POLITECHNIKA WARSZAWSKA Wydział Inżynierii Lądowej |
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INSTYTUT MECHANIKI KONSTRUKCJI INŻYNIERSKICH Zakład Wytrzymałości Materiałów, Teorii Sprężystości i Plastyczności |
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Wytrzymałość Materiałów II |
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PRACA PROJEKTOWA nr 2 |
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Temat: |
Kratownica płaska - zagadnienie wyboczenia oraz metoda elementów skończonych |
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Imię i nazwisko: |
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Data wykonania:
22.05.2006 r.
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Grupa dziekańska |
3 |
Rodzaj studiów |
Zaoczne |
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Rok akademicki |
2005/06 |
Semestr |
IV |
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Prowadzący zajęcia: dr inż. Szczepan Lutomirski |
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Ocena:
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2. WYMIAROWANIE PRĘTÓW KRATOWNICY
R= fd = 205 MPa wytrzymałość obliczeniowa stali
Re= ReH = 230 MPa górna granica plastyczności stali
RH = 190 MPa granica proporcjonalności stali
E = 2.05 Gpa moduł Younga stali
Dane:
Przekrój A1 - pas dolny (pręty 1, 2, 3) - Rozciągany siłą+Nmax1 = 579,75 kN
Przekrój A2 - pas górny (pręty 4, 5, 6) - Ściskany siłą -Nmax2 = 550,00 kN
Przekrój A3 - pozostałe pręty (7,8,9,10,11) -Rozciągane siłą +Nmax3 = 237,17 kN
Ściskane siłą -Nmax3 = 459,62 kN
2.1. Przekrój A1 ] [
z założenia:
przyjęto przekrój 2 x ] 120
A1 = 2 * 17,0 = 34,00 cm2
Sprawdzenie nośności przekroju
1)
2)
2.2. Przekrój A2 ] [
μ = 1; ψ = 1; n = 1,6; l = 300 cm; -Nmax2 = 550,00 kN
przyjęto:
A2 - 2 x ] 180 - A2 = 2*28,0 = 56,0 cm2 e = 1,92 cm
Moment i promień bezwładności:
smukłość maksymalna:
smukłość porównawcza:
smukłość względna:
współczynnik wyboczeniowy:
Obliczeniowa siła krytyczna
Nośność obliczeniowa (sprawdzenie):
2.3. Przekrój A3 ┘└
μ = 1; ψ = 1; n = 1,6; l = 424 cm; -Nmax3 = 459,62 kN (pręt 8)
przyjęto:
A3 - 2 x ┘ 100x100x12 - A2 = 2*22,7 = 45,4 cm2 e = 2,90 cm
Moment i promień bezwładności:
smukłość maksymalna:
smukłość porównawcza:
smukłość względna:
współczynnik wyboczeniowy:
Obliczeniowa siła krytyczna:
Sprawdzenie nośności:
Zestawienie przekrojów:
przekrój |
schemat |
Pole przekroju |
pręty |
Jmin |
|
A1 |
] [ |
2x [ 120 |
34,0 cm2 |
1, 2, 3 |
236,34 cm4 |
A2 |
] [ |
2x [ 180 |
56,0 cm2 |
4, 5, 6 |
555,96 cm4 |
A3 |
┘└ |
2x └ 100x100x12 |
45,4 cm2 |
7, 8, 9, 10, 11 |
938,82 cm4 |
3. WYZNACZENIE PRZEMIESZCZENIA PIONOWEGO WĘZŁA K (6)
Siły w prętach kratownicy obciążonej siłą jednostkową w węźle K (6)
Obliczenie przemieszczenia pionowego węzła K (6)
Pręt |
L (m) |
EA [kN] |
N [kN] |
N1 [ - ] |
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1 |
3,16 |
697000 |
342,58 |
0,53 |
0,000823175 |
2 |
3,16 |
697000 |
342,58 |
0,53 |
0,000823175 |
3 |
3,16 |
697000 |
579,75 |
2,11 |
0,005545970 |
4 |
3,00 |
1148000 |
0,00 |
0,00 |
0,000000000 |
5 |
3,00 |
1148000 |
-550,00 |
-2,00 |
0,002874564 |
6 |
3,00 |
1148000 |
-550,00 |
-2,00 |
0,002874564 |
7 |
3,00 |
930700 |
0,00 |
0,00 |
0,000000000 |
8 |
4,24 |
930700 |
-459,62 |
-0,71 |
0,001486666 |
9 |
2,00 |
930700 |
0,00 |
0,00 |
0,000000000 |
10 |
3,16 |
930700 |
237,17 |
1,58 |
0,001272314 |
11 |
1,00 |
930700 |
-150,00 |
0,00 |
0,000000000 |
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Przesunięcie Pionowe węzła K (6) |
0,0157 m |
4. OBLICZENIE SZTYWNOŚCI ELEMENTÓW KRATOWNICY
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Agregacja macierzy sztywności układu
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6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
1 |
1985 0 1098 |
662 0 1098 |
0 |
0 |
-1098 |
-1098 |
-1985 |
-662 |
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2 |
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221 3102 1098 |
0 |
-3102 |
-1098 |
-1098 |
-662 |
-221 |
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3 |
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3827 0 |
0 0 |
-3827 |
0 |
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0 3102 |
0 |
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3827 3827 1098 0 2651 |
0 0 1098 0 -884 |
0 |
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-3827 |
0 |
-2651 |
884 |
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0 0 1098 4654 295 |
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-4654 |
0 |
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884 |
-295 |
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1985 1985 0 |
662 662 0 |
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-662 |
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221 221 4654 |
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-662 |
-221 |
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3827 3827 0 |
0 0 0 |
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-3827 |
0 |
10 |
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0 0 9307 |
0 |
-9307 |
0 |
0 |
11 |
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1985 1985 2651 0 |
662 662 -884 0 |
-1985 |
-662 |
12 |
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221 221 295 9307 |
-662 |
-221 |
13 |
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1985 3827 |
662 0 |
14 |
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221 0 |
Zagregowana macierz sztywności
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11 |
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1 |
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3083 |
1760 |
0 |
0 |
-1098 |
-1098 |
-1985 |
-662 |
0 |
0 |
0 |
0 |
0 |
0 |
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2 |
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4421 |
0 |
-3102 |
-1098 |
-1098 |
-662 |
-221 |
0 |
0 |
0 |
0 |
0 |
0 |
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3 |
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3827 |
0 |
-3827 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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4 |
