Abstract: Steel structure is a structure composed of steel materials and is one of the main types of building structures. The structure is mainly made of steel and steel plates, and various components or parts are usually connected by welds, bolts or rivets. Because of its light weight and simple construction, it is widely used in large factories, venues, super high-rises and other fields. Next, let’s learn more about it with the editor. Steel structure engineering installation methods
1. Preparations before installation
1. Technical preparations
(1) Preparation of construction organization design:
Contents include: project overview and characteristics, construction organization and deployment, construction preparation plan, construction procedures and process design, hoisting plan, construction progress plan, construction site layout 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 construction organization design should be based on the specific characteristics of each project and be targeted and operable. For the lifting positions and lifting ring structures of large, slender, and poorly stable components, special detailed design and stability checks should be made, and reinforcement and protection measures should be adopted when necessary.
(2) Before installing the steel structure, the relevant drawings and technical documents should be carefully read and reviewed. If any problems are found, the owner and the design unit should be contacted in a timely manner to solve the hidden dangers in a timely manner.
(3) Preparation of steel column foundation and supporting surface Before installation, the strength of the foundation concrete must meet the design requirements. Conduct technical review of foundation axis, elevation, anchor bolts, etc. based on the measurement control network. Check the exposure of the anchor bolts. If there is any bending, deformation or damage to the threads, they must be corrected. Pop the seating axis of the column onto the surface of the column base so that the steel column can be seated accurately. Leveling the column base elevation: 50 to 60 mm is generally reserved for the concrete column base elevation, and steel pads or grout bearing plates are used for leveling during installation. When a steel backing plate is used as the supporting plate, its area should be calculated and determined based on the compressive strength of the foundation concrete, the load borne by the secondary grouting column bottom under the column foot plate, and the tightening tension of the anchor bolts. When using mortar to support the slab, use non-shrinkage mortar. The mortar grade should be one level higher than the strength of the foundation concrete, and there should be enough area to meet the load-bearing capacity.
2. Preparation of mechanical equipment:
The construction characteristics of single-story factory buildings are large area and large span, and mobile lifting equipment can be selected. Such as truck crane (light), crawler crane (heavy), etc. Other machines include: welding machines, bolting machines, winches, chains, jacks, electric wrenches, etc.
3. Preparation of components and materials:
(1) Steel structural components
Steel components are usually made in processing plants and transported to the site for hoisting and assembly. The principle of stacking should be "emphasize the near and despise the far". For larger projects, separate storage areas should be set up.
When stacking, stack them close to both sides of the crane's route to avoid secondary misfortune. In order to ensure that stacking does not cause deformation and meets safety requirements, the stacking height should not exceed 2m or three layers.
(2) Welding materials
Inspect the variety, specifications and performance of welding materials.
(3) High-strength bolts
The number and quality of the required bolts should be inspected according to the design requirements and supplied to the site. Sampling inspection should be carried out on batches of products.
2. Installation process of steel columns
1. Hoisting of steel columns
(1) Generally, steel columns have better rigidity and are easier to correct during hoisting. , using one-point lifting, the cup mouth column lifting is as follows: clean the bottom of the cup before lifting. After the operators hoist the steel column above the mouth of the cup, they stand in their respective positions, stabilize the foot of the column and insert it into the mouth of the cup. Stop the hook when the column drops to the bottom of the cup, use a crowbar to pry the column to align it with the center line of the bottom of the cup, and then slowly drop the column to the bottom. Tighten the stud bolts.
Key points for double-machine lifting construction: Try to use the same type of crane. According to the lifting capacity, load distribution is carried out on the lifting points. The load of each crane cannot exceed 80% of its lifting capacity. During the lifting process, they must cooperate with each other and coordinate their movements.
In case one crane is weightless and the other is overloaded, an accident may occur. Signal command: Sub-commanders must obey the general commander.
2. Correction of steel columns:
(1) Adjustment of column base elevation. According to the actual length and flatness and the distance between the corbel and the bottom of the column, the control foundation is used to find the elevation while ensuring the elevation value of the corbel.
(2) Plane position correction. Without decoupling the crane, align the positioning line at the bottom of the column with the foundation positioning axis, and slowly lower it to the elevation position.
(3) Steel column correction. The wind rope correction is preferred (place pads at the gap between the bottom of the column and the foundation). For steel columns where it is inconvenient to use wind ropes, adjustable struts can be used for correction.
(4) In order to prevent the axial displacement of the steel column after correction, 10mm thick steel plates should be positioned around the bottom plate of the column and fixed with welding. After the steel columns are recalibrated, the anchor bolts are tightened and the load-bearing pads are spot welded up and down.
3. Installation of crane rails
1. The specifications and technology of the crane rails should comply with the relevant national standards. If there is any deformation, it can be installed only after correction.
