Time-domain solution for transient dynamic response of a large-diameter thin-walled pipe pile

Thepropagationofstresswavesinalarge-diameterpipepileforlowstraindynamictestingcannotbeexplainedproperlybytraditional1Dwavetheories.Anewcomputationalmodelisestablishedtoobtainawaveequationthatcandescribethedynamicresponseofalarge-diameterthin-walledpipepiletoatransientpointloadduringalowstrainintegritytest.Ananalyticalsolutioninthetimedomainisdeducedusingtheseparationofvariablesandvariationofconstantmethods.Thevalidityofthisnewsolutionisverifiedbyanexistinganalyticalsolutionunderfreeboundaryconditions.Theresultsofthistimedomainsolutionarealsocomparedwiththeresultsofafrequencydomainsolutionandfieldtestdata.Thecomparisonsindicatethatthenewsolutionagreeswellwiththeresultsofprevioussolutions.Parametricstudiesusingthenewsolutionwithreferencetoacasestudyarealsocarriedout.Theresultsshowthatthemodenumberaffectstheaccuracyofthedynamicresponse.Amodenumbergreaterthan10isrequiredtoenablethecalculateddynamicresponsestobeindependentofthemodenumber.Thedynamicresponseisalsogreatlyaffectedbysoilproperties.Thelargerthesideresistance,thesmallerthedisplacementresponseandthesmallerthereflectedvelocitywavecrest.Thedisplacementincreasesasthestresswavespropagatealongthepilewhenthepileshaftisfree.Theincidentwavesofdisplacementandvelocityresponsesofthepilearenotthesameamongdifferentpointsinthecircumferentialdirectiononthepiletop.However,thearrivaltimeandpeakvalueofthepiletipreflectedwavesarealmostthesameamongdifferentpointsonthepiletop.