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a' August 28, 1991 BALBI&CHANG ASSOCIATES <br /> File No. 1525-69 <br /> soils should be thoroughly moistened to close all cracks prior to the placement of <br /> footing concrete. Openings for utilities within the perimeter wall footings should be <br /> sealed to prevent moisture migration'. All footing excavations should be observed by <br /> a representative of the geotechnical engineer to verify the competence of the bearing <br /> material. If soft or undesirable material is encountered within the footing excavation, <br /> the area should be over-excavated and replaced with either engineered fill or concrete.. <br /> We estimate that post-construction settlement of the structures will be less than one <br /> inch. Differential settlements for foundations proportioned for the bearing values <br /> recommended above are expected to be less than half of an inch. <br /> 2. Canopy and Facility Sign <br /> i <br /> Because canopy and facility sign may subject to additional lateral and/or up-lift loads, <br /> .deepen footing or pier foundation may be used to compensate for the extra loadings. <br /> For up-lift resistance of the deepen footing, the design engineer should evaluate the <br /> most critical condition, which the failure plane through the soil is vertical. Under <br /> such condition, up-lift resistance is limited to the weight of footing concrete plus the <br /> weight of soil above the footing, if any. Also, proper safety factor should be applied <br /> in determine the up-lift capacity of the foundation system. <br /> If the deepened footing cannot adequately support the canopy or facility sign structure, <br /> drilled pier foundation may be used. All piers to be constructed at this site should be <br /> designed as friction piers. An allowable skin friction value of 400 pounds per square <br /> foot (psf).may be used for dead plus live loads. This value may be increased by one- <br /> third for transient loadings such as wind and seismic effects. Due to construction <br /> disturbance, the load carrying ability 'of the upper two feet of soil should be neglected <br /> in determining the allowable pier capacity. For uplift resistance, the pier uplift <br /> capacity is half of the compression capacity plus the weight of pier concrete. <br /> Actual drilled pier designs (diameter, length, and spacing) should be based on building <br /> load conditions as determined by the structural engineer. However, no drilled pier <br /> should be designed with a diameter less than 12 inches, or a embedment depth less <br /> than 5 feet measured from the lowest adjacent ground surface to the bottom of pier. <br /> Minimum spacing between piers should be 3 times the pier diameter, center to center. <br /> Maximum spacing should be determined by the design engineer. Due to construction <br /> constraints, drilled piers should not be designed with a length to diameter ratio greater <br /> than 15. - <br /> I <br /> Page 1I of 17 <br /> I <br /> it <br />