Dynamic properties of mobile materials handling equipment during once‐in‐a‐century earthquakes

Knowledge of the seismic behavior of load‐bearing structures is essential for reliable seismic design. For the first time, it was possible to capture and analyze the behavior of continuous ship unloaders via video observations in two different real once‐in‐a‐century earthquakes. By means of professional video analysis, not only the seismic behavior and damage can be filtered but also decisive dynamic properties that are important for nonlinear seismic analysis. Furthermore, an interesting phenomenon can be unveiled that may be crucial for the seismic damage potential of large mobile equipment. When exposed to seismic action, large mobile material handling equipment without any anchoring to their subsoil are able to uplift and rock before derailment or major damage occurs. The observations of the continuous ship unloaders in the once‐in‐a‐century earthquakes state this fact, which was also found in previous nonlinear time history analysis. In addition to the video analysis in real earthquakes, vibration measurements were performed on real stackers, from which further essential dynamic properties were determined. All these new findings will be another step forward toward safe and economical earthquake‐resistant design for large mobile equipment with the ability of uplift.