Investigations On Local Buckling And Nonlinear Deformation Behaviour Of Welded Stainless Steel I-section Flexural Members

In view of the remarkable corrosion resistance,durability and favourable architectural appearance,the introduction of stainless steel structures can provide a fundamental solution to the corrosion problem of ordinary carbon steel structures in the structural material level,which has raised their promising prospect in structural applications.However,the material properties of stainless steels differ significantly from those of carbon steels,and hence the existing design methods for carbon steel structures may not be directly applied to stainless steel structures.The local buckling and nonlinear deformation behaviour of welded stainless steel I-section flexural members have been extensively investigated in this dissertation by means of experimental testing,numerical modelling and analytical analysis,based on which novel design methods have been proposed.The following research work has been conducted in this dissertation:(1)A total of 126 tensile and compressive coupon tests on both austenitic grade S30408 and duplex grade S22253 were carried out to determine the material properties and to obtain the full stress–strain curves.Two advanced measuring techniques were employed to acquire initial local geometric imperfections of the beam test specimens.(2)A series of experimental tests were conducted to explore the local buckling behaviour of welded stainless steel plate girders,including seven shear buckling tests on plate girders with transverse stiffeners,two shear buckling tests on plate girders reinforced with diagonal stiffeners,six tests on plate girders subjected to combined bending moment and shear force,and five other tests on stainless steel plate girders with both transverse and longitudinal stiffeners under combined bending and shear.The critical buckling stresses,the ultimate resistances and the post-peak response were recorded and carefully analysed.(3)The experimental programme was complemented by parallel numerical investigations.Elaborate finite element(FE)models,capable of accurately predicting the local buckling behaviour of stainless steel plate girders under various loading conditions,were developed by means of the FE software package ABAQUS and were validated against the test results.The web buckling mechanism under shear and combined bending and shear was separately studied.The influences of transverse stiffeners,diagonal stiffeners and longitudinal stiffeners were all explored.Subsequent systematic studies on key parameters for the web buckling behaviour were conducted.The existing design methods for predicting web buckling resistances were evaluated,and new design proposals were provided for stainless steel plate girders.The reliability of the newly proposed design methods was further verified by statistical reliability analysis.(4)Five welded stainless steel I-section simply supported beams and five continuous beams were tested to failure subjected to three-point and five-point bending condition,respectively.The load versus deflection relationships for both simply supported and continuous beams were recorded and analysed.Advanced FE models were developed by taking into account the material non-linearity,initial geometric imperfections and welding residual stresses,and were validated against the experimental results afterwards.Upon the validated numerical models,the existing methods for calculating nonlinear deflections of stainless steel beams were evaluated,and newly revised calculation formulae were developed for predicting the deflections of welded stainless steel I-section beams.