How to "build building blocks" in prefabricated buildings? Detailed explanation of the parameters of 11 mainstream structural systems - Industrial Insurance Network
1. PC frame system
Prefabricated concrete frame structures include prefabricated integral concrete frame structures and other prefabricated concrete frame structures. The former means that all or part of the frame beams and columns are assembled using prefabricated components through reliable connections. The latter mainly refers to various types of dry-connected frame structures, which are mainly used in conjunction with shear walls, seismic supports, etc.
1.1 Main precast components
Precast floor slabs (including precast solid slabs, precast hollow slabs, etc.), precast beams (including precast solid beams, precast composite beams, etc.), precast walls ( Including prefabricated solid shear walls, prefabricated hollow walls, etc.), prefabricated columns (including prefabricated solid columns, prefabricated hollow columns), prefabricated stairs (prefabricated stair sections, prefabricated rest platforms), and other complex special-shaped components (prefabricated bay windows, prefabricated bay windows, prefabricated bay windows, etc.) Window walls, prefabricated corner facades, etc.).
Prefabricated stairs
1.2 Connection method
Wet connection: Prefabricated beams, columns or T-shaped components are connected or anchored by steel bars at the joints, and are connected through existing The connection method of pouring concrete to form an integral frame.
Dry connection: mainly divided into prestressed connection and hybrid connection. Prestressed connections apply prestress by tensioning prestressed tendons to connect prefabricated beams and columns as a whole. The hybrid connection adds ordinary steel bars to the prestressed connection and uses its yield to dissipate energy, forming a hybrid connection of prestressed steel bars and ordinary steel bars.
1.3 Advantages and Disadvantages
Assembled monolithic frames mainly include two categories: post-cast frame nodes and prefabricated frame nodes. The prefabricated components of the former are connected by post-cast concrete at the beam-column nodes. Prefabricated components are in a straight shape; the connecting nodes of the latter are located in the middle of frame columns and frame beams. Due to the difficulty of making, transporting, and on-site installation of prefabricated frame nodes, they are rarely used in residential projects at this stage.
2. Prefabricated steel structure system
Prefabricated steel structure is a structure composed of steel materials. At present, the traditional structural systems of high-rise prefabricated steel structure buildings include pure frames and frame-support systems, while new ones include containers, steel pipe bundles, steel special-shaped columns, etc. The prefabricated steel structure is mainly composed of beams, steel columns, steel trusses and other components made of section steel and steel plates, and adopts rust removal and anti-rust processes such as silanization, pure manganese phosphating, washing and drying, and galvanizing.
Container system
2.1 Main prefabricated components
Prefabricated floor panels, exterior wall panels, stairs, etc. Prefabricated steel structure buildings advocate the use of non-masonry walls and the use of factory prefabricated wall panels. The types of floor slabs used in prefabricated steel structures mainly include reinforced truss floor deck composite floors and truss reinforced concrete composite slabs. Stairs can use prefabricated steel stairs or prefabricated concrete stairs.
Steel frame columns, steel beams, etc. The "industrialized residential" system mainly uses steel frame structure to configure the main building model, and needs to be combined with the "steel bundle combination" model to design components.
2.2 Main connection methods
Weld connection: arc welding is mainly used, that is, at the joint of the components, the high temperature generated by the arc is used to place the welding rod or wire metal at the weld. Melt to join the components together.
Bolt connection: The connection parts include bolt rods, nuts and washers. For high-strength bolt connections, special wrenches are used to tighten the high-strength bolts and apply the specified pretension force to them.
Riveting: Except for lightweight steel structures, it is basically no longer used.
2.3 Advantages and Disadvantages
Steel structure buildings have the unique advantages of short construction period, energy saving and environmental protection. They are ideal green building materials and therefore have great advantages in residential buildings. However, the proportion of steel structure residences at this stage is very low. First, the cost of steel structure residences is higher than that of concrete building structures for various reasons such as economies of scale have not yet been achieved; second, for steel structure manufacturing, which is in the middle of the steel structure manufacturing industry chain, The industry is in a weak position of subcontracting, which has resulted in steel structure companies not having a large scale so far.
3. Wood structure system
Prefabricated wood structure building refers to the main wood structure load-bearing components, wood components and parts that are prefabricated in the factory and installed on site. Structural building.
Prefabricated wooden structure buildings should comply with the principle of sustainability throughout the building's life cycle, and should meet the "six modernizations" of standardized design, factory production, assembly construction, integrated decoration, information management and intelligent application of prefabricated buildings. "Require.
3.1 Main prefabricated components
Prefabricated beam-column components and wooden trusses: the most flexible components in prefabricated wood structure buildings, require secondary processing on site. Wooden trusses refer to trusses composed of wooden components and are the main load-bearing structures of wooden roofs and wooden towers.
