b'Design Example 2 Calculate the Maximum Pier Spacing for Design Example 1 Aninspectionofthepropertysuggeststhatthe X = Pier Spacing = P DSL /P L (Equation 1)structure is well built and the foundation appears Where:sound. X = Pier Spacing (ft) ASafeUseDesign usingthePPB-350SteelPierwithadesignloadof43,000poundsis P DSL= 43,000 lbDesign Service Loadselected. This represents a strong and economical P L = Estimated Lifting Load = 7,200 lb/lin.ftpier for this project. (Table 1Chapter 6) X = 43,000 lb / 7,200 lb/ft = 5.97 feet A Factor of Safety of 2:1 is used. X = Use 6 feet , (maximum) AccordingtotheanalysisinExample1the The pier placement design may now be preparedstructure requires a Factored Lifting Force of 7,200 and a pricing estimate for this project is possiblepounds per lineal foot of perimeter beam. with piers spaced not to exceed 6 feet on center.Equation 1 from Chapter 6 is used to determine End Design Example 2the pier spacing relative to pier capacity.Design Example 2AAdjusting for Pier Buckling in Weak Soil While discussing this project design, the engineer Look for a Pier Configuration in Table 12 withmentioned that consolidation of a weak soil layercaused the settlement.Upon further investigations a Working Load greater than 43,000 lb in weakofthesoildata, thesoilanalysis indicated soil with N at 1 bpf and higher:approximately sixfeetofuncompactedloosefill Notice that the PPB-350-EPS with PPB-350-SBwith Standard Penetration Test values, N = 1 to 3blows per foot near the surface. ExternalSleeve (shownbelow). Thepier Below six feet deep, the soil is firm clay with SPT configurationat#2 willprovide asuitablevalues exceeding N = 5 blows per foot. working load capacity of 58,000 lb. AccordingtotheanalysisinExample1thestructure requires a factored lifting force of 7,300 Table 12 Working Loads Under Buckling Conditionspounds per lineal foot of perimeter beam. For Budgetary Estimating (Factor of Safety = 2)FirstMethod:Therearetwowaysto handle Shaft Size Uniform Soil ConditionOrganics Very Soft Clay Soft Clay Loose Sandthis new information.The first method accounts N 1 N = 1- 2 57,000 lb 47,000 lbforthereductioninpierpipecapacity dueto PPB-300-EPS (2-7/8 dia.) 19,000 lb 22,000 lb N = 2 - 4 N = 2 - 4buckling and adjust the spacing accordingly. PPB-300-EPS + PPB-300-IP 23,000 lb 27,000 lb 55,000 lb 47,000 lbExample2determinedthatthe PPB-350Steel PPB-350-EPS (3-1/2 dia.) 1 26,000 lb 30,000 lb 86,000 lb 71,000 lbPiershould be installed at 6 feet on center for PPB-400-EPS (4 dia.) 34,000 lb 40,000 lb 97,000 lbfull foundation support with a F.S. of 2:1. PPB-350-EPS + PPB-350-IP 36,000 lb 42,000 lb 99,000 lb 97,000 lb1. Determinethe WorkingLoadUnder PPB-350-EPS + PPB-350-SB 2 50,000 lb 58,000 lb 99,000 lbBuckling Conditions for PPB-350 Steel Pier. PPB-350-EPS + 350-IP + 350-SB 99,000 lb 66,000 lbTable1 in Chapter6liststhe Recommended 2. Change specification to the sleeved pier pipeDesign/ServiceLoad in competentsoilfora configurationwiththeoriginalplacementPPB-350 pier pipe at 43,000 lb, but referring to spacing of 6 feet on center.The PPB-350-EPSTable 12 in Chapter 6 (shown at right) #1 shows Steel Pierwill be installed to the full depth andthat the Critical Buckling of PPB-350 pier pipe havethree42 longsectionsofPPB-350-SBin clay with, SPT, N = 1 is 30,000 lbs. external pipe sleeves installed at the upper 10-1/22. Calculate New Pier Spacing, X: feet.Thiswillstrengthenthepierpipe passingX = P SU Des /P L (Equation 1) through the 6 ft of very weak soil. X = 30,000 lb / 7,300 lb/ft = 4.11 ft The three pieces of PPB-350-SB sleeve shall be Use X = 4 feet, (maximum) installedafterthe 3-1/2diameter pierpipe isdriven to load bearing, but prior to proof testing.SecondMethod:Chooseanewproduct The three sleeve sections will stiffen the pier pipeconfiguration that offers a more rigid pier section and joints to a depth of 10-1/2 feet, which meansand maintain the original pier placement spacing. that sleeve extends more than three feet beyondthe depth of the weak fill soil.End Design Example 2AECP Technical Design Manual Steel Pier Design Examples2021 Earth Contact Products, L.L.C.2021-09 Chapter 7 - Page 135 All rights reserved'