Vulnerability assessment of container cranes under stochastic wind loading

Container cranes, an essential component in any seaport facility system, are highly susceptible to failure during natural disasters such as severe windstorms. Damage or collapse of these structures can lead to significant amount of economic loss in terms of both repair or replacement and downtime. To study how various parameters such as boom position, yaw angle, gradient height and gradient wind speed affect the failure vulnerability of a crane, in this work, a representative container crane has been modelled in a commercial software considering both material and geometric nonlinearities. Stochastic wind fields are simulated as a stationary process by means of the spectral representation method using power spectrum in conjunction with along- and across-wind coherence functions. Wind fields are also simulated as a non-stationary stochastic process utilising the modulation functions from the available literature to consider the situations of thunderstorm downbursts. Nonlinear time history analyses are then performed and a few responses are compared for stationary and non-stationary wind field cases. It is observed that for the given simulation parameters, the responses considering stationary wind fields are larger than those of the non-stationary wind fields. Failure vulnerability of the crane is then assessed in terms of fragility curves. The results of this study show that the failure vulnerability may not be maximum for the set of parameter values for which the aerodynamic forces are maximum. This study provides a better understanding of crane vulnerability that may be utilised to achieve a better crane design.