SYNOPSIS
Reinforced concrete shells are no longer fashionable. Space structures have taken their place "under the spotlight" due to their multiple terrestrial applications and potential extra-terrestrial uses. Yet, with the advent of construction automation, both these forms of structures will become increasingly popular. This is due to their economy, simplicity, minimal use of material, and for their proven and lasting structural performance.
The author has dedicated his professional life to the development of original automated construction technologies to render the construction of special structural forms such as concrete shells (refs 1 & 3) and space structures (refs. 4 & 5) as efficient and economical as possible.
This paper presents the technologies that have been the fruit of twenty-five years of personal research in construction automation. It is divided in two sections.
The first part describes and critiques the author's development and utilization of "automated construction processes" applicable to reinforced concrete shells and space structures of different dimensions and shapes. The second part of the paper presents various joint research efforts that are now in their initial developing stages. Most of said research efforts are being closely developed together with Shimizu Corporation of Tokyo (Japan). They are applicable to a wide variety of "automated structures," from "semi-traditional" multistory buildings, to city infrastructures and from extra-terrestrial space structures to self-shaping and self-sinking Shelters and Habitats for Lunar Outposts.
PART 1
On July 4th, 1965, in Crespellano, (Bologna), Italy at 4 pm, Dante N Bini made the world's first attempt at using an automatic, self-shaping construction process to build a fully reinforced concrete structure on a previously built floor and footing system.
This new experiment was successfully completed by 7 pm. In only three hours, a dome 12 m. in diameter and 6 m. In height had been pneumatically lifted from the ground and shaped into an hemispherical thin shell structure.
During the pneumatic lifting process, the auto-positioning of the required steel reinforcement was successful, but the control and the final distribution of the wet concrete was inadequate. This was due to a lack of command of the temporary asymmetrical lifting sequence lasting less than 60 minutes.
Internal view of the first Binishell built in Crespellano, Bologna, Italy (1966)
This structure was soon proven sound by severe load-tests carried out by the school of Engineering of the University of Bologna.
For 20 years this building was utilized as an office. Later on it was demolished only because that area in Crespellano was classified as multi-story residential zone.
(Fig. 1): The world’s first experiment in Crespellano. Bologna. Italy. (1965)
Sequence of the inflation and completed 12 m. diameter spherical dome
A year later, on July 6 .1966, in Castelfranco Emilia, (Italy) after some spine-tingling moments, another major experiment was undertaken. At 7:00 am, from 25 ready-mix trucks, a special-blend, lightened-concrete, was poured at ground level on top of a pre-shaped, folded, l mm. thick, semi-elliptical membrane anchored to a circular footing structure and covered with a different self-positioning steel reinforcement. Again, in spite of a severe lack of lifting control, at 6:00 pm both steel and concrete had been lifted up and shaped by one man operating a small fan generating a pressure of 60cm of H20.
In less than four hours, l15 cubic meters of wet concrete and flat steel was shaped into an elliptical reinforced concrete dome 36 m. in diameter and 12 m in height. During the inflation process the previously built circular reinforced concrete footing structure, (0.70 m x 0.60 m x 114 m) was almost lifted from its trench. Very hard work was also required to manually maintain uniform the thickness of the concrete during its suspenseful, uneven inflation. In spite of these difficulties during construction, a quarter of a century later this structure is still standing.
(Fig 2): The first 30 m. diameter experiment in Castelfranco Emilia, Modena. (1966)
Detail of the footing system.
On May 16th, 1967 at 3:45 pm an improved and definitive version of this automatic method of construction, provided with an unique control system necessary for its lifting process, was presented in New York by the author, together with the Chairman of the Architectural Technology Division at Columbia University, Prof. Mario Salvadori. The perfected lifting sequence was controlled by a powerful network of multi-directional steel springs (anchored to the footing and imbedded in the wet concrete) This innovation provided an efficient, symmetrical guiding force acting in opposition to the inflation process. The proper setting of the concrete was
achieved through the use of an additional external membrane. After the inflation was completed, this membrane also allowed a number of vibrating carts to roll all over it and re-compact the still wet concrete retained between the inner and outer membranes. For the first time in the United States, a fully controlled, compacted and sound, self-supporting shell structure was automatically shaped and built two hours after the concrete had been poured at ground level directly from two ready-mix concrete trucks. After all scientific tests were successfully carried out. The structure was demolished. This was in accordance with the request of the local authorities and this proved to be the only major problem related to this structure.
