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SEC. 91.1810.  DEEP FOUNDATIONS..
   (Amended by Ord. No. 182,850, Eff. 1/3/14.)
 
   Section 1810 of the CBC is adopted by reference, except Sections 1810.3.1.5, 1810.3.2.4, 1810.3.3.1.4, and 1810.3.10.4 of the CBC are not adopted; and, in lieu, LAMC Paragraphs 91.1810.3.1.5, 91.1810.3.2.4, 91.1810.3.3.1.4, 91.1810.3.10.4, and Subdivision 91.1810.4.8 are added.  (Amended by Ord. No. 185,587, Eff. 7/16/18.)
 
91.1810.3.1.5.  Helical Piles. Helical piles shall be designed and manufactured in accordance with accepted engineering practice to resist all stresses induced by installation into the ground and service loads.  Helical piles shall not be used for support of new structures.  Helical piles may be used to underpin foundations of existing structures or retrofit or remediate deficient foundations of existing structures.  Helical piles shall not be used to resist any horizontal loads. 
 
91.1810.3.2.4. Timber.  Timber deep foundation elements shall be designed as piles or poles in accordance with AF&PA NDS.  Round timber elements shall conform to ASTM D 25.  Sawn timber elements shall conform to DOC PS-20.  Timber shall not be used in structures assigned to Seismic Design Category D, E or F.
 
91.1810.3.3.1.4. Allowable Frictional Resistance.  (Amended by Ord. No. 186,488, Eff. 12/27/19.)  The assumed frictional resistance developed by any uncased cast-in-place deep foundation element shall not exceed one-sixth (1/6) of the bearing value of the soil material at minimum depth as set forth in CBC Table 1806.2, up to a maximum of 500 psf (24 kPa), unless a greater value is allowed by the Department on the basis of a geotechnical investigation as specified in LAMC Section 91.1803 or a greater value is substantiated by a load test in accordance with CBC Section 1810.3.3.1.2.  Frictional resistance and bearing resistance shall not be assumed to act simultaneously.
 
91.1810.3.10.4. Seismic Reinforcement.  (Amended by Ord. No. 185,587, Eff. 7/16/18.)  For structures assigned to Seismic Design Category C, a permanent steel casing shall be provided from the top of the micropile down to the point of zero curvature.  For structures assigned to Seismic Design Category D, E or F, the micropile shall be considered as an alternative system in accordance with LAMC Subdivision 91.104.2.6.  The alternative system design, supporting documentation and test data shall be submitted to the Department for review and approval.
 
91.1810.4.8.  Hollow-stem Augered, Cast-in-Place Elements.  An indicator pile program shall be performed to confirm the installation procedure and to determine the pile capacity by static load testing.  Upon completion of the pile load testing, at least one test pile shall be entirely exhumed to examine the pile integrity.  Prior to the installation of production piles, the results of the testing, and confirmation or revision to the pile capacity shall be determined.  Where concrete or grout is placed by pumping through a hollow-stem auger, the auger shall be permitted to rotate in a clockwise direction during withdrawal.  As the auger is withdrawn at a steady rate or in increments not to exceed 1 foot (305 mm), concreting or grouting pumping pressures shall be measured and maintained high enough at all times to offset hydrostatic and lateral earth pressures.  Concrete or grout volumes shall be measured to ensure that the volume of concrete or grout placed in each element is equal to or greater than the theoretical volume of the hole created by the auger.  Where the installation process of any element is interrupted or a loss of concreting or grouting pressure occurs, the element shall be redrilled to 5 feet (1524 mm) below the elevation of the tip of the auger when the installation was interrupted or concrete or grout pressure was lost and reformed.  Augered cast-in-place elements shall not be installed within six diameters center to center of an element filled with concrete or grout less than 12 hours old, unless approved by the building official.  If the concrete or grout level in any completed element drops due to installation of an adjacent element, the element shall be replaced.