Prefabricated architecture and its development

How to "build blocks" for prefabricated buildings? 1 1 Detailed explanation of main structural system parameters-industrial protective net

1, PC framework system

Assembled concrete frame structure includes assembled integral concrete frame structure and other assembled concrete frame structures. The former means that all or part of frame beams and columns are assembled by prefabricated members through reliable connection. The latter mainly refers to various dry-connected frame structures, which are mainly used in conjunction with shear walls and seismic braces.

1. 1 main prefabricated members

Precast floor slab (including precast solid slab and precast hollow slab, etc.). ), precast beams (including precast solid beams and precast composite beams, etc. ), precast wall (including precast solid shear wall and precast hollow wall, etc. ), prefabricated columns (including prefabricated solid columns and prefabricated hollow columns), prefabricated stairs (prefabricated stair sections and prefabricated rest platforms) and other complex special-shaped components (prefabricated bay windows, prefabricated walls with bay windows, prefabricated corners).

Precast stairs

1.2 connection mode

Wet connection: precast beams, columns or T-shaped members are connected or anchored with steel bars at the joint, and connected with cast-in-place concrete to form an integral frame.

Dry connection: mainly divided into prestressed connection and mixed connection. Prestressed connection is to connect precast beams and columns into a whole by stretching prestressed tendons and applying prestress. Hybrid connection is to add ordinary steel bars on the basis of prestressed connection, and use their yield to consume energy, thus forming a hybrid reinforced connection between prestressed steel bars and ordinary steel bars.

Advantages and disadvantages of 1.3

Assembled integral frame mainly includes post-pouring of frame joints and prefabrication of frame joints. The precast members of the former are connected by post-pouring concrete at the beam-column joints, and the precast members are in a straight line; The connection node of the latter is located between the frame column and the beam. Precast frame joints are rarely used in residential projects at this stage because of the difficulties in field production, transportation and installation.

2. Assembled steel structure system

Assembled steel structure is a structure composed of steel. At present, the traditional structural system of high-rise assembled steel structure building includes pure frame and frame-support system, and the new structural system includes container, steel tube bundle and steel special-shaped column. The fabricated steel structure is mainly composed of steel beams, steel columns, steel trusses and other components made of section steel and steel plates. The rust removal and rust prevention processes such as silanization, pure manganese phosphating, washing and drying, and galvanizing are adopted.

Container system

2. 1 Main precast members

Precast floor slab, external wall slab, stairs, etc. Assembled steel structure buildings advocate the use of non-masonry walls and factory prefabricated wallboard. The floor types used in fabricated steel structures are mainly reinforced truss floor and truss reinforced concrete composite slab, and the stairs can be prefabricated steel stairs or prefabricated concrete stairs.

Steel frame columns, steel beams, etc. The "industrial residence" system mainly adopts steel frame structure to configure the main building model, which needs to be combined with the "steel tube bundle combination" model for component design.

2.2 Main connection modes

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

Bolted connection: the connector includes bolt rod, nut and washer. For high-strength bolt connection, use a special wrench to tighten the high-strength bolt and apply the specified pre-tightening force.

Riveting: Except for light steel structure, it is basically not used now.

2.3 Advantages and disadvantages

Steel structure building has the unique advantages of short construction period, energy saving and environmental protection, and is an ideal green building material, so it has great advantages in residential buildings. However, at present, the proportion of steel residential buildings is very low. First, the cost of steel structure residence is higher than that of concrete building structure because it has not reached economies of scale and other reasons. Second, the steel structure manufacturing industry, which is in the middle of the industrial chain of steel structure manufacturing industry, is in a weak position of subcontracting, which leads to the fact that steel structure enterprises have not formed too large scale so far.

3. Wood structure system

Assembled wood structure building refers to the main wood structure load-bearing components, wood components and components prefabricated in the factory and installed on site. Assembled wooden buildings should conform to the principle of sustainability in the whole life cycle of buildings, and meet the requirements of standardized design, factory production, assembly construction, integrated decoration, information management and intelligent application of assembled buildings.

3. 1 Main precast members

Precast beam-column members and wood truss: The most flexible members in prefabricated wood structures need secondary processing on site. Wood truss is a truss composed of wooden members, which is the main load-bearing structure of wooden roof and wooden tower frame.

