load-bearing and enclosing elements of buildings and structures made from stone masonry (foundations, walls, columns, partitions, arches, and vaults).
Artificial and natural stone materials are used for masonry construction, including construction brick, solid and hollow ceramic and concrete stone and blocks, stone from heavy or light rock (limestone, sandstone, tuff, and coquina), mortars, and large blocks of ordinary (heavy), silicate, and light concretes. The material for stonework is chosen according to the size and importance of the structure, the strength and thermal-insulation properties of the structural elements, and the availability of local raw materials, and also on the basis of economic considerations. The stone material should satisfy requirements for strength, cold resistance, heat conductivity, water and air resistance, water absorption, and resistance in an aggressive medium, and it should also have a certain shape, dimensions, and finish of the outer surface. The demands made on mortars include strength, convenience in laying, and water-retention capacity.
Masonry construction is one of the oldest types of construction. In many nations a large number of outstanding architectural monuments of stonework have survived. Masonry construction is durable and resistant to fire, and local raw materials may be used; these factors have determined its extensive use in modern construction.
Among the drawbacks of masonry construction are its comparatively great weight and high thermal conductivity. The laying of piece stonework also requires significant expenditures of manual labor. In this regard the efforts of builders have been aimed at the development of effective lightened masonry construction using thermal insulation materials. The cost of masonry construction (foundations and walls) is 15–30 percent of the total cost of a building.
In contemporary construction, masonry construction (mainly brick and stone walls and foundations) is one of the widespread types of structural elements (large-panel construction predominates only in large cities). The practices of construction using stone have significantly furthered the development of the science of masonry construction. Empirical rules and insufficiently sound methods of calculation, which have not permitted full use of the load-bearing capacity of masonry construction, have been used in the design stage. The teachings on strength and the methods of calculation for masonry construction, which are based on extensive experimental and theoretical research, originated in the USSR in 1932–39 with L. I. Onishchik. A study was made of the principles of masonry work using various types of stone and mortar, as well as of the factors influencing its strength. It was established that, upon transmission of a force throughout the cross section in masonry consisting of individual alternating layers of stone and mortar, a complex stressed state arises, and individual stones (bricks) are not only compressed but are also subject to bending, tension, shear, and local compression. The reasons for this are unevenness in the stone bedding and the irregular thickness and density of the horizontal masonry joints, which reflect the thoroughness of mixing of the mortar, the degree to which it is smoothed out and compacted in laying the stone, and the conditions of hardening. Masonry laid by a skilled mason is 20–30 percent stronger than that laid by a worker of average skill. Another reason for the complex stressed state of masonry work is the different elastic and plastic properties of the mortar and stone. Significant lateral deformations arise under the influence of the vertical forces in the mortar joint, leading to the early appearance of cracks in the stone. The greatest compressive strength when using regularly shaped stone is found in masonry work of large blocks, and the least is found in rubble quarrystone and brick. The larger stones also have a greater resistance moment, which significantly increases their resistance to bending. The strength of vibration-set brick masonry under optimum vibration conditions is approximately twice the strength of hand masonry and approaches the strength of the brick because of the better compacting and filling of the mortar joint and closer contact between the mortar and the brick.
In masonry buildings, the most important elements—that is, the exterior and interior walls and the roof—are connected in a single system. Calculation of their combined spatial performance, which provides the strength of the building, makes possible the most economical design of masonry construction.
In calculating masonry construction, a distinction is made between masonry buildings with rigid and flexible structural schemes. The first group includes buildings with close placement of cross walls, in which the slabs between the floors are viewed as fixed stiffeners that create rigid ties for the walls with the effect of the cross and eccentric longitudinal loads. Such a system is used in calculating the walls and internal supports of multistory residential buildings and most public buildings. The second group consists of large-span buildings with significant distances between the cross walls. In such buildings the roofs also link the walls and the internal supports into a single system, but they cannot be viewed as fixed stiffeners; consequently, the combined deformations of the interconnected building elements are taken into account in the calculations. Most industrial buildings with load-bearing stone walls are calculated according to this system. In designing the masonry construction, the calculation of the spatial performance of the walls makes possible a substantial reduction in the calculated bending moments in the walls and of the thickness of the walls, as well as lightening of the foundations and an increase in the number of stories.
Depending on the design system of the buildings, masonry walls are divided into load-bearing walls, which receive the load from their own weight and from floors, facings, and building cranes; self-supporting walls, which bear the weight of all the floors of the building, as well as wind loads; and curtain walls, which take the load from their own weight and the wind within the limits of one floor. Masonry walls made of dimension stone and brick are divided into solid and laminar (light). The thickness of solid walls is set as a multiple of the basic brick dimensions, that is, 0.5, 1, 1.5, 2, 2.5, and 3 bricks. Material consumption, labor intensity, and the cost of erecting the walls depend on correct selection of the design and the degree to which the properties of the materials are used. The use of solid masonry construction made of heavy materials is not advisable for the exterior walls of low-rise heated buildings. In this instance, light laminar walls with thermal insulation or walls made of hollow ceramic stone, as well as stone made from light and cellular concretes, are used. A structural scheme with internal transverse load-bearing walls, which makes possible the use of exterior walls made of light, efficient materials, such as ceramics with thermal insulation, is preferable for buildings made of dimension brick or stone and having a large number of stories.
To increase its strength, masonry work is reinforced with steel or reinforced concrete (complex structural elements), as well as with casings (that is, the placement of the masonry work in reinforced-concrete or metal casings).
REFERENCESOnishchik, L. I. Kamennye konstruktsiipromyshlennykh igrazhdanskikh zdanii. Moscow-Leningrad, 1939.
Spravochnik proektirovshchika: Kamennye i armokamennye konstruktsii. Edited by S. A. Sementsov and V. A. Kameiko. Moscow, 1968.
Poliakov, S. V., and V. N. Falevich. Proektirovanie kamennykh i krup-nopaneVnykh konstruktsii. Moscow, 1966.
StroiteVnye normy i pravila, part 2, sec. C, chap. 2: “Kamennye i armokamennye konstruktsii: Normy proektirovaniia.” Moscow, 1962.
V. A. KAMEIKO