Capacity Requirements Of Non-dissipative Components In Concentrically Braced Frame Design

The concentrically braced steel frame structure has been widely used in multi-storey and high-rise steel structures because it can fully reflect the advantages of steel material: light weight and high strength,be convenient for various standardized operations and have good seismic resistance performance.With the progress of society and prosperity of economy,people put forward higher requirements for the performance of steel structure buildings under severe earthquake and pay more attention to the design method of how to make the structure successfully resist the severe earthquake.In this paper,numerical simulations were done to explore the severe earthquake effect of centrically braced steel frame.Some studies have exposed the inadequacy of the design regulations about non-dissipative components of centrically braced steel frame structure in the current code,so supplementary design methods are proposed.The finite element software ABAQUS is adopted to build 19 models designed with different height,different seismic intensity and different design methods of colums and beams in concentrically braced steel frame.A group of ten earthquake records were chosen respectively to meet demands of nonlinear time history analysis under severe earthquake.The results show dynamic earthquake response process of centrically braced steel frame.Forces and displacement response of non-dissipative components,coloum and beam,were studied.Diffierent calculation methods of design strength of columns in the specifications of China and the USA were compared.Considering effects of height and seismic intensity,a formula for axial force amplification factor of columns was proposed.By amplifying axial desigh force of columns,the force redistribution after brace yielding or buckling under severe earthquake could be checked.The unbalanced vertical force of beam in models with various height and seismic intensity was researched.The results show that beam sections designed in current codes are too big in some stories.The effect of buckling bearing capacity coefficient on beam demand under severe earthquake was investigated and design suggestion was given.