11 mainstream prefabricated building structure systems

1. PC frame system

Prefabricated concrete frame structures include prefabricated monolithic concrete frame structures and other prefabricated concrete frame structures. The former means that all or part of the frame beams and columns are assembled from 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 and seismic supports.

1.1 Main prefabricated components

Prefabricated floor slabs (including prefabricated solid slabs, prefabricated hollow slabs, etc.), prefabricated beams (including prefabricated solid beams, prefabricated composite beams, etc.), prefabricated walls (including prefabricated solid shear walls, prefabricated hollow walls, etc.), prefabricated columns (including prefabricated Solid column, prefabricated hollow column), prefabricated stairs (prefabricated stair section, prefabricated rest platform), other complex special-shaped components (prefabricated bay window, prefabricated bay window exterior wall, prefabricated corner exterior wall, etc.).

1.2 Connection method

Wet connection: A connection method in which prefabricated beams, columns or T-shaped members are connected or anchored by steel bars at the joints, and are connected to the overall frame through cast-in-place concrete.

Dry connection: mainly divided into prestressed connection and hybrid connection. The prestressed connection connects the prefabricated beams and columns as a whole by applying prestressing through the tensioning prestressing tendons. The hybrid connection adds ordinary steel bars on the basis of the prestressed connection, and uses its yield to dissipate energy, forming the connection of prestressed steel bars and ordinary steel bars.

1.3 Advantages and disadvantages

The prefabricated monolithic frame mainly includes two categories: post-casting of frame nodes and pre-casting of frame nodes. The precast members of the former are connected by post-cast concrete at the beam-column nodes, and the precast members are in-line; while the connection nodes of the latter are located at the frame columns and frame beams. In the middle part, due to the difficulty of making, transporting and on-site installation of prefabricated frame joints, it is rarely used in residential projects at this stage.

2. Prefabricated steel structure system

The fabricated steel structure is a structure composed of steel materials. At present, the traditional structural systems of high-rise prefabricated steel structure buildings include pure frame, frame-support system, and new ones include containers, steel tube bundles, and steel special-shaped columns. The fabricated steel structure is mainly composed of beam steel, steel column, steel truss and other components made of section steel and steel plate, and adopts rust removal and rust prevention processes such as silanization, pure manganese phosphating, washing and drying, and galvanizing.

2.1 Main prefabricated components

Prefabricated floor slabs, exterior wall panels, stairs, etc. The prefabricated steel structure building advocates the use of non-masonry walls and factory prefabricated wall panels. The types of floor slabs used in prefabricated steel structures mainly include reinforced truss floor deck composite floor and truss reinforced concrete composite slab, etc. The stairs can be prefabricated steel stairs or prefabricated concrete stairs.

Steel frame columns, steel beams, etc. The "industrialized housing" system mainly uses the steel frame structure to configure the main building model, and needs to combine the "steel tube bundle combination" mode to design components.

2.2 Main connection methods

Weld connection: Arc welding is mainly used, that is, at the connection of components, the high temperature generated by the arc melts the electrode or wire metal placed at the weld, and the components are connected together.

Bolted connection: The connection parts include bolt rods, nuts and washers. For high-strength bolted connections, use a special wrench to tighten the high-strength bolts and apply the specified pre-tension to them.

Riveting: Except for light steel structures, it is basically no longer used.

2.3 Advantages and disadvantages

Steel structure buildings have the advantage of short construction period and are ideal green building materials, so they have great advantages in residential buildings. However, the proportion of steel structure residential buildings is very low at this stage. First, the cost of steel structure residential buildings is higher than that of concrete building structures due to various reasons such as economies of scale have not yet reached; The industry is in a weak position of subcontracting, which has led to the fact that steel structure enterprises have not yet formed a large scale.

3. Timber Structure System

The prefabricated wood structure building refers to the wood structure building in which the main wood structure load-bearing components, wood components and parts are prefabricated in the factory and installed on site. The prefabricated wood structure building should comply with the principle of sustainability in the whole life cycle of the building, and should meet the "six modernization" requirements of standardized design, factory production, prefabricated construction, integrated decoration, and information management of prefabricated buildings.

3.1 Main prefabricated components

Prefabricated beam-column elements and wood trusses: the most flexible components in prefabricated wood structures, requiring secondary processing on site. A wooden truss refers to a truss composed of wooden components, which is the main load-bearing structure of a wooden roof and a wooden tower.

