1、Technical preparation work
(1) Preparation of construction organization design.
Contents include: project overview and characteristics, construction organization and deployment, construction preparation plan, construction procedure and process design, hoisting plan, construction progress plan, construction site plan, labor force, mechanical equipment, material and component supply plan, quality assurance measures and safety measures, component transportation methods, stacking and site management, environmental protection, etc.
Preparation requirements: The preparation of the construction organisation design should be combined with the specific characteristics of each project, with relevance and operability. For the lifting position and ring construction of large, slender and less stable members, special detailed design and stability check should be made, and reinforcement and protection measures should be adopted if necessary.
(2) Before the installation of the steel structure, the relevant drawings and technical documents should be carefully read and examined, and any problems found should be promptly contacted with the owner and the design unit to solve hidden problems in a timely manner.
(3) Preparation of steel column foundation and supporting surface
-Before installation, the concrete strength of the foundation must meet the design requirements.
-Technical review of the foundation axis, elevation and footing bolts according to the measurement control network.
-Check the exposed condition of the ground bolts, if they are bent and deformed, or if the screw teeth are damaged, they must be corrected.
-Survey the axis of the column in position on the surface of the column base so that the steel column can be accurately positioned.
-Level the column base elevation: concrete column base elevation pouring generally reserved 50 ~ 60mm, in the installation of steel mat plate or sitting slurry bearing plate leveling. When using steel plate for support plate, its area should be determined according to the compressive strength of the foundation concrete, the load borne by the bottom of the second grouting column under the column footing plate and the tightening tension of the footing bolts. When using the slurry bearing plate, using non-shrink mortar, mortar grade should be higher than the strength of the foundation concrete a grade, and there is enough area to meet the bearing capacity.
2、Machinery and equipment preparation.
The construction of single-storey plant is characterized by a large area and a large span, and mobile lifting equipment can be selected. Such as truck cranes (light), crawler cranes (heavy), etc.. Other machinery and equipment: electric welding machine, pegging machine, winch, inverted chain, jack, electric spanner, etc.
3、Component and material preparation.
(1) Steel structure components
Steel components are usually made in the processing plant and transported to the site for lifting and erecting. For larger projects, a separate stacking site should be set up.
When stacking, stack along both sides of the crane route to avoid secondary backing. To ensure that the stacking does not produce deformation and safety requirements, the stack height should not exceed 2m or three layers.
(2) Welding materials
Check the variety, specification and performance of the welding materials.
(3) High strength bolts
The number and quality of bolts required should be checked according to the design requirements and supplied to the site as a package. Sampling and inspection should be carried out on batches of products.
1、Slinging of steel columns
(1) The general steel column is more rigid and is lifted by one point in order to facilitate the correction, and its cupped column is lifted as follows: clean the bottom of the cup before lifting. After the operator has lifted the steel column above the cup, each stands in a good position and steadies the foot of the column to insert it into the cup. Stop dropping the hook when the column is lowered to the bottom of the cup, pry the column with a skid stick to align it with the centre line of the bottom of the cup and then drop the column slowly to the bottom. Tighten the column foot bolts.
Key points for double lift construction.
-Use the same type of crane as far as possible.
-Distribute the load to the lifting points according to the lifting capacity.
-The load of each crane should not exceed 80% of its lifting capacity.
-Coordinate the lifting process with each other. To prevent one crane from losing weight while the other is overloaded, which may cause accidents.
-Signal command: sub-commanders must obey the general command.
2. Correction of steel columns.
(1) Column base elevation adjustment. According to the actual length and flatness and the distance of the bull leg from the bottom of the column, control the base to find out the elevation while ensuring the elevation value of the bull leg.
(2) Plane position correction. Without decoupling the crane, align the positioning line at the bottom of the column with the positioning axis of the foundation and slowly drop to the elevation position.
(3) Steel column correction. Priority is given to the use of wind rope correction (pad at the gap between the bottom of the column and the foundation), for the inconvenience of the use of wind rope steel column can be corrected using adjustable braces.
(4) To prevent axial displacement of the steel column after correction, a 10mm thick steel plate should be used around the column base plate and fixed with welding. After the steel column has been re-calibrated, the footing bolts should be tightened and the load-bearing spacers should be fixed by spot welding at the top and bottom.
1、The specification and technology of the crane track should be in accordance with the relevant national standard provisions in force, if there is deformation by correction before installation.
2、The installation baseline position shall be put with an ink line, or a steel line may be drawn on the top surface of the crane beam as a baseline for track installation.