Prefabricated components (walls, buildings and roofs): Slab prefabrication is to decompose the walls, buildings and roofs of the whole building into flat plates with different functions through structural decomposition, that is, into prefabricated components, which are prefabricated in the factory and transported to the site for hoisting.

Prefabricated space modular components: Space modular components are generally three-dimensional units, including walls, floors and roofs, which are the components with the highest degree of prefabrication, including waterproof and thermal insulation, exterior wall decoration, water and electricity connection, etc.

3.2 connection mode

Plate-pin connection: Plate-shaped hardwood pins are used to prevent relative movement of assembled parts. The plate pin mainly transmits force under the condition of bending along the wood grain, which has high bearing capacity, so attention should be paid to making the wood grain perpendicular to the assembly joint.

Open-ring connection: it was first applied, and the connection point slightly weakened the stress area of wood, with high bearing capacity, but the connection mainly depended on the shear force of wood, with poor toughness.

Shear disk connection: Paired steel disks (shear disks and toothed disks) are respectively embedded in the ring grooves of the members on both sides of the connection node, and the wood members mainly bear shear force and bearing capacity through fastening bolts.

Pin connection

3.3 Advantages and disadvantages

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

4. Assembled shear wall high-rise residential system

Assembled shear wall structure is an assembled concrete structure composed of precast concrete members, such as shear wall, beam and plate, which are the main stress members of vertical structure. The assembled shear wall structure is the most mature and widely used assembled concrete structure system at present, and it is the first choice for high-rise residential buildings.

4. 1 Main precast members

Shear wall: the name of shear wall comes from the stress angle, which is divided into reinforced concrete shear wall, steel plate shear wall and embedded steel plate support shear wall. Shear walls are generally load-bearing walls (load-bearing walls are walls that support the upper floors).

Laminated slab: Floor refers to the load-bearing structure of buildings, which can be divided into wood floor, brick arch floor, reinforced concrete floor and steel lining floor according to the different materials used.

Composite beam: the beam with shorter length is cast in situ, and the rest is prefabricated. The coupling beams above the doors and windows are prefabricated together with the shear wall. The joint surface of precast beam and post-cast concrete laminated layer should be provided with rough surface, and the end surface of beam should be provided with keyway to increase seismic strength.

4.2 connection mode

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 connected by bolts or welding.

Wet connection: after the steel bars between two load-bearing members are connected with each other, the whole structure is connected by pouring joints, so that the joints 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 workload of steel formwork for prefabricated concrete shear wall structure is large and the cost of prefabricated components is relatively high, it has become the research and development focus of comprehensive enterprises integrating real estate, engineering design, prefabricated components production and construction in recent years due to its application in high-rise residential buildings and sufficient demand for construction.

5. Fully assembled low-rise residential system

The whole building is composed of dense column-supported frame structure system and container-type modules, and several container-like modules are combined. First, it is prefabricated and integrated in the factory, then packaged into containers, transported to the construction site by standard vehicles, and constructed in the form of assembly at the site.

5. 1 main component system

Foundation system: simple pile foundation and foundation beam are mainly used. The pile foundation adopts precast pile or steel pile, and the foundation beam adopts precast concrete beam. This can reduce the wet operation on site, improve the assembly degree and speed up the construction progress.

Structural system: light steel frame structures such as square steel, H-beam and thin-walled light steel keel are adopted, and the connections between plates and between plates and beams are connected by full-strength bolts.

Enclosure system: it is planned to adopt the sandwich structure form of polymer foamed cement board, silicon-magnesium light lath, GRC light lath and other enclosure wallboard materials plus thermal insulation and decoration integrated board. The interior wall is made of interior materials such as wallpaper, paint and decorative board. The equipment system includes energy system, drainage system, kitchen and bathroom system, fresh air system, floor heating system (electric heating and water heating), solar energy system, lighting system and sewage treatment system.

5.2 Advantages and disadvantages

Due to the relatively cheap land price and inconvenient transportation in rural areas, the fully assembled low-rise residential system is easy to install and more popular in rural areas and suburbs.

