Parametric study on seismic behaviour of dual-concentrically braced steel frames

Abstract

The earthquake resistance design plays an essential role in the design of steel structures. Cyclic behaviour of beam-to-column in crucial in seismic behaviour of moment resisting steel frames. At the moment, the European design code in practice does not provide analytical tools to predict rotational capacity and cyclic performance of selected connection typology, but the code requires design supported by experimental testing or existing data on experimental tests performed on similar connections, what is unfeasible from designer’s point of view. A European project has recently been started with the aim to develop design tool with typical beam-to-column connections used in European practice. In that way, designers will be able to directly use pre-qualified connection without performing experimental tests or literature reviews. One part of this European project is to estimate the seismic demand of the joints in typical D-CBF frames. In order to achieve these objectives seismic performance and dynamic response were estimated on basic of non-linear static analysis and non-linear time history analysis. Numerical models were create in order to perform non-linear static and dynamic analysis using OPENSEES software. Both analysis were performed in accordance with current European design code. The results of non-linear static analysis are presented in form of pushover curve and schematic illustration of formed plastic hinges. Dynamic response was estimated in term of i) maximum floor acceleration, ii) maximum interstorey drift ratio, iii) residual interstorey drift ratio and iv) maximum beam rotation ratio (at the exterior, one-side beam-column joints) at three performance levels: design (D), near collapse (NC) and twice near collapse (2xNC). As main conclusion, the analyses have showed that lateral resistance of D-CBFs is suddenly decrease when brace in compression buckles. This decrease is immediately followed by an increase of lateral stiffness. In seismic demand between selected parameters an important rule have hazard level and height of a structure.