The construction of super high-rise core tubes demands strict quality control. Any data discrepancies caused by insufficient testing or inadequate verification can compromise construction accuracy and reduce overall project quality. So, how can these issues be prevented during construction?
1. Design Considerations for Super High-Rise Buildings
1.1 Standard Floor Area Control
The standard floor area of a super high-rise building plays a crucial role. If the floor area is too small, it can result in a high structural aspect ratio, unstable stress distribution, and a low building occupancy rate. Conversely, an excessively large floor area may exceed the limits of a single fire zone, necessitating additional evacuation staircases and fire elevators. It may also cause the building to appear squat and bulky due to a low aspect ratio, as modeled in BIM software.
Typically, for buildings under 200 meters, the standard floor area ranges between 1,500 and 2,000 m². For buildings taller than 250 meters, it generally falls between 2,000 and 3,000 m². In some cases, the standard floor area decreases gradually with height, effectively segmenting the building and creating a visually appealing, upright architectural form.
1.2 Floor Height and Column Span Control
To ensure comfortable work environments and adequate ventilation and lighting, net floor heights in Chinese super high-rise office buildings typically range from 2.8 to 3.0 meters. Accounting for beams, equipment pipelines, and ceilings (usually 1.2 to 1.5 meters), the total floor height for Grade A office buildings reaches 4.0 to 4.2 meters.
With the trend toward larger spans in office spaces, structural columns have become larger and beams higher to support the increased loads. Economically, the optimal main column span is about 12 meters, with beam heights ideally controlled within 0.8 meters to balance cost and performance.
1.3 Core Tube Layout and Economic Efficiency
(1) Rationality, Economy, and Efficiency Principles
Super high-rise buildings typically require numerous rooms serving different functions. Therefore, the core tube layout must maximize rational use of space, especially in corridors, elevator shafts, and bathrooms. The goal is to optimize overall space utilization, minimizing waste and inefficiency.
The core tube usually occupies 15% to 20% of the standard floor area. If this exceeds the limit, optimization is necessary.
(2) Spatial Integrity Principle
Designing the core tube with spatial integrity means considering the entire building holistically. Various core tube types exist, classified by the number and arrangement of elevator zones—such as cross, combined, or parallel types—each suited to different building functions.
(3) Centralized Layout Principle
Service rooms like stairs and elevators are generally concentrated within the core tube, which is typically positioned at the building’s center for design and construction convenience. This centralized layout enhances building visibility, improves external space connectivity, and significantly boosts natural lighting. Additionally, it aids space segmentation and plays a vital role in fire prevention and safe evacuation.
2. Typical Installation Process for Embedded Parts
2.1 Layout
(1) Elevation Drawing: Using the elevation benchmark from the first or second floor, measure upward with a tape measure. To ensure accuracy, transfer elevation from two separate points and average the results.
(2) Centerline Setup: Use a total station to mark the centerline of 2 or 3 embedded parts in each reinforced wall. Mark the centerline with a paint pen. Use a tape measure to check distances on both sides and verify inflection points at reinforced wall corners.
(3) Elevation Setting: Set a level to draw reference lines above each embedded part position based on the elevation benchmark. Mark the top elevation and welding “mountain” position of each embedded part with a paint pen, usually corresponding to the lowest row of anchor bars.
2.2 Lifting
Typically, tower cranes are used to lift embedded parts sequentially following the installation plan and elevation.
(1) Division: Prior to hoisting, divide embedded parts into sections according to positioning requirements.
(2) Lifting: For lighter embedded parts, use a single crane. Securely bind parts with slings and lift carefully, paying attention to quantity and orientation.
(3) Placement: Align embedded parts with the marked centerline and insert anchor bars into the steel bar crotch. Slowly lower parts to match the elevation and stability requirements. Once in place, release the hook and temporarily tie weak reinforcement areas with iron wire to prevent displacement.
2.3 BIM Calibration Tutorial
Calibration is the final positioning step, performed in accordance with acceptance standards. It primarily uses instrument marking, supplemented with manual measurement and secondary verification.
(1) Instrument Setup: Deploy both a total station and a level.
(2) Leveling: Hang a chain block above embedded parts, lift them, and use a level ruler to ensure vertical and horizontal alignment. Weld support bars 1 and 2.
(3) Elevation Setting: Measure the top elevation with a level to confirm it falls within allowable error. Weld horizontal reinforcement No. 2.
(4) Centerline Setting: Use a total station to measure embedded parts’ vertex coordinates, ensuring compliance with error tolerances. Weld vertical reinforcements 1 and 2.
(5) Access Control: Adjust embedded parts’ position and weld support bars 1 and 2. The bars should match the core tube wall thickness, securing embedded parts tightly against the formwork.
(6) Secondary Verification: After calibration, perform a secondary check using the total station and level to confirm accuracy of all embedded parts.
