Runaway characteristics of gantry cranes for container handling by wind gust

Gantry cranes used for container handling at container terminals (hereinafter referred to as cranes) have experienced unexpected runaways caused by wind. In the present paper, a method of dynamic simulation analysis for runaway of cranes caused by wind is described and the dynamic behavior of a standard-size crane while approaching runaway and after runaway as a result of a wind gust was clarified. In the dynamic simulation analysis, the crane was modeled by combining three-dimensional finite elements. The interaction forces generated between the wheels and the rails and the braking force of the rail clamps used to prevent crane runaway as a result of wind were modeled and calculated. The time change of wind velocity of a wind gust was modeled in terms of the increase ratio and the time change rate, and the wind load acting on the crane was calculated. Based on these models, a standard-size crane was analyzed herein. According to the analysis results, when the gust acted in the rail direction under the condition in which the friction coefficients between the pads of the rail clamps and the rails and those between the wheels and the rails decreased, the sea-side clamp pads and driving wheels entered the slip state, after which the land-side clamp pads and driving wheels entered the slip state. Then, the entire crane started to run away. Due to the time lag like this, the crane may run away even though the total wind load is smaller than the total resistance force acting to prevent runaway, which is simply calculated as the sum of the maximum static friction forces generated between the clamp pads and the rails and between the wheels and the rails. Moreover, although the increase ratio of the wind velocity is small, if a wind gust having a large time change rate blows and the fluctuation of the inertial force in the rail direction becomes large as a result of the swinging of the upper part of the crane, the probability of crane runaway increases when the inertial force increases in the runaway direction.