used to connect the column as a whole, and additional supports are added. Add braces to reduce column length and improve positive bearing capacity. The stability of the column is proposed under the condition that the section standard is unchanged; Change the calculation chart to reduce the external force or internal force of the column; The reinforced concrete wrapped around the steel column can obviously improve the bearing capacity of the column.
3. Reinforcement of steel structure column base
There is no reinforcement method for the thickness of the column floor in the reinforcement of the steel structure workshop: add the stiffening rib of the column base to reduce the bending moment of the bottom plate, and pour concrete between the column base steel to make the column base plate become a rigid block, so as to improve the adhesion of the column base surface and eliminate the corrosion of the paint and the column base surface.
There is no reinforcement method for column foot anchor in steel structure workshop reinforcement: add additional anchor. Select when the concrete foundation is wide.
Drill holes on the concrete foundation, insert additional anchor rods, pour epoxy mortar or sulfur mortar (the hole diameter is 20 mm for the anchor rod, and the depth is more than 30 d), and wrap the entire column base with reinforced concrete. The new reinforcement shall extend into the foundation and be welded with the original reinforcement in the foundation.
4. Checking calculation of bearing capacity of steel structure column reinforcement
The important problem of reinforcement accounting under load is whether the stress after reinforcement can be redistributed, that is, whether the original section after reinforcement can distribute the original stress to the newly reinforced member section. If it can be redistributed, the sum of new and old loads can be evenly distributed to the new and old sections, otherwise the original load will still be borne by the original section, and the new and old loads will be evenly shared by the new and old sections (i.e. the total section after reinforcement).
So far, the redistribution of stress after reinforcement has not been fully proved by experiments (at least in the elastic stage), but for static loaded structures, when a part of the section enters the plastic situation, the stress will eventually be redistributed, so the static loaded structures can be accounted for by working together with new and old sections; In the case of dynamic load structure, the plastic zone is difficult to form, without considering the redistribution of stress, the situation before and after reinforcement is calculated separately, and then the sum is calculated.
The above problems do not exist when strengthening under unloading. Under the unloading condition, the section checking calculation shall be based on the total section after reinforcement, and the reinforcement reduction coefficient shall be considered. It shall be calculated according to the current standard, that is, according to the static load checking formula of the reinforcement section effect under the load condition. The same is true for the bar frame members and beams.
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