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3102 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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5 |
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11403 |
214 |
0 |
0 |
-3827 |
0 |
-2651 |
884 |
0 |
0 |
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6 |
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6047 |
0 |
-4654 |
0 |
0 |
884 |
-295 |
0 |
0 |
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7 |
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3970 |
1324 |
0 |
0 |
-1985 |
-662 |
0 |
0 |
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8 |
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5096 |
0 |
0 |
-662 |
-221 |
0 |
0 |
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9 |
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7654 |
0 |
0 |
0 |
-3827 |
0 |
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10 |
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9307 |
0 |
-9307 |
0 |
0 |
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11 |
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6621 |
440 |
-1985 |
-662 |
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12 |
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10044 |
-662 |
-221 |
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13 |
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5812 |
662 |
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14 |
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221 |
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Modyfikacja macierzy sztywności przez wprowadzenie warunków brzegowych
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2 |
3 |
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6 |
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9 |
10 |
11 |
12 |
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14 |
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1 |
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1 |
0 |
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0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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2 |
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1 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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3 |
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3827 |
0 |
-3827 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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4 |
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3102 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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5 |
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11403 |
214 |
0 |
0 |
-3827 |
0 |
-2651 |
884 |
0 |
0 |
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6 |
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6047 |
0 |
-4654 |
0 |
0 |
884 |
-295 |
0 |
0 |
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7 |
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3970 |
1324 |
0 |
0 |
-1985 |
-662 |
0 |
0 |
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8 |
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5096 |
0 |
0 |
-662 |
-221 |
0 |
0 |
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9 |
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7654 |
0 |
0 |
0 |
-3827 |
0 |
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10 |
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9307 |
0 |
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0 |
0 |
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11 |
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6621 |
440 |
-1985 |
0 |
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12 |
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10044 |
-662 |
0 |
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13 |
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5812 |
0 |
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14 |
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1 |
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Pełna macierz sztywności: K
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6 |
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11 |
12 |
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14 |
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1 |
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0 |
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1 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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0 |
0 |
0 |
0 |
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3 |
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0 |
0 |
3827 |
0 |
-3827 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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4 |
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0 |
0 |
0 |
3102 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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5 |
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0 |
0 |
-3827 |
0 |
11403 |
214 |
0 |
0 |
-3827 |
0 |
-2651 |
884 |
0 |
0 |
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6 |
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0 |
0 |
0 |
0 |
214 |
6047 |
0 |
-4654 |
0 |
0 |
884 |
-295 |
0 |
0 |
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7 |
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0 |
0 |
0 |
0 |
0 |
0 |
3970 |
1324 |
0 |
0 |
-1985 |
-662 |
0 |
0 |
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8 |
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0 |
0 |
0 |
0 |
0 |
-4654 |
1324 |
5096 |
0 |
0 |
-662 |
-221 |
0 |
0 |
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9 |
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0 |
0 |
0 |
0 |
-3827 |
0 |
0 |
0 |
7654 |
0 |
0 |
0 |
-3827 |
0 |
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10 |
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0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
