Akira Maekawa

Abstract In high-temperature piping, a gap is provided in the piping support part to release the thermal expansion of the piping. As a result, impact vibration occurs during an earthquake, causing impact loads and nonlinear vibrations. This study proposes an analysis method that can simulate the impact phenomenon from moment to moment and consider the influence of the structural and vibrational characteristics of the impacted object, rather than an analysis method that uses a restitution coefficient that does not take into account the temporal nature of the impact process. In order to analyze the impact vibration of the piping system with gap, the mechanical model of the impact phenomenon is expressed in a one-degree-of-freedom system of mass-spring and an analysis model using a beam element as piping is created. The time history response of the vibrating piping colliding with the piping support is computed by Runge-Kutta method. Using this proposed method, the influence of the gap size (clearance) on the seismic design and vibration characteristics of the piping is investigated. As a result, it was found that the vibration response changed rapidly depending on the gap size (clearance). This change in vibration response was noticeable during resonance. It is necessary to clarify the gap size (clearance) which is the threshold for change.

Abstract This paper proposes an improved contactless measurement method for vibration stress of piping systems, by which the measurement time is shorter and the measuring works are more simple. The proposed method includes two processes, in which the bending mode shape of piping vibration is identified by a transmission-type light emitting diode (LED) displacement sensor and the vibration stress is calculated based on beam theory using the approximated curve of the bending mode shape. The proposed method uses one advanced LED displacement sensor to measure the vibration stress in contrast to multiple conventional LED sensors, which must be used in the previous method developed by the authors. Therefore, the measuring system could be reduced in size and a light-weight and portable measurement instrument was developed. The measurement accuracy and reliability of the new method were validated by the vibration experiment using a mockup piping system.