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<br />EM 1110.2-2504 <br />31 Mar 94 <br /> <br />and spread Ihe reaction. The designer should weigh Ihe <br />risk of impacl and resulting damage as il applies 10 his <br />situation. If conditions require !he inclusion of ei!her of <br />Ihese boat impacl forces in !he design, Ihey should be <br />evalualed based on !he energy 10 be absorbed by Ihe <br />wall. The magnilOde and location of !he force trans- <br />milled 10 !he wall will depend on !he vessel's mass, <br />appoach velocity, and approach angle. Military Hand- <br />book 1025/1 (Departmenl of Ihe Navy 1987) provides <br />excellenl guidance in this area. <br /> <br />b. Mooring pulls. LaIeraI loads applied by a <br />moored ship are dependenl on Ihe shape and orienlalion <br />of Ihe vessel, Ihe wind pressure. and cmrents applied. <br />Due 10 !he use of strong synlhetic lines, large forces can <br />be developed. Therefore. il is recommended lllal <br />mooring devices be designed independenl of Ihe sheel <br />pile wall. <br /> <br />c. Ice forces. Ice can affecl marine-type struclures <br />in many ways. Typically, lateral pressures are caused <br />by impacl of large floating ice masses or by expansion <br />upon freezing. Expansive lateral pressures induced by <br />waler mezing in !he backfill can be avoided by back- <br />filling wilh a clean me-draining sand or gravel or <br />installation of a drainage colleclOr system. EM 1110-2- <br />1612 shouJd be references when Ihe design is 10 include <br />ice forces. <br /> <br />4-8 <br /> <br />d. Wind forces. When sheet pile walls are con- <br />structed in exposed areas, wind forces should be <br />considered during construction and lhroughoUI !he life <br />of Ihe sUuclure. For sheet pile walls wilh up 10 20 feet <br />of exposure and subjected 10 hurricanes or cyclones wilh <br />basic winds speeds of up 10 100 mph, a 5O-pound per <br />square fool (pst) design load is adequate. Under normal <br />circumslances, for Ihe same height of wall exposure, a <br />30-psf design load should be sufficienl. For more sever <br />conditions, wind load should be computed in accordance <br />wilh American National Slandards Instilute (ANSI) <br />AS8.l (ANSI 1982). <br /> <br />. <br /> <br />e. Earthquake forces. Earthquake forces should be <br />considered in zones of seismic activily, The earth pres- <br />sures should be determined in accordance wilh proce- <br />dures oullined in EM 1110-2-2502 and presented in <br />delail in Ihe Ebeling and Morrison report on seismic <br />design of walelfronl relaining struclures (Ebeling and <br />Morrison 1992). In Ihe worst case, Ihe supporting soil <br />may liquify allowing Ihe unsupported wall 10 fail. This <br />possibilily should be evaluated and addressed in Ihe <br />design documenlalion. If accepting !he risk and conse- <br />quences of a liquefaction failure is unacceptable, consid- <br />eration should be given 10 replacing or improving Ihe <br />liquefiable malerial or belter yel, relocating Ihe wall. <br /> <br />e) <br /> <br />e) <br />