Assembled Buildings｜Introduction of Advanced Mature and Applicable New Technologies-Assembled Steel Frame Interlocking Truss Structural System

Technical content

The assembled steel frame staggered truss structure system is composed of frame columns, transverse plane trusses and floor slabs. The columns are arranged in the periphery of the house without center columns, the height of trusses is the same as the height of the floors, and the length is the same as the width of the house structure, and the ends of trusses are supported on the periphery frame columns, and along the direction of the height, the trusses are arranged on the adjacent frame columns for the staggered arrangement of the upper and lower floors. One end of the floor slab is supported on the upper chord of the truss, and the other end is supported on the lower chord of the neighboring truss. It can form a large opening with twice column spacing, obtaining larger opening and depth in terms of architectural function and facilitating free arrangement. It can be made into rectangular doorway, set up corridor or connect neighboring rooms without inclined webs between sections in the span of joist. At present, almost all steel structure products for apartment buildings adopt steel frame structure, steel frame-support structure, steel frame-shear wall structure, etc., which use large amount of steel, have high cost and fail to adapt to the demand of high standardization of apartment buildings, and the characteristics of interlocking truss structure are highly compatible with the needs of apartment buildings.

Fig. 1 Staggered truss axonometric drawing

Due to the characteristics of space force coordination of staggered truss structure, the floor slab is involved in the overall structural calculation under the horizontal force generated by seismic action or wind load, and the characteristics of the floor slab working together should be taken into full consideration in the overall analysis and calculation at the design stage, and the deformation coordination between the floor slab and the main structure cannot be considered by adopting the theory of the traditional framing system, and the seismic structural measures and calculation review of the connection between the floor slab and the planar truss chord must be considered especially. Especially, the seismic-resistant structure of floor slab and plane truss chord connection should be considered and the calculation should be reviewed.

The structure of staggered truss mainly includes steel columns, plane trusses and frame beams. In the production stage, besides meeting the quality standard of steel structure, the steel components should focus on ensuring the precision of plane trusses, adopting standardized molding platforms for processing and production, and taking measures to ensure that there is no deformation of trusses outside of the truss surface during the transportation process.

When installing columns, trusses, beams, braces and other big members in the construction process of staggered joist, it is appropriate to correct and fix them in separate units to form a spatial stabilization system. In the process of installing floor slab, symmetrical lifting should be adopted to prevent the stabilization of trusses in the process of out-of-face construction.

Figure 2 Lifting construction of the truss

Technical indicators

1. Technical indexes in design

(1) The design and construction of interlocking truss structure technical system shall comply with the relevant provisions of the current national standards, such as “Interlocking Truss Steel Structure Design Regulations” JGJ/T 329, “Code for Earthquake Resistant Design of Buildings” GB 50011, and “Standard for Design of Steel Structures” GB 50017;

(2) The safety grade and design service life of the structure shall meet the provisions of the current national standards “Unified Standard for Reliability Design of Engineering Structures” (GB 50153) and “Unified Standard for Reliability Design of Building Structures” (GB 50068); staggered truss structure shall be designed for the limit state of load bearing capacity and the limit state of normal use;

(3) Staggered truss structure should not be counted with combined beam effect when analyzing vertical loading; staggered truss structure should be counted with combined beam effect when analyzing horizontal transverse loading;

(4) The economic height-to-width ratio of staggered truss structure shall be 3~6, and the span of truss shall not be more than 21m; the span-to-height ratio of truss shall be 5~6; the longitudinal column spacing of the structure shall be 6~9m;

(5) When hollow web truss is used in design, truss nodes should be designed as rigid nodes, and the connection between truss chords and columns should be designed according to rigid connection; when hybrid truss is used, chords should be continuous, and the connection between truss web and chords, and the connection between truss and columns can be designed according to articulation.

2. Technical indexes in production and manufacture

After fabrication of members, inspection department shall check and accept the finished products according to the requirements of construction detail drawing and provisions of this specification. The deviation of shape and geometric dimension of truss should be in accordance with the design requirements and relevant provisions of GB 50205 and JGJ 99 of GB 50205 and JGJ 99 of GB 50205 and JGJ 99 of GB 50205 and JGJ 99 of GB 50205, the current national standard of “Code for Acceptance of Quality of Construction of Steel Structure Project”.

3. Technical indexes in construction and installation

(1) The construction organization design for installation of interlaced truss steel frame structure shall be carried out according to the requirements of design documents and construction drawings, and the steel structure installation shall be carried out according to the construction organization design. The installation procedure must ensure that the structure forms a stable space system and does not lead to permanent deformation of the structure.

(2) Installation of staggered joist steel frame structure and construction of building cover shall be carried out successively, and the distance between the two operations shall not exceed 5 floors.

Technological advantages

1. Standardization of staggered truss structure: Due to the unique stress characteristics of staggered truss structure, the specification of truss can be locked so as to realize standardized production;

2. integrated integration technology: realize the integrated integration technology of staggered structure with building maintenance system, equipment system and decoration system, especially the integrated technology of truss and inner partition wall solves the fireproofing problem of steel structure and the integrated integration of pipeline, so as to reduce the dosage of fireproofing paint and the secondary cutting in the construction site, reduce the dust and realize the green construction;

3. industrialized production of staggered truss structure; hot rolled H-type steel columns are used for steel columns and finished rectangular steel pipes are used for truss web bars, which combined with automated welding equipments can realize automated production of staggered truss structure;

4. Good economic performance: steel consumption is saved by 20% and foundation is reduced by 30%;

5. Good spatial transformability: single-span structure without columns in the middle can be realized, which is convenient for later building transformation;

6. High construction efficiency: nodes are fully bolted, convenient construction;

7. high structural rigidity, good comfort in use.

Scope of application

Staggered joist structure is suitable for multi-high-rise buildings with regular building plan such as apartment, hotel, dormitory, hospital and so on in the area of 6~8 degree seismic intensity. Staggered joist and steel frame structure, steel frame support structure can be mixed to meet the specific needs of the building.