9910 EVERGREEN WAY SPRINT ANTENNA 2018-01-01 MF Import

LSI Adapt Lateral Canacities: For desio against lateral forces acting against the drilled pier, two methods are typically used. Thc parameter used to select the appropriate desi�m method is thc length to }: ier stiffness ratio LJT, where L is the pier Iength in inches, and T is the relative stiffness factor. The relative stiffness factor (T) should be c�mputed by: T=rnl`o l l where E= modulus of elasticity (psi) I = moment of inertia (in") nh = constant of horizontal subgrade rcaction (pci) The factors E and 1 are govemed by the intemal material strength characteristics of the pier. A representative value of nh for the soil types encountered at this site is presented bclow in Table 4. Piers with a L/T ratio of less than 2 may be assumed to be relatively rigid and acting as a pole. The passive pressure approach may be used for this condition. For piers with a L/T ratio greater than 2, the modulus of subgrade reaction method is typically used. Both of these methods are discussed below: Passive Pressure Method: The passive pressure approach is conservative by neglecting the redistribution of vertical stresses and shear fcrces that develop near the bottom of the pier and contribute to resisting ]ateral loads. We recommend using the allowable passive earth pressure (expressed as equivalent fluid unit weights) listed in Table 3. The allowable passive pressure for soils below the maximum depth of the [est borino may be assumed to be as that shown for the lowest depth increment below. Tablc 3 Allowablc Passivc Pressures Depth (feet) Allowable Passive Pressure (pc� 0-2 p 2-12 250 12-20 175 20-29.5 200 The allowable passive earth pressure presented in Table 3 may be assumed to be acting over an area measuring 2 pier diameters in width by 8 pier diameters in depth, neglec[ing the uppermost 2 feet of emb:dment below the ground suriace. According to the NAVFAC Design Manual 7.02 (19R6), a lateral dellection equal to aboul 0.01 times the pier leneth would be required to mobilize the allowable passive pressure presented above. Higher detlections would mobilize higherpassive pressures. When developing the alloxable pa�sive pressure listed in Table 3, we have incorporated a safery factor of at least I.S, which is commonly applied to transient or seismic loading conditions. Spnn� PCS :.ugus� 4.2003 �/�) ndapi Pwjcct ha. WA03-4710 Page 7