(Fig. 3): Sequences of inflation of the first Binishell experiment successfully built in the U.S.A. (1967)
Original design of the third Binishell built in Italy and photo of the interior (1967).
The above-described method of construction is now
known as Binishells. It requires some expensive and sophisticated equipment, but continues to be the cheapest and fastest method to produce circular-based, monolithic, reinforced concrete shell structures, with elliptical sections ranging in size from 12 to 36 meters in diameter. Yet even automation is affected by human error. It is important to report in this paper that between 1970 and 1990, 3 of over 1,600 Binishells successfully built in 23 countries of the world have suffered severe failures and have been demolished or re-built. (ref. 2 & 3)In the Seventies the author, as a further improvement to the Binishells concept, devised two additional systems:
A) The first method of construction, called "Binix", was developed to reduce the amount of concrete necessary to build a ribbed dome structure while increasing its span. This method introduced an assembly of prefabricated elements, laid on top of a flat pneumatic system at ground level. These elements were positioned to provide the form-work for the reinforced concrete. The prefabricated steel was properly located between and within the forms and the concrete was poured in at ground level. The entire flat structure was then lifted up and shaped only by air pressure. This System may produce a large, hexagonal-based, monolithic, framed or ribbed dome structure, which may span up to 100 meters. A small Binix prototype was successfully built in Australia in 1976.
The only problem experienced during the construction of the prototype was related to the process of re-compacting and vibrating the concrete inside the raised form-network. (ref. 4)
(Fig. 4): The Binix experiment produced in NSW. Australia.(1977)
B) The second system, called "Minishell", produces 8m.x8m. or 10m.xl0m. square-based, monolithic, reinforced concrete shell structures, provided with four large reinforced openings which result from the automated construction process itself. Only 4.6 cubic meters of concrete reinforced with No. 400, 6 mm. diameter corrugated rods, combined No. 200, 36 mm. ext. diameter hard drawn 2 mm. spring were are necessary to complete this structure.
The Minishell system is considered to be one of the fastest and cheapest systems for building permanent monolithic shelters and is therefore very suitable for low-cost housing. After the floor, footing and reinforcing steel contained within the springs are prepared, the erection time for each structure is reduced to 30 minutes. The required man power results in 1.5 hours per man per each for sq. m. of covered area. Several Minishell Tourist villages are in use in Australia and Italy.
The only two problems experienced during the application of this method of construction were:
a) Structural weakness in the "vertical" portion of the walls when the concrete was still
green.b) Lack of precision and symmetry in the shape and size of the four automatic openings. (refs. 5 & 6)
(Fig. 5): Sequences of construction of the Minishell Tourist Village in Cairns, Australia. (1980)
The "Binistar" system was originally conceived and patented by the author in Australia in 1979. The first 40 m. prototype was successfully built in 1986 in Bari (Italy) by E.GE.CON. and F.lli Dioguardi S.p.A., with the direct assistance and supervision of Binistar Inc. California, U.S.A.
To our knowledge it is the only demountable, automatic
, method of construction capable to shape large-span metal space-frame structures of different shapes and dimensions. Binistars are pneumatically-lifted from their footing-level to their final position by way of an air-tight, special fabric, pre-shaped membrane made of l mm thick self-extinguishing polyester+PVC bands welded at high frequency with 4-6 cm of overlap. At the end of the construction process, this membrane, remains in tension, suspended from the structure s nodal points as a leak-free final cover. The galvanized steel-space frame structure is composed of a series of telescopic pipes some (or all) of which are variable in length and mechanically fixed after the inflation is completed.The weight of the metal portion of the structure is 10-19 kg./sq.m. depending on the free span required. The set up and erection time fluctuates between 0.40-0.50 hours per man per sq.m. of covered surface, depending on local conditions, shape and dimensions. (A 20m. by 40m. torroidal structure requires 400 working hours, a 40m. by 42m. barrel vault structure requires 1,000 working hours). The inflation process necessitate 3-4 blowers capable of producing a pressure of 70-100 mm of H2O. each provided with a flow of 15-20,000 cubic meters per hour.
