Effects of Boundary Condition Models on the Seismic Responses of a Container Crane

Abstract

In recent years, several large earthquakes have caused the collapse of container cranes, which have resulted in halting of freighting, and significantly affected the economy. Some reports are concerned the uplift and derailment events of crane legs, and the collapse of the crane itself. In this study, the effects of different boundary conditions used in the numerical method are investigated for a container crane under seismic excitation. Three different boundary conditions are considered in terms of the connection of the crane’s legs (wheels) and the ground (rails), namely pin support (PIN), gap element (GAP), and Friction contact (FC) elements, by using the SAP2000 program for a typical container crane. Then, time history dynamic analyses are conducted using nine recorded ground motions. Dynamic behaviors of the container crane are studied in terms of the total base shear, portal drift, and relative displacement of legs, by investigating the three types of base boundary conditions. The results of the study show that when the intensity of earthquakes is large enough to create uplift and derailment events, the selection of the boundary condition model considerably affects the dynamic responses of the container crane. In addition, when uplift and derailment of the crane occur, the FC support condition is the most compatible with the real behavior of the crane. On the other hand, under low seismic excitation, there is no significant difference of the crane behavior according to the choice of boundary condition model.

Fragility Assessment of a Container Crane under Seismic Excitation Considering Uplift and Derailment Behavior

“…Zero-length link elements of SAP2000 (or a friction isolator element as above-mentioned) were assigned to the model's toes to simulate the contact friction, enabling both uplift and derailment, because the behavior of these elements was similar to the real interaction between the crane wheel and the rail during the operation of the crane. The uplift and derailment behaviors changed the horizontal displacement of the entire structure; thus, the corresponding fragility curves were different from those obtained from other boundary conditions such as pin or gap elements [29,33]. The friction isolator element exhibited a vertical behavior similar to that of the gap element (see [24]); However, the gap element did not remove itself from the horizontal direction during uplift.…”

“…Here, the frictional coefficient (µ is assumed to be 0.75) ignored the difference between static and kinetic friction. For the friction isolator element, both the horizontal and vertical reactions of the legs will reach zero if the legs have uplift and derailment events [33]. In this study, the stiff spring constant (k k ) of the friction isolator element is assumed to be 43,782 kN/cm [24].…”

Fragility Assessment of Container Crane under Seismic Excitation Considering Uplift and Derailment Behavior

“…Zero-length link elements of SAP2000 (or friction isolator element) were assigned to the model's toes to simulate the contact friction, allowing both uplift and derailment, because the behavior of these elements is similar to the real interaction between the crane wheel and the rail during the operation of the crane. The uplift and derailment behaviors will change the horizontal displacement of the whole structure; thus the corresponding fragility curves would be different from those obtained from other boundary conditions, such as pin or gap element [29,33]. Based on both physical test and analytical model of the previous studies, the seismic response of the container crane over time can be divided into three stages [1,6,34], as shown in Fig.…”

Seismic Response of Container Crane under Near-Field and Far-Field Ground Motions

“…In past studies conducted by various researchers, the two methods used to evaluate the seismic response of a container crane are the finite element method on a prototype container crane and the shaking table test of a scale container crane. In the finite element method [2][3][4][5][6], real earthquakes or artificial earthquakes were used to analyze container crane by time history analysis. Tran et al [3] used 20 real earthquakes to evaluate the sensitivity of parameters for the ship-to-shore container crane.…”