Effects of boundary condition on seismic performance of container crane

Abstract

Container crane structure plays a crucial role in loading and unloading goods from a container ship to harbors. In any case, a breakdown of the container crane would harm the economy of a country. The modern crane is bigger to satisfy the demand of the owner; therefore, it is less stable under seismic excitation. Engineers often encounter an issue for choosing the boundary condition of the simulated model of the container crane as the legs can be uplifted or derailed under strong earthquakes. In this case, the simple work of pinned boundary condition can be replaced by the elastic-no-tension element between the structure and the ground. In this way, the leg base is free to move in vertical direction, and its vertical reaction reduces to zero. The objective of this paper is to evaluate the seismic performance of a container crane by the time history acceleration analysis using two different base supports, i.e., pin and elasticno-tension supports. Firstly, horizontal response spectra of actual earthquakes are adjusted by scaling the amplitude of each ground motion to coincides with a specific target spectral acceleration at the fundamental period of the container crane and then determined the scale factor. Afterwards, the ground motions are generated based on the scale factor, and they are used as input data for dynamic analysis by time history method. Two cases of target spectral accelerations will be determined to evaluate the dynamic responses of structure for uplift and no uplift phenomenon. Some response characteristics, i.e., total base shear and portal drift, are investigated. From that, the results show that the elastic-no-tensions supports are suitable for simulating the real behavior of the container crane when it is analyzed under high seismic excitation.