Research On Seismic Performance Of Irregular Steel Frame Structure With L-shaped Flat

In the process of the development of the construction industry,the form of architectural structure is also constantly enriched.Irregular building is one of the common forms,they not only add the beauty of the building but also bring the difficulty in design.Compare with other Materials,steel structure has the advantages of high intensity,light weight,good toughness and so on.Under the premise of meeting the shape and use requirements,one of the important things in the development of steel structure is developing advanced and reasonable structure systems according to the principles of modern techniques and economic rationality.This paper first introduces the type of flat irregular buildings and the characteristics of steel structures,then introduces the failure forms of steel structures in earthquake.Reviewing the present research state of structure with irregular plane and steel frame structure.This paper using the large-scale finite element analysis software SAP2000 establishes three steel frame structure model with irregular plane of L-shape,the first model is pure steel frame structure,the second model is eccentrically braced steel frame structure,the third model is concentrically braced steel frame structure,modal analysis,horizontal two-dimensional response spectrum analysis,time history analysis,Pushover analysis and nonlinear time history analysis on the three models,get the seismic response,analysis the influence of different support forms on the seismic performance of steel frame structure,providing reference for engineering design.Through the modal analysis,gets the first 12 steps natural vibration periods and mass participation coefficient of the three models,we find the first vibration type is Y direction translation,the second vibration type is reverse,the third vibration type is X direction translation.It is known from the flat and torsional characteristics of the three models,the support significantly enhanced the torsion resistance of the pure frame structure.In addition,the ratio of the torsional translational period of the three models decreases in turn.The contribution of support in improving the torsional rigidity of the structure is further confirmed.Performing horizontal two-dimensional response spectrum analysis on the three models,the horizontal displacement and interlayer displacement angle of the three models are obtained.By the horizontal two-way floor displacement of the three models,the floor displacement of the three models in Y direction are all bigger than the X direction at eachfloor.Compared with the pure frame model,the two support models have a significant reduction,but there is little difference between the two support models,proving that both the central support and the eccentric support can significantly improve the lateral stiffness of the structure,but there is little difference.Form the story drift of the three models we can find that the torsion stiffness of the three models is enhanced in turn.We select two actual strong earthquake records are Elcentro seismic wave and Tangshan seismic wave,then select an artificial simulated acceleration time history curve Lanzhou wave,observing the floor displacement and story drift in X direction of the three models under the three seismic waves.It is found that the weak position and the value of maximum interlayer displacement angle of the same model is different under different seismic waves,even if the time history curve we choose is from the same site category and classification of design earthquake,the seismic responses of the structure are also different.Using Pushover analysis gets the ATC-40 capacity spectrum diagram of the three models.We can find the anti-lateral capacity spectral curves of the three models increase monotonously with the increase of the spectral displacement in the frequent earthquakes.Observing the development of plastic hinge in the process of Pushover,It is found that the plastic hinge in the first model first appears in the narrow span,it shows that the model is weak in the narrow span,the braces in the second and third model effectively dissipate the seismic energy,they improve the stability of the structures.We still select Elcentro wave,Tangshan wave and Lanzhou wave,perform nonlinear time history analysis on the three models.We find that the maximum interlayer displacement angle of the first model exceeds the limit value of 1/50 in the seismatic code,the maximum interlayer displacement angles of the two models after layouting braces have decreased in varying degrees and have met the requirements of the seismatic code.Performing nonlinear time history analysis under rarely occurred earthquake on the three models,both the position and plastic deformation state of the plastic hinge all have significant difference with the situation in Pushover analysis.