abgeschlossene Promotionen & Habilitationen

Dissertation

Turntable ladders are important and indispensable vehicles of fire fighting and res-cue. To meet the requirements in practice, the working length of the ladder set is increasingly required longer. Today the maximum rescue height of turntable ladder can usually reach up to 68 m. Characteristics of the ladder set during work are long cantilever length, high slenderness and heavy concentrated mass (e.g., rescue cage, bodies, equipment and materials) at the ladder top. They are the causes of high dis-placement and oscillation at the top. Hence, the beings in the rescue cage can feel uncomfortable, unsafe and scared. The potential for instability of the ladder structure is high. In principle, in order to increase the length of the ladder, of course, its stiff-ness must be enhanced. The material cross section of each ladder section would be larger. The ladder mass would also be increased. Thus, the displacement and stress can be not reduced. Moreover, the mass of the entire truck is extended to ensure steady conditions of the ladder during its operation. In another aspect, the mass and dimension of the turntable ladder are limited by the load capacity of the ground and the size of the road. Therefore, the ladder length only reaches a limited length.
There have been many studies to improve its performance as well as the ladder length. They can be mentioned here e.g., the use of high-strength steel, the re-placement of materials, the rational design of the ladder structure and vibration re-duction controls. These studies have shown their effectiveness. They have been ap-plied in practice to make the vehicle more sophisticated.
For similar purposes, in this study steel wire ropes are proposed to be added into the hollow handrails of each ladder section. One end of each rope is fixed to one end of the handrail. The other end is linked to the operating part of a hydraulic actuator mounted on the handrail. The actuator has the effect of stretching the rope and con-trolling the oscillation as needed. It works based on the available hydraulic power source in the truck. This solution strengthens the bending stiffness of the ladder whi-le its mass is almost constant. Each ladder section becomes straighter. The vertical deflection of the top reduces. The likelihood of instability due to large deflection and oscillation is minimized. The ladder sections move relative to each other smoother. The proposal provides a new method to control the rapid extinguishing of the vibrati-on at the ladder top.
Based on relevant studies, this research synthesizes and analyses their advantages and disadvantages to propose the new idea. From a theoretical point of view, the proposal had shown to be effective. Research results had been simulated on the basis of the parameters of the available ladder structure which had been confirmed about its superiority. A typical equipment cluster which creates and controls the ten-sion of the steel wire rope in the lower ladder section of a three section ladder had been designed.
The recommended devices are compact. Their dimensions are suitable for easy in-stallation in the hollow interior and at the ends of the handrails. Their installation does not affect the normal operation of the vehicle. They are organized of standard devices and details which are commercially available. Hence, the production process is not complicated and the product cost is low. This shows that the applicability in practice is high.
For the scope of application, this work should be applied to all turntable ladders which have the maximum rescue height of 30 meters or more. The application may include upgrading existing turntable ladders (on the market or being used) and pro-ducing new ones.

Turnable Ladder, Workability