In this article, the possibility and the pertinence of using 3D printed polymeric materials for models in modal tests on shaking tables were recognized. Four stages of the research have been linked: The material properties investigation, the field experiment on the modal properties of the reinforced concrete chimney (a prototype), the shaking table tests on the modal properties of the 3D printed polymer model of the chimney, scaled according to the similarity criteria, and the numerical calculations of the FE model of the 3D printed mockup. First, the investigation of the properties of 3D printed polymer materials revealed that the direction of lamination had no significant effect on the modulus of elasticity of the material. This is a great benefit, especially when printing models of tall structures, such as chimneys, which for technical reasons could only be printed in a spiral manner with the horizontal direction of lamination. The investigation also proved that the yield strength depended on the direction of the lamination of the specimens. Next, the natural frequencies of the chimney, assessed through the field experiment and the shaking table tests were compared and showed good compatibility. This is a substantial argument demonstrating the pertinence of using 3D printed polymer materials to create models for shaking table tests. Finally, the finite element model of the 3D printed polymer mockup was completed. Modal properties obtained numerically and obtained from the shaking table test also indicated good agreement. The presented study may be supportive in answering the question of whether traditional models (made of the same material as prototypes) used in shaking table tests are still the best solution, or whether innovative 3D printed polymer models can be a better choice, in regard to the assessment of the modal properties and the dynamic performance of structures.
Abstract. The proposal for improving the constructive scheme of the supporting frame of the suspension building has been considered. The strains in its bearing elements due to earthquakes are significantly less than in the traditional cantilever buildings. In former schemes the vertical components of strains develop during horizontal oscillations of the grounds. This disadvantage has been eliminated now. It is shown that in the improved design of the structure under the earthquake the vertical component of vibrations is practically absent, due to arrangement of the suspension device strictly vertically. The numerical data for calculation results with variation of some characteristics of the supporting frame and suspensions have been shown in order to allow adjusting the dynamic strains at the vibrations of the base. The scheme for installation the vertical elements of the frame have been proposed. Its usage will allow to build the high-rise suspension buildings.Keywords: suspension building, seismic safety, dynamic forces, Lagrange's equations of the second kind The problem statementThe issue of protecting buildings subjected to earthquakes is always one of the most important tasks for design and construction in the seismic areas. The usage of the damping devices, disconnecting constraints is an effective protection measures [1][2][3][4][5]. However the dynamic forces from the action of the earthquake still large enough, so that strengthening of the building structures is required, and the cost of construction is increasing.Another highly effective way for the substantial reduction of the dynamic forces acting on the bearing structures is the suspension of the building to the bearing frame [6,7]. According to the preliminary calculations by the simplified dynamic schemes, the suspension of the very building allows to reduce the loading of the bearing structures several times. The unusual solution to the problem of the suspension building entails facilitation in installation of structure of the bearing frame, improving its shape to reduce the vertical components of force during oscillation, and a study of change of the efforts to the support frame depending on various factors, including the length of the suspension thread and the stiffness of the supporting frame.
This paper presents the refined technique of dynamic calculations for suspension earthquake-resistant building. The improved design schemes of suspension buildings and structures have been demonstrated. Two versions of suspension buildings have been analysed. For the system with the building as a point mass suspension on the fixed bearing frame thread, a system of Lagrange differential equations of the second kind has been derived. For the building presented as a rigid rod with the length equal to its height, also suspended on the supporting frame, the solution is performed using principles of dynamic calculations and methods of theoretical mechanics. It has been demonstrated, that the horizontal force in the suspension building is ten times less than the force in a traditional cantilever building, and that for the real horizontal stiffness of the supporting frame the dynamic strains are far from resonant values. The possibility of adjusting dynamic forces by regulating the stiffness of the supporting frame, length of the thread of suspension and other parameters. The proposed calculation schemes are useful for the preliminary calculations, and the finite design of the suspension building can be performed in modern software packages (e.g., Ansys, Abacus, etc.).
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