The construction quality of prefabricated buildings is a critical factor in ensuring overall engineering excellence. Achieving prefabricated buildings that meet seismic, quality, and aesthetic standards requires stringent construction management practices.
To produce high-quality prefabricated buildings, strict control over both design and construction is essential, particularly addressing the following “6+1” critical steps.
1/6 Deepening Design
01 Mastering Deepening Design Requirements
(1) Detailed drawings for the production of prefabricated components must be based on the reserved and embedded requirements from various disciplines, production, and construction. Any conflicts identified in the drawings should be promptly addressed to allow timely modifications to the component design.
(2) Verify detailed drawings to ensure compliance with regulatory and installation standards. The construction team should be familiar with national standards and specifications for prefabricated components and confirm that the drawings support production, quantity calculations, and installation needs.
02 Completing Detailed Design Content
(1) For exterior wall decoration and finishing, detailed designs should specify the layout of tiles, decorative concrete, stone, and other materials. Material types and quantities must meet design standards, and stone procurement should satisfy strength and aesthetic requirements.
(2) Insulation and energy-saving structures for exterior walls must fulfill building functionality, emphasizing appropriate insulation materials, connectors, and precise layout details. Design performance verification and calculation checks are necessary.
03 Focus on Prefabricated Component Production
(1) Production Planning: The construction team should actively participate in designing and adjusting production plans to ensure smooth manufacturing operations.
(2) Mold Scheme: Ensure that drawings meet construction needs and collaboratively review mold production to identify and suggest early modifications.
(3) Personnel Organization: Assign dedicated personnel to oversee quality control during production, ensuring strength, dimensions, and appearance meet standards. A representative should maintain communication with component factories, providing timely feedback and conveying construction requirements.
(4) Technical Quality Control: Component quality significantly impacts assembly and installation. Maintain timely communication with manufacturers, conduct strength tests, and arrange rework if components fail to meet installation standards. Address significant size discrepancies promptly.
(5) Storage and Transportation: Optimize readiness and minimize transportation distances to support efficient prefabricated installation and land conservation.
2/6 Organizational Planning and On-Site Layout
01 Organize and Plan
Once the project specifics are clear, develop a detailed construction organization plan that highlights prefabricated structural installation features. This plan should scientifically demonstrate the rationality of construction processes, technical and economic feasibility, and implementation viability. It should guide site operations and resource mobilization—including personnel, machinery, materials, and tools—to efficiently complete prefabricated installation. Solutions to technical challenges should also be proposed.
02 Construction Site Layout Plan
(1) Component Storage Yard: The yard should accommodate assembly requirements and ensure safe access and loading/unloading for large transport vehicles and cranes. It must be enclosed to prevent unauthorized entry.
(2) Loading and Unloading Points: Given the volume and duration of component transport, loading/unloading points should be strategically located to avoid traffic disruption and ensure smooth site operations. These points need to be within the reach of tower cranes or lifting equipment and should not obstruct roads.
3/6 Vertical Lifting
01 Vertical Lifting Equipment and Tools
(1) Tower Cranes: Currently, tower cranes are classified by installation methods as fixed, attached, or internal climbing, and by slewing forms as small car or boom slewing types.
(2) Tower Crane Selection: For prefabricated structures, tower crane lifting height must equal the building height plus safe lifting height, maximum component height, and rigging height.
(3) Crane Coverage: The tower crane model determines boom length and amplitude. Crane placement should ensure full coverage of yard components to avoid blind spots and reduce secondary handling.
02 Lifting Sequence
The typical lifting order for prefabricated components is: prefabricated walls → composite beams → composite panels → staircases → balconies → air conditioning panels.
External wall hoisting begins with corner walls, which act as positioning references for other walls. The PCF board is installed after adjacent prefabricated external walls are hoisted and aligned.
4/6 Construction Key Points
01 Installation of Prefabricated Composite Panels
(1) Use modular lifting beams during panel hoisting and proceed slowly to maintain stability.
(2) Pause about 300mm above the working surface to adjust and position the panel carefully, avoiding collisions. Lower the panel steadily to preserve its integrity.
(3) Temporary supports should be placed at the bottom, spaced every 150cm, with 2-3 rows per bay.
(4) For structural layer work, install double-layer supports. Remove supports only after cast-in-place concrete reaches at least 70% of design strength.
02 Installation of Prefabricated Staircase Boards
(1) When lifting stair treads, pause 500mm above the work surface to adjust orientation and lower them slowly to prevent damage from shaking or folding.
(2) Once roughly positioned, fine-tune with a pry bar according to control lines, then weld and secure the stair treads.
03 Key Points for Prefabricated Beam and Slab Construction
(1) Prepare prefabricated pedestals carefully, ensuring proper anti-arch settings.
(2) Conduct concrete pouring with adequate vibration compaction and apply release agents to formwork.
