leads to a compression of the underlying porous soil or rock structure. Since subsidence is due to a secondary influence (extraction of oil or groundwater), its effect on the structure would be included in the second basic type of settlement. 6.5.3 Foundation Design Parameters Determining the settlement of the structure is one of the primary obligations of the geotechnical engineer. In general, three parameters are required: maximum total settlement (max), maximum differential settlement (), and rate of settlement. Another parameter that may be useful in the design of the foundation is the maximum angular distortion ( /L), defined as the differential settlement between two points divided by the distance between them. Figure 6.19 illustrates the maximum total settlement (max), maximum differential settlement (), and maximum angular distortion ( /L) of a foundation. Note in Fig. 6.19 that the maximum angular distortion ( /L) does not necessarily occur at the location of maximum differential settlement 6.5.4 Allowable Settlement The allowable settlement is defined as the acceptable amount of settlement of the structure and it usually includes a factor of safety. The allowable settlement depends on many factors, including the following (D. P. Coduto, Foundation Design, Principles and Practices, Prentice-Hall, Inc., Englewood Cliffs, N.J.): The Type of Construction. For example, wood-frame buildings with wood siding would be much more tolerant than unreinforced brick buildings. TABLE 6.13 Allowable Settlement Type of movement Limiting factor Maximum settlement

Step 3: Follow the procedures Follow the written instructions as well as those shown on the labels of proprietary cleaners. Always clean a small test area first to ensure the cleaning method has worked to your satisfaction. Step 4: Safety precautions are essential Make sure you read safety precautions thoroughly, wear protective clothing and store any chemicals safely. Note: Hydrochloric Acid is commonly used to clean mortar stains from brickwork when it is initially laid. It does not need to be used at any other time during the life of your brickwork. If used incorrectly it can cause unsightly staining that is extremely difficult to remove. 3.1.3 Removing Common Stains Adhesive tape Remedy: Wipe with petrol, lighter fluid or paint stripper. Blood Remedy: Wet the stain with water then cover it with an even layer of sodium peroxide powder. Sprinkle with water or cover with a water soaked bandage and leave for five minutes. Scrub vigorously with clean water and then neutralise using a five percent solution of acetic acid (vinegar) and rinse with water at end of treatment.

Tapping screws are an alternative means of attaching steel roof deck to structural support members, which should be at least 1/16 in thick. All edge ribs and a sufficient number of interior ribs should be connected to supporting members at intervals not exceeding 18 in. When standard steel roof deck spans 5 ft or more, adjacent sheets should be fastened together at midspan with either welds or screws. 8.21.5 Roof Deck Insulation and Fire Resistance Although insulation is not ordinarily supplied by the roof-deck manufacturer, it is standard practice to install 3/4- or 1-in-thick mineral fiberboard between roof deck and roofing. SDI further recommends that all steel decks be covered with a material of sufficient insulating value to prevent condensation under normal occupancy conditions. Insulation should be adequately attached to the steel deck by means of adhesives or mechanical fasteners. Insulation materials should be protected from the elements at all times during storage and installation. FIGURE 8.16 Roof-deck details. The UL Fire Resistance Directory, Underwriters Laboratories, Inc., 333 Pfingsten Rd., Northbrook, IL 60062, lists fire-resistance ratings for steel roof-deck construction. Some systems with fire ratings up to 2 h are listed in Table 8.14. Several different designs of cellular steel panels and fluted steel panels for floor and roof construction are available. Sections of some of these panels are illustrated