> Rincent ND Applications, a specialist in non-destructive testing, and Rincent Alpes, have carried out non-destructive dynamic tests on existing anchoring rods on the tie beam of a cabin cableway support tower in the Mont Blanc massif.
The investigation focused on:
> the length of the elements
> the dynamic stiffness, related to the inertia of the element tested in its environment and to the existing tension force.
The tests implemented consist of:
> to vibrate the anchoring rod with an impact caused in the direction of its axis; this impact is caused by a hammer equipped with a force sensor,
> to record the vibration V of the anchoring rod using a speed sensor fixed on the support plate,
> to analyze the Speed / Force curve as a function of the frequency after a mathematical treatment of these signals.
The equipment is semi-annually audited as per the test standard. The analysis of the curve focuses on:
> the frequency response,
> the value of the dynamic stiffness.
The frequency response allows the calculation of:
> the total length of the anchoring rod
> in some configurations the "free" length,
> or other singularities.
Dynamic stiffness is the modulus of a complex number which is inversely proportional to the slope at the origin of the V / F curve as a function of frequency.
The stiffness characterizes the operation of the anchoring rod.
The work of Rincent Laboratoires on the determination of efforts in the anchoring rods from dynamic stiffness® is the result of a theoretical research that resulted in the filing of an international patent. The tests carried out for more than 20 years constitute a strong experience in the field, however a database is totally insufficient to interpret these tests.
Rincent BTP Services SAS
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