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Alliance Residence October 18,2016 <br />J.N.: 2530.00 <br />Page 13 <br />Shallow spread footings may be used to support the garage structure i f they are underlain by rammed <br />aggregate piers, displacement grout columns (DGC), or other ground improvement technologies. <br />Specific designs for ground improvement techniques should be provided by a geotechnical engineer <br />that specializes in the design of such systems to limit the total and differential settlement to tolerable <br />limits. In such cases, the allowable bearing value may be as recommended by the specialty <br />contractor and may supersede the values indicated in Section 6.3.4. <br />Foundations should be designed for total and differential settlement up to 1 inch and M-inch over 30 <br />feet, respectively. These estimated magnitudes of settlement should be considered by the structural <br />engineer in design of the proposed structures at the site. <br />6.3.4 Allowable Bearing Value <br />Provided site grading is performed in accordance with the recommendations provided by the project <br />geotechnical consultant, a bearing value of 2,000 pounds per square foot (psf) may be used for <br />continuous footings or beams on post-tensioned slab systems having a minimum effective width of <br />12 inches and founded at a minimum of 12 inches below the lowest adjacent grade. This value may <br />be increased by 180 psf and 500 psf for each additional foot in width and depth, respectively up to a <br />maximum of 3,500 psf. Recommended allowable bearing values include both dead and live loads, <br />and may be increased by one-third for wind and seismic forces. <br />6.3.5 Lateral Resistance <br />Provided site grading is performed in accordance with the recommendations provided by the project <br />geotechnical consultant, a passive earth pressure of 300 pounds per square foot per foot of depth up <br />to a maximum value of 1200 pounds per square foot may be used to determine lateral bearing for <br />beams. This value may be increased by one-third when designing for wind and seismic forces. A <br />coefficient of friction of 0.30 times the dead load forces may also be used between concrete and the <br />supporting soils to determine lateral sliding resistance. No increase in the coefficient of friction <br />should be used when designing for wind and seismic forces. <br />The above values are based on footings placed directly against compacted fill or competent native <br />soils. In the case where footing sides are formed, all backfill against the footings should be <br />compacted to at least 90 percent of the laboratory standard (ASTM D 1557). <br />6.3.6 Minimum Foundation Dimensions and Reinforcement <br />All spread and continuous exterior footings should have minimum widths of 24 and 12 inches, <br />respectively and a minimum embedment of 18 inches. All interior footings should have a minimum <br />width of 12 inches and minimum embedment of 12 inches below the bottom of slab. <br />All continuous footings and grade beams should be reinforced with a minimum of two No. 4 bars on <br />top and two No. 4 bars on the bottom. <br />6.3.7 Conventional Slab on Grade <br />Interior concrete slabs constructed on grade should have a minimum thickness of 5 inches and <br />should be reinforced with at least No. 3 bars spaced 12 inches each way. Care should be taken to <br />ensure the placement of reinforcement at mid-slab height. The structural engineer may recommend <br />ALBUS-KEEFE & ASSOCIATES, INC.