(3) Perform prestressing and tensioning after wet curing, once concrete strength reaches 80%.
(4) Tension symmetrically and verify with stress-controlled elongation measurements.
(5) Tensioning procedure: 0 → initial stress → 5% over-tension with 2-minute hold → anchoring.
(6) Apply timely grouting (typically with cement slurry or mortar) at pressures between 0.5-0.7 MPa.
04 Installation of Prefabricated Bay Windows
(1) Lift bay windows by connecting lifting ears, bolts, and reserved nuts.
(2) Slowly position the bay window about 300mm from the working surface, align bolts with wall panel holes, use a customized U-shaped horizontal interlocking device, and pull with a sliding rope to insert bolts into connection holes.
5/6 Seismic Construction
Seismic performance is a vital factor for the safety and quality of prefabricated buildings, requiring coordinated efforts between design and construction teams.
Shock-absorbing columns are designed to absorb all earthquake energy, protecting key columns and beams from damage. These columns feature symmetrical steel plates with flanges connected to beams, with a softer, low-yield steel plate in the center.
Placement typically involves three-span PC columns within the inner cylinder—two on each side, eight per floor. The inner cylinder frame bears significant horizontal force, especially at corners where deformation is pronounced. Positioning shock-absorbing columns here maximizes energy absorption and structural protection.
Columns are arranged to cover three-quarters of the height, as the base bears the main horizontal shear force and overturning moment. The top displacement is controlled within safe limits, supported by bottom shock absorbers that also regulate acceleration.
For high-rise bending-shear structures, maximum horizontal shear force usually occurs mid-floor. Installing lower yield point steel in this area enhances shear force resistance and energy dissipation.
During construction, special attention must be paid to node connections, which are critical for ensuring overall seismic performance.
Structural connections include equivalent cast-in-place connections and prefabricated connections. Equivalent cast-in-place nodes must meet or exceed the seismic performance of traditional cast-in-place concrete joints, commonly realized with post-cast integral joints and prestressed splicing joints. Prefabricated connections differ mechanically and often use welded or bolted joints.
6/6 Preventive Measures
01 Utilizing Auxiliary Tools
(1) L-shaped lifting equipment effectively protects corner panels during transport and lifting by transferring tensile forces, reducing damage.
(2) Flat panels are vulnerable at corners during transport; plastic or rubber corner protectors should be fabricated based on component thickness and size.
(3) Employ the “increase spacing and multiple small loads” approach for flat panel transport—widen spacing between panels, select smooth transport routes, and increase transport frequency to minimize breakage.
02 Reducing Composite Panel Span
To prevent fractures caused by excessive spans during lifting, collaborate with design teams to limit composite panel spans within allowable deflections, thereby reducing on-site damage.
03 Lifting Truss Reinforcement
Pre-embedded parts may detach during composite panel lifting. Reinforce areas around embedded parts or lift using truss bars directly. This approach saves costs, enhances lifting safety, and allows flexible lifting point adjustments based on site conditions.
04 Appropriately Increasing Alignment Apertures
Alignment between prefabricated steel bars and on-site rebar holes is a common challenge. Increasing the number of steel bar alignment holes within regulatory limits can improve penetration rates, enhance longitudinal integrity, and strengthen connections. Additionally, improving communication between on-site teams and component factories enhances production accuracy and on-site steel reinforcement standardization, reducing errors.
05 Securing Pre-Embedded Components Before Vibration
Junction box misalignment often occurs during concrete vibration of wall panels. Welding junction boxes in place before vibration effectively secures them. For pre-embedded water and electrical pipes, implement a three-step process: inspection before vibration, observation during vibration, and re-inspection afterward. This significantly reduces pipe detachment and improves finished product quality.
+1 Full Process Acceptance
Although connection methods for prefabricated structures have improved, quality risks remain at component joints. Superior construction methods often make post-capping inspection difficult, and construction personnel’s professional skills and techniques require ongoing enhancement.
01 Acceptance of Prefabricated Components
(1) Verify that the number and quantity of received components match the supply order.
(2) Confirm that surface markings are complete, and production dates, qualification status, and strength meet certification requirements.
(3) Inspect surfaces for defects such as honeycombing, roughness, or cracks.
(4) Check that dimensional deviations comply with tolerance requirements.
(5) Ensure that deviations in reserved steel bars meet specifications.
(6) Verify that embedded parts’ processing, installation, and fixation deviations are within acceptable limits.
(7) Confirm that pre-embedded pipeline positions conform to design tolerances.
(8) Review completeness of quality certification documents and process data.
02 On-Site Construction Acceptance
(1) Following successful quality acceptance of prefabricated structural engineering, all documentation should be properly filed under the concrete structure sub-project.
(2) Inspect concrete structure batches by classification: raw materials for prefabricated components, installation of prefabricated components, and grouting engineering should each be inspected per flow section as separate batches.
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