Analysis
Principal steps

Define loads and critical conditions

Define boundary conditions

Modeling

Check mechanics of model

Check run

Actions on checks

Find solution

Criteria check
 
Check on stress concentration and risk of fatigue

Conclusions

EN-UK 
Strength analysis of ship's structures

Experienced in Structural Analysis

Our assessment is always represented in a detailed planning. Furthermore we think the KISS principle is the best first approach. But if it no longer can be kept simple than we are working out cases according detailed, carefully defined plans using modern tools.We take care for approved procedures by customers and authorities. At the milestones we will decide about the next steps with all participants....
define loads
Prior to modeling, the most relevant loads and load combinations are to be described carefully. A matter of fact is that results may not be reliable due to a lack of attention for this matter. In many cases the real loads on a ship structure in the live cycle of the vessel are not exactly to describe beforehand and the applied loads on a model have to be a representative approximation depending on the applicable criteria. On the other hand one should try to find the most critical load condition to avoid calculations of less interest. This job requires experience and deliberation.
modelling
The next job prior to modeling is to define the good boundary conditions to avoid too large models. Take into account that lager models are not automatically more reliable. There are many rules to take into account while describing boundary conditions. Furthermore modeling is a matter of experience en knowledge how to describe a structure using abstract element as realistic as possible. It’s much more important than the knowledge about the theory of solving finite element equations! There are thousands of way’s to build a model, however only one might be the good one!

Often annalists are satisfied if there is a suspected relation between deformation and loads and they can represent hot spots at the end of there investigations as shown in a figure of stresses like the figure below.analysis results

However the job is not finished when hot spots are found; the real job is still to do:
How to avoid high peak stresses and make the structure detail save without this peak stresses. Peak stresses means an enlarged risk of fatigue failure, even when the maximum value is lesser than the allowable stress. The most efficient way to avoid fatigue failures is to design structure details with care. Everyone should realize that fatigue cracks really occur on many places in the structure and even on small vessels.
Even in superstructures, formerly when made from light alloy, the risk of fatigue often is neglected because nobody suspect fatigue there!
Top of document
crack in coamingToo less attention for how to avoid stress concentrations, for example in face plates of the primary structure, as well as less attention for quality of workmanship results in many fatigue cracks. These failures may be hidden beyond furniture and makes vibration impediment predictable. One should realize that this inconvenient effect may grow during the lifetime of the structure from zero when the ship is delivered to an unacceptable level.

Especially light alloy structures are very sensitive regarding fatigue! Even on small vessels and yachts an increase of fatigue failures are predictable. We have experience and the knowledge how to handle structure details.

ASC delivers not only the results of the calculations but also advises for alternatives if the structure does not match your expectations. We can offer analysis’s for a fixed price based on a clearly defined plan. 
Top of document
Please contact us for questions