Overall Sciences ... Overall Designs... Do we need always to consider Factor of Safety ... ?
Dear Om Prakash Chhangani ...Thanks for answering ..
Factor of safety are essential in order to account for variation in material properties and variation in loads. Some of these are taken care by defining characteristic values which will take care of inherent variations. In working stress method these are taken care of by defining material stresses as permissible values with certain factor of safety whereas these are taken care of more rationally by defining partial factor of safety for materials and actions.
Yes we need factor of safety in construction works, we are responsible of a lot of people's life, everything maybe happen variations of load or materials properties.
give current information to safety officers so that training of all laboratory workers can be improved and specific guidance can be given to individual workers ... and give information to laboratory leaders so that they can learn how to use, test, and procure appropriate personal protective equipment (PPE) and other types of equipment to improve safety.
Factors of safety or more appropriately "factors of ignorance" are necessary in all designs to avoid failure. The more we research on materials behavior and on applied loads the more confident we will become in reducing these factors.
I think the factor of safety is very important to consider everywhere
If you are planning engineering designs, you certainly need to study in all aspects, especially the safety aspect ... God bless you
It depends on the design method we use is it Allowable strength design (ASD) or Load and Resistance Factor Design(LRFD).
In allowable strength design (ASD), a member is selected that has cross-sectional properties such as area and moment of inertia that are large enough to prevent the maximum applied axial force, shear, or bending moment from exceeding an allowable, or permissible, value. This allowable value is obtained by dividing the nominal, or theoretical. strength by a factor of safety.
LRFD is similar to plastic design in that strength, or the failure condition, is considered. Load factors are applied to the service loads, and a member is selected that will have enough strength to resist the factored loads. In addition, the theoretical strength of the member is reduced by the application of a resistance factor.
because of the flexibility it gives for designer and its economical manner to a certain limit now a days LRFD is adopted in design codes.
I would agree with Alex. A factor of safety is an insurance policy for all the things we didn't consider in our design. Or the unforseen events that occur beyond our consideration. But it does depend on the situation. If failure of the part/structure/design can have no risk to people's safety, or damage to other objects, then perhaps fos can be reduced to one. The only instance though I can imagine you would actually do this, is in building test rigs to measure a certain aspect. Otherwise, consider have you really considered all the consequences of failure? A failure of a non critical component, could have catastrophic impacts on critical components.
The so called elastic (actual) loads are still used to determine deflections, so it's better to compute them and have them at hand. AMM
Good design engineers must consider so many factors when designing a part or component. Design for assembly, cost, logistics, manufacturability, reliability, and other qualities all require forethought and creativity. Perhaps one of the most important qualities to be considered when creating parts or products is safety...and naturally, an entire industry has cropped up around the need to manufacture safe products and structures for consumer use.
must we need to follow FOS and minimum we need to follow FOS 1.5
Based on our design criteria. Actually we need to consider the safety factor always
yes sir,poor workmanship,non quality material and accidental load we need
Each individual process must adhere to an FS of 1.5 or greater to ensure that the overall FS is at least 1.5 or more.
The factor of safety idea comes from a Royal Commission report in England in about the 1860s. The Commissioner was looking at bridge failures due to train loads usually in cold weather. These accidents killed a lot of people. He asked 7 of the world's best engineers what safety factor should be used, he added up the numbers and divided by 7 and got 3 and so it was recommended. It turns out from most perspectives it is a not a bad choice, but it is not a scientific selection method. I once saw a paper by a very well respected Professor who said he had worked out the overall safety figure for all the modern codes is about 3, I just smiled of course it is. So no matter what you do to all the numbers, we are stuck close to 3.
Safety factors account for different uncertainties involved with the performance of the produced design. Some of these are related to our knowlege and correctness of the models used; so, part of the safety factors can be reduced (not fully eliminate) as we increase our understanding and modeling capabilities. However, others are related to the properties of the materials and the actual demand in the future. Hence, although it is plausible to optimize such factors, some degree of overdesign of the estimated capacity over the estimated demand is needed.
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