FARM STRUCTURES NEEDS In 1957, the American Society of Agricultural Engineers submitted the following 3 questions to about 25 well-informed persons in each State (4): 1. What is the most urgent problem affecting farm buildings or the farmstead as a whole? 2. What major changes in farm practices that will affect farm buildings do you expect by 1965? 3. What major problems related to farm structures or the farmstead will need solution by 1965? The problems and needs reported most often are listed below: How to adapt existing buildings for more efficient production Labor requirements in many farmhouses and service buildings remain excessive because the buildings are not adapted to use of laborsaving equipment or methods. Since it is impractical to replace all obsolete buildings in the near future, ways must be found to improve them. Adaptation of existing buildings for the transition from diversified operations to larger, more specialized enterprises requires special attention. Lower cost, more efficient, and more flexible buildings for tomorrow Farmers believe that building costs are out of line with farm income and that ways should be found to lower them. Buildings for tomorrow must be efficient and easily adapted to a rapidly changing agriculture. Suggestions included new structural designs, use of lower cost materials, and the "package building." Engineered farmstead design Design of farmsteads for efficient flow of materials, fire safety, and adaptability to meet future requirements. Mechanization Development of efficient but not too costly systems for handling materials, coordinated with building design and suitable for inclusion in the building package. Better utilities More adequate and sanitary water supplies; waste disposal systems that are sanitary and permit utilization of the wastes; and more adequate electric service. These replies (from consulting agricultural engineers, representatives of industry, country bankers, extension workers, agricultural specialists in the colleges, leading farmers, rural businessmen, and other leaders of the agricultural community) reflect a widespread recognition of the need for greater efficiency on the farmstead. More particularly, they present a tremendous challenge to the research worker to develop farmstead building design and layout criteria that will conserve manpower and material resources while improving the competitive position of the farmer. BRIEF REVIEW OF CURRENT RESEARCH AND POTENTIAL APPLICATIONS CONSTRUCTION MATERIALS AND METHODS New and improved construction materials and methods are continually being developed by industry, by design and consulting engineers, and by contractors. Agricultural engineers, mindful of the unique requirements of farm buildings, are constantly studying these new materials and methods for their applicability to use on the farmstead. In addition, research agricultural engineers are also experimenting with new materials and better ways of using existing ones for farm construction. The objectives of the research and development work being done by agricultural engineers in this field include utilization of plentiful materials; conservation of scarce resources; increased strength with less material; simplicity of erection; greater durability; increased flexibility of use, reuse, or both; and reduction of building costs. All these objectives must be achieved while maintaining or increasing the effectiveness and efficiency of the buildings in serving their intended functions. Examples of this research are presented below. Earth building blocks stabilized with portland cement Earth building blocks stabilized with portland cement are proposed for use where there is ample labor and little capital (18). They are made in a hand-operated press designed by an engineer in Chile and manufactured in Bogotá, Colombia, and Richmond, Va. The blocks are nominally 4 by 6 by 12 inches for modular construction. The material is organic-free earth, with from 5 to 10 percent by volume of portland cement. The objective is a block that is more resistant to weathering than adobe brick, but lower in cost than concrete block. Sandier soils provide a better base material than soils with clays or organic materials. Laboratory tests show that the 28-day compressive strength is highly variable, much lower than the strength of brick or concrete but many times that required for the ordinary building wall. Field tests show the block has a tendency to spall when in positions subjected to large changes in moisture. Hand manufacture of the block is very time consuming. Only about 100 blocks can be made per man-day. Their resistance to weathering is not as good as concrete block or structural clay masonry. They are not satisfactory for use in fully exposed walls in humid climates subjected to freezing and thawing. They should be used only above grade where they are protected from capillary water and splash from the building eave-and not directly on top of floor slabs. Material costs are low ($0.02 per block), but at wage rates of only $0.50 per hour, a square foot of wall 5%1⁄2 inches thick will cost about $0.30 in place. Materials are readily available. 18 Mortar-surfaced polystyrene building panels Mortar-surfaced polystyrene building panels (fig. 8) were developed for farm and rural application (19, 28). They can be lifted and placed by two men and do not require heavy cranes. They present a smooth interior finish desirable for milking rooms and similar applications where insulation and sanitation are important. Windows may be cast into the panels. The panels are 2 feet by 8 feet by 3 inches thick, and have a 2-inch core of expanded polystyrene, foamed glass, polyurethane, or semirigid insulative material. The weathering faces are 2-inch thickness of portland cement mortar, reinforced with 14-gage galvanized prestretched wire, spaced 1 inch on centers. The faces are tied together with reinforced buttons of mortar to serve as a connecting web. Laboratory tests show reasonably consistent performance under load. Ultimate strength is sufficient to support a uniform loading of about 60 pounds per square foot. In field tests, panels have been mounted horizontally and fastened with a single lag screw to pressuretreated wooden posts placed on the exterior. Calked horizontal joints without ship lapping or tongue-and-grooving have resisted water penetration satisfactorily. Tests to date have indicated no particular restrictions on use of these panels in normal rural construction. Materials costs presently are about $0.30 per square foot. Volume purchase should reduce this figure to about $0.20 on the present market. Availability of the materials going into these panels should increase and their prices should decrease. Sheet materials for hyperbolic paraboloid (HP) roofs Hardboard, plywood, sheet metals, and plastics such as polyesters, concrete, or fiberglass reinforced asphaltic materials can be used to span roof areas by taking advantage of the structural properties of the sheet to resist design loads (20). Application to rural structures is being studied (fig. 9). The HP shape utilizes the shear strength of sheet materials by giving them a warpage that subjects one directional element within the material to compression and another, at the same point in the shell, to tension, resulting in only shear stress in the material. This principle causes the shell stress to be a linear (not quadratic) function of the span. Loading tests on prototype roofs have been used to check computed stresses with attendant deflections. Field trials have been. made with roofs fabricated of aluminum, plywood, hardwood, insulation board, and thin shell plaster. Weather coating surfaces of polyester and fiberglass reinforced asphalt are being evaluated. In designing HP roofs with sheet materials, deviations from the true HP shape cause secondary stresses to be of major concern and further studies are being made to formulate expected secondary stresses. The principal limitation on the use of sheet material in this method of construction is the need for economical fabrication techniques, particularly in fastening the sheets together to obtain adequate shear strength in the joints. Also, weatherproofing problems are greater on curved roofs than on plane roofs. The cost of materials for a given span is less with HP roofs than with conventional roofs. Fabrication techniques, at present, are more expensive. |