Steel structure installation - details you should pay attention to

2018-07-28 13:45:01 Click:

Factory structure

 

The single-storey factory steel structure is generally a space rigid skeleton composed of beams, skylight frames, roof trusses, brackets, columns, crane beams, brake beams (or trusses), various supports, and wall frames.

These components, according to their function, can be merged into the following systems:

(1) Transverse plane frame - is the basic load-bearing structure of the plant, consisting of columns and beams (roof). It bears the horizontal horizontal load and vertical load acting on the plant and is transmitted to the foundation.

(2) Longitudinal plane frame - consists of columns, brackets, crane beams and inter-column support. Its role is to ensure that the longitudinal direction of the plant frame is not deformable and rigid, and to withstand longitudinal horizontal loads (longitudinal braking force of the crane, longitudinal wind, etc.) and transmitted to the foundation.

(3) Roof system - consists of purlins, skylight frames, roof trusses, brackets and roof supports.

(4) Crane beams and brake beams – mainly subject to the vertical and horizontal loads of the crane and transmitted to the transverse frame and longitudinal frame.

(5) Support – including roof support, inter-column support and other additional support. Its function is to connect the individual plane frames into a space system to ensure the necessary rigidity and stability of the structure, and also to withstand the wind and the braking force of the crane.

(6) Wall frame - to withstand the weight and wind of the wall.

In addition, there are some minor components such as work platforms, ladders, doors and windows.

The ratio of the amount of steel used for various components to the total amount of steel used in the entire plant steel structure is roughly as shown in the table.

 

The amount of steel used in the plant area per unit area is an important indicator for assessing the economic rationality of the design. The statistics of the amount of steel used per unit area of ​​various workshops are shown in the table below.

 

Type of column

 

Columns can be divided into: equal-section columns and stepped columns according to the structure.

The columns are divided into sections according to the section of the column: solid belly columns and lattice columns.

 

The column foot is divided according to the boundary conditions of the internal force of the structure, and can be divided into two categories: the hinged column foot and the rigid fixed column foot. The articulated column foot only transmits vertical and horizontal loads, and the rigid fixed column foot transmits the bending moment in addition to the vertical and horizontal loads. The rigid fixed column legs can be divided into three forms according to their configuration: exposed column legs, embedded or inserted column legs, and outsourced column legs. According to the structure of the column foot, it can be divided into a unitary column foot and a separate column foot.

The installation method of the steel column generally adopts three methods, namely, a steel backing plate scheme, a seat padding scheme, and a leveling nut and a leveling steel plate scheme.

 

 

Assembly site assembly

 

Component assembly is the assembly of several segmented members or single pieces on the ground into a complete component or combination of components as designed.

(1) Single component assembly

1). Steel column assembly

Large steel columns are generally segmented at variable sections or upper sections of the shoulder beam for segmental transport. After the construction site is assembled, it is connected by welding or high-strength bolts to form a whole column for lifting.

Firstly, the assembled gantry is set on one axis, the lower part of the steel column is hoisted on the gantry, the level is flattened and the center line is determined, and then the upper part of the column is hoisted to the joint, so that the two column plug ends are aligned and spliced Once in place, carefully align the center axis and length dimension of the column, etc., and then weld or high-strength bolt connection according to the drawings.

 

2). Steel roof truss and skylight frame assembly

Generally, the flat spelling method is adopted, that is, the block members are laid flat on the assembly platform. The skylight frame can also be assembled into one piece with the roof member under the conditions of the crane's performance. When assembling steel trusses, the span error and distortion should be strictly controlled so as not to exceed the allowable value. When turning the truss, in order to prevent deformation, a reasonable lifting point should be determined, and temporary reinforcement should be carried out if necessary.

For large-span trusses with skylights or tall trusses, the vertical spelling method is used because the truss flipping is very difficult.

 

(1) Assembly of components

When large lifting appliances are available and, as the conditions permit, many components can be assembled on the ground into a stable unit block for overall lifting. This can reduce the high-altitude operation, is conducive to safe construction and improve work efficiency, and ensure the stability of component lifting. For example, the combination of two truss trusses and diagonal braces, the inclined bridge frame and the combination of the truss trusses.

The assembly of components is assembled at the installation site, and the assembly position must be within the scope of the installation crane. The assembled project and scale must be determined according to the performance of the crane, the strength of the components, stiffness, stability and construction environment.

