The Influence of Base Isolation to the Required Ductility of Soft Storey Buildings

The Response Spectrum Analysis of the structures is based on the allowable ductility considered for that structure. In the case of a 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 analyses 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 modelling of the structural elements and bilinear modelling 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

3D nelinearna dinamična analiza kamnite pregrade, ki temelji na IZIIS softwaru

This paper treats the 3D nonlinear dynamic behavior of a rock-fill dam based on the Mohr-Coulomb failure criterion. The dam is situated in a steep, narrow, “V-shaped” rigid canyon. The concept of a massless rock foundation is treated, for which a certain part of the rock is included in the model. The dam-rock interface was modeled by contact elements, which allowed certain relative displacements between the two media of different stiffnesses. The generation of the 3D mathematical model was related to the topology of the terrain, and the nonlinear dynamic response was based on the "step-by-step" linear-acceleration direct-integration method, making use of the Wilson-θ method. The convergence process was in accordance with the Newton-Raphson method. First, the initial static effective stresses existing in the conditions of the established stationary filtration through the clayey core were defined. The analysis was based on an original FE program for the static and dynamic analyses of rock-fill dams, as well as a FE program for the solution of the stationary filtration process through the clayey core. The dynamic response of the 3D model of the dam was defined for the effect of harmonic excitations. Dynamic analyses in the linear and nonlinear domains were performed for the purpose of comparing the results. The time histories of the linear and nonlinear responses were defined for selected sections and nodes of the model, the tension cut-off zones, the plastic deformations, and the stress-shear strain relationships. The coefficient against the sliding of the potential sliding surfaces was also defined. It can be concluded that 3D analyses as well as a nonlinear material treatment of the soils built in the dam are imperative for a proper assessment of the stability of rock-fill dams situated in narrow canyons.V tem prispevku je opisano 3D nelinearno dinamično obnašanje kamnite pregrade. Za kamnito maso je upoštevan material, ki zadovoljuje Mohr-Coulombov kriterij porušitve. Pregrada se nahaja v strmem, ozkem, ostrem kanjonu, v obliki črke \u27V\u27. Obravnavan je koncept modela »brezmasnega kamnitega temelja«, pri čemer je določen del kamnine vključen v model. Kontaktna ploskev med kamnino in pregrado je modelirana s kontaktnimi elementi, ki omogočajo relativne premike med materialoma različne togosti. 3D matematičnega modela je bil izbran glede na topologijo terena. Nelinearni dinamični odziv temelji na direktni integracijski metodi linearnega pospeška, kis e izvaja \u27korak za korakom\u27 z uporabo metode Wilson-θ. Konvergentni postopek je v skladu z Newton-Raphsonovo metodo. Najprej so bile določene začetne statične efektivne napetosti, ki so v stacionarnih pogojih filtracije skozi glinasto jedro. Analiza temelji na originalnem programu s končnimi elementi za statično in dinamično analizo kamnitih pregrad, kakor tudi na programu s končnimi elementi za reševanje stacionarnih filtracijskih procesov skozi glinasto jedro. Dinamični rezultat 3D modela pregrade je definiran za efekt harmoničnih indukcij. Dinamične analize v linearni in nelinearni domeni so bile izvedene zaradi primerjave rezultatov. Časovni poteki linearnih in nelinearnih odzivov so bili določeni za izbrane odseke in točke modela, natezne razpoke, plastične deformacije in napetostno deformacijske odnose. Določili smo tudi koeficient varnosti potencialnih drsnih površin. Ugotavljamo, da so 3D analize, kakor tudi nelinearno obravnavanje materialov vgrajenih v pregrado, nujne za pravilno oceno stabilnosti kamnitih pregrad izvedenih v ozkih kanjonih

Simplified method for generating slope seismic deformation hazard curve

A simplified method for generating slope deformation hazard curve that takes into account the variations of input parameters is presented in this paper. The main assumption in the new approach is that the occurrence of peak slope deformation is Poisson's process. The procedure is based on logic tree analysis, commercial software and routines programmed by the authors for generating sets of input files, and forming slope performance curve. The methodology was applied to a real landslide in order to demonstrate the advantages and limitations of the proposed approach. The results of the analysis showed the influence of the certain input factors on sliding displacement as well as the advantages of employing continuum mechanics approach