Abstract
The PTC-140/200 DS is the newest generation super heavy lift crane designed by Mammoet. This modular crane can be build in several different configurations and has a capacity of 3200 tonnes maximum. The PTC-140/200 DS is designed to meet both European and American safety standards. Both standards prescribe multiple safety factors to account for the various loads on the crane. However, the loads that occur during exceptional/accidental events, are hard to predict and are thus usually not accounted for by standards.
The goal of this report is to provide more insight in the impact of exceptional loadcase on the struc-tural integrity and overall stability of the PTC-140/200 DS. The following exceptional loadcases are investigated;
1. Sudden release of load
2. Breakage of a mainboom luffing wire rope 3. Breakage of a jib luffing wire rope
4. Breakage of a hoisting wire rope
5. Activation of the slewing emergency stop
Each loadcase is investigated by means of a finite element model (FEM) that also accounts for the dynamic effects. The FEM model has been verified by the results of a second analytical calculation. The first loadcase investigates the impact of the sudden release of load. The sudden ‘removal’ of load causes an impulse load that gives the boom enough energy to rebound. It has been found that the worst-case configuration does not tip over, because the boomstops stop the boom at 88.88◦
(initial angle: 85◦). Moreover, the stresses found in the structure are all below yield stress. It is
however recommended to further investigate the uplifting forces after load release since the reaction forces at the front of the crane become negative in the first seconds. In the second loadcase, the impact of the breakage of a mainboom luffing wire rope is investigated. Half a second after breakage, the back left bogies start to come off the rail, which results in an increase of the hoist radius. This is aggravated by the swinging of the load and together, this leads to exceedance of the moment equilibrium between counterweight and load. Within six seconds after breakage, all rear bogies are lifted from the rail and ultimately, the crane tips forward. The third loadcase describes the breakage of a jib luffing wire rope. The jib luffing wire ropes transfer forces from the jib through the struts to the under carrier. Due to breakage, the struts are eccentrically loaded. The torsion in the masthead reducer section is 1.5 times the design limit and the upper and lower strut exceed this with a factor of 2.7 and 4.3 respectively. So the breakage of a jib luffing wire results in the plastic deformation of the struts and the masthead reducer section. Whether this leads to a total collapse of the struts, has to follow from an analysis of a detailed model that includes plastic material behavior. The fourth loadcase, breakage of a hoist wire rope, shows similarities with the breakage of a jib luffing wire, because both result in an eccentric loading of the construction. In this loadcase, the eccentric load directly applies to the masthead which gives a higher torsion in the masthead reducer section (two times higher than allowed). The torsion in the struts are below design limits. In the last loadcase, a slewing emergency stop is simulated by applying the brake deceleration to the constraint model. The brake capacity of the crane is sufficient to stop the crane within the specified maximum stopping time. However, it was also found that the back of the crane will come much earlier to a standstill than the front, which could lead to high bending stresses in the components that connect the front- and back base frames.
This investigation showed that a sudden release of load and an emergency stop have no conse-quences for the structural integrity and stability of the PTC-140/200 DS. Breakage of a wire rope however does compromise the structural integrity of the crane. The breakage of a mainboom luffing wire even results in the fall over of the whole crane.
Since the breakage of wire ropes have significant impact on the crane, it is recommended to pay special attention to the inspection procedure of the wire ropes. Further more, it is recommended to consider alternative jib/mainboom luffing systems that limit the eccentric loading in case of breakage.
