1、 On site installation of steel structure

（1） On site installation scheme

The structural form of the steel structure project is frame. Combined with the component form, weight, location and the actual situation of the construction site, as well as the performance of various lifting parameters of the tower crane set on site, the steel structure of the project adopts the comprehensive installation method.

1.Site installation method of steel structure:

The weight of frame column, beam and other components of the workshop is light, and nk250 25t truck crane is mainly used for hoisting.

2.Site installation sequence of steel structure:

The steel structure hoisting adopts the principle of “from the middle to the outside, from the column to the beam, from the bottom to the top”.In the middle part of the plant, a stable frame system is first formed, and then the remaining steel columns and beams are symmetrically installed.The sequence is shown in the following figure:

Schematic diagram of construction sequence of single plant (from middle to both ends)

（2） Analysis of main installation components

The main components of the project are steel column, steel beam, purlin, diagonal brace and other components.The steel material is Q345 B.The weight is not too heavy, as follows:

（3） Selection and arrangement of lifting equipment

1.Crane selection

According to the site layout plan, a total of 5 steel structure workshops need to be installed. Combined with their lifting performance and working condition analysis, four nk250 25t truck cranes are equipped on site.

The main application areas and uses are as follows:

2.The working condition performance of truck crane is shown in the table below

The rated total lifting capacity of nk250 25t truck crane is as follows (unit: T)

（4） Installation process of steel structure

1.Overall process of installation process

Re survey of anchor bolt → unloading of steel members → site inspection of components → direct hoisting of truck crane in place → temporary fastening of anchor bolts → temporary binding and stabilization of cable wind rope → adjustment of axial position and verticality of steel column → fastening and welding of steel column bolt and column base pressing plate → installation of next steel column → installation of tie bar between steel columns → formation of the first stable lattice system → assembly of steel roof truss into a whole and doubleThe first steel roof truss is formed by machine lifting and hoisting in place → column and roof truss system are installed symmetrically on both sides →The installation is completed and the structure is accepted. 

2.Steel structure installation area division

The project consists of five parts: Meat freezing, meat market, vegetable storage, vegetable market and open sales area. According to the division of construction flow section, it is divided into five areas. The specific division areas are shown in the figure below.

3.Overall installation sequence of steel structure

According to the overall plan of the project, it is planned to arrange two construction teams to carry out construction at the same time. The overall construction sequence of the five areas is as follows: Zone 1, zone 2Five districts. 

For the same workshop, the installation sequence of steel members adopts the method of “reducing error, from the middle to both ends”.

4.Installation sequence of steel structure

(1) Install the first row of steel columns.

(2) Install the second row of steel columns.

(3) Install coupling beam (or tie bar) between steel columns.

(4) The first steel roof truss was installed by double crane.

(5) The second steel roof truss is installed by double crane.

(6) The purlins between the two roof trusses are installed to form a stable frame system.

(7) Continue to install the steel column, coupling beam, roof truss and purlin of the next frame.

(8) Continue to install the roof truss according to the above sequence, and install the support between the columns.

(9) , continue with installation.

(10) Roof truss installation completed.

5.Installation of support between columns

The joint plate bolt connection and welding connection are adopted for the inter column support and steel column. The manufacturing and installation deviation of steel column may have a great influence on its installation. The inter column support is transported to the site for installation after the whole frame is assembled in the factory.The weight of the support between columns is light, and it can be hoisted with a 25t truck crane.

The hoisting sequence of cross column support is as follows:

During hoisting, it is divided into three units 1, 2 and 3 for hoisting respectively.The three units are plane truss structure, and the hoisting is integral hoisting.During the installation, install 3 first, then use the chain block to pull it to the steel column for temporary fixation, then install 1, connect the nodes of 3 and 1, remove the chain block, and then install 2.The three single trusses of the whole hoisting are hoisted at four points by 25t truck crane.

6.Installation of roof truss beam

(1) Deformation prevention measures for long steel frame hoisting

The long steel frame is 56 meters long. In order to prevent the deformation of the long steel frame in the lifting process, the method of double crane lifting and four point hoisting is adopted for the hoisting of long components. During the four point hoisting, the four points are stressed synchronously, and the distance between the lifting points is ensured to be about 6 meters. In this way, the steel frame can be evenly stressed during the hoisting process, and the design size can be maintained in accordance with the specification requirements.The details are shown in the following figure:

Schematic diagram of double crane steel roof truss hoisting

(2) Hoisting machinery and construction measures

When the roof truss steel beam is hoisted, a chain block is connected in series with the steel wire rope to adjust the posture of the steel beam in the air.

After the roof steel beam is hoisted in place, the relevant roof steel purlins should be connected before the hook is released to form a stable structure of space frame.If the roof steel purlin cannot be installed before the hook is released, the cable wind rope should be set to prevent the steel beam of roof truss from skewing.Before hoisting, the cable wind rope is fixed to the steel beam of roof truss, with four cables in total. The pulling position is 1 / 3 of the length of the steel beam, and the bottom is set at the foot of the nearby steel column.The cable wind rope is selected as Ф 13.5mm and tightened with 1t chain block.After the coupling beam between the main steel beams of the roof is installed, the cable wind rope can be removed.