Prefabricated panel components (walls, floors, roofs): Panel prefabrication is to decompose the walls, floors and roofs of the entire building into flat panels with different functions through structural decomposition, that is, into prefabricated panel components. After the factory prefabrication is completed, it is transported to the site for hoisting and assembly.

Prefabricated space modular components: Space modular components are generally three-dimensional units, including walls, floors and roofs.

3.2 Connection method

Board-pin connection: Use plate-shaped hardwood pins to prevent the relative movement of the components to be joined. The board-pin mainly transmits force under the condition of bending along the grain, and has a high bearing capacity, so it should be noted that the wood grain is perpendicular to the joining seam.

Split ring connection: The earliest application, the connection point weakens the stress area of the wood less, and has a high bearing capacity, but the connection mainly relies on the shear force of the wood, and the toughness is poor.

Shearing disk connection: Paired steel disks (shearing disks and toothed disks) are embedded in the ring grooves of the members on both sides of the joint, and the shearing force is transmitted through the tie bolts, and the wooden members are mainly sheared and compressed.

3.3 Advantages and disadvantages

Due to the lack of domestic timber and the long growth cycle, the technical requirements from design deepening, industrial splitting to construction and construction are relatively high, and the unit cost of wood structure is much higher than that of concrete. Moreover, there is no load-bearing beam, and the wood structure is suitable for some low-rise buildings, so there are few domestic wood-structured houses.

4. Prefabricated shear wall high-rise residential system

The prefabricated shear wall structure is a prefabricated concrete structure composed of prefabricated concrete components such as shear walls, beams, slabs, etc., the main stress-bearing components of the vertical structure. The prefabricated shear wall structure is a kind of prefabricated concrete structure system with mature technology and wide application, and it is the structural system of high-rise residential buildings.

4.1 Main prefabricated components

Shear wall: The name of the shear wall comes from the force angle, which can be divided into reinforced concrete shear wall, steel plate shear wall, and built-in steel plate support shear wall. Shear walls are generally load-bearing walls (load-bearing walls are walls that support upper floors).

Laminated slabs: Floor slabs refer to the load-bearing structure of a building, which can be divided into wooden slabs, brick arch slabs, reinforced concrete slabs, and steel lining slabs according to the different materials used.

Laminated beams: Beams with shorter lengths are cast-in-place, and the rest are prefabricated. The coupling beams above the doors and windows are prefabricated together with the shear walls. The junction surface between the prefabricated beam and the post-cast concrete superimposed layer shall be provided with a rough surface, and the end surface of the beam shall be provided with a keyway to increase the seismic strength.

4.2 Connection method

Dry connection: There is no need to pour concrete on the construction site, all prefabricated components, embedded parts and connectors are prefabricated in the factory, and the connection is realized by bolts or welding.

Wet connection: After connecting the steel bars between the two load-bearing members to each other, the overall connection of the structure is realized by pouring the nodes, so that the nodes are equivalent to cast-in-place.

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 of prefabricated concrete shear wall structure is heavy and the cost of prefabricated components is relatively high, due to its application in high-rise residential buildings and full construction Quantity, in recent years, has become the research and development focus of integrated enterprises integrating real estate, engineering design, prefabricated component production and construction.

5. Fully assembled low-rise residential system

The whole building is a combination of dense column support frame structure system and container-type modules, and several modules similar to containers are combined. First prefabricated and integrated in the factory, then packaged into containers, transported to the construction site by standard vehicles, and constructed in an assembled form on site.

5.1 Main composition system

Foundation system: It mainly adopts the foundation type of simple pile foundation and foundation beam. The pile foundation adopts prefabricated piles or steel piles, and the foundation beam adopts prefabricated concrete beam. In this way, the wet work on site is reduced, the degree of assembly is improved, and the construction progress is accelerated.

Structural system: It adopts light steel frame structure such as square steel, H-beam, thin-walled light steel keel, etc. The connection between plates and between plate beams adopts full high-strength bolt node connection.

Enclosure system: It is proposed to use polymer foamed cement board, silicon-magnesium lightweight slats, GRC lightweight slats and other enclosure wall panel materials, plus a sandwich structure of thermal insulation and decoration integrated boards. The interior walls use interior materials such as wallpaper, paint and decorative panels. The equipment system includes energy system, drainage system, kitchen and bathroom system, fresh air system, floor heating system (electric heating, plumbing), solar energy system, lighting system, sewage treatment system, etc.