9307 |
0 |
-9307 |
0 |
0 |
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11 |
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0 |
0 |
0 |
0 |
-2651 |
884 |
-1985 |
-662 |
0 |
0 |
6621 |
440 |
-1985 |
0 |
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12 |
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0 |
0 |
0 |
0 |
884 |
-295 |
-662 |
-221 |
0 |
-9307 |
440 |
10044 |
-662 |
0 |
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13 |
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0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
-3827 |
0 |
-1985 |
-662 |
5812 |
0 |
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14 |
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0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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1 |
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Wektor przemieszczeń |
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Wektor obciążeń węzłowych |
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Wektor przemieszczeń |
Wektor obciążeń węzłowych |
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u1 |
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d1 |
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Px1 |
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P1 |
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d1 |
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P1 |
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v1 |
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d2 |
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Py1 |
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P2 |
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d2 |
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P2 |
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u2 |
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d3 |
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Px2 |
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P3 |
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d3 |
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P3 |
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v2 |
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d4 |
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Py2 |
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P4 |
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d4 |
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P4 |
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u3 |
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d5 |
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Px3 |
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P5 |
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d5 |
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P5 |
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v3 |
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d6 |
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Py3 |
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P6 |
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d6 |
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P6 |
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u4 |
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= d = |
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d7 |
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Px4 |
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= P = |
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P7 |
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K. |
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d7 |
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= |
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P7 |
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v4 |
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d8 |
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Py4 |
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P8 |
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d8 |
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P8 |
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u5 |
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d9 |
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Px5 |
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P9 |
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d9 |
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P9 |
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v5 |
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d10 |
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Py5 |
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P10 |
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d10 |
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P10 |
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u6 |
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d11 |
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Px6 |
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P11 |
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d11 |
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P11 |
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v6 |
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d12 |
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Py6 |
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P12 |
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d12 |
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P12 |
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u7 |
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d13 |
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Px7 |
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P13 |
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d13 |
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P13 |
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v7 |
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d14 |
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Py7 |
