Amanda Shaver

COA 8903

9/17/02

Draft Report Section 1

Tilt- Wall Panel Construction

The tilt-wall panel construction sector of the building construction industry is very complex. It is a compilation of architects, engineers, general contractors, and subcontractors that work together to produce a product. This product is a concrete panel poured on site and tilted into place to form the walls of a building. Tilt-up construction is most frequently used for one-story commercial buildings such as warehouses or office buildings, though two-, three-, and four-story office buildings are becoming commonplace. Condominiums and hotels as tall as ten stories have been constructed with tilt-up concrete.[1]

The Tilt-Up Concrete Association is the national professional organization associated with this sector. According to their data there are approximately 700 to 1000 contractors that do tilt-up work, some more exclusively than others. There are far fewer architects and engineers that focus on tilt-up design. The association also reports that in 2001 the industry constructed 255 million square feet of wall panels enclosing around 600 million square feet of building.[2]

The tilt-up construction process starts with the owner and architect/structural designer deciding to design a building with tilt-up panels. There is an initial flow of information that leads to this decision including site information, building height, building shape, ability to have multiple walls with the same shape, and possible future expansions. There are many other questions to be addressed once the decision is made. The design of the panels takes into account information from many different sources. The structural design can be done using software, such as Enercalc, to account for building loads as well as additional forces applied when lifting the panels into place.[3] This software only provides a sketch of the panels and the specifications of the joints needed. Most of the architectural design of panels is done in CAD programs and is transferred to the general contractors through 2-D drawings.

The general contractors then assimilate more information regarding site layout and project schedule. They hire a subcontractor with experience in the industry to perform the work. There is also a subcontractor responsible for the reinforcing steel in the panels. The rebar contractor generally produces his own set of drawings that show the specifics of the reinforcing steel. Some contractors such as Martin Concrete provide the service of producing in-house panel layout drawings for tilt-wall projects. They pull information from architectural drawings, structural drawings, lift and brace engineering, rebar shop drawings, structural steel shop drawings, and joist shop drawings and generate a detailed AutoCAD drawing for each panel. These drawings contain all the information required for constructing and erecting the tilt wall panels. When completed, submitted, and approved by the general contractor, architect, and structural engineer, the whole team can be confident that the building will be built safely and without costly errors.[4] This is not always done. Some form of drawing of the compiled information is submitted for approval before construction. Most of these are 2-D drawings as well. The general contractor then works with the subcontractor to layout, form, pour, and tilt the panels into place.

As listed in the information from Martin Concrete, the tilt-up industry is in direct contact with the structural steel manufacturers that produce the roof and any temporary supports for the panels. They are also in contact with contractors that will require openings in the walls, such as HVAC, plumbing, doors and windows, fire protection and other specialty contractors. Using this form of construction does allow for design changes up to two days before the pouring of the panels but once they are poured changes are very costly due to the loads on the panels.[5]

In conclusion, due to the number of parties involved in the industry and the complexity of the products provided, the industry is very information intensive. Information comes from different sources at different stages of the project and things can easily be overlooked in the current process. Thus far, the only information technology I have found in the industry is the structural design software and AutoCAD.

Questions still being researched

  • Cost: How much does tilt-up construction cost? What percentage of projects? What percentage of construction industry?
  • What is actual information flow in general contractors office before pouring of panels?
  • Are there any designers using 3-D modeling?
  • What kind of programs do the companies like Martin Concrete use to provide shop drawings and assimilate all the information they are provided?

1

[1]

[2]

[3]

[4]

[5]