Nội dung của nó bao gồm việc tính toán các lực đỡ, nội lực và biến dạng do tác động của ngoại lực lên một hệ chịu lực của công trình xây dựng. Bên cạnh tĩnh lực còn có các tác động khác: thay đổi nhiệt độ, co ngót ẩm, từ biến, biến dạng gối. | That is to say if a wall has returns at right angles to the direction of the shear force the area of the returns is neglected in calculating the shear resistance of the wall. THE TENSILE STRENGTH OF MASONRY Direct tensile strength Direct tensile stresses can arise in masonry as a result of in-plane loading effects. These may be caused by wind by eccentric gravity loads by thermal or moisture movements or by foundation movement. The tensile resistance of masonry particularly across bed joints is low and variable and therefore is not generally relied upon in structural design. Nevertheless it is essential that there should be some adhesion between units and mortar and it is necessary to be aware of those conditions which are conducive to the development of mortar bond on which tensile resistance depends. The mechanism of unit-mortar adhesion is not fully understood but is known to be a physical-chemical process in which the pore structure of both materials is critical. It is known that the grading of the mortar sand is important and that very fine sands are unfavourable to adhesion. In the case of clay brickwork the moisture content of the brick at the time of laying is also important both very dry and fully saturated bricks lead to low bond strength. This is illustrated in Fig. which shows the results of bond tensile tests at brick moisture contents from oven-dry to fully saturated. This diagram also indicates the great variability of tensile bond strength and suggests that this is likely to be greatest at a moisture content of about three-quarters of full saturation at least for the bricks used in these tests. Direct tensile strength of brickwork is typically about mm2 but the variability of this figure has to be kept in mind and it should only be used in design with great caution. Flexural tensile strength Masonry panels used essentially as cladding for buildings have to withstand lateral wind pressure and suction. Some stability is .
