Seismic performance of dual steel frames of CFRHS and welded beam-to-column joints

Abstract

The aim of the thesis was to observe the behaviour and to characterise in terms of stiffness, capacity and ductility, the seismic performance of welded beam-tocolumn joints for multi-storey building frames of CFT high strength steel columns and mild carbon steel beams. For this purpose, two connection solutions (with reduced beam section and with cover-plates) have been proposed for the beam-to-column joints. A set of frames were analysed using static and dynamic nonlinear analyses in order to assess the seismic performance and to determine the seismic demand for beam-column joints. Results from the experimental investigations are shown related to material samples (concrete and steel), steel-concrete connection (friction, friction+ connectors), and beam-to-column joints. The behaviour and response of the joints were investigated also through advanced finite element modeling. Consequently, pre-test numerical simulatons were performed with the aim to have an accurate prediction of the response for each joint configuration. The numerical models of the joints were further calibrated based on tests performed under monotonic and cyclic loading. In addition, numerical simulation of complementary cases were perormed in order to assess the influence of different parameters (i.e. concrete core, beams welded on two sides, axial force in the column) on the behaviour of the beam-to-column joints. A component method approach was developed for the design of dual steel IPE beam-toCFRHS column welded joints with reduced beam section, and respectively cover-plate connections. The relations for the design capacity of the joint components were validated by experimental and numerical means. Conclusions of the PhD study, the main contributions of the author and dissemination of results are finally presented.