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Abstract: Based on the explicit finite element (FE) software ANSYS/LS-DYNA, the FE model for a sliding lead rubber bearing (SLRB) is developed. The design parameters of the laminated steel, including thickness, density, and Young’s modulus, are modified to greatly enlarge the time step size of the model. Three types of contact relations in ANSYS/LS-DYNA are employed to analyze all the contact relations existing in the bearing. Then numerical simulations of the compression tests and a series of correlation tests on compression-shear properties for the bearing are conducted, and the numerical results are further verified by experimental and theoretical ones. Results show that the developed FE model is capable of reproducing the vertical stiffness and the particular hysteresis behavior of the bearing. The shear stresses of the intermediate rubber layer obtained from the numerical simulation agree well with the theoretical results. Moreover, it is observed from the numerical simulation that the lead cylinder undergoes plastic deformation even if no additional lateral load is applied, and an extremely large plastic deformation when a shear displacement of 115 mm is applied. Furthermore, compared with the implicit analysis, the computational cost of the explicit analysis is much more acceptable. Therefore, it can be concluded that the proposed modeling method for the SLRB is accurate and practical.

This paper addresses the issue of efficient finite element (FE) modelling of lead-rubber bearings used for the seismic isolation of building structures. A particular commercial software is used for the task and focus is given on increasing the time step required in conducting non-linear response history analysis without suffering from numerical instabilities due to large deformations expected to develop in the bearings under severe ground excitation intensity. It is proposed by the authors to use artificially small values for the mechanical properties of the steel sheets increasing their thickness such that they become compatible with the properties of the rubber sheets, while increasing the thickness of the steel sheets. Although from a numerical/computational viewpoint the fact that the two materials have now similar properties and therefore a larger time-step can be used in the analysis leading to computational efficiency, this heuristic consideration does not represent reality as the two different materials have very different properties. To this end, the authors undertake verified by experimental data obtained from testing actual bearings in the shaking table to demonstrate that the induced error due to adopting artificially low mechanical properties for the steel sheets do not induce significant errors in predicting the seismic response of the considered specimens tested in the lab. From a technical viewpoint, the paper presents a "smart" way to reduce the time-step in the analysis of lead-rubber bearing which, although raises questions on its rationality, it does seem to yield encouraging results when compared with experimental data. This can be classified as a practical paper which may be of use to practicing engineers undertaking design and verification of base isolated buildings for earthquake resistance. There is always, of course, an issue on whether the proposed heuristic technique is applicable and accurate to different types of lead-rubber bearings not considered in the experimental campaign used in the paper. However, such bearings are always tested in the lab before deployment and, therefore, in each case a similar preliminary analysis can be done by practicing engineers along the lines of the paper to test the validity of the proposed scheme, which may then be used for computationally efficient design verification purposes with confidence.

一种可滑移式铅芯橡胶支座的显式数值模拟与试验验证

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