6. Prestressed structural system

Prestressed concrete structure is to artificially stress the structural members before the external load, and the resulting prestressed state is used to reduce or offset the tensile stress caused by the external load, that is, to make up for the lack of tensile strength with the help of the higher compressive strength of concrete, thus delaying the concrete cracking in the tensile area.

6. 1 prestress technology type

Pre-tensioning method: the prestressed tendons are tensioned to the design control stress before the concrete pouring of members, and the prestressed tendons are released after the concrete strength reaches a certain level, so that the prestress is applied to the concrete frame.

Post-tensioning method: before concrete pouring of members, holes are embedded in the corresponding positions of prestressed tendons or unbonded prestressed tendons are buried. After the concrete strength reaches a certain level, the prestressed tendons are tensioned to the design tensile stress, and the prestressed tendons are fixed at the end of the concrete members with special anchors. Bonded prestressed tendons need to be filled with grouting materials in the reserved holes to bond prestressed tendons with concrete.

External prestressing technology: the prestressing tendon is located outside the member, or the structural member is composed of prestressing tendon and other materials.

6.2 Advantages and disadvantages

The production process of prestressed concrete is complex, which requires high quality of products, producers and machines and is expensive. At present, domestic residential projects are rarely used.

7. Steel-concrete structural system

Assembled steel-concrete composite structure refers to a structure in which I-beam and precast concrete members produced in factory are combined into a whole in a certain structural way on site, which has the characteristics of steel structure and concrete structure and bears the load together.

7. 1 main components

Composite beam: It consists of steel beams, connectors and reinforced concrete slabs. The upper flange of the composite beam has a reinforced concrete plate with a large cross-sectional area to bear the pressure, which reduces the cross-section of the upper flange of the steel beam, thus saving steel, while the lower flange of the steel beam bears the tension, which is the mechanical characteristics of the composite beam.

I-steel

Laminated slab: Laminated slab structure is formed by welding connectors on pressed steel plates and then pouring reinforced concrete plates. The connector is made of lead studs or steel bars.

Composite truss: the steel truss is welded with steel bars or flexible connectors with studs, and then the reinforced concrete slab is poured.

Composite column: it is made of thin-walled steel tube filled with concrete, also known as concrete-filled steel tube column. Cross-sectional shapes are round and square.

7.2 Connection mode of reinforcement and section steel

Reinforcement connector connection: This method is to weld the connector to the steel member when the member is manufactured, and tighten the reinforcement sleeve with the connector when installing.

Connection of steel bar connecting plate: The steel bar overlapping plate needs to be welded to the steel member as much as possible, and then the steel bar is welded to the overlapping plate during installation.

Steel bar perforated connection: This method is to pre-open steel bar holes in the steel members in the factory, and the steel bars will pass through during the site construction.

7.3 Advantages and disadvantages

Light steel and light concrete structural system can improve the shortcomings of high cost and poor comfort of low-rise light steel residential buildings in rural areas. The application of steel reinforced concrete composite structure technology is still in the exploratory stage, and it is not widely used in China, and the construction technology is not very mature, so there is relatively little construction experience to learn from.

8. Modular structural system

Modular building is to divide a traditional building into a single room or a three-dimensional building space as a building module unit, prefabricate and install the floor, ceiling and wall of the module unit in the factory in advance, transport these building module units to the site after completion, and stack them together like "building blocks" with lifting equipment to form a complete building.

Schematic diagram of modular components (wood structure)

8. 1 connection mode

Intra-module connection: the single truss of modular components is the same as the traditional truss, and all components are connected or extended through toothed plates.

Connecting with the external wall: after the roof truss components are transported to the construction site, the truss is hoisted in place and fixed on the double-layer top beam slab or wall 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 the slab building. Save manpower and material resources, and have high assembly degree. Most of the construction work, including the installation of water, heating, electricity, sanitation and other facilities and house decoration, has been moved to the factory to complete. Only when the components are hoisted and the nodes are handled well can the pipeline be used. Little environmental pollution, and the construction process is green. Convenient for later expansion.

Disadvantages: modular component prefabrication plant has a large investment. Transportation and installation require large equipment. The cost is higher. The area of single module is limited, and the application scope of building is low.

