[DE] KB 001612 | Method for determining the allowable deformation of crane girders

Subject:

Method for determining the allowable deformation of crane girders



Comment:

This article describes the different options for determining the allowable deformation of crane girders. Since multi-span beams and flexible lateral supports (curling bracing) are used in practice, clarity is to be created here about the selection of the correct method.



Description:

General



In addition to the ultimate limit state design, the serviceability limit state design is of particular importance for craneway girders. Compliance with deformation limit values is not only important for the serviceability but also for the reduction of wear. Thus, large horizontal deformations can lead to an increased skewing of the crane and thus cause an increased wear of tracking means. Likewise, vertical deformations must be avoided to the greatest possible extent in order to avoid excessive vibration of the crane during operation. Finally, it is also necessary to limit the inclination (slope) of the crane girder because otherwise the crane will not be able to move under full load.



Method 1: Deformation related to undeformed system



Method 1 can be used for single-span beams with fixed and rigid supports.



The following boundary conditions apply:



The deformation is determined as follows:



U -c ... Deformation of the cross-section

U -L ... Deformation of the left support

U -R ... Deformation of the right support

x ... Coordinate of the cross-section in the local axis system

L ... Distance of supports



The following applies:



The deformation is determined as follows:



The following applies:



At the turning points:



U -c ... Deformation of the cross-section

U -Li ... Deformation of the left turning point

U -Ri ... Deformation of the right turning point

x ... Coordinate of the cross-section in the local axis system

L ... Distance between left and right turning points



Another advantage of this method is that the supports can also have different spring stiffnesses.



Crane runway girder with cantilevers



For cantilever arms, the bending line is similar to the half-inverted bending line of a single-span beam. Therefore, the following calculation is performed for method 1:



If Method 3 is activated, the limit deformation of a cantilever is checked by rotating the cantilever on the support about the local y-axis.



The limit condition is as follows:



Results cantilever of example file 4 with method 1:

${\mathrm\delta}_{\mathrm z}\;=\;\left|7,618\;\mathrm{mm}\right|\;\;600$



Results cantilever of example file 4 with method 3:

${\mathrm\varphi}_{\mathrm y}\;=\;4,258\;\mathrm{mrad}\;=\;0,004258\;\mathrm{rad}\;



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Keywords:

#DlubalKnowledgeBase #Deformation #Horizontal_Vertical #Method #LimitDeformation #DeformationAnalysis #DlubalKB #KnowledgeBase #TechnicalContributionToDlubalSoftware

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