Installation of Precast Beams in Prefabricated Houses

The installation of precast beams in prefabricated houses requires adherence to specific procedures and requirements, with core steps including surveying and setting out, component lifting, temporary fixation and alignment, and subsequent construction, while following the installation principle of 'main beams first, secondary beams next, low before high'.

1. Surveying and Setting Out
   Before installation, it is essential to determine the precise position of the precast beams through surveying and setting out, which is a critical step to ensure the overall accuracy of the structure. Surveying should be conducted in conjunction with architectural plans and construction control networks, using tools such as total stations or laser positioning instruments to mark the axis, edge lines, and elevation control points of the beams on column tops or already installed components, ensuring that the installation positions of the beams are consistent with the design drawings.

2. Component Lifting
   Precast beams are typically lifted using cranes such as tower cranes, and specialized tools like steel spreaders should be used to reasonably set the lifting points during lifting. The lifting points should be located near the center of gravity of the beam to avoid tilting or cracking of the component due to uneven force. During the lifting process, the component should be kept horizontal, lifted slowly, and the lifting arm moved uniformly. As it approaches the installation position, manual assistance should be provided for centering and positioning to prevent collisions with column edges or already installed components.

3. Temporary Fixation and Alignment
   After the beam is in place, temporary fixation should be carried out immediately, usually using methods such as bolt connections, welding, or diagonal bracing to prevent displacement. During the alignment process, the axis position, perpendicularity, and elevation of the beam should be checked, and deviations should be verified using laser levels or plumb lines. For composite beams, the height difference and width of the bottom joint of the slab should also be checked. If the height difference does not meet the requirements, the beam should be lifted again and adjusted to the design-allowed range using adjustable supports (generally, the height difference should be ≤3mm).

4. Subsequent Construction and Support Removal
   After the installation of the precast beams is completed, subsequent procedures such as reinforcement binding of beams and slabs and concrete pouring should be carried out to form an integral structure. Temporary support systems (such as independent steel supports or ring-lock scaffolding) should not be removed until the strength of the post-poured concrete reaches the design requirements (usually more than 75% of the design strength) to avoid structural deformation or cracking due to premature removal of supports.

Installation Principles and Precautions
The installation of prefabricated buildings should follow the sequence of 'main beams first, secondary beams next, low before high', prioritizing the installation of main beams with greater stress before installing secondary beams and connecting beams to ensure structural stability. During construction, procedures should be scientifically arranged to shorten the construction period through standardized production of prefabricated components and on-site assembly construction. At the same time, strict control should be exercised over the quality of components and installation accuracy to ensure the safety and durability of the project.