Prefabricated panel components (walls, floors, roofs): Panel prefabrication is to decompose the walls, floors and roofs of the entire building into plane plates with different functions through structural decomposition, that is, It is broken down into prefabricated panel components and transported to the site for hoisting and assembly after prefabrication in the factory.
Prefabricated space modular components: Space modular components are generally three-dimensional units, including walls, floors and roofs. They are the most prefabricated components, including waterproofing and insulation, exterior interior decoration and water and electricity penetrations. Tube.
3.2 Connection method
Plate-pin connection: Use plate-shaped hardwood pins to prevent the relative movement of the spliced ??components. The plate-pins mainly transmit force under bending conditions along the grain, and have a relatively high High load-bearing capacity, so care should be taken to make the wood grain perpendicular to the joints.
Split ring connection: The earliest application. The connection point weakens the stress area of ??the wood less and has a higher load-bearing capacity. However, the connection mainly relies on the shear force transmission of the wood and has poor toughness.
Shear disc connection: Use pairs of steel discs (shear discs and toothed discs) to be embedded in the ring grooves of the components on both sides of the connection joint. The shear force is transmitted through the fastening bolts, and the wooden components are mainly subjected to shear. and under pressure.
Pin connection
3.3 Advantages and Disadvantages
Due to the lack of domestic wood and the long growth cycle, the technical requirements from design deepening, industrial splitting to construction are relatively complex. High, the cost of wooden structure units is much higher than that of concrete. Moreover, since there are no load-bearing beams, wooden structures are suitable for some low-rise buildings, so there are relatively few wooden structures in the country.
4. Prefabricated shear wall high-rise residential system
The prefabricated shear wall structure is a vertical structure where the main force-bearing components, such as scissor walls, beams, and slabs, are made of prefabricated concrete components. Prefabricated concrete structure. Prefabricated shear wall structure is currently the most mature and widely used prefabricated concrete structure system, and is the preferred structural system for high-rise residential buildings.
4.1 Main prefabricated components
Shear walls: Shear walls are named from the stress angle and can be divided into reinforced concrete shear walls, steel plate shear walls, and built-in steel plate supports Shear wall. Shear walls are generally load-bearing walls (load-bearing walls are walls that support upper floors).
Laminated slab: Floor refers to the load-bearing structure of a building, which can be divided into: wooden floor, brick arch floor, reinforced concrete floor, and steel lining floor according to the different materials used.
Composite beams: The shorter beams are cast-in-place and the remaining beams are prefabricated. The connecting beams above the doors and windows are prefabricated together with the shear walls. The joint surface between the precast beam and the post-cast concrete superimposed layer should be provided with a rough surface, and the end surface of the beam should be provided with a keyway to increase the seismic strength.
4.2 Connection method
Dry connection: No need to pour concrete at the construction site. All prefabricated components, embedded parts, and connectors are prefabricated in the factory and realized by bolts or welding. connect.
Wet connection: After connecting the steel bars between two load-bearing components to each other, the overall connection of the structure is achieved by pouring nodes, so that the nodes are equivalent to cast-in-situ.
4.3 Advantages and Disadvantages
Concrete shear wall structure is the main structural form of high-rise residential buildings at present. Although the installation of steel formwork for prefabricated concrete shear wall structure is heavy and the prefabricated components are The cost is relatively high, but due to its application in high-rise residential buildings and its strong construction demand, in recent years it has become the focus of research and development for integrated enterprises integrating real estate, engineering design, prefabricated component production and construction.
5. Fully prefabricated low-rise residential system
The entire building is composed of a dense column support frame structure system and container-type modules, and is composed of several modules similar to containers. First, it is prefabricated and integrated in the factory, and then packaged into containers and transported to the construction site using standard vehicles, where it is constructed in an assembled form.
5.1 Main components of the system
Foundation system: mainly adopts the foundation type of simple pile foundation and foundation beam.
Pile foundations use precast piles or steel piles, and foundation beams use precast concrete beams. This will reduce on-site wet work, improve the degree of assembly, and speed up the construction progress.
Structural system: It adopts light steel frame structure such as square steel, H-shaped steel, thin-walled light steel keel, etc. The connections between plates and plate beams are connected by full high-strength bolt nodes.
Enclosure system: It is planned to use polymer foam cement boards, silicon-magnesium lightweight strips, GRC lightweight strips and other enclosure wall panel materials, plus a sandwich structure of integrated insulation and decorative panels. Interior materials such as wallpaper, paint and decorative panels are used for interior walls. The equipment system includes energy system, drainage system, kitchen and bathroom system, fresh air system, floor heating system (electric heating, water heating), solar system, lighting system, sewage treatment system, etc.
