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Alliance Residence October 18,2016 <br />J.N.: 2530.00 <br />Page 15 <br />most flooring finishes that can accommodate some vapor emissions. However, this system may emit <br />more than 4 pounds of water per 1000 sq. ft. and therefore, may not be suitable for all flooring <br />finishes. Additional steps should be taken if such vapor emission levels are too high for anticipated <br />flooring finishes. <br />Special consideration should be given to slabs in areas to receive ceramic tile or other rigid, crack- <br />sensitive floor coverings. Design and construction should mitigate hairline cracking through the use <br />of additional reinforcing and careful control of concrete slump. <br />Prior to placing concrete, subgrade soils below slab-on-grade/mat areas should be thoroughly <br />moistened to provide moisture contents that are at least 110 percent of the optimum moisture content <br />to a depth of 12 inches. <br />Based on the guidelines provided in the "Design of Post-Tensioned Slabs-on-Ground" 3rd Edition by <br />Post-Tensioning Institute, the em and ym values are summarized below: <br />TABLE 6.2 <br />PTI Design Values <br />)]*UEXIMONF '.. 9©[jIO <br />Edge Lift Moisture Variation Distance, em 4.2 feet <br />Edge Lift, ym 2.37 inches <br />Center Lift Moisture Variation Distance, em 7.9 feet <br />Center Lift, ym 1.71 inches <br />6.3.9 Mat Foundations <br />The following recommendations are presented for preliminary design purposes.Final <br />recommendations will be subject to revision based on review of the final foundation plans and actual <br />structural loading. <br />A mat foundation system may be used in lieu of a conventional slab on grade and spread footings. <br />The outer 12 inches should be thickened to provide a minimum embedment of 8 inches below lowest <br />grade. An average net bearing pressure of up to 600 pounds per square foot (psf) under static <br />conditions may be used to design a mat foundation to support proposed structures. Local bearing <br />pressures under static and seismic conditions should be limited to 3,000 psf and 4,000 psf, <br />respectively. <br />Design of the mat may be based on a modulus of subgrade reaction (Kvi) of 40 pounds per cubic <br />inch (pci). The modulus is based on an effective loading area of I foot by 1 foot. The modulus may <br />be adjusted for other effective loading areas using the equation provided below. <br />c b+1 ,4 (pci) = 40 1 - where "b" is the effective width of loading (minimum dimension) in feet. <br />2b <br />Lateral resistance of the mat may be based on the values provided in Section 6.3.5. <br />ALBUS-KEEFE & ASSOCIATES, INC.