Effects of braking by sliding friction against rail on runaway behavior of gantry cranes for container handling receiving wind gust

Abstract

The purpose of this paper is to clarify the effects of operation of braking devices by sliding friction against rails (rail brake) on the dynamic characteristics of gantry cranes for container handling after runaway caused by unexpected wind gust by a numerical analysis and to obtain the scientific knowledge which serves to develop the technology for safe stopping. Dynamic characteristics of the crane were calculated by the dynamic numerical simulation analysis using FEM. The crane was modeled by three-dimensional beam elements. The interaction forces that define the resistance characteristics of the crane runaway generated at the contact part between wheels of the traveling system and the rails were modeled. And the interaction forces at the contact part between the rail brakes and the rails were also modeled. For the wind gust that becomes runaway driving source, the wind direction, the velocity distribution in the vertical direction and the time change of the wind velocity were modeled. The load that the crane receives by the wind was calculated based on the ISO standard of the wind load assessment of cranes. In the analysis conditions of this paper, the runaway of the whole crane started when the driving wheels of the land side became slide state after those of the sea side became slide state. The dynamic characteristics through the stop of the crane after the operation of the rail brakes concerning cases of varying rail brake operation characteristics were analyzed and considered. The operating characteristics were defined by the time increase rate of the pressing load of the brake shoe, dPB/dt, the maximum value of it, PBmax, and the timing that the operation starts. The crane reached the stop after the runaway velocity decreased with the swing of the rail longitudinal direction of the crane structural system which consists mainly of the legs, the boom and the girder. When the acceleration of the upper part of the crane structural system increases by the rail brake operation, the generated inertial force reached the level that should be considered in checking of the structural safety. Finally, the relationship between the braking distance as an evaluation index of braking performance of the rail brake and the braking operation characteristics was presented and discussed.

Keywords

• material handling equipment
• gantry crane
• dynamic characteristics
• wind gust
• wind load
• resistance force
• braking device
• runaway
• numerical simulation
• safety