Exposure Proof Course in Aggressive Soils AS 3700 classifies a marine environment as: 1km to 10km from a surf coast, or 100m to 1km from a non-surf coast. AS 3700 classifies a severe marine environment as: within 1km of a surf coast, or within 100m of a non-surf coast. It is important to take into consideration the given environment during the design and construction of brickwork buildings, to minimise the potential for salt attack. The most suitable mortar joints for aggressive environments are ironed or weather struck joints. The mortar classifications given in the table and the types of mortar joints possible are discussed in more detail in the mortar section of this manual. It should also be noted that raked mortar joints should not be used in severe marine environments. The minimum durability classification of built-in components is particularly relevant to the use of wall ties in masonry constructions. AS /NZS 2699.1 classifies the durability of masonry wall ties as:

Eccentricity of load with respect to the weld patterns causes stresses in the welds that must be considered in addition to direct shear. Assumed forces, eccentricities, and induced stresses are shown in Fig. 7.48b. Stresses are computed as in the example in Art. 7.34, based on vector analysis that characterizes elastic design. The capacity of welds A or B that is smaller will govern design. If ultimate strength (plastic design) of such connections is considered, many of the tabulated elastic capacities are more conservative than necessary. Although AISC deemed it prudent to retain the elastic values for the weld patterns, recognition was given to research results on plastic behavior by reducing the minimum beam-web thickness required when welds A are on opposite sides of the web. As a result, welded framed connections are now applicable to a larger range of rolled beams than strict elastic design would permit. FIGURE 7.48 Welded framed connections on beam web: (a) weld locations along connection angles; (b) forces on

(See Plank and Beam Framing for Residential Buildings, WCD No. 4, American Forest & Paper Association, Washington, D.C.) FIGURE 10.23 Platform framing for two-story building. FIGURE 10.24 Plank-and-beam framing for one-story building. FIGURE 10.25 Wood foundation on a concrete footing. Plywood and lumber walls are an alternative to concrete for foundation walls for one-story and multistory houses and other light-frame buildings. Main components of a wood foundation wall are plywood, 5/8 in or more thick, and wood studs, spaced 12 in or more on centers, both pressure-treated with preservative (Fig. 10.25). Some advantages of a wood foundation over concrete are faster construction, because there is no delay due to the wait for concrete or unit masonry to cure, easier interior finishing, because wood foundations provide nailable studs for the usual finishes, the ability to erect the system in virtually any weather, and generally drier basements due to the use of gravel backfill, which facilitates drainage of water away from the foundation. Wood basements also are much warmer and more comfortable for the occupant in cold weather. Plywood should be an exterior type or an interior type that has been bonded with exterior glue, both types manufactured to meet the requirements of U.S. Product Standard PS 1 for Construction and Industrial Plywood. Lumber should be grade marked by an approved inspection agency, should be capable of accepting pressure preservative treatment, and should be of a species for which allowable design values are given in Art. 10.3. Treatment for the plywood and lumber involves impregnating into the wood under heat and pressure ammoniacal copper arsenate or chromated copper arsenate (A, B, or C). Salt retention should be at least 0.60 lb / ft3 of wood, 50% more than building codes usually require for ground-contact applications. After pressure treatment, plywood should be dried to a moisture content of 18% or less, and lumber, to 19% or less. Portions of the wall more than 8 in above the ground, however, need not be pressure treated. If any of the materials have to be cut after treatment, the cut edges, unless they will be 8 in or more above grade, should be field treated with the preservatives used in the original treatment but with a minimum concen- TABLE 10.39 Stress Values for Treated Wood Poles*