Several procedures for non-linear static and dynamic analysis of structures have been developed in recent years. This paper discusses those procedures that have been implemented into the latest European and US seismic provisions: non-linear dynamic time-history analysis; N2 non-linear static method (Eurocode 8); non-linear static procedure NSP (FEMA 356) and improved capacity spectrum method CSM (FEMA 440). The presented methods differ in respect to accuracy, simplicity, transparency and clarity of theoretical background. Non-linear static procedures were developed with the aim of overcoming the insufficiency and limitations of linear methods, whilst at the same time maintaining a relatively simple application. All procedures incorporate performance-based concepts paying more attention to damage control. Application of the presented procedures is illustrated by means of an example of an eight-storey reinforced concrete frame building. The results obtained by non-linear dynamic time-history analysis and non-linear static procedures are compared. It is concluded that these non-linear static procedures are sustainable for application. Additionally, this paper discusses a recommendation in the Eurocode 8/1 that the capacity curve should be determined by pushover analysis for values of the control displacement ranging between zero and 150% of the target displacement. Maximum top displacement of the analyzed structure obtained by using dynamic method with real time-history records corresponds to 145% of the target displacement obtained using the non-linear static N2 procedure.

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It is well known that seismic links are usually designed to remain in elastic region during ordinary loading but withstand nonlinear deformation during seismic event having capability to dissipate seismic energy. The use of short seismic links is recommended because they are capable of dissipating seismic energy in larger quantity by shear, while the webs in these links are expected to yield in shear during large seismic events, i.e. dissipation of seismic energy by bending in links is negligible. Shear deformations are basically plane deformations of the cross section web of the link, without any significant tendency towards lateral torsional buckling. To achieve the required plastic rotation, local instabilities such as flange or web buckling should be delayed. The flange local buckling is delayed by specifying width to thickness ratio, while the web local buckling will be prevented by adding number of transverse stiffeners along the web of the link. The main purpose of the stiffeners is to preserve buckling of the seismic link web, i.e. to achieve plastification of the cross section by shear. Dissipation of energy in the stiffened link will occur sooner through inelastic shear deformations than through inelastic web buckling. The seismic links were chosen having the same cross section and the same length, but with different number of stiffeners, i.e. with three couples of stiffeners, two, one and without any stiffener respectively. A finite element modelling approach in investigating the structural behaviour of short links is presented. Both the material and geometric nonlinearities are considered in the FE modelling using the software ABAQUS and the Shear force -Displacement relationships was obtained. The FEA results are validated against the test results and the comparisons indicated that the FE analysis procedures agree well with the test results.

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