Study On Local Stability And Ultimate Bearing Capacity Of Hybrid Castellated Beams

As a new form of steel beam,the hybrid castellated beam not only has good economic performance and the advantages of light weight like castellated beams but also can make full use of the material like hybrid beams.It makes the stress of steel girders more reasonable and economic.This paper launched a test and finite element study on the local stability and ultimate bearing capacity of the hybrid castellated beam in various combinations of steel plates.The p test of 9 full-size hybrid castellated beams was studied.The influence factors such as the ratio of web thickness to thickness,flange width to thickness ratio,hole height ratio and combination of steel numbers were considered.Combined with numerical simulation,the failure morphology,buckling position and bearing capacity of the test beam were analyzed.The results show that when the lateral bracing is enough,the castellated beams are prone to local buckling;the local buckling of each component generally occurs at the beam bridge above the hole and shows a sinusoidal waveform distribution and the wavelength is the length of a hole unit and the number of waves is equal to the number of holes.The hybrid castellated beam with direct-hole is recommended to use the combination of upper flange reinforcement and upper flange and web reinforcement;the hybrid castellated beam by dislocation welding is recommended to use up-stronger and down-weaker combinations.However both are not recommended to combine across two steel grades.In order to study the bending buckling coefficient and the mutual restraining effect of the castellated beam‘s flange and web,finite element analysis was performed on 291 castellated beams.Based on thin plate theory and finite element analysis,formulas for calculation of the flanges and webs buckling coefficients of castellated beams with hexagonal holes under pure bending are formulated and the limit formulas of the ratio of height to thickness of the web of web beams and the ratio of the width to the thickness of the flanges are given;a coefficient method for judging the buckling order of the honeycomb beam flange and web is proposed,which is helpful to control the critical parts in advance;based on the calculation of the bearing capacity of the same kind of steel honeycomb beam,the buckling load of the mixed steel honeycomb beam is calculated.The formula of ultimate bearing capacity and meets the accuracy requirements can be applied in practice.