Steel Buildings in Europe

Part 3: Actions 3 - 12 Considering both crab positions leads to the maximum and minimum loads per wheel acting on the crane runway. An eccentricity of application for these loads, generally taken as ¼ of the rail head, also has to be considered. In order to consider some features such as impact of wheels at rail joints, wear of rail and wheels, release or lifting of the working load etc., dynamic factors are applied to the above static action values. For vertical action, the dynamic factors are called  1 to  4 (refer to Table 2.4 of EN 1991-3). 6.2.3 Horizontal actions The following types of horizontal forces should be taken into account:  Horizontal forces caused by acceleration and deceleration of the crane in relation to its movement along the runway beams  Horizontal forces caused by acceleration and deceleration of the crab in relation to its movement along the crane bridge  Horizontal forces caused by skewing of the crane in relation to its movement along the runway beam  Buffer forces related to crane movement  Buffer forces related to movement of the crab. Only one of the 5 types of the above horizontal forces should be considered at the same time. The third one is generally assumed to be covered by the fifth one. The two last ones are considered as accidental forces. The following details considering the first two types are generally those that lead to dimensioning configurations for the crane runway: 1. Forces that result from acceleration and deceleration of the crane along its crane way. They act at the contact surface between the rail and the wheel. They have to be amplified by a dynamic factor  5 (see Table 2.6 of EN 1991-3) whose value may vary from 1,0 to 3,0, the value 1,5 being generally relevant. These forces consist of longitudinal forces ( K 1 and K 2 ) and transverse forces ( H T,1 and H T,2 ) as shown in Figure 6.2. The longitudinal forces correspond to the resultant drive force K ; such force must be transmitted through the driven wheels without skidding even when the crane carries no working load. The resultant of the drive force does not pass through the centre of mass ‘S’, generating a couple that causes a skewing moment each time the crane accelerates or brakes. This moment is distributed on each runway according to their distance from the centre of mass.