SP-90 A collection of 15 papers dealing with concrete formwork, this volume will prove invaluable to designers and constructors alike. With formwork representing anywhere from 35 to 60 percent of the cost of a concrete structure, formwork should be carefully considered when selecting building designs, layouts, structural member sizes and construction methods. Forming Economical Concrete Buildings will offer the reader substantial savings through the integration of the forming system into the total building process. Key subjects include: challenges in making concrete economical, effect of form tie selection on project cost; and quality management of accelerated construction.

As the speed of construction of concrete frame structures has increased and the sophistication of design has improved, there has been an increased need for a more thorough understanding as to the way construction loads are disbursed into the structure. During the 60's and 70's, several designers and researchers proposed methods of analyzing the loads in multistory structures during construction. A computer program employing one of these methods has been developed. In the 1982 PCA conference the author used the results of this proqram to show how the number of levels of equipment, cycle time, and attained concrete strength affected the number of levels of reshores required. This paper describes in detail the process used to calculate the reshorinq requirements for a 35 story flat plate structure built using a three day construction cycle. The discussion includes the practical implications of providing reshorinq for a mild steel structure. The hand calculation procedure presented parallels the computer program and is sufficiently detailed to provide the reader a practical procedure that can be used on the next project.

Presents a basic analytical method for shoring and re-shoring loads of multistory buildings. Discusses the factors that must be considered, the assumptions for simplification of the analysis and shows the method for determining the estimated loads that will be transferred to the structure. Presents the procedure required to determine the ability of the structure to resist the estimated loads with an appropriate safety factor and the adjustments to the construction procedure that must be made in the event the applied loads are in excess of the capacity of the structure.

The new World Headquarters Building for Elf Aquitaine in Paris, France was designed by a Canadian architectural firm who won the commission in an invited design competition in 1979. Work on construction documents began in Paris in January 1981 and construction began early in 1982. Bouyges, the contractor for the reinforced concrete structure, undertook extensive studies to develop a special formwork system for the facade structure since there is little if any background of experience to draw on in France in the construction of high-rise buildings. At 48 stories this was a building of very significant height and would require a whole new approach. The result of these studies was a very ingenious system of facade forms, fabricated entirely in steel and consisting of column and beam forms, complete with integrated working platforms, access ladders, and 2 story high protective mesh screens. A system of alignment nibs insured faithful adherence to the allowable tolerances both vertically and horizontally. Although the research and capital costs were significant, substantial cost savings were nevertheless made in the erection of the structure both in time and labor thus confirming the validity of this formwork design.

In the last systematic review of reinforced concrete column costs in 1973, ACI Committee 439 limited its cost comparisons to concrete strengths from 4000 to 8000 psi and reinforcing steels with design yield of 60,000 psi with speculative estimates of steel with 80,000 psi yield. Design then was based upon the 1971 ACI Building Code. At that time the leading structural engineers had successfully utilized concrete with f'c = 9000 psi under the current code. A number of general conclusions on costs were presented as trends. To bring this review of reinforced concrete column costs up to date, we must consider changes in code requirements, more general availability of still higher strength concretes, superplasticizer admixtures, building code limitations and general lack of economy in a Grade 80 reinforcement, and later laboratory testing and field research on properties and performance of high-strength concretes. A recent detailed comparative cost study of reinforced concrete columns which resulted in appreciable cost savings in a Chicago high-rise building, reinforces some of the 1973 report under conditions today. As might be expected in dealing with the numerous variables involved in comparative column design costs, the detailed study was made effective only through a computer program. The essential features of this program are described in detail in the CRSI Bulletin.