Analysis Of Bearing Capacity And Deflection Of Circular-castellated Beams With I-shaped Cross Section

The opening of the web of castellated beam is weakened and its force is complex,which leads to the fact that the classical mechanics theory can not be applied completely in calculating.Scholars in various countries have carried out a great deal of research on the strength,stiffness and stability of castellated beams by means of experiments,theories and finite element methods,and some meaningful results have been obtained through the study.Some foreign countries have defined the design method of castellated beam in the specification.However,the development of castellated beams in China is relatively slow,and we have not incorporated the design method of castellated beams into specifications so far,which will seriously restrict the popularization and application of castellated beams in our country.Especially for the honeycomb beam,it is a kind of variable section flexural member with reasonable mechanical and economic benefits.But The study on the bearing capacity and deformation analysis of castellated beams is not mature enough.Therefore,it is of great significance to study the mechanical behavior and deformation characteristics of the castellated beams.In this paper,the numerical model of simple supported round hole castellated beam with different opening parameters and different load types is established,and the failure mechanism,ultimate bearing capacity,stress distribution and deformation characteristics of each model are mainly studied.Through the above numerical calculation,the following conclusions are obtained:(1)The hole edge of castellated beam is affected by the shear bending stress,and its stress is greater and plastic hinge is easier to form.Therefore,the stress at the edge of the hole should be calculated when designing.(2)The ultimate bearing capacity of castellated beam decreases with the increase of hole height ratio,but it is not obvious with the change of distance to height ratio.Therefore,considering the bearing capacity of the castellated beam and the ability to pass through the pipeline,it is suggested that the opening parameter of the castellated beam should be: the hole height ratio and the aspect ratio are controlled between 0.4 and 0.6,and the span depth ratio is greater than 20.(3)The opening of the web is weakened and the shear resistance of the web is reduced,which makes the shear deformation account for a great proportion of the total deflection.Therefore,it is impossible to calculate the castellated beam according to the deflection calculation of the traditional spandrel beam.(4)The deflection of castellated beams with high coefficient of hole ratio increases;decreases with increasing distance ratio,but the decline was not obvious;decreases with the increase of span,and when the span is more than 20,and gradually to the 1 smooth approximation.When the span of castellated beam is small,the deflection is mainly controlled by shear deformation.When the span is large,the deflection is controlled mainly by bending deformation.Therefore,it is recommended that the castellated beam be applied to the larger span of the building structure.(5)The simplified formula of deflection is deduced by practical calculation method of deflection.The calculation method considers the factors more comprehensively and the calculation results are close to the true deformation of the castellated beam.It is a simple and practical method of calculation.