Calculation of one beam to compression

Calculation of a right beam in Compression

This calculation is done according to the formula:

------------ ---------------------- | S >= F/S | with the condition | S <=/(n1*n2*n3) | where is ----------- ----------------------

S is the acceptable tension in the section of calculation in N/mm2 (Example: For the mild steel S = 240 N/mm2)
F is the compressive force which is exerted on the beam in NR (Newton)
S is the section of the beam where one calculates the tension in mm2
is the elastic tension Limite materials in N/mm2
n1 is the safety coefficient (of 1,5 and 3)
N2 is the coefficient of stress concentration which takes account of the abrupt variations of the section at the place of calculation (from 1,5 to 3)
n3 is the coefficient of dynamic overload due to the shock (from 2 to 10: possible calculation if the load falls from a certain height). If the load is applied gradually by released immediate, n3=2.

Attention! If the length of the beam is too high, compression can become a Flambage, i.e. a side inflection by discharge of the beam. The Institute of standardization considers that the request is Flambage when:

----------------- -------------- | tf = L/I > 20 | and | I = (I/S) ½ | where ----------------- --------------

tf is the degree (or the coefficient) of twinge: without unit
L of buckling in Misters This length is the length is equal to that of the beam if the ends are articulated.
I is the minimum ray of inertia of the beam in mm
I is the minimum moment of inertia in mm4
S is the section of the beam in mm2

For example, there is risk of buckling, in the case of a circular beam of section and whose ends are free, if its length is higher than 5 times its diameter.

Calculation of the shortening of a homogeneous right beam

This calculation is done according to the formula:

------------------- | has = (F*l)/(S*E) | where -------------------

has is the shortening of the beam in mm
F is the compressive force on the beam in NR
L is the length of the beam in mm
S is the constant section of the beam in mm2
E is the Modulus Young (longitudinal modulus of elasticity) of materials in N/mm2 (Example: Mild steel: E = 215000 N/mm2

In certain situations, lengthening known and is limited to an imposed maximum value. In this case, the unknown factor is the section (S) of the beam ou/et its composition (E). It is necessary, in this case, to check that the maximum tension is not exceeded.

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