   Due to the allowable deviation of steel column installation, and the roof truss beam and steel column are connected by high-strength bolts, when hoisting in place, one end shall be connected first (but not fastened). If the other end can be directly connected, it shall be directly connected in place. If the deviation is too large, the cable rope of steel column shall be adjusted and the height spacing of roof beam shall be adjusted. However, the deviation of steel column itself shall meet the requirements of specificationsPlease.

 2、 Construction of roof and wall system

（1） Purlin installation

1.Ground transportation of purlin 

The purlin shall be transported to the crane position by truck or flatbed truck from the raw material stacking site, and then bound with steel wire rope.

2.Vertical transportation:

The tightly bound purlins shall be lifted to the installation position by the on-site crane.Because the purlin has small unit weight and is a linear member, it is easy to bind. During hoisting, the main time-consuming is to lift and drop the hook. In order to improve the installation speed, the method of one hook and multiple cranes is adopted to improve the working efficiency, as shown in the figure.

3.Overall installation sequence of purlin

The installation sequence of purlin and purlin bracket is as follows:

Installation of purlin bracket → installation of purlin → installation of roof system

erection sequence

Installation process of purlin bracket and purlin

4.Installation and positioning of purlin

(1) determine whether the height difference of each purlin positioning point needs to be adjusted according to the production and installation standards of roof panel of the system project and the survey data handed over by the steel structure construction unit. If it needs to be adjusted, the steel plate with the required adjustment amount shall be used for height adjustment.The number of purlins shall not be more than three, and welding treatment shall be adopted between blocks to make the whole purlin surface basically smooth according to the installation standard.The cushion block must be derusted before installation, and the coating treatment shall be in accordance with the painting requirements of purlin.

(2) the positioning and installation of metal roof panel system is mainly divided into purlin supporting plate positioning and steel support positioning. The installation shall be carried out in strict accordance with the approved design drawings.The total station and theodolite shall be used for setting out according to the design requirements, and the positioning line shall be installed on the steel support.

5.Installation of purlin

(1) purlin bracket positioning

Purlin bracket is welded on steel structure beam and support.The positioning method of purlin bracket is as follows: according to purlin distance and axis, the intersection line between purlin and steel structure beam (the positioning line popped by setting out) is determined, which is the installation line of purlin supporting plate.

(2) installation of purlin bracket

As shown in the figure below, the angle between purlin bracket and flange plane of steel beam shall be ensured to be 90 ± 1 ° after positioning, and the position deviation shall be within 5mm.In the process of welding, measures should be taken to reduce the deformation. First, symmetrical spot welding should be carried out to check the angle of purlin bracket, and then welding should be carried out after it is qualified. The unqualified angle should be corrected.Spot welding should be firm.The diameter of electrode is 4mm, and the model of electrode is E5016.When welding, the current should be appropriate, and there should be no air hole, crack, undercut and overlap after the weld forming. The weld size should meet the design requirements, the welding wave should be uniform, and the weld shape should be beautiful.

(3) anti corrosion treatment

After welding, anti-corrosion treatment shall be carried out on the weld and its surrounding areas. The anti-corrosion material shall be the paint meeting the design requirements, and two coats of paint shall be applied.Before anticorrosion, the coating and dirt on the weld surface shall be removed.

(4) purlin fixation

All purlins in the project are connected with purlin supporting bolts. After the purlins are lifted in place, it is necessary to check whether the top surface of the purlins being installed is flush with the top surface of adjacent purlins installed. If the purlins are not flush, adjustment shall be made.When the height difference of the top surface of the adjacent purlins is within 2mm, the bolts can be tightened. During the installation, the top surfaces of the two adjacent purlins should be adjusted to be consistent as far as possible.

（2） Gutter installation

1.Installation of gutter support

(1) in this project, small section steel is used as gutter support;

(2) install the gutter support according to the designed spacing, and check whether the top elevation of the support is consistent.

2, gutter installation

(1) sectional gutter splicing

Before butt joint of gutter, the cutting edge shall be polished. During butt joint, the gap between butt joints shall not exceed 1 mm. Spot welding shall be carried out every 10 cm to confirm that the welding requirements are met.The type of electrode shall be determined according to the base metal.The weld is formed in one pass.In order to speed up the installation speed of the gutter, two or three gutters can be assembled on the ground, and then lifted to the installation position or the nearest position with a 16 ton crane. This can not only improve the docking quality of the gutter, but also greatly improve the working efficiency.

In order to control the deformation caused by welding, the method of spot welding first and then welding in sections must be adopted.After welding, discoloration will appear in the range of 20 mm on both sides of the weld, which should be removed by grinding and polishing with cloth grinding wheel immediately.

