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1、00习题要求：1．将题目转化为MicrosoftWord文档；2．解题过程用MicrosoftWord文档，公式用公式编辑器，只交电子文档作业；3．期末考试前必须作对所有所给题目，否则不能参加期末考试，请于指定时间前交作业。第一题（2010年3月5日前交该题作业）星期五1.21Determinethesmallestallowablecross-sectionalareasofmembersBD,BE,andCEofthetrussshown.Theworkingstressesare20000psiintensionand12000psiincompression
2、.(Areducedstressincompressionisspecifiedtoreducethedangerofbuckling.)SolutionThefree-bodydiagramofhomogeneousBCinFig.(b).Theequilibriumequationare,P=24(kips)=24000(lb)Thefree-bodydiagramoftrussinFig.(c).Theequilibriumequationare,PBD=－8.944(kips)(Compression)PCE=24(kips)(Tension)PBE=-11
3、.32(kN)(Compression)ThenormalstressofamemberCE,DEandDFis(Compression)ABD=0.745(in.2)(Compression)ABE=0.943(in.2)(Tension)ABE=1.2(in.2)1.37ComputethemaximumforcePthatcanbeappliedtothefootpedal.Thel/4-in.-diameterpinatBisinsingleshear,anditsworkingshearstressis4000psi.ThecableattachedatC
4、hasadiameterof1/8in.andaworkingnormalstressof20000psi.SolutionThefree-bodydiagramofbracketinFig.(b).Theequilibriumequationare,P=0.05788T(a),PBx=-0.9848T,PBy=0.2315TAccordingtothenormalstressesformula,wehaveT=245.4(lb)Accordingtotheshearstressesformula,wehaveT=194.1(lb)Accordingtoformul
5、a(a),wegetP=0.05788T=0.05788×194.1=11.2(lb)第二题（2010年3月10日前交该题作业）星期三2.37Aninitiallyrectangularelementofamaterialisdeformedintotheshapeshowninthefigure.Findεx,εy,andγfortheelement.SolutionAccordingtothedefinitionoftheaxialstrain,wehave:2.69（g）ThebarsAB,ACandADarepinnedtogetherasshowninth
6、efigure.Calculatetheaxialforceinthestrutcausedbythe10-kipload.Foreachsteelbar.A=0.3in.2andE=29x106psi.Forthealuminumbar,A=0.6in.2andE=10x106psi.SolutionEquilibrium:CompatibilityHooke’slaw:wegetweobtainandSoweobtainPAC=3.53×103(lb)PAB=2.56×103(lb)PAD=4.80×103(lb)第三题（2010年3月15日前交该题作业）星期一
7、3.27Thecompoundshaft,composedofsteel,aluminum,andbronzesegments,carriesthetwotorquesshowninthefigure.IfTC=250lb.ft,determinethemaximumshearstressdevelopedineachmaterial.Themoduliofrigidityforsteel,aluminum,andbronzeare12x106psi,4x106psi,and6x106psi,respectively.SolutionAccordingtothe
