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<br /> <br />Further support and resistance to lateral loads <br />is provided by two inch by six inch pressure treated <br />wood cross bracing. The pier design, anchorage, <br />cross bracing, and footing details needed to <br />elevate a manufactured home are then combined <br />to form the elevated foundation as shown in Figure <br />4.34. <br /> <br />~JOi't <br /> <br />2",SfeelllJlllsher <br />1/4' lhick <br /> <br /> <br />Pierdellgn per <br />111ble 4.11 <br /> <br />Chessl,l*Sellm <br /> <br />Strllll) connected <br />10 ground IInthor <br /> <br />2-1/2', Anchor bolts, <br />1'-D"'ong !linn 2" hoot <br /> <br />Shim using <br />metal II. <br />tlsneeded <br /> <br />2"H4' Pressure <br />treotedlumber <br /> <br />/,/,~" ~ <br />// %~~ ~~ <br />'i/h ~~~~ ~~ <br />.~~ ..'C <br />:=>;; <br />~ 0 <br />, " <br />;..,,'"": <br />o <br />E <br />. <br /> <br />.. <br /> <br />~I .. <br />~:~j0r;,:,; I8.mln. <br />~---~-----J+..---~---~ _ <br /> <br />Figure 4.34 Elevated Pier Design <br /> <br />Where floodwaters are anticipated to rise above <br />the floor of the manufactured home, then addi- <br />tional ground anchoring must be provided to <br />secure the manufactured home against vertical <br />and lateral flood forces. Anchoring by connec- <br />tion of the manufactured home to the piers will <br />not resist flotation. Note, as previously discuss- <br />ed and shown in Appendix E, additional ground <br />anchoring to resist flood loads will be effective in <br />only limited cases. Additional elevation by increas- <br />ing pier height will eliminate this concern. <br /> <br />Posts and Piles-The vertical members (posts or <br />piles) of an elevated foundation must support <br />manufactured home loads which are subsequently <br />resisted by end bearing on undisturbed soil or con- <br />crete footings as shown in Figure 4.35. <br />As previously discussed, the first consideration <br />in designing an elevated foundation is the cap- <br />ability for the soil to support the anticipated loading <br />imposed by the vertical support members. Without <br />such consideration, the entire foundation can <br /> <br /> <br />Figure 4.35 Posts and Piles <br /> <br />settle or sink into the ground. Prior to selecting <br />the vertical members (posts or piles), the bearing <br />capacity of the soil on the manufactured home site <br />must be determined, This value will become the <br />maximum allowable design load for selection of <br />the vertical members. <br />Pile foundations, as opposed to other vertical <br />wood members, rely on a combination of end bear- <br />ing and side friction caused by the pile driving pro- <br />cess to resist both vertical and horizontal loads. <br />The frictional capability of piles is heavily depen- <br />dent on local soil conditions and driving methods. <br />For this reason, a full scale pile load test at the <br />manufactured home site is the most reliable <br />method of determining pile capacity. The results <br />of such a test can be used in lieu of the vertical <br />member capacity values presented in Tables 4.13. <br />to 4.16. If pile capacity tests are not conducted, <br />then the information on vertical member capacity <br />in Tables 4.13 to 4.16 must be used. <br />Tables 4.13 to 4.16 provide data on square and <br />round vertical wood member capacity as a func- <br />tion of total vertical member length, diameter, wind <br />load, and manufactured home width. Total vertical <br />member length as used in these tables includes <br />height above grade, depth of embedment, and <br />scour considerations. Note that for a double sec- <br />tion manufactured home, these values are <br />applicable, and two side-by-side foundation <br />systems must be constructed. <br /> <br />53 <br />