by Source: Architectural Skills magazine This paper analyzes the implementation cases of four deepening design projects, and briefly introduces the characteristics and requirements of deepening design of prefabricated building projects.
The case involves the external wall cladding system of public buildings, prefabricated bleachers system of sports buildings and prefabricated component system of residential buildings.
1.
Research on the Optimization Design of the Architectural Scheme of As cast Concrete Exterior Wall Cladding 1.1 The project is located in Zhongguancun Software Park, Haidian District, Beijing, with a building height of 20.7m, five floors above the ground and two floors underground.
The first floor is 4.2m high, and the second to fifth floors are 3.9m high.
The building is arranged in a rectangular plane with an axis grid spacing of 8.4m.
The main structure is reinforced concrete frame shear wall, and the exterior wall is made of fair faced concrete hanging plate system (Figures 1 and 2).
▲ Fig.
1-2 Comparison between the exterior view and details of the R&D building of Softcom Power 1.1.1 Building exterior wall scheme The stone curtain wall system is proposed to be used in the original design scheme of the exterior wall of the building.
After the coordination between the Beijing Research Institute of Prefabricated Building Engineering and the owner and the design unit, the consultant proposed that the prefabricated concrete exterior wall hanging board system can be used, and the finish is fair faced concrete.
By comparing the advantages and disadvantages of the two curtain wall schemes (Table 1), the Employer and the Designer agree with the Consultant’s prefabricated exterior wall scheme by comprehensively considering the facade effect, wall body practice and performance, project cost and other factors.
Table 1 Comparison of Advantages and Disadvantages of Exterior Wall Schemes Precast Concrete Exterior Wall Cladding System Stone Curtain Wall System 1 Overall prefabrication of wall units with facade effect, fair faced concrete decoration effect, and fewer abutments, which is very suitable for the facade grid scheme of this project.
The stone blocks are broken, and can not reflect the upright feeling of the column and the repeatability of the overall unit.
2 In terms of cost, fair faced concrete slabs replace stone, keel, and enclosure wall, and are 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, outstanding fire resistance of steel keel and embedded parts, weak fire resistance 4.
Structural details, such as drip, slope, slope, waterproof opening, are prefabricated as a whole through the formwork manufacturing process.
5.
The installation of nodes is simple and easy to operate, and the installation can be completed once hoisting, 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.
According to the facade modeling characteristics of this project, we conducted a comparative study on the facade grid scheme.
Scheme 1 is a grid scheme with one window as the prefabricated unit (Figure 3), and Scheme 2 is a grid scheme with two windows as the prefabricated unit (Figure 4).
▲ Figure 3: Scheme 1 of wall cladding blocks ▲ Figure 4: Scheme 2 of wall cladding blocks compares the two schemes from five aspects: facade 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 agreed by the Owner and the Designer.
Table 2 Comparison of facade division schemes Facade effect Facade change Quantity of embedded parts Production efficiency Installation efficiency Scheme 1 There are more open joints, more are lower, 2 There are less open joints, less are higher 1.1.3 Architectural structure design of external wall cladding The architectural structure design of this project mainly includes waterproof, fireproof, thermal insulation, etc.
Since the thickness of concrete slab is 230mm, the waterproof and fireproof performance of external cladding itself is superior, the key is to do a good job of joint waterproof structure The specific practices of node fire protection and interlayer fire protection structure are as follows:.
▲ Fig.
5 (a) Structure of horizontal joint (2) The vertical joint of hanging plate is an “L” joint with structural waterproof characteristics, and the outer layer is sealed with filling backing material and embedded with building sealant (Fig.
5b).
▲ Fig.
5 (b) Vertical joint structure (3) Make waterproof tongue and groove around the window, seal the joint between the window frame and the hanging plate with sealant, make a drip trough at the upper opening, and make a slope design at the lower opening (Fig.
5c).
▲ Fig.
5 (c) Window structure (4) The installation seam between the cladding plate and the cast-in-place structure is filled with rock wool insulation board, and the installation gap between the cladding plate and the cast-in-place wall at the parapet is sealed with metal aluminum gusset plate, which can effectively solve the waterproof problem of the overhead joint (Fig.
5d).
1 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 coping ▲ Fig.
5 (d) Parapet structure (5) The horizontal joint of the cladding is located in the middle of the structural beam, so the focus of the horizontal joint fire prevention is to do a good job of interlayer fire prevention.
The 50mm construction installation joint reserved between the cladding and the main structure is filled with rock wool and the external opening of the joint is sealed with elastic mortar, so as to give consideration to the thermal insulation and fire protection structure.
(6) The upper and lower openings of the main structural beam are equipped with hanging plate installation nodes, which is the key point of fire protection.
We use semi wet spraying rock wool to seal the installation nodes.
(7) The external enclosure of this project adopts the internal insulation construction method, which meets the design requirements of the project itself.
All internal insulation uses 50mm thick self extinguishing extruded polystyrene board.
The gap between the external hanging board and the main structure is filled with rock wool insulation to form a complete insulation system.
1.1.4 The connection structure of external wall hanging plate is designed to have a large dead weight of concrete hanging plate.
In consideration of the seismic design conditions, each hanging plate is provided with two bracket support points.
The vertical load of the hanging plate can be transferred to the main structure by projecting the steel bracket from the structure..
