Eager.sterk, Calculation of crane capacity charts

Calculation of crane capacity

Cranes are getting higher with increased slenderness as a result. What does this mean for the determination of capacities of cranes? Since the 2nd order effect increases for slender (high) cranes, calculations get more complex and more time consuming due to its non-linear (cyclic) character.

2nd order effect? What is that?!

Additional loads on the crane induced by geometrical changes

  • Additional loads on the crane induced by geometrical changes
  • Additional sideward bending moment due to change of shape
  • Additional longitudinal bending due change of shape

For every boom-, jib length and lifting radius it requires a cyclic (nonlinear) calculation to predict the deformations. These calculation are historically done by “nonlinear” FEM (finite element method).  It is not a quick process, especially when it comes to many different configurations of a crane. Satisfying customer needs, when it comes to crane capacity calculations, becomes very slow.

This gave reason for the development of a hand written code,
applicable to run different configurations at the same time,
without the need for re-modelling.


Our in-house design software Eager.sterk for Calculation of crane capacity

Eager.sterk © is our in-house design software to calculate capacity charts for all kinds of cranes, independent from any brand.

The software consists of 6 parts:

  1. A calculation code
  2. Describes the validation of the STERK code with STERK. (Free to look into, for third parties)
  3. Interpretation of STERK source code, using STERK during the making of ratings
  4. Spreadsheet for completely describing the crane (pre-processing).
    Every cell has a graphical remark to guide the STERK user
  5. Spreadsheet for completely describing the ratings (post-processing).
    Every load chart value ( SWL@Radius ) has a remark, describing the critical issue (strength, stability, etc.)
    For every rating-position or configuration a graphical output of the crane can be generated
  6. Complete summary of all results for a single load chart position (SWL@radius ). Including :
  • Deflections
  • Stresses
  • Bending moments
  • Shear forces

Different configurations


Upgrade of capacity charts of mobile and offshore cranes

Do you need 10-15% more capacity in the chart? We can help you! Our engineers work with STERK © to calculate the limits in crane design. We will research the crane structure in order to find the weakest spot. With this information we can advise you for reinforcements of the crane to increase the strength. This maximizes the crane capacity within the required safety standards.


Interested to learn more about STERK ©?

Check out our presentation or contact me!


Lead Structural Engineer
Phone: 0031 (0)30 2 40 80 60

What we do

As an independent partner, we advise about, design and construct everything from concept study to project completed. Our in-house developed design software calculates everything concerning mobile cranes and bespoke heavy equipment, while our people offer the expertise and skills that secure your success.


Consultancy / Design & Construction

Our 40 years of experience provides the basis of a successful start of your project: right from the FEED phase. Preparation is vital. Therefore our concept studies, method statements and mission equipment offer you all the support you need.


Consultancy / Design & Construction

Our aim is to optimize your project team’s results. With our exclusive knowledge of lifting and transportation we eliminate and manage risks. This is how we reach our collective goal: Zero Accidents, Zero Incidents.



We have built up a great deal of experience with the design of (mobile) cranes and bespoke heavy equipment such as piling machines and excavators. Our customer base includes the most prominent producers of cranes and heavy machinery worldwide.

We are eager to hear from you

Call +31 (0) 30 240 80 60 or use the contact form. We always respond within 24 hours.

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