by Source: Architectural Technology magazine this article analyzes the implementation cases of four deepening design projects and briefly introduces the characteristics and requirements of the deepening design of prefabricated construction projects.
The case involves the external wall cladding system of public buildings, the prefabricated stand system of sports buildings, and the prefabricated component system of residential buildings.
1.
Research on Optimization Design of building scheme of as cast concrete external wall cladding 1.1 soft power R & D building this project is located in Zhongguancun Software Park, Haidian District, Beijing.
The building height is 20.7m, with 5 floors above ground and 2 floors underground.
The first floor is 4.2m high and the second to fifth floors are 3.9m high.
The building plane is rectangular, with an axis grid spacing of 8.4m.
The main structure is a reinforced concrete frame shear wall, and the external wall is a fair faced concrete hanging plate system (Fig.
1 and 2).
▲ Figure 1-2 comparison between the exterior view of softcom power R & D building and detail 1.1.1 building exterior wall scheme: the original design scheme of this building exterior wall proposed to adopt the stone curtain wall system.
After the coordination between Beijing prefabricated building engineering research institute and the owner and the design unit, the consultant proposed to adopt the prefabricated concrete exterior wall cladding system scheme, with the finish of fair faced concrete.
By comparing the advantages and disadvantages of the two curtain wall schemes (Table 1), the owner and the designer unanimously agree with the consultant’s Prefabricated exterior wall scheme by comprehensively considering the external wall facade effect, wall body practice and performance, project cost and other factors.
Table 1 Comparison of advantages and disadvantages of external wall scheme comparison of the project’s prefabricated concrete external wall hanging plate system and stone curtain wall system 1 facade effect: the wall unit is prefabricated as a whole, with fair faced concrete decoration effect and fewer joints, which is very suitable for the project’s facade division scheme.
The stone blocks are broken, and cannot reflect the upright feeling of the upright column and the repeatability of the overall unit.
2 in terms of cost, fair faced concrete plate replaces stone, keel and enclosure wall, which is easy to install, Good economy, large amount of keel and embedded parts of stone curtain wall system, high requirements for thermal insulation materials, and high comprehensive cost 3.
Fire resistance of 230mm thick fair faced concrete hanging plate is prominent, and the fire resistance of steel keel and embedded parts is weak 4.
Structural details: the overall prefabrication of drip, slope, slope, waterproof opening and other details through the formwork manufacturing process is complicated 5.
The installation nodes are simple and easy to operate, and the installation can be completed once, The installation efficiency is high because the partition is very broken, there are many embedded keels, the installation steps are complex, the workload is large, and the efficiency is low.
1.1.2 optimization of the partition scheme of the external wall cladding plate and the optimization of the elevation partition scheme are conducive to improving the technical economy and Implementation effect of the prefabricated building project.
According to the facade modeling characteristics of this project, we have conducted a comparative study on the facade partition scheme.
Scheme 1 is a lattice scheme with one window as the prefabricated unit (Fig.
3), and scheme 2 is a lattice scheme with two windows as the prefabricated unit (Fig.
4).
▲ Figure 3 external wall cladding blocking scheme 1 ▲ Figure 4 external wall cladding blocking scheme 2 compares the two schemes from five aspects: elevation effect, design change amount of the original scheme, reserved quantity of structural embedded parts, production efficiency and installation efficiency (Table 2).
It can be seen that scheme 2 is superior to scheme 1.
The final optimization scheme has been unanimously agreed by the owner and the designer.
Table 2 Comparison of facade division schemes: facade effect; number of embedded parts for facade modification; production efficiency; installation efficiency; scheme 1: there are many open joints, which are lower; scheme 2: there are few open joints, which are lower; scheme 2: there are few open joints, which are higher; 1.1.3 architectural structure design of external wall cladding: the architectural structure design of the project mainly includes waterproof, fire prevention and thermal insulation.
Since the thickness of concrete slab is 230mm, the waterproof and fire prevention performance of external cladding is superior.
The key is to do a good job in joint waterproof structure The joint fire protection and inter floor fire protection structures are as follows: (1) the waterproof structure of all joints adopts the combination of material waterproof and structural waterproof.
The waterproof structure of horizontal joints of external cladding is to reserve openings at the upper and lower openings of external cladding.
After the installation of external cladding, the outer side is filled with backing materials and sealed with building sealant (Fig.
5a).
▲ Figure 5 (a) horizontal joint structure (2) the vertical joint of the hanging plate is an “L” shaped joint with structural waterproof characteristics.
The outer layer is filled with backing materials and embedded with building sealant (Figure 5b).
▲ Fig.
5 (b) vertical joint structure (3) waterproof tongue and groove shall be made around the window, the joint between the window frame and the hanging plate shall be sealed with sealant, the upper mouth shall be made with drip groove, and the lower mouth shall be designed with slope water (Fig.
5C).
▲ Figure 5 (c) window structure (4) the installation joint between the external cladding and the cast-in-situ structure is filled with rock wool insulation board.
The installation gap between the external cladding and the cast-in-situ wall at the parapet is sealed with metal aluminum gusset plate, which can effectively solve the waterproof problem of the upward joint (figure 5d).
1 external hanging board; 2 building sealant; 3 backing material; 4.
Rock wool shall be filled for thermal insulation; 5 self extinguishing extruded polystyrene insulation; 6 drip tank; 7 windows; 8 cast in situ parapet; 9 roof waterproof roll up; 10 metal capping ▲ Figure 5 (d) parapet structure (5) the horizontal joint of the external cladding plate is located in the middle of the structural beam, so the fire prevention focus of the horizontal joint is to do a good job of interlayer fire prevention.
The 50mm construction and installation joint reserved between the external cladding plate and the main structure is filled with rock wool and the outer opening of the joint is sealed with elastic mortar, so as to give consideration to the thermal insulation and fire prevention structure.
(6) The upper and lower openings of the main structure beam are provided with hanging plate installation nodes, which is the key point of fire prevention.
We use semi wet spraying rock wool to close the installation nodes.
(7) The external enclosure of the project adopts the internal insulation structure, which meets the design requirements of the project.
All internal insulation adopts 50mm thick self extinguishing extruded polystyrene board, and the gap between the external cladding and the main structure is filled with rock wool insulation to form a complete insulation system.
1.1.4 the design of external wall hanging plate connection structure is that the dead weight of the concrete hanging plate is large.
Under the consideration of the seismic design conditions, each hanging plate is provided with two corbel support points.
The vertical load of the hanging plate can be transmitted to the main structure through the steel corbel..
