Ease of installation and maintenance Light distribution from fixtures, to summarize, may be accomplished by means of transmission, reflection, refraction, absorption, and diffusion. Reflectors play an important role. Their reflectance, consequently, should be highat least 85%. The shape of a reflectorspherical, parabolic, elliptical, hyperbolicshould be selected to meet design objectives; for example, to spot or spread light in a building space or to spread light over a fixture lens that controls light distribution. (The need for a curved reflector, which affects the size of the fixture, can be avoided by use of a Fresnel lens, which performs the same function as a reflector. With this type of lens, therefore, a smaller fixture is possible.) Light control also is affected by shielding, baffles, and louvers that are positioned on fixtures to prevent light from being emitted in undesirable directions. A wide range of light control can be achieved with lenses. Flat or contoured lenses may be used to diffuse, diffract, polarize, or color light, as required. Lenses composed of prisms, cones, or spherical shapes may serve as refractors, producing uniform dispersion of light or concentration in specific directions. Types of Installations. Luminaires may be classified in accordance with type and location of mountings, as well as with type of lighting distribution: flush or recessed (Fig. 15.13), ceiling mounted (Fig. 15.14), pendent (Fig. 15.15), wall mounted (Fig. 15.16) or structural. Structural lighting is the term applied to lighting fixtures built into the structure of the building or built to use structural elements, such as the spaces between joists, as parts of fixtures. Structural lighting offers the advantage of a lighting system conforming closely to the architecture or interior decoration of a room. Some types of structural lighting are widely used in residences and executive offices. For the purposes of accent or decorative lighting, for example, cornices, valences, coves, or brackets are built on walls to conceal fluorescent lamps. For task lighting, fixtures may be built into soffits or canopies. For general lighting, large, low-brightness, luminous panels may be set flush with or recessed in the ceiling. Lighting objectives can be partly or completely met with portable fixtures in some types of building occupancies. For the purpose, a wide variety of table and floor lamps are commercially available. Because the light sources in such fixtures are usually mounted at a relatively low height above the floor, care should be taken to prevent glare, by appropriate placement of fixtures and by selection of suitable

R  rain loads W  wind loads E  seismic loads Building codes usually permit a smaller factor when the probability is small that combinations of extreme loads, such as dead load plus maximum live load plus maximum wind or seismic forces, will occur. Generally, for example, a factor of 0.75 is applied to load-combination sums (2) to (6). Such factors are equivalent to permitting higher allowable unit stresses for the applicable loading conditions than for load combination (1). The allowable stress is obtained by dividing the unit stress causing excessive deformation or failure by a factor greater than 1. In loadandresistance factor design, the various types of loads are each multiplied by a load factor, the value of which is selected in accordance with the probability of occurrence of each type of load. The factored loads are then added to obtain the total load a member or system must sustain. A structural member is selected to provide a load-carrying capacity exceeding that sum. This capacity is determined by multiplying the ultimate-load capacity by a resistance factor, the value of which reflects the reliability of the estimate of capacity. Load criteria generally used are as follows: 2. 1.2D  1.6L  0.5(Lr or S or R) 3. 1.2D  1.6(Lr or S or R)  (0.5L or 0.8W) 4. 1.2D  1.3W  0.5 (Lr or S or R) 5. 1.2D  1.0E  (0.5L or 0.2S) 6. 0.9D
(1.3W or 1.0E) For garages, places of public assembly, and areas for which live loads exceed 100 lb/ft2, the load factor usually is taken as unit for L in combinations 3, 4, and 5. For roof configurations that do not shed snow off the structure, the load factor should be taken as 0.7 for snow loads in combination 5. For concrete structures where load combinations do not include seismic forces, the factored load combinations of ACI 318 Section 9.2 shall be used. For both allowable stress design and strength design methods, elements and components shall be designed to resist the forces due to special seismic load combinations a) 1.2D  0.5L  Em

Figure 4 Grey* Examples of same brick with different mortar colours Figure 5 Off White* Figure 6 Grey* * Colours shown are an indication only. Mortar colours will vary depending on the type of cement, sand and pigments used. Working with Bricks Brick Technical Manual 21 Mortar Mixes Mortar mixes are always specified as the proportion of cement to lime to sand. For example, a common mortar made from Portland cement has one part cement, to one part lime and 6 parts of sand is abbreviated C1:L1:S6 or 1:1:6 (the chief cementing agent will always be expressed as one). The type of mortar mix is classified according to the Australian Standard AS 3700 as M1, M2, M3 or M4. The grade chosen by the masonry designer should match the requirements of the design. AS 3700 lists the deemed-to-satisfy proportions for the various grades. A brief description of the various mixes is given in the table below. For a more detailed description of the masonry mixes, grades and their applications refer to AS 3700 or to the Think Brick Manual 10; Construction Guidelines for Clay Masonry.