5.2 Advantages and disadvantages

Due to the relatively cheap rural land prices and inconvenient transportation, light and easy-to-install fully-fabricated low-rise residential systems are popular in rural and suburban areas.

6. Prestressed structural system

The prestressed concrete structure is to artificially apply pressure to the structural member before it is subjected to the external force load, and the resulting prestressed state is used to reduce or offset the tensile stress caused by the external load, that is, with the help of concrete higher The compressive strength can make up for the lack of its tensile strength and achieve the purpose of delaying the cracking of concrete in the tensile zone.

6.1 Types of prestressing techniques

Pre-tensioning method: The prestressed tendons are stretched to the design control stress before the concrete is poured. After the concrete strength reaches a certain level, the prestressed tendons are released, so that the prestressing is applied to the concrete frame.

Post-tensioning method: Before the concrete of the component is poured, pre-buried tunnels or unbonded pre-stressed tendons are embedded in the corresponding positions of the pre-stressed tendons. After the concrete strength reaches a certain level, the pre-stressed tendons are stretched to the design tensile stress. , and use anchors to fix the prestressed tendon at the end of the concrete member. If there is a bonded prestressed tendon, grouting material needs to be poured into the reserved hole to bond the prestressed tendon and the concrete into a whole.

External prestressing technology: Prestressing tendons are located outside the component, or structural components are composed of prestressing tendons and components formed from other materials.

6.2 Advantages and disadvantages

The production process of prestressed concrete is relatively complicated, the requirements for the quality of the product itself, the production personnel and the machine are relatively high, and the price is relatively high. At present, residential projects in my country are rarely used.

7. Steel-concrete structure system

Prefabricated steel and concrete composite structure refers to a structure that uses factory-produced steel beams and concrete prefabricated components to form a whole on site through a certain structural method, which has the characteristics of steel structure and concrete structure and bears the load together.

7.1 Main Components

Composite beams: Consists of steel beams, connectors and reinforced concrete slabs. The upper flange of the composite beam has a reinforced concrete slab with a large cross-sectional area to bear the pressure, which reduces the cross-section of the upper flange of the steel beam, thereby saving steel, and the lower flange of the steel beam bears the tensile force, which is the stress characteristic of the composite beam.

Combination plate: The connecting piece is welded on the profiled steel plate first, and then the reinforced concrete plate is poured to form a composite plate structure. Connectors use headed studs or steel bars.

Composite truss: The steel truss is welded with steel bars or flexible connectors with headed studs, and then reinforced concrete slabs are poured.

Composite column: It is formed by pouring concrete into a thin-walled steel tube, also known as a concrete-filled steel tube column. Sectional forms are round and square.

7.2 Connection method of steel bar and section steel

Rebar connector connection: This method is to weld the connector to the steel component during the production of the component, and tighten the steel bar sleeve and the connector during installation.

Reinforcement connecting plate connection: The reinforcing bar lap plate should be welded to the steel member as far as possible, and the reinforcing bar should be welded on the lap plate during installation.

Shaped steel perforation connection: This method is that the factory pre-opens piercing holes on the steel components, and the steel bars are passed through during on-site construction.

7.3 Advantages and disadvantages

The light steel light concrete structure system can improve the disadvantages of high cost and poor comfort when low-rise light steel houses are applied in rural areas. The application of steel-concrete composite structure technology is still in the exploratory stage. It is not widely used in my country, and the construction technology is not very mature.

8. Modular structure system

Modular building is to divide a traditional house into a single room or a certain three-dimensional building space as building module units, and prefabricate the floor, ceiling and walls of the module units in the factory in advance. After completion, these building module units are delivered to the site. Use lifting gear like "building blocks" to stack and connect them together to form a complete building.

8.1 Connection method

Connection within the module: The single truss truss of the modular component is the same as the traditional truss method, and each component is connected or lengthened by the tooth plate.

Connection with the outer wall: After the roof truss components are transported to the construction site, the trusses are fixed on the double-layer roof beams or wall studs of the building wall through metal connectors after being hoisted in place.

