Tilt-Up Construction

Tilt-up construction is a building technique where the floor slab of the new building is used as a casting bed to form the concrete exterior wall panels. Although originally used primarily for industrial facilities, Tilt-up is now being used for up scale commercial and retail facilities.

With the evolution of tilt-up to a more “uptown” setting, problems with floor slab performance have become more common. After the tilt-up panels are cast, it is necessary that a service crane lift the panels and place them on the exterior wall footings. For safety reasons, the “lifts” are almost always performed with the service crane being supported on the interior building floor slab. This subjects the floor slab to the initial lifting loads, and dynamic wheel loading as the service crane carries the panel across the slab to its designated position.

Tilt-up construction is a building technique where the floor slab of the new building is used as a casting bed to form the concrete exterior wall panels. Although originally used primarily for industrial facilities, Tilt-up is now being used for up scale commercial and retail facilities.

With the evolution of tilt-up to a more “uptown” setting, problems with floor slab performance have become more common. After the tilt-up panels are cast, it is necessary that a service crane lift the panels and place them on the exterior wall footings. For safety reasons, the “lifts” are almost always performed with the service crane being supported on the interior building floor slab. This subjects the floor slab to the initial lifting loads, and dynamic wheel loading as the service crane carries the panel across the slab to its designated position.

Where Tilt-Up Is Used

Where tilt-up is used as an industrial product, this is less of a problem. Industrial floor slabs are usually designed for heavy loads. Retail and commercial construction, however, place less loading demands on the floor slab and more emphasis on the external appearance. Accordingly, commercial and retail construction typically have floor slabs that are not designed for industrial or construction type loading.

For retail and commercial tilt-up, the floor slab can rarely “theoretically” support the load of the service crane.
Although a heavily overloaded slab can usually tolerate one or two passes of the crane, structural failure often
occurs after only a few passes.

Where Tilt-Up Is Used

Where tilt-up is used as an industrial product, this is less of a problem. Industrial floor slabs are usually designed for heavy loads. Retail and commercial construction, however, place less loading demands on the floor slab and more emphasis on the external appearance. Accordingly, commercial and retail construction typically have floor slabs that are not designed for industrial or construction type loading.

For retail and commercial tilt-up, the floor slab can rarely “theoretically” support the load of the service crane.
Although a heavily overloaded slab can usually tolerate one or two passes of the crane, structural failure often
occurs after only a few passes.

Our “Lessons Learned” experience to reduce the impact of slab overloading include the following observations and suggestions:

  • When a building is planned for tilt-up construction, the governing floor slab thickness may be the construction load, and not the service load. Both should be considered.
  • Repeated passes of the service crane is the primary mechanism of failure. The lifting sequence should be designed to minimize repeated passes over a single floor slab area.
  • Open graded gravel tends to allow more flexure in the slab than what is caused by a slab supported directly on a properly prepared subgrade or on a well graded granular layer. Consistent with subgrade drainage requirements, supporting the slab directly on the subgrade, or on a more densely packed gravel (example: 21-A) reduces flexure and cracking.
  • Seal the slab joints with an elastomeric sealant prior to construction of the panels. Water infiltration through control joints in the slab softens the subgrade, which greatly reduces the strength of the floor slab subgrade soils. Procedures to minimize water infiltration through cracks in the slab, and removing water from the perimeter of the building area, helps minimize floor slab cracking.
  • Use wooden matting, or even the unlifted panels, as a working platform for the crane to help reduce the load on the floor slab surface.
  • On small buildings, consider other building systems. Small buildings generally require repeated passes of the service crane over small areas. Tilt-up construction may not be appropriate for very small buildings with high bay requirements.

Our “Lessons Learned” experience to reduce the impact of slab overloading include the following observations and suggestions:

  • When a building is planned for tilt-up construction, the governing floor slab thickness may be the construction load, and not the service load. Both should be considered.
  • Repeated passes of the service crane is the primary mechanism of failure. The lifting sequence should be designed to minimize repeated passes over a single floor slab area.
  • Open graded gravel tends to allow more flexure in the slab than what is caused by a slab supported directly on a properly prepared subgrade or on a well graded granular layer. Consistent with subgrade drainage requirements, supporting the slab directly on the subgrade, or on a more densely packed gravel (example: 21-A) reduces flexure and cracking.
  • Seal the slab joints with an elastomeric sealant prior to construction of the panels. Water infiltration through control joints in the slab softens the subgrade, which greatly reduces the strength of the floor slab subgrade soils. Procedures to minimize water infiltration through cracks in the slab, and removing water from the perimeter of the building area, helps minimize floor slab cracking.
  • Use wooden matting, or even the unlifted panels, as a working platform for the crane to help reduce the load on the floor slab surface.
  • On small buildings, consider other building systems. Small buildings generally require repeated passes of the service crane over small areas. Tilt-up construction may not be appropriate for very small buildings with high bay requirements.

We hope these “Lessons Learned” will be helpful to you in your next tilt-up construction project. Contact us to learn more!

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