(3) after the gutter is installed, the bottom shall be flat without ponding.

3.Water test of gutter

After the gutter is installed, the gutter should be filled with water to check whether the gutter is leaking. After the gutter is not leaking, check and accept it.In case of leakage, the leakage shall be repaired by welding again, polished, and repeated leak proof test until qualified.

（3） Installation of profiled steel sheet for roof and wall

The roof profiled steel sheet of the project is planned to adopt 90 thick lined polyurethane color steel plate, and the wall profiled steel plate is planned to adopt 70 thick lined thermal insulation polyurethane color steel plate.

1.Basic requirements:

(1) the plate should be handled with care to avoid collision and dragging the floor to avoid damaging the plate.

(2) first, determine the starting point of installation, which is determined according to the design drawings and site conditions, generally from one side to the other side.During installation, the datum line should be snapped to avoid accumulated error.

(3) determine the installation direction, and install from one end to the other after ejecting the datum line.

(4) the edge lap of two parallel surfaces should be straight to ensure the indoor beauty.The joint direction of the panel should avoid the main angle of view. When the main wind direction is obvious, the lap edge of the panel should face the downwind direction.

(5) the profiled steel sheet shall be reliably overlapped on the supporting member, and the lap length shall meet the design requirements and shall not be less than the provisions in the following table.

Lap length of profiled steel sheet on supporting member (mm)

(6) the allowable deviation of profiled steel plate installation shall meet the requirements in the table below.

Allowable deviation of profiled steel plate installation (mm)

2.Installation method:

(1) set up pedestrian walkway on purlin to ensure construction safety and construction progress.

(2) during installation, the plate shall be lifted to the roof with a crane.The lifting belt must use nylon belt or cloth belt for flexible hoisting, and steel belt is not allowed.Protective wood strips should be inserted between the package and the sling or package to prevent deformation of the plate edge.

(3) before installation, the surface of the board should be cleaned and cleaned first, and then check whether there are residues on the board surface, such as cleaning agent and water to clean the mixture.Dry the surface with a dry cloth.

(4) the laying direction of the board must be against the dominant direction.In the process of roof panel installation, the line must be snapped at any time to prevent accumulated error.

(5) in the process of roof panel installation, roof ridge cover plate and waterproof plug must be installed at the same time.

(6) the slab is sensitive to the concentrated load, so the construction personnel shall not gather together to avoid the local damage of the slab caused by the concentrated load.

(7) when installing the roof panel, it is necessary to lift and install the roof panel at the same time. At least, the plate on the roof should be installed on the same day. For the board that has not been installed on the same day, corresponding measures must be taken to prevent falling.

(8) quality requirements: the dimension of the profiled plate shall be correct, the surface shall be clean, there shall be no visible concave convex and crease, the joint shall be straight, the vertical and horizontal overlapping shall be straight, and the joint shall be even and neat, tight without warping and wrong drilling holes.

3.Installation of ridge plug and ridge plate:

(1) setting out to locate the starting datum line of the first ridge plate, and determine the installation control line of the ridge plug and the two sides of the ridge plug along the installation direction.

(2) install the roof ridge plug plate. The contact part between the plug plate and the profiled plate shall be fully coated with waterproof glue, and then the installation shall be carried out. The plug shall be sealed with waterproof glue to prevent leakage, and the subsequent plugs shall be installed in turn.

(3) install the first ridge plate and adjust the positioning according to the initial datum line and control line.Measure and mark the positioning plate of the bent water baffle on the roof ridge plate, cut the opening with scissors, fix the ridge plate on the profiled plate with the specified riveting top, seal the fixed parts with waterproof glue, and bend the water baffle according to the bending positioning line drawn.

4, flashing, corner wrapping, expansion joint cover plate installation:

(1) set out the starting datum line of the first block, and determine the control lines of the lines on both sides of the board along the installation direction.

(2) install the first plate, install the second plate according to the reference line and control line, adjust the positioning, fix it on the fixed plate, and seal the fixed parts with waterproof glue to prevent leakage.

(3) measure and draw the overlap positioning line between the second plate and the first plate on the first plate, apply waterproof glue on the lap joint of the plate, install the second plate to adjust the positioning, fix the fixing parts and coat waterproof glue for sealing, and then install the second plate and subsequent plates in turn.

5.Wall panel installation

Installation process of wall panel: installation of profiled steel plate of inner wall plate → installation of thermal insulation layer → installation of color profiled steel plate of outer wall plate → installation of color plate accessories of wall surface → completion of wall engineering

Key process practices:

a. Before the construction and installation of the inner wall panel, the sliding frame shall be erected first, and the sliding frame shall be suspended.

b. One lap joint shall be considered longitudinally, and the lap joint shall be considered at purlin position, the lap length shall not be less than 100 mm, and the upper opening of lower plate shall not exceed the upper edge of purlin.

c. Lines must be drawn before installation to ensure the plate and screw vertical and accumulated error.