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Units of measurement

The International System S.I. of units is used. The primary units are the following:

meter (m) for length, kilogram (kgr) for mass and second ( sec) for time.

Force and stress are derived quantities, measured in Newton (N) and Pascal (Pa), respectively.

1 N=1 kg·m/sec2

1 Pa=1 N/m2

In practice the following units are used:

  • Concentrated force kN
  • Distributed force kN/m, kN/m2
  • Moment kNm
  • Stress and strength MPa(=N/mm2), kPa
  • Density kg/m3, t/m3
  • Modulus of elasticity GPa
  • Acceleration m/sec2 (g=9.81m/sec2≈10 m/sec2)

In the past, the technical system of units was used, where the fundamental units of measurement were m for length, sec for time and kg* weight for force.

By the definition of weight kilogram derives that:

1kg *=9.81 kg·m/sec2=9.81 N≈10N →

1 Ν=0.1 kg* → 1 kN=0.1 t* → 1 t*≈10 kN →

1 t */m≈10 kN/m → 1 kg*/cm2≈0.1 MPa → 1 MPa=0.1 kg*/cm2


 
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