5.2 Advantages and Disadvantages
Because rural land prices are relatively cheap and transportation is inconvenient, fully prefabricated low-rise residential systems that are lightweight and easy to install are more popular in rural areas and suburbs.
6. Prestressed structural system
Prestressed concrete structure is a prestressed state produced by artificially applying pressure to the structural members before they are subjected to external loads. It is used to reduce or offset the tensile stress caused by external loads, that is, to use the higher compressive strength of concrete to make up for its lack of tensile strength, so as to delay the cracking of concrete in the tensile zone.
6.1 Types of prestressed technology
Pre-tensioning method: before the concrete is poured, the prestressed tendons are stretched to the design control stress. After the concrete strength reaches a certain level, the prestressed tendons are The stress tendons are released, allowing prestress to be applied to the concrete frame.
Post-tensioning method: Before the concrete is poured into the component, tunnels or unbonded prestressed tendons are pre-buried at the corresponding positions of the prestressed tendons. After the concrete strength reaches a certain level, the prestressed tendons are Tension to the designed tensile stress, and use special anchors to fix the prestressed tendons at the ends of the concrete components. For bonded prestressed tendons, grouting materials need to be poured into the reserved holes to bond the prestressed tendons and the concrete as a whole. .
External prestressing technology: The prestressed tendons are located outside the component, or the structural component is composed of prestressed tendons and components made of other materials.
6.2 Advantages and Disadvantages
The production process of prestressed concrete is more complicated, has higher requirements on the quality of the product itself, production personnel and machines, and is relatively expensive. At present, residential projects in my country Use less frequently.
7. Steel-concrete structural system
Assembled steel and concrete composite structure refers to the use of factory-produced steel beams and concrete prefabricated components that are combined on site through a certain construction method. As a whole, it has the characteristics of steel structure and concrete structure, and is a structure that can bear the same load.
7.1 Main components
Composite beam: composed of steel beams, connectors and reinforced concrete slabs. The upper flange of the composite beam has a reinforced concrete plate with a larger cross-sectional area to bear the pressure, causing the upper flange section of the steel beam to be reduced, thus saving steel, while the lower flange of the steel beam bears tensile force, which is the stress characteristic of the composite beam.
I-beam
Composite plate: The connectors are first welded on the profiled steel plate, and then the reinforced concrete slab is poured to form a composite plate structure. Connectors use headed studs or steel bars.
Combined truss: Flexible connectors of steel bars or headed studs are first welded to the steel truss, and then the reinforced concrete slab is poured.
Combined columns: formed by pouring concrete into thin-walled steel tubes, also called concrete-filled steel tube columns. The cross-sectional forms are round and square.
7.2 Reinforcement bar and section steel connection method
Reinforcement bar connector connection: This method is to weld the connector to the steel component when the component is made, and put the steel bar on it during installation. Tighten the connector.
Reinforcement bar connecting plate connection: The steel bar overlapping plate needs to be welded to the steel component as much as possible when allowed, and the steel bars are welded on the overlapping plate during installation.
Shaped steel perforation connection: This method is to pre-open steel holes in the factory and pass the steel bars through during on-site construction.
7.3 Advantages and Disadvantages
The light steel and light concrete structural system can improve the disadvantages of high cost and poor comfort when low-rise light steel residences are used in rural areas. The application of steel-concrete composite structure technology is still in the exploratory stage. It is not widely used in our country, the construction technology is not yet very mature, and there is relatively little construction experience to draw from.
8. Modular structural system
Modular construction is to divide traditional houses into building module units into single rooms or a certain three-dimensional building space, and the modular unit floors, The ceilings and walls are prefabricated and installed in advance. After completion, these building module units are transported to the site, and lifting equipment is used to stack and connect them together like "building blocks" to form a complete building.
Schematic diagram of modular components (wood structure)
8.1 Connection method
Intra-module connection: The single-truss truss of modular components is the same as the traditional truss. The components are connected or lengthened by tooth plates.
Connection to the exterior wall: After the roof truss components are transported to the construction site, they are hoisted in place and fixed to the double-layer roof beam plate or wall stud column of the building wall through metal connectors.
8.2 Advantages and Disadvantages
Advantages: The construction speed is fast, and the construction period can be shortened compared with slab construction. It saves manpower and material resources and has a high degree of assembly. Most of the construction work, including the installation of water, heating, electricity, sanitary and other facilities and house decoration, are completed in the factory. Only components hoisting and node processing are left at the construction site, and the pipelines can be used. . There is very little environmental pollution, and the construction process is green and environmentally friendly. Convenient for later expansion.
Disadvantages: The investment in prefabricated factories for modular components is large. Transportation and installation require large equipment. The cost is higher. The area of ??a single module is limited and the scope of building application is low.
