Study On Flexural Behavior Of Double-web Open-hole Inner-rolled Castellated Beam

With the continuous development of steel structure form and technology,the use of largespan structures and high-rise buildings is gradually increasing,and the advantages of castellated components in the construction industry are gradually reflected due to their light weight and the ability to cross pipelines in the holes,In this thesis,a new component form,double web perforated castellated Beam with inner curling edge,is proposed.Its structure is exquisite.In addition to maintaining the original advantages of castellated Beam,curling edge forms a regular circular constraint boundary in the web,which can improve the bearing capacity of the web.Under the condition that the web height does not change,the thin web can still ensure the local stability,So as to obtain greater economic benefits.The web will produce shear,bending moment and shear secondary bending moment when the web perforated with inner crimping castellated Beam is under load,which will lead to a more complex stress state and failure mode.In the current standard,there is no clear provision for the design of Web perforated with inner crimping castellated Beam,so it is necessary to carry out research on its mechanical performance and failure mode.In this thesis,the ABAQUS finite element simulation software is used to establish the model of ignoring the geometric initial defects.By changing the hole angular curvature,inner hem width,web thickness,opening rate and other influencing factors,the failure mechanism and bearing capacity of the mid span pure bending section of double web castellated Beam with inner hem under the concentrated load of the third equinox are studied.It is found that the bending capacity of castellated Beam with inner crimping is higher than that of ordinary castellated Beam in pure bending state.Crimping can improve the bending capacity of castellated Beam,and improve the stability of castellated Beam bridge and web at pier;The results show that when the hole angle curvature parameter is changed more than 20 mm,the stress results of the model are similar,the bearing capacity changes little,and the distribution of the maximum stress points is the same;The results show that the width of inner hem has a certain influence on the stiffness.The larger the width of inner hem is,the smaller the deflection is,but the yield strength is similar and the failure mode is the same.All of them occur in the plane.When the width of inner hem is 40 mm,the stress of the member is reasonable;The ratio of web height to thickness and the opening ratio have great influence on the flexural performance of castellated Beams with double web openings and inner crimping.By extracting the load displacement curve of castellated Beam with double web openings and inner crimping,it is found that when the web height to thickness ratio is large,the yield load and ultimate load are low.When the web height to thickness ratio is greater than 80,the bridge instability is easy to occur,and the bearing capacity is better when the web height to thickness ratio is small;When the opening ratio is larger,the yield load and ultimate load are both smaller.When the opening ratio exceeds 0.6,the web bridge is prone to buckling failure.When the opening ratio is 0.47,it shows good bending performance.The curve has a certain decline after reaching the ultimate load.According to the finite element analysis results,the correction coefficient K is introduced to establish the spatial relationship surface between it and web height thickness ratio and opening ratio,The calculation formula of flexural strength and bearing capacity of castellated Beam with double web openings and inner crimping is fitted,and the accuracy of the formula is verified by comparing the finite element results with the data obtained from the calculation formula.By analyzing the failure modes of the cellular beam with crimping under different parameters,it can be found that the structural form of crimping can change the stress level of the web between the holes,the stress distribution at the corner of the hole can be transferred to the inner crimping,which can effectively improve the deficiency of the larger stress at the corner of the hole in the traditional cellular beam,and the strength failure occurs when the member bears the bending force,When the opening ratio is large in a certain range,the deformation of the member is better and the ultimate bearing capacity is improved.In this thesis,a better structural form of castellated Beam with inner crimping is given,and a high-precision calculation formula of bending capacity is proposed,which provides the basis for the subsequent research of castellated Beam with inner crimping and the design basis for the application of castellated Beam with inner crimping in real life.