8.2 Advantages and disadvantages

Advantages: The construction speed is fast, and the construction period can be shortened compared with the slab building. Save manpower and material resources The degree of assembly is high. Most of the construction work, including the installation of water, heating, electricity, sanitary facilities and house decoration, are moved to the factory for completion. Only the components are hoisted and node processing is left on the construction site, and the pipeline can be used. . Very little pollution to the environment, the construction process is green. Convenient for later expansion.

Disadvantage: The prefabrication of modular components requires a large investment. Transportation and installation require large equipment. Higher cost. The area of a single module is limited, and the scope of application of the building is low.

9. Primary and secondary frame structure system

9.1 Frame structure and connection method

Also known as a mega frame structure. The primary and secondary frame structure is a structural system in which the primary structure composed of large-scale components such as giant beams and columns and the secondary structure composed of conventional beam and column components work together. The main frame is a giant frame, and the geometric dimension, area and moment of inertia of the structural section are very large; the secondary frame is an ordinary frame, and the geometric dimension, 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 generally set up every few or more than a dozen floors, and the beam height generally accounts for one or several floors.

The main frame beam and column material is concrete, and when the secondary frame adopts steel structure, the main and secondary frame connection methods mainly include rigid connection, semi-rigid connection and hinged connection. Rigid connection means that the components are a whole. After the failure, the angle between the beam and the column is zero, and all the internal forces are transmitted to the giant beam by the column. Hinged means that after the structure is stressed, the beam and column 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 joints and hinged joints.

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 Structural System

It refers to a large-span space structure composed of prefabricated reinforced concrete columns or steel columns, steel trusses, prefabricated floor slabs and other prefabricated components.

On each axis in the transverse direction of the building, the plane truss spacers are arranged, and they are arranged staggered on the adjacent axis. Between adjacent trusses, one end of the floor slab is supported on the upper chord of the next-level plane truss, and the other end is supported on the lower chord of the upper-level truss, so as to realize less support or even no support during construction.

10.1 Main components and connection methods

Main components: columns, trusses, floors, inclined rods

The connection method of truss and column: first place the steel truss on the corbel, lay the prefabricated floor, tighten the bolts of the gusset plate and the column, at this stage the corbel bears all the vertical shear force; The shear force is shared by the corbel and the gusset plate, and the horizontal tension is transmitted by the gusset plate bolts.

10.2 Advantages and disadvantages

The staggered truss structure is mainly composed of wood and steel structures. Currently, it is mostly used in public buildings in my country, and there are few residential projects.

11. Double-sided superimposed shear wall structural system

The double-sided superimposed shear wall structure is a new type of prefabricated structural system. It is composed of prefabricated components such as prefabricated balconies, lightweight slats, and cast-in-place shear walls, cast-in-place concrete joints, and cast-in-place floor slabs.

11.1 Main components and connection methods

The double-sided superimposed shear wall is a prefabricated shear wall made of two factory-produced prefabricated concrete wall panels connected by truss steel bars to form a prefabricated shear wall panel with an internal cavity. member.

Ordinary prefabricated shear walls are prefabricated walls in the factory, and concrete is poured into the reserved grouting holes on site, which is equivalent to fixing the built wall and the factory prefabricated wall together with "adhesive". In the vertical direction of the laminated plate shear wall, the upper and lower walls are connected as a whole by inserting ribs in the cavity, and then pouring concrete into the cavity, and the joint surface is larger. Since the size of the cavity of the superimposed wall is much larger than the space required for the insertion of the reinforcement, the superimposed wall is more convenient for construction during the installation process. Due to the small diameter of the sleeve of the ordinary prefabricated wall, the adjustment space is relatively limited.

The superimposed shear wall does not need sleeve or grout anchor connection. The upper and lower, left and right connections of the superimposed shear wall are made of cast-in-situ layer and cast-in-place edge components, etc., and the connection is made by inserting reinforcement, which is convenient for construction, and there is no steel bar and sleeve. It is difficult to locate, and the construction quality is easy to ensure; at the same time, it also avoids the high cost of sleeves and grouting materials.

11.2 Advantages and disadvantages

The double-sided laminated wall has different thickness specifications. Due to the existence of the cavity, the weight of the wall with the same width and height is about half lighter than that of the ordinary wall. Due to the slow construction speed of the vertical steel bar connection of ordinary prefabricated shear walls, the superimposed wall can play a role, but there is not much engineering experience that can be used for reference in China.