Nonbuilding and Special Structures
Roller coasters are unique structures and there is little information available on its structural analysis methods. The problem is in the type of loads it needs to withstand – loads produced by train with passengers moving along rail path of complex trajectory. In bridge design, calculations for moving loads have to be performed, in seismic or dynamic wind analysis the load is stationary but is a function of time. For roller coaster both of the above mentioned cases apply, structure needs to be analyzed for loads, which are not only moving with variable speed but also change their direction and magnitude with time and position.
Paper describes the design process of a steel roller coaster starting from trajectory analysis and determination of train velocity and g-forces via kinematic calculation. Trajectory parameters for kinematic analysis are defined using algorithm built with Grasshopper for Rhinoceros 3D. Data obtained from kinematic analysis is then used to determine track loads and load time-functions for time-history analysis. Calculation model is then created using text interface of SOFiSTiK FEA software. Usage of text interface is dictated by complex geometry of structure and tremendous amount of load cases each having unique time-function. Subsequently, two types of analysis are performed: 1st – static analysis for series of independent load cases, 2nd – dynamic time-history analysis. Results of dynamic and static analysis for several variants of track sections and column layouts are compared in order to assess the impact of dynamic effects on the structure.
The topic will primarily be of interest to practicing structural engineers involved in design of structures subjected to moving dynamic loads and structures with complex geometry. The audience will learn about usage of Grasshopper graphical algorithms as a tool for analysis of structure’s geometric parameters which is a vital skill in modern structural design due to recent architectural tendencies to use abstract geometric forms. Methods for modeling complex dynamic actions will be presented. Finally, ultimate advantages of coupling graphical algorithms with text interface of FEA software for creation of calculation model will be demonstrated. Practitioners of structural design will find approaches and techniques described in the study as a practical solution for problems they are facing in their work.