Calculation of crane capacity charts with Eager.sterk

Cranes are getting higher with increased slenderness as a result. What does this mean for the determination and calculation of the crane capacity? 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 side-ward bending moment due to change of shape
  • Additional longitudinal bending due to change of shape

For every boom-, jib length and lifting radius it requires a cyclic (nonlinear) calculation to predict the deformations. Historically, these calculations are done by “nonlinear” FEM (finite element method).  However, this is not a quick process, especially when it comes to many different configurations of a crane.

Therefore, to speed up this process has developed a handwritten code, applicable to run different configurations at the same time, without the need for re-modelling.

Eager.sterk© calculates your crane capacity charts

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

The software consists of 6 parts:

  1. A calculation code
  2. Description of 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 complete description of 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
Configuration graphical output crane

Different configurations


Upgrade of capacity charts for 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 your 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©?

Please download our presentation using the button below or contact us. We would be happy to discuss your specific situation.




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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.

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