9. Primary and secondary frame structure system
9.1 Frame structure and connection method
Also known as giant frame structure. The primary and secondary frame structure is a structural system in which the primary structure composed of large-scale components, giant beams, giant columns, etc., and the secondary structure composed of conventional beams and column components work together. The main frame is a giant frame, and the geometric scale, area, and moment of inertia of the structural section are very large; the secondary frame is an ordinary frame, and the geometric scale, area, and moment of inertia of the component section are relatively small, and the two are not of the same order of magnitude. Giant columns are usually composed of buildings, elevator shafts or large-section solid columns. Giant beams are usually set up every few or a dozen floors, and the beam height generally accounts for one or several floors.
The main frame beams and columns are made of concrete, and when the secondary frame adopts a steel structure, the main connection methods of the primary and secondary frames include rigid connection, semi-rigid connection and hinged connection. Rigid connection means that the components are a whole. After destruction, the angle between the beams and columns is zero, and all the internal forces are transmitted from the columns to the giant beams. Hinge means that after the structure is stressed, the beams and columns can rotate freely without other constraints. Each node is independent of each other, and the beam cannot transmit the upper bending moment to the column. Semi-rigid connection is a new type of connection between steel connection and hinged connection.
9.2 Advantages and Disadvantages
The primary and secondary frame structure can increase the space and height of the building, and is more suitable for large-space buildings such as exhibition halls. It is rarely used in residential buildings in China.
10. Staggered truss structure system
Refers to a long-span space structure composed of prefabricated reinforced concrete columns or steel columns, steel trusses, prefabricated floors and other prefabricated components. The main structure adopts assembly A building with a staggered truss structure, equipped with exterior walls, interior partition walls and floor systems.
On each transverse axis of the building, planar trusses are arranged in intervals, while they are staggered on adjacent axes. Between adjacent trusses, one end of the floor plate is supported on the upper chord of the plane truss on the next floor, and the other end is supported on the lower chord of the truss on the upper floor, achieving construction with little or no support.
10.1 Main components and connection methods
Main components: columns, trusses, floor slabs, diagonal rods
Connection method between trusses and columns: First place the steel trusses on On the corbels, lay prefabricated floor slabs, and tighten the bolts between the gusset plates and columns. At this stage, the corbels bear all the vertical shear force; then concrete is poured in place, and the vertical shear force generated by the new load is controlled by the corbels and gusset plates*** The horizontal tension force is transmitted by the gusset plate bolts.
Staggered trusses and prefabricated floors
10.2 Advantages and Disadvantages
Staggered truss structures are mainly wood structures and steel structures, and are currently used more in public buildings in our country* **There are fewer construction and residential projects.
11. Double-sided laminated shear wall structure system
Double-sided laminated shear wall structure is a new type of prefabricated structural system, which is composed of double-sided laminated shear wall, prefabricated Composite beams, prefabricated composite floor slabs, prefabricated external bay windows, prefabricated non-load-bearing walls with bay windows, prefabricated stairs, prefabricated balconies, lightweight slats and other prefabricated components, as well as cast-in-place shear walls, cast-in-place concrete joints, cast-in-place The cast-in-place parts such as floor slabs are composed of the same components.
11.1 Main components and connection methods
Double-sided laminated shear wall is a prefabricated wall with an internal cavity that is connected by two factory-produced precast concrete wall panels through truss steel bars. For shear wall panels, concrete is poured on-site in the formed cavity to form an overall stressed structural member.
Ordinary precast shear walls are prefabricated in the factory, and concrete is poured into the reserved grouting holes on site, which is equivalent to using "adhesive" to combine the already built wall and the factory prefabricated wall. The walls are fixed together. The vertical direction of the composite plate shear wall is to insert reinforcements into the cavity and then pour concrete into the cavity to connect the upper and lower walls into a whole, with a larger joint surface. Since the size of the cavity of the superimposed wall is much larger than the space required for inserting the bars, the superimposed wall is easier to construct during the installation process. Due to the small diameter of the sleeves of ordinary prefabricated walls, the adjustment space is relatively limited.
Superimposed shear walls do not require sleeve or slurry anchor connections. The upper and lower, left and right connections of the superimposed shear walls are made of cast-in-place layers and cast-in-place edge components. They are connected by inserting bars, making construction convenient. , there is no difficulty in accurately positioning steel bars and sleeves, and the construction quality is easy to ensure; at the same time, it also avoids the high cost of special sleeves and grouting materials.
11.2 Advantages and Disadvantages
Double-sided laminated walls have different thickness specifications. Due to the existence of cavities, the weight of a wall of the same width and height is about half lighter than that of an ordinary wall. . Due to the slow construction speed of vertical steel connection of ordinary precast shear walls, superimposed walls can play a unique role, but there is currently not much engineering experience in China that can be used for reference.