Steel Buildings in Europe

Part 3: Actions 3 - 13 1 2 l  1 l  2 l H T,1 H T,1 H T,2 H T,2 K 1 K 2 K=K 1+ K 2 S M l s 3 3 1 Rail 2 Rail 3 Driven wheels Figure 6.2 Acceleration forces 2 Forces that result from skewing of the crane in relation to its movement along the runway beam The forces described hereunder are due to the oblique travel of the crane when it assumes a skew position, for any reason, and then continues obliquely until the guidance mean comes in contact with the side of the rail. The lateral force on the side of the rail increases to reach a peak value ‘ S ’; due to the action of this force, the crane returns to its proper course, at least temporarily. Guidance systems can be either specific guide roller or the flanges of the track wheels. The calculation of the corresponding forces depends on the type of drive system (drive units without synchronisation of the driven track wheels or central drive unit coupled to the wheels), the fixing of wheels according to lateral movement and the location of the instantaneous centre of rotation. Forces resulting from skewing consist of longitudinal and transverse forces such as indicated in Figure 6.3. These loads act at each wheel ( H S,i,j,k ) and a guide force S (also called steering force) acts at the guidance system. In the forces H S,i,j,k the indexes refer to:  S for ‘skewing’  i for beam runway  j for wheel pair (the number 1 refers to the farthest from the centre of rotation)  k for direction of the force, L if acting longitudinally or T if acting transversally. The force S equilibrates the sum of the transverse forces.