PSI - Issue 44

Andrea Santangelo et al. / Procedia Structural Integrity 44 (2023) 626–632 Andrea Santangelo/ Structural Integrity Procedia 00 (2022) 000–000

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in active quake zones. The most common earthquake waves effects on the hyperloop above-ground structure are: • Horizontal Forces • Horizontal Displacements • Vertical Forces (especially with direction opposed to gravity)

The design of an earthquake-proof infrastructure is nowadays quite known and the modern techniques of analysis (from the evaluation of local Response Spectrums to the most sophisticated nonlinear time-history analysis) can accurately predict and design the infrastructures to withstand to violent earthquakes. Besides, the adoption of the seismic isolation design for the hyperloop infrastructure will reach the continued functionality level, to retain post-earthquake functionality and strongly limit the overall structural and non-structural damages. While it is a proven approach to design the infrastructure system to safely withstand and reduce the earthquake effects, it is also significant to evaluate the seismic displacements that could occur during an earthquake, and, in case of seismic isolation, those displacements could reach large displacements that could easily exceed 1 meter and more in near fault zones. The technological advance on earthquake prevention has developed and established, in many parts of the world, smart networks of stations that can provide an efficient early warning system (for example, TERRA systems) to protect and safely shut down all kind of systems, from trains to bridges to industrial facilities. The adoption of such of prevention system could make the hyperloop vehicles to safely “land” in the closest emergency station in case of an approaching strong seismic wave. It is then essential to provide a structured braking system (acting directly on the propulsion system and /or using other aerodynamic braking) plus a more conventional disk braking equipment for the hyperloop EDS levitation systems. In case instead of smaller and more frequent earthquakes, the vehicles could keep travelling inside the vacuum tubes using the vertical and horizontal recentering force system included in the guidance and levitation system. This recentering system is proportional to the vehicle speed, i.e., the faster the vehicle is operating, the greater this force becomes. The EMS hyperloop system has a quite lower offset tolerance than the EDS (almost 10 times less) making the alignment more critical in case of horizontal forces /displacements due to earthquakes or any other dynamic force acting on the vacuum infrastructure. 5. Conclusions The hyperloop is an innovative concept of a transportation system that could transform the concept of travelling. At the present time it is not supposed to substitute any of the actual transportation technologies but could instead fill the gap and optimize the actual transport network while raising the bar of the development of new and more performant materials and technologies. The investigation of the safety of this new transportation system undergoing seismic forces must be one of the priorities while designing the vacuum tubes and the supporting system since the operative speeds are close to the speed of sound, the deflection tolerances are stringent and the environment inside the tubes should be kept at operative pressures as low as 1/1000 of an atmosphere. The design of the modern infrastructures relies on common seismic design practice that unfortunately, mostly of the time, is still not adequate for reliability, quality, and capacities. The hyperloop must follow a more rigorous approach, that should not be based on avoiding permanent structural damages, collapses, or even long disrupting times of the service. The correct path to evaluate the earthquake safety of the hyperloop should instead be focused on minimizing the structural damages and to maintain the continued functionality of the system. While we have reached in a just few years an impressive level on the research of this fascinating system, many are the unknown and unsolved variables that are spread along the way to the construction of the first commercial hyperloop. The challenges are quite hard but looking back at the history the hard work, together with the exceptional human ingenuity, it is always awarded.