9, primary and secondary frame structure system

9. 1 Frame structure and connection mode

Also known as mega-frame structure. Primary and secondary frame structure is a structural system in which the main structure composed of large components such as giant beams and columns and the secondary structure composed of conventional beams and columns 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 sub-frame is an ordinary frame, and the geometric size, area and moment of inertia of the component section are relatively small, not an order of magnitude. Giant columns usually consist of buildings, elevator shafts or large-section solid columns. Giant beams are usually set every few floors or several floors, and the height of beams generally accounts for one or several floors.

When the main frame is concrete and the secondary frame is steel structure, the main connection modes of the primary and secondary frames are rigid connection, semi-rigid connection and hinge. Rigid connection means that the parts are a whole. After the failure, the included angle between the beam and the column is zero, and all internal forces are transferred from the column to the giant beam. Articulation means that after the structure is stressed, the beam-column can rotate freely without other constraints, and the nodes are independent of each other, so the beam can not transfer the upper bending moment to the column. Semi-rigid connection is a new type of connection between steel joints and hinges.

9.2 Advantages and Disadvantages

Primary and secondary frame structures can increase the space and height of buildings, and are more suitable for large-space buildings such as exhibition halls, which are rarely used in domestic houses.

10, staggered truss structure system

It refers to a long-span spatial structure composed of precast reinforced concrete columns or steel columns, steel trusses, precast floors and other prefabricated components. The main structure adopts assembled staggered truss structure, with external wall, internal partition wall and floor system.

Plane truss interlayers are arranged on the transverse axes of the building, but staggered on the adjacent axes. Between adjacent trusses, one end of the floor slab is supported on the upper chord of the next plane truss, and the other end is supported on the lower chord of the previous truss, thus realizing little or no support during construction.

10. 1 main components and connection methods

Main components: columns, trusses, floors and diagonal bars.

Connection mode of truss and column: firstly, put the steel truss on the bracket, lay the prefabricated floor, and tighten the bolts between the joint plate and column. At this stage, the support bears all vertical shear forces; Then cast-in-place concrete, the vertical shear caused by the new load is borne by the bracket and the gusset plate, and the horizontal tension is transmitted by the gusset plate bolt.

Staggered truss and precast floor slab

Advantages and disadvantages of 10.2

Staggered truss structure is mainly composed of wood structure and steel structure. At present, it is mostly used in public buildings and less used in residential projects in China.

1 1, double-sided superimposed shear wall structure system

Double-sided superimposed shear wall structure is a new type of fabricated structural system, which is composed of prefabricated components such as double-sided superimposed shear wall, precast superimposed beam, precast superimposed floor, precast convex window, precast non-bearing wall with convex window, precast stairs, precast balcony and light slats, and cast-in-place shear wall, cast-in-place concrete joint and cast-in-place floor.

1 1. 1 main components and connection methods

Double-sided composite shear wall is a precast shear wall plate with a cavity formed by strengthening and connecting two precast concrete wall panels produced by the factory through trusses, and concrete is poured into the cavity to form a structural member with overall stress.

Ordinary prefabricated shear wall is a wall prefabricated in the factory. By pouring concrete into the reserved grouting hole on site, it is equivalent to fixing the built wall with the factory prefabricated wall with "adhesive". In the vertical direction, the composite slab shear wall connects the upper and lower walls into a whole by inserting steel bars into the cavity and then pouring concrete into the cavity, and the joint surface is larger. Because the cavity size of the composite wall is much larger than the space required for inserting steel bars, it is more convenient for construction when installing. Due to the small diameter of the casing of the common prefabricated wall, the adjustment space is relatively limited.

The composite shear wall does not need sleeve or mortar anchorage connection, and the upper and lower, left and right connections of the composite shear wall are composed of cast-in-place layers and cast-in-place edge members. The construction is convenient, there is no difficulty in accurately positioning the steel bar and the sleeve, and the construction quality is easy to ensure; At the same time, it also avoids the high cost of special casing and grouting materials.

Advantages and disadvantages of 1 1.2

Double-faced wall pressing has different thickness specifications. Because of 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. Because of the slow construction speed of vertical steel bar connection of ordinary precast shear wall, composite wall can play a unique role, but there is not much engineering experience available in China at present.