![]() ![]() The ratio of masonry unit height to least horizontal dimension of masonry unit and the ratio of masonry unit height to effective thickness of masonry wall has been limited to a definite range for different wall types.Construction control category (as defined in code provision).Masonry unit category (as defined in code provision).Solid aggregate concrete blocks collar jointed.Solid aggregate concrete blocks laid flat.Aggregate concrete blocks (of various porosity). Type of bricks used and their properties.In order to better use of the module, selection based material properties are given such as,.The design module allows the user to capture the actual site / design requirements via various options such as,.If the resultant is located outside the middle third, a factor of safety of at least 1.5 should be maintained against overturning i.e., the restoring moment should be at least 1.5 times the overturning moment. If, as is mostly the case, the resultant strikes within the middle third, adequate safety against overturning exists, and no special check need be made. 17.4, which is the same as saying that the resultant would have to strike outside the edge b. For this to occur, the overturning moment \Ph about point b would have to be larger than the restoring moment (Wg Pyi) in Fig. 17.5c).Ī third mode of failure is the possibility of the wall overturning bodily around the front edge b (Fig. If the foundation is on very incompressible soil, such as well-compacted gravel or rock, the resultant can be allowed to fall outside the middle third (Fig. In a foundation on such a soil, the resultant, therefore, should strike at or very near the center of the footing. 17.5b would result in a much larger settlement of the toe than of the heel, with a corresponding tilting of the wall. ![]() If the wall is founded on a highly compressible soil, such as certain clays, a pressure distribution as in Fig. This will not only reduce the magnitude of the maximum bearing pressure but will also prevent too large a nonuniformity of pressure. It is good practice, in general, to have the resultant located within the middle third. Equilibrium requires that Rv pass through the ccntroid of the pressure distribution triangle, from which the formula for </, for this case can easily be derived. 17.5c will develop, which implies a slight lifting off the soil of the rear part of the footing. in this case the pressure distribution of Fig. Obviously, tension cannot be developed between soil and a concrete footing that merely rests on it. (17.8) would indicate tension at and near point a. If the resultant were located outside the middle third (a < I 3), Eq. (17.8) results in the formula given there. (a) Resultant in middle third (c) Resultant outside middle thirdĮdge of the middle third (a - / 3), the pressure distribution is as shown in Fig. ![]()
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