3、When the rail joint is connected by fishtail plate, it should be noted that.
-The track joint should be top tight, the gap is not more than 3mm, the misalignment is not more than 1mm.
-Expansion joints according to the design requirements, the error is 3mm
-When using the track press to connect with the crane beam, it should be tightly fitted, the distance is not more than 0.5mm.
4、The clearance between the rail joint and the car block should be in accordance with the design requirements, and when the requirements are not clearly stated, the clearance should be left free for expansion according to the temperature.
1、Steel roof frame lifting.
(1) Crawler cranes or tower cranes can be used for lifting.
(2) The lateral stiffness of the steel roof frame is poor and its stability should be determined before installation.
(3) Construction points.
-The tying point must be at the node to prevent deformation of the steel roof frame at the lifting point.
-To ensure that the steel roof frame does not sway and that other elements collide, the ends should be tied with a sliding rope before lifting and relaxed as they are lifted to maintain the correct position.
-When in position, the positioning marks of the lower chord of the steel roof frame are strictly aligned with the marks on the top of the column, and are temporarily fixed by spot welding. -After the first steel roof frame has been lifted into position, it should be fixed with cable ropes on both sides symmetrically. After the second bay of steel roof frame is in place, use one inter-frame adjuster per slope for verticality correction, and install horizontal and vertical supports at the fixed ends of the supports.
2. Steel roof frame correction: use a latitude and longitude meter placed on the top side of the column, parallel to the axis, at a distance of a. Mark a point on the opposite column at the same distance of a. Pick a distance from the centre line of the roof frame, and three points on a vertical plane will make the roof frame vertical.
1. Choice of installation method: portal steel frames generally have a large span, steep slope, little lateral stiffness and are easily deformed, so it is vital to choose the right method. Commonly used methods: Half-bay steel frame is assembled flat in place, installed by a single machine or by a double machine crane, and assembled at the same time. Half-bays are assembled by force on the foundation, lifted by a single machine and closed simultaneously. Two half-bays are assembled on the foundation, and the whole bay is lifted by double or multiple machines, etc.
2. Tying and positioning of lifting points.
(1) The position of the half-bay steel frame should be determined according to the turning radius of the crawler crane and site conditions. The selection of the lashing point of portal steel frame is very important, because the upper chord point is very easy to deform, if the lashing point is not selected properly, it will produce great deformation in the process of straightening and lifting. The lashing method of four points straightening (two points each for the upper and lower chords), two points lifting and sliding of the captive head is commonly used. In this method, the slings of the upper and lower strings are passed through a pulley so that they can be rotated when straightened. At the same time, the hook head sling is placed on the pulley to accommodate the change in hook head position from straightening to lifting, and is pulled with a safety cable to avoid slipping through.
(2) During the lifting process of the steel frame, the height of the hook head, the length of the sling and the tension in the sling are calculated according to the straightened state of the steel frame.
(3) When lifting, the left and right halves are lifted at the same time. When lifting to the design position, the column foot is fixed first, and then the installer stands on the temporary working platform built with the tower crane to install the two half-bay steel frame top hinge pins.
3. Temporary fixing and correction: After lifting, the first steel frame is temporarily fixed with cable ropes (two on each side of each half-bay), and after the second steel frame has been lifted, do not release the hook first, but install all the purlins and horizontal supports, and correct the steel frame at the same time, so that the two steel frames form a whole before releasing the hook. From the third bay onwards, it is sufficient to install a few purlins to temporarily fix the frame. The alignment of the rigid frame is mainly to correct the top hinge and the middle of the column footing, the transverse axis perpendicular to the column footing and the straightness of the upper chord of the rigid frame.
1、Before installation, the construction unit should check the product certificate of conformity, design documents and pre-assembly records of the components, and recheck the dimensions of the recorded components. Deformation and defects of the steel structure beyond the permissible deviation should be dealt with.
Before installation, a detailed measurement and correction process should be prepared. Welding of thick steel plates should be carried out before welding and installation to simulate the process test of the product structure and prepare the corresponding construction process. A certain degree of arching should be preset for the assembled roof frame.
2、After the steel structure is lifted into position, the control points of the component positioning axis, elevation and other design requirements should be measured and marked, and the quality of the lifting butt joint should be checked before welding. Install temporary supports and steel cables to make the steel roof frame safe and stable during the construction process.
3、When the steel structure is installed, the construction unit shall submit the elevation dimensions, welding and painting of each beam after lifting to the supervisor for acceptance respectively.
