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TEST CASE 6.6 SYSTEM WITH TWO DEGREES OF FREEDOM IN THE PRESENCE OF FRICTION

Reference:

Вовкушевский А.В., Шойхет Б.А., Расчёт массивных гидротехнических сооружений с учётом раскрытия швов. – М.: Энергия, 1981. – (Б-ка гидротехника и гидроэнергетика; Вып. 70). Стр. 115-121.

 

Problem description:

Bar system is loaded by two mutually perpendicular concentrated forces at point E. In this point is applied a supporting spring, which can slide in horizontal plane. Determine horizontal and vertical displacements at point E u and w respectively at follow variants:

  • at first system is loaded by vertical force and after by horizontal load;
  • at first system is loaded by horizontal force and after by vertical load.

 

Problem sketch:

Type of created problem:

Plane truss or beam-wall (X, Z).

 

Geometric characteristics:

Rod length AE and BE: L = 1 m.

 

Rigid and dissipative properties:

Relative stiffness of bar АЕ: EA/L = 955 tf;

Relative stiffness of bar ВЕ: EA/L = 2.5 tf;

Axial spring stiffness: k = 10000 tf/m;

Friction coefficient: f = 0.15.

 

Boundary conditions:

Points A and B: X = Z = 0.

 

Loads:

F = 1 tf.

 

Model description:

The system is modeled by 2 general finite elements of spatial bar (FE type is 10) and 1 physically nonlinear single-noded, one-sided friction element (FE type is 263). For nonlinear solution, iterative process is used (number of steps is 50, minimum number of iterations is 15000).

 

Calculation results:

Variant

Target value

Analytical solution

LIRA 10

Deviation, %

1

uE, mm

23.473

23.473

0.00

wE, mm

2.2222

2.2222

0.00

2

uE, mm

23.473

23.460

0.055

wE, mm

2.2222

2.2204

0.081