文档介绍：,截面抗弯刚度EI,梁上有一个集中质量m,忽略梁自身的质量,受到图示简谐荷载??tPSintP??作用,求该体系振动时结构最大的侧移。图4a2amP(t)解:2a/3??EIaaaaaEI9432323222113?????????????3491maEIm????232249911????maEIEI????233max494???maEIPaPy???,截面抗弯刚度EI,梁上有两个集中质量,均为m,忽略梁自身的质量,试用柔度法写出该结构体系的特征方程。a图5mam解:a2aaM1M2EIaaaaEI332211311?????EIaaaaEI3823222211322??????EIaaaaEI6526521132112????????特征方程为:设EImaA3?;21???038656531222121212111??????????????,在梁跨中有一集中质量m=100kg,集中质量上作用简谐荷载,P(t)=P0·sinθt,其中n=1200r/min,P0=5kN,EI=×105N·m2(梁的自重不计),求梁的最大弯矩和最大挠度。解:(1)、计算ω:δ=EI1(21×1×21)×(32×21)=EI61=1/(6××105)=×10-7m/Nω=?m1=1/???=(s1)(2)、计算β:θ=602n?=2××1200/60=(s1)β=2)(11???=2)(11?=(3)、Mmax=lmg4+)4(0lp×β=?????=·mfmax=(mg)δ+(p0δ)β=(1+5×)×2×103××10-7==、图示简支梁具有均布质量m,试用集中质量法将其简化为单自由度体系,并求第一自振频率近似值。LmEI简化为δ=)4221(1llEI??×32×4l×2=EIl483ω=?m1=EIllm482113?=。aEIamEI12解:(1)作M图,计算δ:δ11=EIaaaaaaaEI34322113??????????????δ22=EIaaaaEI3322113??????δ12=δ21=EIaaaaEI22113?????a1aa11M图2M图(2)计算ω:D=)3(22)34()()(3333222121212111?????????????mEIamEIamEIamEIammmm=0?)31(2121)34(????????=0(其中EIma3??)?2236735??????=0?λ1=;λ2=??????322814