Conservative assumption

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A conservative assumption is an assumption, hypothesis , simplification or approximation based on facts, experience, intuition, linearization, limit value observations or the like. A conservative assumption is on the safe side. It often represents a simplification which could also be used to bridge gaps in data or understanding.

In engineering , assumptions are often made for boundary conditions , prerequisites, theories or parameters . Such an assumption is called conservative if it contains the requirements of safety reserves. A conservative assumption is a simplification that is not on the unfavorable side, that is, it can agree with the exact calculation in certain cases, but it can also oversize on the safe side. In today's standardization, low failure probabilities ( ) are required in the life of the building and therefore loads above the expected value are often assumed in the calculation in order to compensate for variations. However, this has nothing to do with a conservative assumption; a conservative assumption, on the other hand, says that a simplification is made that reliably complies with the required level of safety, but no longer has the full complexity and could therefore lead to oversizing in some cases. If the component is oversized, it fulfills higher requirements and is then often thicker, wider, contains more reinforcement , more stiffening, better material quality, smaller imperfections, better notch class, .... But with that you are on the safe side . If one were to place the assumption of the requirements under the maximum expected load, the dimensioning would be too weak and one would be on the uncertain side .

Of conservative assumptions , which represent a simplification, you have to unfavorable assumptions distinguish which is not a simplification but a relevant for the rated load case. Loads are called unfavorable if they increase the utilization for the respective load case. Even if one were to start from a single individual member, innumerable load cases can be relevant here, not only because there are different combinations of internal forces (normal force, bending moment, shear force), but also because the internal forces must be adhered to at every point on the member, which is especially true in the case of gradations , e.g. B. of welded sheets, is decisive.

The term conservative assumption is common in the technical language of engineers , but is also used in economic contexts, for example in banking, and has already found its way into everyday language. The term represents a cautionary estimate or a worst-case scenario . It can be used in risk assessment to estimate something that is on the disadvantageous side. In radiology , a conservative assumption is defined in such a way that the effects on humans and the environment are very likely to be overestimated.


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