Steps for Lifting Prefabricated Beams in Houses
The steps for lifting prefabricated beams in houses are as follows:
Surveying and Marking: First, mark the control line for the length of the prefabricated beam's placement on the prefabricated column, for example, a 10-millimeter control line. At the same time, use a chalk line to mark the beam bottom elevation and beam edge control lines on the corrected wall to ensure accurate subsequent installation positions.
Installing Support Frames: Install support frames for the prefabricated beams and composite floor slabs according to design requirements. The bottom of the support frame should be padded with a 20-millimeter-thick wooden pad. Adjustable bases should be used at the bottom and top to accommodate different height requirements. The main structure of the frame uses steel pipes with a diameter of 48 millimeters, connected by couplings to form a stable framework. The main battens also use steel pipes with a diameter of 48 millimeters, while the secondary battens use square timbers measuring 50×100 millimeters to ensure the load-bearing capacity of the support system meets requirements.
Component Inspection: Before lifting, conduct a comprehensive inspection of the prefabricated beams, including checking if the serial numbers match the drawings, whether the lifting rings have cracks or deformations, if the specifications and dimensions meet design requirements, and if the quantity and positions are accurate. Also, confirm that the positions of the secondary beam openings are correctly reserved to avoid installation failures due to component defects.
Component Lifting: Use a lifting beam spreader for lifting. Fix the lifting hook at the preset lifting points on the prefabricated beam. When lifting, first raise the beam about 500 millimeters above the ground, pause to check if the lifting cables are twisted or stuck, and confirm that the load is evenly distributed across all lifting points to prevent damage or overturning of the component due to excessive local stress.
Component Positioning: After the prefabricated beam is placed steadily, unhook it. The length of its placement should meet design requirements, for example, some projects require 10 millimeters or 15 millimeters, and adjust it with 1-10 millimeter shims at the placement points. During positioning, complete the axis alignment in one go according to the control lines, and adjust the beam bottom elevation through the lower independent supports to ensure installation accuracy.
Elevation Re-measurement: Use a level or other tools to re-measure the elevation of the prefabricated beam. The allowable error should be strictly controlled within 5 millimeters. If it exceeds this range, promptly adjust the support height or shim thickness to ensure structural flatness.
Subsequent Installation: Install other prefabricated beams in sequence and re-measure their elevations. After confirming that all axes and elevations are correct, spot-weld the main reinforcement of the prefabricated beams to the reinforcement of the shear walls or beams, and finally remove the lifting cables. Note that each prefabricated beam should have at least two independent supports according to its span size. The main beam bottom formwork and independent supports at the junctions of main and secondary beams should be positioned in one go to avoid secondary adjustments affecting structural stability.
