7laha in truss


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7laha in truss

  1. 1. 7laha in Truss Never stop thinking With: kites Team
  2. 2. Brief methods to solve truss problem method Simple diagram • Finding zero loading members • Case1:if we have two members in the truss(single/apart from other members) without external force or support reaction applied to their joint . the two members the two members should be zero force members • In this case Fdc=Fde=0 F c D Ef BA
  3. 3. Zero force member method • Second case • If three members form a joint in in truss where two members are collinear and there is not any external force or support reaction . • The third member is zero force member • Simple diagram • ∑Fx=0 fda=0 f E D C A B F da F dc F de x
  4. 4. Sections method • Illustration • Imagine that you cut apart from the truss , we consider the members where the cut happen have external forces according to the reminder part so we can use the equilibrium rules • example A B G C D F E P P Fbc Fg c Fgf fbc fgc fgf yd xd Re
  5. 5. Smart example • 5KN5KN 7.5KN a b N m c L D K J E I F h G 4.5KN 2.5m2.5m2.5m2.5m 2.5m 2.5m 2.5m
  6. 6. • 1-Determine the force in members CD , LD and KL • 2-Determine zero force members • 3-Determine the force in the member FH • 4-determine the force in the members JI and ML • Solution: • First there are not zero –force members • From the equilibrium • ∑f y=0 so y G+YA=17.5KN • MA=0soYG=11KN • ∑f x= 0 so XG=4.5 KN
  7. 7. solution • At point G: • Θ=45 deg • So FGF=4.5√2KN • FGH=6.5KN • At point H: • ∑FY=0 • FIH=6.5√2 KN • ∑FX=0 • FFH=6.5KN FGH 11KN 4.5KNFGF θ θ FIH FGH FfH
  8. 8. • 1-when we cut at KJ , JD , ED • ∑FY=0 • FJD=(11-5)*√2 =6√2KN • ∑FX=0 • FDE-FKJ=10.5 KN • MJ=0 • FDE*2.5=4.5*7.5 • So FDE=13.5KN • FKJ=3KN FED J E FKJ FJD 5K N G 4.5 KN 11K N
  9. 9. • When we cut at LK ,LD and CD. • ∑FY=0 • So FLD cos45 =6.5-5 • FLD=2.12KN • ∑FX=0 • FKL=4.5+1.5+FCD • ML=0 • So 6.5*5=FCD*2.5 • FCD=13KN • FKL=19KN 5KN4.5 KN FLD FCD FLK 6.5K N A L
  10. 10. FML*cos45=FKL-FLD*cos45 -4.5 so FML=13√2 KN • FJI*Cos45=FDJ*cos45+FK J=9kN
  11. 11. 7laha • • Determine the force in members JI and DE of the k truss. • Hint : use sections aa and bb • Final answer :Fji=10.67KN FDE=10.67KN L k J I H A B C D E F G 6K N 7.5 KN 9K N 6m6m6m6m6m 4.5m 4.5m a a b b M N o P