 

(1) Assembly of components

When large lifting appliances are available and, as the conditions permit, many components can be assembled on the ground into a stable unit block for overall lifting. This can reduce the high-altitude operation, is conducive to safe construction and improve work efficiency, and ensure the stability of component lifting. For example, the combination of two truss trusses and diagonal braces, the inclined bridge frame and the combination of the truss trusses.

The assembly of components is assembled at the installation site, and the assembly position must be within the scope of the installation crane. The assembled project and scale must be determined according to the performance of the crane, the strength of the components, stiffness, stability and construction environment.

 

 

Pad setting

 

(1) The support pads provided under the column bottom plate shall comply with the following requirements:

a. The backing plate should be placed under the stiffener of the column bottom plate near the anchor bolt. Each anchor bolt side should be provided with 1~2 sets of pads. The pad should be in a flat and tight contact with the base surface. The secondary pouring concrete front plate group should be spot welded and fixed.

b. The stack of each set of slabs should not exceed 5 pieces, and the slabs should be exposed 10 to 30 mm.

c. The pad and the base surface should be close and stable. The area should be determined according to the basic compressive strength and the load on the column bottom before the secondary pouring of the column foot and the tightening pre-tension of the anchor bolt.

d. The edge of the pad should be cleaned of iron oxide slag and burrs. Each pad should be tightly fitted, and each set should bear the force.

e. When using a pair of inclined pads, the slope of the two plates should be the same, and the length of coincidence should not be less than 2/3 of the length of the pad.

(2) The use of a seat mat should meet the following requirements:

a. The location, quantity and area of ​​the seat pad should conform to the design and current specifications;

b. The top surface elevation of each foundation pad should be determined according to the measured distance from the bottom of the column to the distance between the legs. The allowable deviation of the elevation, level and positioning of the seat pad should meet the requirements of the following table.

c. When using a slurry pad, a non-shrinking mortar should be used. The strength of the mortar test block before the column is hoisted should be higher than the strength of the base concrete.

 

 

Pillar installation

 

(1) The elevation observation point and the centerline mark shall be set before the column is installed. The observation points and mark setting positions of the same project shall be consistent and shall comply with the following provisions:

1). The setting of the elevation observation point should meet the following requirements:

Ÿ The setting of the elevation observation point should be based on the support surface of the bull's leg (shoulder beam), and it is located at the column for easy observation;

Ÿ No leg (shoulder beam) column, based on the center of the top mounting hole where the top of the column is connected to the truss.

2). The setting of the centerline sign should meet the following requirements:

设 Set a center mark on the upper surface of the upper surface of the column bottom, and set a center mark on each side of the column line direction;

设 Set a center line on the upper line and the column line on the surface of the column. Each center line has a center mark at the bottom, middle (bull or shoulder beam) and top of the column;

Ÿ The double-legged (shoulder beam) column has a center mark on the surface of the two columns in the direction of the line.

 

(2) When installing multi-column columns, it should be assembled into a whole hoisting.

(3) Steel column installation calibration should meet the following requirements:

1). The deviation caused by the side illumination of the sunlight should be excluded;

2). The column verticality deviation should be controlled according to the temperature (season) and should meet the following requirements:

Ÿ The column supported by each column should be referenced (the verticality correction is close to “0”), and the multi-span building in the row direction should be based on the two columns rigidly connected with the roof truss;

Ÿ When the temperature is higher than the average temperature (summer), the other columns should be inclined to the opposite direction of the reference point;

Ÿ When the temperature is lower than the average temperature (winter), the other columns should be inclined to the reference point direction;

The tilt value of the 柱 column should be determined according to the temperature difference between the temperature and the average temperature during construction and the span or reference point distance of the components (crane beam, vertical support and roof truss, etc.).

3). The allowable deviation of column installation should meet the requirements of the following table. After the crane beam, roof truss installation and crane beam adjustment and fixed connection, the column should be retested, and the deviation should be adjusted.

(4) For pillars with a large slenderness ratio, temporary fixing measures should be added after lifting.

(5) The installation of the support between the columns should be carried out after the column is aligned. The column support should be installed under the condition of ensuring the verticality of the column, and the support should not be bent.

Enterprise dynamic