Tilt slab
From Wikipedia, the free encyclopedia
Tilt up or Tilt-slab is a type of building, and a construction technique using concrete.
In this method concrete elements (i.e. walls, columns, structural supports, etc.) are formed on a building site for their given thickness. These elements are generally formed on a slab of concrete that is the building floor or a temporary concrete casting surface near the building footprint. The elements (generally wall panels) are allowed to cure and then are tilted from horizontal to vertical with a crane and braced into position until the remaining building structural components (roofs and intermediate floors) are secured.
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[edit] Forming walls
Once the pad (casting surface or floor slab) has cured, forms are built on top. A high quality plywood or fiber board that has at least one smooth face is typically used although aluminum or steel forms are also frequently used. Carpenters will work off engineered drawings for each panel or element to design and construct the forms on site. They will accommodate all openings (windows, doors, etc...) as well as style accents known as reveals and any other desired shapes that can be molded into concrete. Studs, gussets and attachment plates are located with the form for embedding in the concrete. The forms are usually anchored to the casting surface with masonry nails or adhered to prevent damage to the floor slab.
Next, a chemical release agent is sprayed on the casting surface to prevent the bond between it and the fresh concrete to be placed in the forms allowing the new element to separate from the casting surface once it has cured. This is a critical step for the success as improper chemical selection or application will result in preventing the lifting of the panels and costly demolition.
A rebar grid is constructed inside the forms, spaced off the casting surface to the desired location in the thickness of the new concrete element with plastic "chairs". The rebar size and spacing is generally specified by the engineer of record.
Concrete is then placed into the forms, filling the desired thickness and surrounding all steel inserts, embedded features and rebar. The forms are removed when the concrete is cured and the element is tilted into place.
[edit] Structure
Concrete walls are very heavy (over 300,000 pounds is the record) and are most often engineered to work with the roof structure and/or floor structures to resist all forces. The connections to the roof and floors are usually steel angles and studs that were secured into the forms prior to concrete placement. These attachment points are bolted or welded. The upper attachment points are made to the roof trusses. Interior walls may be present for additional stiffness in the building structure as necessary, known as shear walls.
[edit] Uses
Tilt up buildings grew in popularity after World War II generally used for industrial/warehouse applications. Today they are used in nearly every type of building from schools to office structures, houses to hotels and many more applications. They range from single story to more than seven and have nearly reached 100 feet in height.
Tilt up construction is a dominant method of construction throughout North America, Australia and parts of the Pacific Rim. It is also increasing in popularity in many other worldwide regions as the resulting buildings are strong and durable, energy efficient and increasingly attractive. They have developed into a building solution that creates a strong and inspiring image for many owners including churches, athletic facilities, civic buildings and detention centers.
[edit] Appearance
Many finish options are available to the tilt-up contractor, from paints and stains to pigmented concrete, cast-in features like brick and stone to aggressive erosion finishes like sand-blasting and acid-etching. Shapes are also a feature that have become dominant in the tilt-up market, with many panels configured with circular or elliptical openings, panel tops that are pedimented or curved, facades that are curved or segmented and featured with significant areas of glazing or other materials.
[edit] Association
The Tilt-Up Concrete Association (TCA) is the international trade association for Tilt-Up concrete construction. TCA is a membership based association, with nearly 500 members world-wide. TCA members can be Contractors (General Contractors or Tilt-Up Subcontractors), Engineers, Architects, Developers, Consultants, Suppliers, Specialty Trade firms, Educators and Students.
TCA offers primarily educational, networking and exposure benefits to its members. TCA also offers an Achievement Awards program annually, recognizing the best examples of Tilt-Up construction over a variety of end uses.
The mission TCA is to expand and improve the use of Tilt-Up as the preferred construction method by providing education and resources that enhance quality and performance.
