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M&N 8415-02 <br /> February 18,2015 As-Built Pile Axial Capacity and Soil Stiffness Memorandum <br /> stiffness that was assumed in design,therefore the design calculations for the mobile harbor crane loads <br /> are unaffected by any softening of the pile springs. <br /> For the load combinations using 1000 psf uniform live load,the maximum factored pile loads for all of the <br /> new piles and the existing piles on gridlines A and B were less than 390 kips.This indicated that for these <br /> piles a 2000 kip/in soil spring was still appropriate. However,the existing piles on gridlines C, D, E, F, G, <br /> and H had maximum factored axial loads that exceeded 390 kips, indicating that a reduced soil spring <br /> value was required. For these piles,the soil spring stiffness was taken to be 500 kips/in. <br /> The linear-elastic finite element analytical model used in design was updated to reflect these as-built soil <br /> spring values. The analysis showed that using these soil stiffness values, the existing pile cap was <br /> overloaded by 13 percent in positive flexure between gridlines C and D, and overloaded by 6 percent in <br /> positive flexure between gridlines E and G.The factored moment diagram envelopes for all of the existing <br /> pile caps are shown in Figure 1 below.Note that this analysis uses the elastic moment diagram to estimate <br /> the demands at the ultimate limit state. <br /> 3000.0 I I 1 I <br /> I I I I <br /> 2000.0 <br /> 1000.0 —_ — I *,, <br /> " ,• <br /> I I I <br /> 4.1 <br /> E -1000.0 i r- <br /> 0 <br /> I I I I <br /> 2 I I I <br /> -2000.0 <br /> I I I I <br /> I I I I I <br /> -3000.0 L L _L_ <br /> I I I I I <br /> I I I I I <br /> -4000.0 I I <br /> 0 20 40 60 80 100 120 <br /> Length along Member(ft) <br /> Max Moment --Min Moment Positive Capacity Negative Capacity <br /> Figure 1—Existing Pile Cap Flexural Demands <br /> Because inelastic action is allowed to occur at the ultimate limit state,ACI 318-08 Section 8.4 allows the <br /> redistribution of moments in continuous flexural members. Section 8.4.1 states "it shall be permitted to <br /> decrease factored moments calculated by elastic theory at sections of maximum negative or maximum <br /> positive moment in any span of continuous flexural members for any assumed loading arrangement by <br /> mot fat? & plchol 3 <br />