2. Use an ink line to place the installation baseline position. You can also stretch a steel wire on the top of the crane beam as the track installation baseline.
3. When the track joints are connected by fishplates, attention should be paid to: The track joints should be tightened, the gap should not be greater than 3mm, and the misalignment should not be greater than 1mm. The expansion joints are carried out according to the design requirements, with an error of 3mm. When using rail clamps to connect the crane beams, they should be tightly fitted and the spacing should not be greater than 0.5mm.
4. The gap between the track joint and the car stop must meet the design requirements. When no requirements are explicitly stated, a gap for free expansion should be left according to the temperature.
IV. Installation process of steel roof trusses
1. Hoisting of steel roof trusses:
(1) Crawler crane or tower crane can be used for hoisting.
(2) The lateral stiffness of the steel roof trusses is poor. Its stability needs to be determined before installation. If it is insufficient, it should be reinforced.
(3) Construction points: The binding points must be at the nodes to prevent the steel roof trusses from deforming at the hanging points. In order to prevent the steel roof truss from swinging and other components from colliding, the two ends should be tied with slide ropes before hoisting and relaxed as they are hoisted to maintain the correct position. When in place, the positioning marks on the bottom chord of the steel roof truss and the column top marks are strictly aligned and temporarily fixed by spot welding. ?After the first steel roof truss is hoisted in place, cable wind ropes should be arranged symmetrically on both sides to fix it. After the second steel roof truss is in place, use an inter-roof adjuster for each slope to correct the verticality, and install horizontal and vertical supports at the fixed end supports.
2. Calibration of steel roof trusses: Use a theodolite on one side of the column top, parallel to the axis, at a distance a. Mark a point with the same distance a on the opposite column, and pick out a from the center line of the roof truss. distance, three points on a vertical plane can make the roof truss vertical.
V. Portal steel frame installation process
1. Selection of installation method: Portal steel frames generally have large spans, steep slopes, small lateral stiffness, and are easy to deform, so Choosing the right method is crucial. ?Commonly used methods: the half-frame steel frame is assembled flat on the spot, installed on a single machine or installed with a double machine crane, and closed at the same time. The half-framed steel frame worked hard on the foundation, was raised by a single machine, and closed at the same time. Two and a half steel frames are assembled on the foundation, and two or more machines can be used to complete the lifting, etc.
2. Lifting point lashing and positioning:
(1) The positioning of the semi-steel frame should be determined according to the slewing radius of the crawler crane and site conditions. The selection of the lashing points of the portal steel frame is very important. Since the upper chord point is easily deformed, if the lashing points are improperly selected, great deformation will occur during the straightening and lifting processes. The commonly used binding methods are four-point straightening (two points each for the upper and lower strings), two-point lifting, and sliding head. In this lashing method, the slings at the upper and lower hanging points are passed through pulleys so that they can rotate when straightening. At the same time, put the hook head sling on the pulley to adapt to the change in the hook head position from straightening to lifting, and use a safety rope to pull it to prevent it from slipping.
(2) During the hoisting process of the steel frame, the height of the hook head, the length of the sling and the tension in the sling are all calculated according to the straight state of the steel frame.
(3) When hoisting, the left and right halves are lifted at the same time. When they are lifted to the designed position, the column feet are fixed first, and then the installer stands on a temporary workbench built with a tower crane to install the two half-frames. Steel frame top hinge pin.
3. Temporary fixation and correction: After hoisting, the first steel frame is temporarily fixed with cable wind ropes (two on each side of each half frame). After the second steel frame is hoisted, Do not loosen the hook first. All purlins and horizontal supports must be installed, and the steel frame must be corrected at the same time to make the two steel frames form a whole before loosening the hook. Starting from the third frame, just install a few purlins to temporarily fix the rigid frame. The correction of the rigid frame is mainly to correct the top hinge and the middle of the column foot, the transverse axis perpendicular to the column foot and the straightness of the upper chord of the rigid frame.
How to control the quality of steel structure construction
1. Before installation, the construction unit should check the product certificates, design documents and pre-assembly records of the components, and re-inspect and record the dimensions of the components . When the deformation and defects of the steel structure exceed the allowable deviation, they should be dealt with.
Before installation, detailed measurement and correction processes should be prepared. For thick steel plate welding, process tests simulating the product structure should be conducted before welding and installation, and corresponding construction processes should be prepared. A certain camber should be preset for the assembled roof trusses.
2. After the steel structure is hoisted in place, the design requirement control points such as component positioning axis and elevation should be measured and marked, and the quality of the hoisted butt joints should be inspected before welding. Install temporary supports and steel corrugated cables to make the steel roof trusses safe and stable during construction.
3. When installing steel structures, the construction unit should submit the elevation dimensions, welding, painting, etc. of each component after hoisting to the supervisor for acceptance.