Presents design and applications of machinery for on-site manufacture and erection of concrete wall panels and roof slabs to create single-story buildings. The precast components are produced and erected with trailer-mounted rotatable and lifting forms. The basic plant requires two or more technological cycles to erect a bay, while a modified version can build a single-room bay in one cycle. Sizes of the bays and design of the structures are intended to meet housing requirements in developing and industrialized countries. Due to the simplicity of the design, high productivity of the machinery and diversity of the product, the suggested forming system can be an effective craneless method of precast concrete construction.

In keeping with the theme of "Forming Economical Concrete Buildings," the end result of the project must be considered. Pumping of concrete walls from the bottom is not the most inexpensive method of wall construction unless the architectural possibilities of form and finish are considered. This concept, by eliminating or minimizing the need of concrete vibration during placement, allows more freedom of form by the designer than other conventional methods and almost guarantees an aesthetically pleasing finish. However, the economy of this technique is predicated upon spreading the initial cost of form fabrication over a broad base through the reuse of formwork. If a project has difficult concrete walls and/or lends itself to form reuse, the concept of pumping from the bottom becomes as economical as other more conventional methods.

A contractor's construction requirements include different factors than are normally considered in concrete mix proportioning. Changes in materials and job conditions during construction can affect concrete and its ability to meet the contractor's construction needs. Computerized analysis of aggregate gradations and concrete mix proportions from project submittals help reveal potential workability problems that will impact pumping, economy, and finishing. Statistical analysis of concrete test results can reduce concrete cost by using the ACI Building Code to determine minimum average strength requirements. Ongoing analysis of changing materials and job conditions can predict and resolve problems rapidly and, therefore, minimize delays. Two computer programs, seeMIX and seeSTAT, are used to demonstrate how computer analysis can aid construction projects.

This text moves from a macro view of the entire building process toward a micro view of the specific details, in an effort to maximize the value of a site-cast concrete building frame. It starts with an economic overview of the development process, including a budget analysis of a concrete framed building. A case is made for three basic principles that lead to constructability, allowing for efficiency during the construction of a site-cast concrete building from a formwork perspective. The text focuses on both horizontal and vertical design strategies, then attempts to integrate these concepts into a total project strategy using a 10-step approach. This paper stresses the need for teamwork. Teamwork is the key to achieving economy in the construction process, and good communications among all parties facilitates the team effort. The text is the product of a collaborative effort by the concrete construction division of a corporation. Their findings and recommendations were organized and integrated by the author. Additional resources are noted at the end of the article.

The lift-slab method of construction, developed 38 years ago in Texas, has undergone detail changes and modernization of equipment over the years. The basic concept however, remains the same. The flat, concrete floor and roof slabs, usually post-tensioned, are poured one on top of the other at ground level, using the slab on ground as the first soffit form. After all the slabs are poured, they are lifted from above using synchronized hydraulic jacks located on the columns. Floor slabs with as many as 32 columns and 25,000 ftý can be lifted in one piece, while larger floor areas would require sectioning. The economical range of lift-slab construction is from 3 to 20 stories with 5 to 12 story buildings being the most common. The economy is inherent in the fact that reinforcing and concrete work are done at ground level, and that 90 percent of the form work is eliminated. Economy, flexible design, and quality construction, along with clean, safe, and efficient working conditions are all reasons to investigate lift-slab construction for multistory housing, offices, and parking garages.