Delft University of Technology
Faculty Mechanical, Maritime and Materials Engineering Transport Technology
R.P.W. Ham NEN-13001
Engineering Assignment, Report 2005.TL.6997, Transport Engineering and Logistics.
Because of the European integration the several national standards are rewritten to new European Standards. For the design of cranes, the old NEN 2019 and NEN 2019 are replaced by the new NEN-EN 13001. There is a need for a comparison between those two to see if constructions have to be made heavier to comply with the standard.
The construction has to be proven on three levels: static strength (yielding), fatigue strength and stability against buckling or crippling. The idea on how to come to a total calculation for a construction is quite similar, only the ways to determine the separate parts can be quite different. The two standards are described next to each other, to be able to compare each step in the process.
In the design of a crane some safety precautions are taken for the event of yielding. This is done in two ways: Maximum stress in the construction is yield stress of the material divided by a factor >1
The design stress generated by the several loads on the construction is based on the loads, like the own weight of the crane and occurring situations, like the dynamic effects by external factors, as driving over a step or a gap. These loads are multiplied by safety factors, which results in a higher design stress than in actual situations, which has to be calculated with.
Fatigue is of major importance in a crane with a long lifecycle, a heavy load spectrum and a large number of load cycles. These parameters are used to determine material properties and measures.
NEN 2018 & NEN 2019 NEN-EN 13001
To come to a calculation for a construction, first the load combination is chosen, based on situations occurring during its lifetime. With the help of the several classes, like class of utilization (number of load cycles) and the load spectrum, the group factor M and load factor ψ can be determined. The combination of the load combination multiplied by the group factor and load factor leads to the appropriate safety factors belonging to the right loads. The result of this is that the design load is much higher than the actual load.
In NEN-EN 13001 load combinations are used, but each type of load has got its own safety factors, instead of the group factor and load factor, as in NEN 2018. Here, each load is multiplied with its belonging safety factor. Then each load is multiplied with another factor (partial safety factor). At the end every part is multiplied with the same risk factor. The result of this is that the design load is much higher than the actual load. The construction has to be proven for yield, fatigue and stability. At first, the
yield calculation is done with the yield point divided by 1.5 for load
combination 1 and 1.33 for other load combinations. The fatigue calculation is done by dividing the notches in groups and determining the stress ratio (κ). This stress ratio is the minimum stress divided by the maximum stress and can be anywhere between -1 for a completely alternating situation and 1 for a non alternating situation with the minimum stress the same as the maximum stress. In case of a very low stress ration, the fatigue condition is the one which has to be focussed on, because the maximum stress can be very low due to the alternating situation.
The construction has to be proven for yield, fatigue and stability. At first, the yield calculation is done with the help of the yield point divided by 1.1 for rolled and non-rolled materials and between 1.1 and 1.47 when tensile stresses perpendicular to the plane of rolling. The fatigue calculation is done with the help of the stress history factor S. This stress history factor is determined by using several classes and parameters, like the load spectrum, the class of utilization and a parameters F2, mass of moving crane parts and mass of hoisting load. This class S is used in the calculation for the permissible stress range (maximum - minimum stress) and the characteristic value of the weld.
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