One of the unique advantages of a Binistar space structure, is its potential for a quick and easy (partial or complete) pneumatic disassembly, with the possibility of immediate relocation. The extremely safe disassembly process is performed through sequences which are the inverse of those necessary for the assembly. A number of Binistar structures have been leased and re-utilized in different locations. This system, fully developed and engineered by the E.GE.CON - F.lli Dioguardi Group, has been designed for high winds (100 km./hr) and heavy snow loads (lm./sm.). It is presently used in Italy, France and Spain and will be soon utilized in U.S.A.
In the first prototype, the extension of each telescopic pipe was controlled by automatic locking devices. This additional level of automation was however subsequently abandoned due to cost and difficulties in manufacturing it. At present each telescopic pipe is manually fixed and secured at it's final automatic extension. This was the case in all commercial Binistars produced and erected in Italy by the E.GE.CON.- F.lli Dioguardi Group for the '90 World Soccer Championship and in Spain for the '92 Olympic Games and for Seville World '92 EXPO. (ref. 6)
(Fig. 6: Sequence of construction of Binistar structures in Italy and details. (1986-68)
Unlike the Binishells, the Binix, the Minishell and the Binistar, the following systems have not as yet been proven commercially or tested through prototypes.
In 1985 the author was requested by authorities of the former Soviet Union to devise a pneumatic erection system for a prefab. single family house, to help solve a severe lack of single low-cost housing in the former Soviet Union. (ref. 5)
The result of such a study was a structural shelter made of 4 different basic prefabricated modular components which were designed to be mass-produced in a mobile or traditional factory. A total of 28 elements either completely finished, or unfinished (made from a combination of the same 4 basic components) are assembled at ground level. These elements coupled with a unique pneumatic footing system make a self-erecting, air-supported low-cost shelter. The working model presented in Moscow was nicknamed "Pak-Home"
(Fig. 7): Pak-Home model presented in Moscow (1986)
In the same period the author developed two other conceptual systems, the "Fold-A-Struct" and the "Autotent" (ref.6) These systems respectively produce:
a) An instant, demountable, square-based, class-room unit, made up of four identical, mass produced components provided with "inner stored energy'' which contribute to the self-assembly process;
b) A folded space frame which may be utilized as a mini-shelter. This shelter is designed as a civilian or military tent which is dropped by low-flying aircraft in case of emergencies. The autotent self-shapes during its fall and is provided with an identification light and with a survival kit.
(Fig. 8): Fold A Struct. self-assembling model (1987)
The author also collaborated with his son Nicolò to design the "Nico-Space" (developed in the U.S.A. only as a working model) This object is a self-shaping, carbon-fiber and kapton-polvcarbonate-graphite-composite-larninate icosahedron, developed for mini space-shelter or mini space- warehouse to store space debris.
(Fig.9): Nico-Space self-shaping model (1988)
PART 2
The above mentioned, unique construction technologies, have relied on air pressure alone to shape, assemble, or lift building's structures. The second part of this paper describes construction systems in which construction automation is complemented with the aid of robotics.
In 1991, the "Lunit" (a self-shaping and self sinking, pressurized, mobile unit for a life-supporting Lunar Outpost) and the "Lunhab" ( a self-shaping and self-sinking pressurized Lunar structure designed as a life-supporting habitat) were Jointly developed together with Dr. Shinji Matsumoto, General Manager of the Institute of Technology and Deputy General Manager of The Space Project Office and other experts of Shimizu Corporation. Both of these developments have been presented by Mr. H. Nakazawa in Washington DC at the 43rd Congress of the International Astronautical Federation ( ref. 8)
The author, together with other experts of the Space Project Office of Shimizu Corporation, is presently working on the joint development of a conceptual interior design for the "Lunit" system. A proposal has been put forth for the construction in 1993-94 of a working scale model of the "Lunhab" at the University of Florence (Italy), affiliated Campus of the International Space University.
