Research on Engineering Structures and Materials

15-34

Authors: Pilade Foti, Aguinaldo Fraddosio, Salvatore Marzano, Gaetano Pavone, Mario Daniele Piccioni

Tensegrity structures are an innovative class of lightweight structures, which have gained the interest of researchers in many different fields, including but not limited to engineering. In particular, such interest is due to their aesthetic value, their large stiffness-to-mass ratio, the possible deployability, together to their reliability and controllability. Tensegrity structures, made of struts in compression and cables necessarily in tension, are innovative structures by itself: they are similar only in appearance to conventional pin-joint structures (trusses), and their mechanical behavior is strongly related to initial feasible self-stress states induced in absence of external loads. In particular, from a kinematical point of view, these self-stress states avoid the activation of possible infinitesimal mechanisms. In this paper, we study an innovative class of tensegrity beam-like grids, obtained by a suitable assembly of three elementary V-Expander tensegrity cells along a longitudinal axis (named x-axis) in the three-dimensional space. In particular, by means of a numerical study, we analyze the feasible self-stress states for seven tensegrity beam-like grids, with increasing degree of complexity, made by an arrangement of V-Expander elementary cells. Moreover, we analyze the influence on the feasible self-stress states of the addition of elements starting from the simplest V-Expander tensegrity configuration.

49-60

Authors: Agim Seranaj, Mihail Garevski

The Response Spectrum Analysis of the structures is based on the allowable ductility considered for that structure. In the case of multi-degree-of-freedom buildings, the required ductility cannot be the same with the allowable ductility; furthermore, the required ductility values are different for different storey. In the case of first soft/weak storey building, the required ductility of this storey is much higher compared to allowable ductility and impossible to achieve. Nowadays there are many cases of existing reinforced concrete structures with the possibility of soft/weak storey. Even new structures are required to have open space at ground floor level as the owners want them for shops or garages usage. This paper analysis the influence of base isolation to the required storey ductility of weak storey buildings. A five storey shear frame type structure is considered as the model. The elastic and elasto-plastic modeling of the structural elements and bilinear modeling of rubber isolators are used. Linear Response Spectrum analysis and Nonlinear Time History analysis are performed in order to determine the required storey ductility for the existing and new soft/weak storey buildings using the SAP2000 computer program. The analysis results show the reduction of the required storey ductility due to the application of base isolation not only in new structures, but in existing structures too. This means that the base isolation technique is a good alternative to be applied in buildings with first soft/weak storey structure.