Coffee stains Remedy: Apply a cloth that has been saturated in a solution of one part glycerin to four parts water. When the stain is drawn into the cloth, rinse with water. Egg Remedy: Wipe the stained area with acetone until the stain is removed. Ink and Biro Different inks require different treatments. Remedy: Wipe with white spirits, acetone or apply an acetone poultice to help draw out the stain. Brick Cleaning and Maintenance Brick Technical Manual 31 Marker pens Remedy: Wipe off with acetone or a poultice of acetone and talc. Oil, grease and animal fats Remedy: Apply an engine degreaser emulsifier or a strong detergent, then rinse well. Organic growths / fungus, mould and moss Porous masonry provides a benign environment for organic growth when it is continuously moist, especially in light but shady conditions and when there are plenty of nutrients available. You will need to check downpipes, flashings etc for ways to stop continuous moist conditions. If brickwork dries, organic growth should not occur.

3. Reinforcing steel resists all the tension due to flexure (Fig. 9.13a and b). 4. The modular ratio, n
Es /Ec, where Es and Ec are the moduli of elasticity of reinforcing steel and concrete, respectively, may be taken as the nearest whole number, but not less than 6 (Fig. 9.13b). 5. Except in calculations for deflection, n lightweight concrete should be assumed the same as for normal-weight concrete of the same strength. 6. The compressive stress in the extreme surface of the concrete must not exceed 0.45c
, where
c is the 29-day compressive strength of the concrete. 7. The following tensile stress in the reinforcement must not be greater than the following: Grades 40 and 50 20 ksi Grade 60 or greater 24 ksi For 3/8-in. or smaller-diameter reinforcement in one-way slabs with spans not exceeding 12 ft, the allowable stress may be increased to 50% of the yield strength but not to more than 30 ksi. 8. For doubly-reinforced flexural members, including slabs with compression reinforcement, an effective modular ratio of 2Es /Ec should be used to transform the compression-reinforcement area for stress computations to an equivalent concrete area (Fig. 9.13b). (This recognizes the effects of creep.) The allowable stress in the compression reinforcement may not exceed the allowable tension stress. Because the strains in the reinforcing steel and the adjoining concrete are equal, the stress in the tension steel s is n times the stress in the concrete c. The total force acting on the tension steel then equals nAsc. The steel area As, therefore can be replaced in stress calculations by a concrete area n times as large. The transformed section of a reinforced concrete beam is a cross section normal to the neutral surface with the reinforcement replaced by an equivalent area of concrete (Fig. 9.13b). (In doubly-reinforced beams and slabs, an effective modular ratio of 2n should be used to transform the compression reinforcement and account for creep and nonlinearity of the stress-strain diagram for concrete.) Stress and strain are assumed to vary with the distance from the neutral axis of the transformed section; that is, conventional elastic theory for homogeneous beams may be applied to the transformed section. Section properties, such as location of neutral axis, moment of inertia, and section modulus S, may be computed in the usual way for homogeneous beams, and stresses may be calculated from the flexure formula,
M/S, where M is the bending moment at the section. This method is recommended particularly for T-beams and doubly-reinforced beams. From the assumptions the following formulas can be derived for a rectangular section with tension reinforcement only.

1/8 in per ft slope 1/4 in per ft slope 1/2 in per ft slope Drain diameter, in Area Flow Area Flow Area Flow * Roof areas and flows are based on a maximum rainfall intensity of 1 in / hr for a duration of 1 hr. For regions with different maximum rainfall intensity in storms with a 100-year recurrence interval, divide tabulated areas and flows by that intensity, in / hr. The area of rectangular leaders should equal or exceed that of the circular leader required. The ratio of width to depth of rectangular leaders should not exceed 3 to 1. TABLE 14.10 Sizes of Semicircular Roof Gutters* Maximum projected roof area, ft2, and flow, gal / min, for gutters of various slopes 1/16 in per ft slope 1/8 in per ft slope 1/4 in per ft slope 1/2 in per ft slope Gutter diameter, in Area Flow Area Flow Area Flow Area Flow * See assumption of rainfall intensity and duration in note for Table 14.9. Gutters other than semicircular may be used if they have an equivalent cross-sectional area. TABLE 14.11 Maximum Capacities of Building Drains and Building Sewers, Fixture