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P14 |
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d14 |
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P14 |
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Odwrócona macierz sztywności: K-1
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14 |
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1 |
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1 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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2 |
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0 |
1 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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3 |
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0 |
0 |
0,0023 |
0 |
0,002 |
-0,002 |
0,0012 |
-0,002 |
0,0018 |
-0,0026 |
0,0019 |
-0,0026 |
0,0015 |
0 |
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4 |
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0 |
0 |
0 |
0,0003 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
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5 |
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0 |
0 |
0,002 |
0 |
0,002 |
-0,002 |
0,0012 |
-0,002 |
0,0018 |
-0,0026 |
0,0019 |
-0,0026 |
0,0015 |
0 |
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6 |
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0 |
0 |
-0,002 |
0 |
-0,002 |
0,0029 |
-0,0015 |
0,0029 |
-0,0018 |
0,003 |
-0,002 |
0,003 |
-0,0015 |
0 |
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7 |
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0 |
0 |
0,0012 |
0 |
0,0012 |
-0,0015 |
0,0012 |
-0,0016 |
0,0011 |
-0,0013 |
0,0013 |
-0,0013 |
0,0010 |
0 |
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8 |
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0 |
0 |
-0,002 |
0 |
-0,002 |
0,0029 |
-0,0016 |
0,0032 |
-0,0018 |
0,003 |
-0,002 |
0,003 |
-0,0015 |
0 |
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9 |
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0 |
0 |
0,0018 |
0 |
0,0018 |
-0,0018 |
0,0011 |
-0,0018 |
0,0018 |
-0,002 |
0,0017 |
-0,002 |
0,0015 |
0 |
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10 |
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0 |
0 |
-0,0026 |
0 |
-0,0026 |
0,003 |
-0,0013 |
0,003 |
-0,002 |
0,0055 |
-0,0023 |
0,0054 |
-0,0015 |
0 |
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11 |
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0 |
0 |
0,0019 |
0 |
0,0019 |
-0,002 |
0,0013 |
-0,002 |
0,0017 |
-0,0023 |
0,0019 |
-0,0023 |
0,0015 |
0 |
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12 |
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0 |
0 |
-0,0026 |
0 |
-0,0026 |
0,003 |
-0,0013 |
0,003 |
-0,002 |
0,0054 |
-0,0023 |
0,0054 |
-0,0015 |
0 |
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13 |
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0 |
0 |
0,0015 |
0 |
0,0015 |
-0,0015 |
0,0010 |
-0,0015 |
0,0015 |
-0,0015 |
0,0015 |
-0,0015 |
0,0015 |
0 |
|
14 |
|
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
1 |
|
|
Wektor obciążeń węzłowych |
Wynikowy wektor przemieszczeń |
|
|||||||
|
|
0 |
|
|
|
0 |
|
u1 |
||
K.d = P |
|
0 |
|
|
|
0 |
|
v1 |
||
|
|
0 |
|
|
|
0,890342281 |
|
u2 |
||
czyli |
|
0 |
|
|
|
0 |
|
v2 |
||
|
|
0 |
|
|
|
0,890342281 |
|
u3 |
||
K-1.P = d |
|
-250 |
|
|
|
-1,186009 |
|
v3 |
||
K-1. |
|
0 |
|
= |
|
0,559070278 |
|
u4 |
||
|
|
0 |
|
|
|
-1,18597045 |
|
v4 |
||
|
|
0 |
|
|
|
0,746947988 |
|
u5 |
||
|
|
-150 |
|
|
|
-1,58034355 |
|
v5 |
||
|
|
0 |
|
|
|
0,848766836 |
|
u6 |
||
|
|
0 |
|
|
|
-1,56422665 |
|
v6 |
||
|
|
0 |
|
|
|
0,603553696 |
|
u7 |
||
|
|
0 |
|
|
|
0 |
|
v7 |
Wyznaczenie sił węzłowych K . d = P
|
|
1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
|
|
|
d |
|
|
Wynikowy wektor sił węzłowych |
||
1 |
|
3083 |
1760 |
0 |
0 |
-1098 |
-1098 |
-1985 |
-662 |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
|
0 |
|
|
|
0 |
|
2 |
|
1760 |
4421 |
0 |
-3102 |
-1098 |
-1098 |
-662 |
-221 |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
|
0 |
|
|
|
216,64 |
|
3 |
|
0 |
0 |
3827 |
0 |
-3827 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
|
0,890342281 |
|
|
|
0 |
|
4 |
|
0 |
-3102 |
0 |
3102 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
|
|
0 |
|
|
|
0 |
|
5 |
|
-1098 |
-1098 |
-3827 |
0 |
11403 |
214 |
0 |
0 |
-3827 |
0 |
-2651 |
884 |
0 |
0 |
|
|
|
0,890342281 |
|
|
|
0 |
|
6 |
|
-1098 |
-1098 |
0 |
0 |
214 |
6047 |
0 |
-4654 |
0 |
0 |
884 |
-295 |
0 |
0 |
|
|
|
-1,186009 |
|
|
|
-250 |
|
7 |
|
-1985 |
-662 |
0 |
0 |
0 |
0 |
3970 |
1324 |
0 |
0 |
-1985 |
-662 |
0 |
0 |
|
|
|
0,559070278 |
|
= |
|
0 |
|
8 |
|
-662 |
-221 |
0 |
0 |
0 |
-4654 |
1324 |
5096 |
0 |
0 |
-662 |
-221 |
0 |
0 |
|
|
|
-1,18597045 |
|
|
|
0 |
|
9 |
|
0 |
0 |
0 |
0 |
-3827 |
0 |
0 |
0 |
7654 |
0 |
0 |
0 |
-3827 |
0 |
|
|
|
0,746947988 |
|
|
|
0 |
|
10 |
|
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
9307 |
0 |
-9307 |
0 |
0 |
|
|
|
-1,58034355 |
|
|
|
-150 |
|
11 |
|
0 |
0 |
0 |
0 |
-2651 |
884 |
-1985 |
-662 |
0 |
0 |
6621 |
440 |
-1985 |
-662 |
|
|
|
0,848766836 |
|
|
|
0 |
|
12 |
|
0 |
0 |
0 |
0 |
884 |
-295 |
-662 |
-221 |
0 |
-9307 |
440 |
10044 |
-662 |
-221 |
|
|
|
-1,56422665 |
|
|
|
0 |
|
13 |
|
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
-3827 |
0 |
-1985 |
-662 |
5812 |
662 |
|
|
|
0,603553696 |
|
|
|
0 |
|
14 |
|
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
-662 |
-221 |
662 |
221 |
|
|
|
0 |
|
|
|
183,36 |
|
Wyznaczenie sił podłużnych w prętach kratownicy:
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
5. PORÓWNANIE OTRZYMANYCH WYNIKÓW
|
z pkt 1 i 2 |
z pkt 4 |
|
[kN] |
RA |
216,67 |
216,64 |
|
N1 |
342,58 |
342,64 |
|
N2 |
342,58 |
342,36 |
|
N3 |
579,75 |
577,94 |
|
N4 |
0,00 |
0,00 |
|
N5 |
-550,00 |
-548,72 |
|
N6 |
-550,00 |
-548,72 |
|
N7 |
0,00 |
0,00 |
|
N8 |
-459,62 |
-458,91 |
|
N9 |
0,00 |
0,00 |
|
N10 |
237,17 |
- 236,09 |
|
N11 |
-150,00 |
-150,00 |
|
RB |
183,33 |
183,36 |
cm |
V6 |
1,57 |
1,564 |
4
WM2 - Praca Projektowa nr 2 - Kratownica płaska- sem.IV, gr.3, st. zaoczne