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• Advanced construction methods in buildings:

Background

• The 20th century saw massive technological progress that surpassed previous millennia.
• Previously, constructing a single building took decades, limiting architects.
• Modern mechanized construction, media, and information sharing now allow for more building construction.
• Varied building designs require specialized assistance for complex structures like airports and hospitals.
• Architectural styles reflect the building's use, needs, and construction methods.
• New architectural trends face both support and opposition.
• Some architects embraced new designs that utilize modern materials and structural possibilities.
• Structural engineers capitalized on industrial advancements to construct industrial buildings and public facilities.
• Reinforced concrete, steel structures, and glass became prominent.
• Human needs drove the innovation of faster construction methods.

Construction Methods

• Lift-Slab Method
• Tunnel Forms (Horizontal Sliding)
• Slip Forms (Vertical Sliding)
• Comprehensive System

Impact of These Systems

• Accelerated engineering work, especially for repetitive tasks
• Improved project economics.
• Enhanced work quality.

Lift Slab System of Construction

• The Lift Slab system originated in the USA in 1948.
• This system's core idea involves pouring high-quality concrete at ground level for ease.

Applications of the Lift Slab System

• Suited for large roof slabs, equal to or greater than 100 square meters.
• It can eliminate beams and applied to multi-story structures with identical floors.
• Common applications include office buildings, residential complexes, and multi-story car parks.

Construction Steps for the Lift Slab System

• Foundations are constructed with cavities for column installation, approximately one meter deep.
• Columns are erected using metal formwork, up to 20 meters in height, or extensions for taller buildings.
• Lifting hooks and steel plates for joint welding are integrated during concrete pouring.
• Metal "shoes" with a special design are installed on columns to meet the slab levels.
• Then, the column is lifted to its place on the foundations.
• The connections are secured within the foundation, leveled vertically, and filled with concrete after the column is braced.
• A concrete layer is poured for the ground floor.
• A vertical barrier is made to contain the slab pours.
• A layer of nylon is laid before pouring the first slab.
• The slab thickness is usually 16-25 cm.
• Flat slabs without beams are necessary.
• The beams have the same thickness as the slab (hidden beams).

Post-Slab Pouring

• Metal collars are fitted around columns before pouring the slab.
• Reinforcing bars are welded to the slab.
• The collars act as guides when lifting the slabs and resist shear forces.
• Another nylon layer is added.
• The next slab is poured.
• Hydraulic jacks are installed atop each column, controlled by a central system.
• Each jack can lift 50-70 tons, connected to the collars with steel cables.
• Slabs are lifted at a rate of 1.20-2.60 meters per hour, according to the slab weight and size.
• Larger slabs can be divided.
• The upper slabs are temporarily secured until the permanent connections are made.
• The permanent connection involves welding the slab's steel collar to the column.
• Spaces are injected with cement.
• All exposed metal surfaces are coated with fire-resistant material if not covered with cement.

Advantages of the Lift Slab System

• Wood formwork is eliminated.
• High quality due to the ease of construction at ground level and effective water curing.
• High speed of implementation.
• Finishing work can begin beneath each slab.
• Well-planned execution reduces plastering needs and enables direct paint/vinyl application.

Disadvantages of the Lift Slab System

• A shortage of skilled labor, specialized equipment, and increased workplace hazards in the column installation and slab fixing.

Tunnel Forms

• Tunnel Forms involve special metal forms that work and adjust hydraulically.
• Made by assembling parts into an inverted U shape supported externally by steel.
• Each part can be in the shape of an inverted L.
• The forms create rooms that are made from 6 mm thick sheet metal reinforced with steel.
• Tunnel Forms move on wheels and have vertical lifts for level adjustment.
• Sloping arms ensure alignment between the ceiling and walls.
• This method casts walls and ceiling in one operation.
• The size of the form depends on the project dimensions.
• The forms are lowered by 7-10 cm to aid in movement after the concrete sets.

Advantages of Tunnel Forms

• Construction speed
• Less labor is needed.
• Smooth surfaces that don't need plastering.
• Bonded, single-piece construction.

Slip Forms

• The slip form system is a site manufacturing method.
• The system conserves significant effort and time, particularly suited for tall structures with no complex features.

Ideal Applications

• Silos
• Water tanks
• Towers
• Elevator shafts
• Bridge supports
• Core structures for reinforced concrete and similar projects.

System Operation

• Continuous concrete pouring, day and night.
• The forms move upward regularly, shaping the concrete.
• The formwork slowly moves upwards before the concrete hardens enough.
• The concrete needs to stay in shape as it hardens.
• Accurate control of the lifting rate is critical for success.
• Rates typically range from 15-30 cm per hour.

Key Elements

• The form structure (wood/steel) forms the desired section, typically 1.20 to 2.00 m high.
• The structure is strengthened with horizontal ties or metal beams.
• Three cantilevered platforms extend from the structure.
• One at the pouring level for workers installing reinforcement and guiding pouring.