| High strength steel has been widely applied in large span or space strutures because of its natural good performance,such as light weight,high strength,better plasticity and toughness.However,high strength steel has the inherent disadvantage compared with ordinary strength steel,such as the reduction of the yield platform,the yield point is not obvious,the yield-strength ratio is too high and so on,making high strength steel difficult to play a role in the structural ductility design.Ductility is a very important evaluation index for flexural members.The current seismic design specification stipulates that the structure should have enough deformation ability to consume seismic energy under the rare earthquakes,that is,the components or the structures must have some ductility to resist the impact of strong loads such as earthquakes.Normally,the ductility of flexural members is mainly expressed by the rotational capacity.Factors affect the rotational capacity of the bending members are the cross-sectional dimensions,slenderness of plates,arrangement of supporting,the loading method and the mechanical properties of material.In this paper,the rotational capacity and the ultimate capacity of the high strength steel H-shaped flexural members with nominal yield strength of 690 MPa are the main subjects.With sufficient lateral support,a total of 10 high-strength steel H-section beams will be tested to inelastic failure under the action of a concentrated force in the mid-span.The cross-section design of the components takes into account the design methods of the steel structure in the United States and the Europe for the division of section sections to study the bending behavior and rotational capacity of different section types.The rotation capacity is expressed by the end rotaion of beam,in this paper,three methods were used to measure these angles during test.Additionally,the Digital Speckle Correlation Method(DSCM)was adopted,and the local buckling of the whole web was photoed.After analysis,the starting point and the extension range of the local buckling of web in the middle span were further reflected.In order to understand the local buckling characteristics of the compressed flange during bending,strain gauges were pasted at the appropriate locations to get the curvature variation of the flange.At the same time,a three-dimensional finite element model based on ABAQUS was established,considering the measured stress-strain relationship and initial defects of components(initial eccentricity and initial bending).The results of the finite element analysis are in good agreement with the results of test.Based on the finite element model,cross-sectional dimensions,slenderness of the specimen and the slenderness of flange and web are studied to obtain the influence of those parameters on the flexural capacity and rotational capacity on high strength steel members.Finally,the results of test and finite elemental analysis are compared to the calculation results of the Chinese specification GB50017-2003(2003),AISC 360-10(2010),AASHTO LRFD(2004)and EC3(2005).The comparison results showed that the limit of the regular slenderness of flange and web should be controlled by 9 and 50,which can make the rotation capacity of the flexural members exceed the international standard 3.0.The innovations of this paper are as follows:(1)The bending resistance and rotation capacity of welded H-beam of high strength Q690 steel under concentrated load and lateral support were investigated through experiments;(2)The specific parameters influencing ductility of Q690 high strength steel beam are obtained through experimental investigation,the degree of their influence were also included;(3)The limit values of flange width and web width ratio for the development of Q690 high strength steel beam ductility have been put forward in this paper. |
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