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ANALISA STRUKTUR METODE MATRIKS RANGKA BIDANG (PLANE TRUSS). Structural Analysis. Classical Methods. Matrix Methods. Vitrual Work. Stiffness by Definition. Force Method. Direct Stiffness. Slope Deflection. Trusses. Moment-Area. Beams. STRUKTUR RANGKA.........???.
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Structural Analysis Classical Methods Matrix Methods Vitrual Work Stiffness by Definition Force Method Direct Stiffness Slope Deflection Trusses Moment-Area Beams
STRUKTUR RANGKA.........??? • Composed of slender, lightweight members • All loading occurs on joints • No moments or rotations in the joints • Axial Force Members Tension (+) or Compression (-)
A Simple Comparison Stiffness by Definition • 2 Degrees of Freedom Direct Stiffness • 6 Degrees of Freedom • DOFs 3,4,5,6 = 0 • Unknown Reactions (to be solved) included in Loading Matrix 6 5 2 1 4 3 Remember.. More DOFs = More Equations
nodal displacemen, terdiri dari ; ui ; vi ; uj ; vj atau vektor displacemen • nodal gaya, terdiri dari ; fi ; gi ; fj ; gj atau vektor gaya
Matriks Kekakuan elemen pada sistem koordinat Lokal dimana : A = luas penampang elemen L = panjang elemen E = modulus elastis bahan
y v x Transformasi Koordinat ui = Ui cos θ + Vi sin θ + 0 + 0 vi = -Ui sin θ + Vi cos θ + 0 + 0 uj = 0 + 0 + Uj cos θ + Vj sin θ vj = 0 + 0 - Uj sin θ + Vj cos θ X, Y ; sistem koordinat global x, y; sistem koordinat lokal
Analog dengan diatas ; fi = Fi cos θ + Gi sin θ + 0 + 0 gi = -Fi sin θ + Gi cos θ + 0 + 0 fj = 0 + 0 + Fj cos θ + Gj sin θ gj = 0 + 0 - Fj sin θ + Gj cos θ
Hubungan gaya dan displacemen pada elemen ; "Pre-multiplied" dengan [T]-1 dan mengingat [T]T = [T]-1 sehingga ;
Matriks kekakuan elemen pada sistem koordinat global ; simetris dimana : c = cos s = sin
OVER-ALL STIFFNESS MATRIX ....untuk 1 elemen dengan node i dan j ......untuk rangka bidang dengan node sejumlah n
BOUNDARY CONDITIONS {Fe}= “Prescribed external force vector” {Fr} = “Un-known reaction vector” {Uu} = “Un-known displacement vector” {Uk} = “Known displacement vector “given by boundary condition. [Kij] = “Sub-matrix of overall stiffness matrix”.
Stiffness by Definition vs Direct Stiffness = X Uunknown Fknown K = X K completed Uknown Funknown Zero Unless Settlement Occurs Reactions
UN-KNOWN DISPLACEMENT & REACTION SEHINGGA DIPEROLEH ;
MEMBERS FORCES dimana ;
2 4,00 m 1 3 3,00 m 5 ton 10 ton
V2 V1 V3 G2 G1 G3 U2 U1 U3 F2 F1 F3 Nodal Force Nodal Displacemen U1 V1 U2 = 0 V2 = 0 U3 = 0 V3 = 0 F1 = -5 ton G1 = -10 ton F2 G2 F3 G3
K2 K2 K2 K2 F} = [K] U} U1 V1 U2 V2 U3 V3 K1 F1 U1 U1 G1 V1 V1 F2 U2 U2 K3 G2 V2 V2 F3 U3 U3 G3 V3 V3
F} = [K] U} U1 V1 U2 V2 U3 V3 Kover-all=K1+K2+K3 - 5 U1 U1 - 10 V1 V1 F2 0 U2 G2 0 V2 F3 0 U3 G3 0 V3
F} = [K] U} U1 V1 U2 V2 U3 V3 - 5 U1 U1 - 10 V1 V1 F2 0 U2 G2 0 V2 F3 0 U3 G3 0 V3