Constructing high-rise office buildings requires precision and a strict adherence to engineering standards. Based on the official Method Statement used for the new office building project, here is the professional step-by-step process for column installation.
I. Pre-Reinforcement Preparation
Before any steel is installed, the foundation or previous floor must be prepared:
1. Chipping and Cleaning: The concrete head of the lower column must be chipped and cleaned of debris or concrete splashes.
2. Line Marking: Survey lines for the column box are established.
3. Rebar Adjustment: If the main bars are misaligned and affecting the concrete cover, they must be adjusted or bent into the correct position.
II. Reinforcement (Steel) Installation
Once the base is clean, the "skeleton" of the column is built:
1. Scaffolding: Temporary scaffolding is erected to facilitate workers in dropping and tying the steel bars.
2. Main Bars and Stirrups: Main bars are installed (including lap splicing where necessary), and stirrups (links) are tied at specific intervals according to the structural drawings.
III. Pre-Formwork Preparation
To ensure the column is clean and protected, the following must occur:
1. Air Cleaning: High-pressure air blowers are used to remove wire scraps and concrete dust from the base.
2. Concrete Spacers: "Concrete biscuits" (spacers) are attached to ensure a consistent protective concrete cover.
3. Corner Anchors: Starter rebars are drilled/fixed at column corners to lock the formwork position.
IV. Formwork Installation & Alignment
The formwork (molds) gives the column its shape:
1. Securing the Mold: Panels are joined using specialized bolts (star bolts) at the corners.
2. Bracing: A combination of short, medium, and long props (bracing) is used to support the mold.
3. Verticality Check: Plumb bobs or laser levels are used to ensure the column is perfectly vertical (alignment) before pouring.
V. The Concreting Process
Pouring the concrete requires careful vibration to avoid structural defects:
1. Base Compaction: The first batch of concrete is poured while workers tap the bottom of the formwork with hammers and use mechanical vibrators.
2. Continuous Pouring: Subsequent batches are vibrated to remove air bubbles and ensure a dense finish.
3. Final Plumb Check: A final alignment check is performed immediately after the pour.
VI. Post-Pouring & Curing
To achieve maximum strength, the work doesn't end after the pour:
1. Curing: The column must be kept moist for at least 3 days.
2. Protection: Columns are typically wrapped in sacks or plastic sheets and sprayed with water regularly.
3. Site Cleanup: Temporary starter bars used for bracing are cut and removed from the slab.
Click here to understand: Method Statement For Foundations