(Fig 11) Lunit & Lunhab Concepts (l991-1992)
The author was also involved in a joint effort to develop a patented automated method of construction, owned by the Institute of Technology of Shimizu Corporation, called "Air-Lift-Up" system. This system will combine an advanced pneumatic construction process and robotics to construct semi-traditional multistory buildings. This system was presented in 1992 by Dr. Haruo Nakazawa, at the First International Symposium of CIB Working Commission W 82. (Ref. 9)
(Fig. 12) The "Air-Lift-Up" System. (1991-l992)
CONCLUSION
The aim of this paper is to contribute to the promotion of Construction Automation and to encourage Universities, Institutes and Industries to invest more effort in this important subject.
Construction Automation eliminates the need for workers to operate in uncomfortable and hazardous conditions, while concurrently saving time, reducing costs and improving the quality of the work place in the construction industry. It is well known that in spite of the employment of sophisticated machinery and equipment and some recent efforts to improve on-site working conditions, construction sites in general offer some of the worst working conditions existing today. As has already been experienced in other industries, the application of automation and robotics can cuts costs, environmental pollution, and dramatically improves safety and quality control to the benefit of living standards in general.
REFERENCES
*(ref. 1): a] "A new pneumatic technique for the construction of thin shells" by D. Bini for the International Association for Shell Structures. Proceedings for the First IASS International Colloquium on Pneumatic Structures. University of Stuttgart, Germany, May 11-12 1967.
b] "Concrete Domes" by D. Bini N.S.W. Builder, Official Journal of the Master Builder Association of New South Wales, Volume 3 Number 7, August 1974.
c] "1,500 Buildings Shaped by Air" by D. Bini. -1984 International Conference of American Value Engineers- SAVE Proceedings, Volume XIX Sacramento, California U.S.A.
*(ref.2): ~The Cause of the Collapse of the Pittwater Binishells" by D. Bini, published by Engineers Australia, issue of May 3rd, 1991.
*(ref.3l: "Why Building Fall Down" by M.Levy & M.Salvadori, published by W.W. Norton & Co., New York and London ,1991.
*(ref.4): "Place 1,000 tons of concrete at ground level, rise a 100 meter dome in one hour" by D.Bini, Bini Consultants Australia, National Ready Mix Concrete Association Convention, Sydney N.S,W. Australia, September 1976.
*(ref.5): "Self Shaping Space Structures" by D. Bini and S. Pietrogrande for the "International Journal of Space Structures" Volume 4 No 2, 1989, published by Multiscience Publishing Co. Ltd. U.K.
*(ref.6): "Pale-Home and Minishell Systems" By D. Bini, '96 Expo Center Seminar organized by The Chamber of Commerce of Moscow, USSR, June 9-10. *(ref.7): "Tower Cityn: A Glance Into The Technologies of the 21 Century", by D. Bini and N. Bini, The International Workshop on innovative Structures, Materials, Designs and Construction for the 21 st Century in MIT Cambridge, \ 1991.
*(ref.8): "Inflatable Lunar Structure with Reinforcing Rings--Self-shaping and Self-sinking System for a Lunar Outposts" by S. Matsumoto, J.Sasaki, T. Saito, K.Nozaki, H.Canamori, Y.Kay, K.Takagi H.Ueno, H. Nakazawa, Y.Yamakawa., D. Bini for the World Space Congress, Washington DC, 28 Aug.-Sept. 1992
*(ref.9): "Air-Lift-Up Construction SystemY by H. Nakazawa, S. Matsumoto, H. Takada, D. Bini. A case Study of future Building construction System. First International Symposium of CIB Working Commission W 82: Construction Beyond 2000, Future of Construction - Construction of the Future. June 15-18 1992 Espoo, Finland.