2.4 Acceptance
(1) Center Point Identification: Directly measuring the embedded part plate’s center point with a long level ruler tends to produce significant errors. Instead, use a long horizontal ruler to mark edge points, then connect them to find and mark the center point on the template edge.
(2) Plane Coordinate Acceptance: Set up a total station, position the prism at each embedded part’s center, and sequentially record coordinate values. These are accepted if within allowable design tolerances.
(3) Elevation Acceptance: Using a level, read the benchmark and measure the embedded part’s top surface elevation. Values within design error margins are accepted.
3. Construction of Thin Steel Plate Shear Walls
3.1 Structural Optimization
This involves two key changes: replacing sleeve connections with reinforcement plate connections, and further upgrading reinforcement plate connections to through-hole connections.
3.2 Steel Plate Shear Wall Processing
(1) Processing Technology: The shear wall steel plates and concealed steel columns are joined by full penetration welds. Plates are butt-welded fully within a 150 mm range above and below the steel concealed beam. Stirrups and tie bars connect continuously to the steel plate, with reinforcement holes drilled as needed. Concrete pouring on both sides requires flow holes in the steel plate shear wall.
(2) Quality Control: Prior to welding bolts, stiffeners, or drilling reinforcement holes, steel plates must be straightened and leveled. Plates are fixed rigidly to the work platform. Mark reinforcement hole positions, drill, weld reinforcing plates, and finally weld bolts onto the steel plate.
3.3 On-Site Installation of Steel Plate Shear Walls
(1) Preparation: Inner walls connect by bolts, outer walls by welding. Before lifting, install anti-slip irons, connecting ear plates, and temporary fixing chains. Choose steel wire ropes and clamps rated for component weight.
(2) Temporary Positioning: After hoisting, fix the shear wall in place with pre-welded anti-slip irons. Single steel plate walls between core steel columns connect by bolts or welding. Temporarily secure with chain blocks.
(3) Installation Process: The core tube steel plate shear wall is installed starting from the four corners, moving inward and from the outside to inside sequentially. The steps are:
- Step 1: Install core cylinder steel columns with connecting plates at two corners, adjust elevation, and fix verticality.
- Step 2: Install shear wall steel plates between core tube steel columns, forming a stable structure. Inner walls use bolts; outer walls are welded for easier error correction.
- Step 3: Expand to adjacent areas by installing more steel columns and adjusting their position.
- Step 4: Continue installing shear wall steel plates between columns.
- Step 5-8: Repeat the above steps to gradually expand and complete the outer ring structure.
- Step 9-12: Divide the work surface into sections and expand inward, installing steel columns and shear walls, adjusting and fixing to form a stable system.
4. Safety Measures for Operation Platforms
(1) Before the first lift of the elevator shaft platform, joint inspections and approvals by the technical and safety departments are mandatory. Subsequent lifts require approval by the project safety director.
(2) The platform is intended only for template installation and dismantling. Stacking materials or using it as template reinforcement support is strictly prohibited.
(3) During lifting, operators must avoid standing on the platform. Hooks should be hung, pins pulled back, the platform evacuated, and lifting commanded by a signal worker.
(4) After every three consecutive lifts, the platform must be lowered to the ground for comprehensive inspection and maintenance before further use, pending safety director approval.
(5) Post-lift, the lower floor elevator shaft must be protected with appropriate soft and hard safeguards.
(6) Platform use requires safety officer review and approval, with lifting records signed by the construction foreman and safety officer.
(7) All components must strictly comply with manufacturing standards; substandard materials are prohibited.
(8) The platform frame cannot serve as a support or tie point for ropes and cables during lifting.
(9) Before lifting, inspect all platform parts for secure lifting bracket connections, absence of severe deformation, and clean, flexible pins.
(10) Construction on the platform is forbidden during adverse weather conditions.
5. Common Quality Issues
5.1 Insufficient Testing
Concrete pouring for the core tube must include thorough testing to ensure concrete strength meets load requirements. Some projects use rebound methods for quality monitoring.
5.2 Inadequate Verification
Lack of proper verification may lead to concrete cracking. Cracks primarily result from significant deformation caused by shrinkage after concrete sets and hardens. Factors such as high temperatures causing water loss and low slump during pouring affect shrinkage. Incorrect shrinkage calculations, especially regarding concrete strength grade, can cause severe cracking.
5.3 Neglected Considerations
During core tube construction, beam steel bars and connecting steel bar sleeves must be accurately pre-embedded and securely fixed. Sleeves should be tightly attached to and protected by formwork. Later, steel bar connecting sleeves are exposed for beam steel bar connection. Quality control over sleeve connections is crucial, including inspection of steel bar ends, thread quality, and implementation of witness sampling to ensure mechanical connection integrity.
Article source: Architectural Technology Magazine
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