| The current castellated beams have a single row of holes in the web.In large-size castellated beams,setting a single row of holes will make the hole size larger,causing the members to resist shear.The bearing capacity drops more,and the web around the hole is more prone to instability.Therefore,this article will propose a castellated beam with double rows of holes on the web.Compared with the traditional single-row castellated beams on the web,the section height is further increased,which plays a significant role in improving the moment of inertia in the section height direction of the member.It can make full use of material properties and save steel.The upper and lower double rows of holes on the web are convenient for piping.Classification management.As castellated beams have been widely used,more in-depth research has been carried out on castellated beams at domestic and abroad.The double-row castellated beam proposed in this thesis is a new type of improvement and attempt for castellated beams.For the related research,this article refers to the research method of single-row castellated beams to study the mechanical properties of double-row castellated beams under pure bending.This thesis studies the difference and connection of the stress process and failure form of the double-row castellated beam,the equivalent single-row castellated beam and the solid web beam.It also studies the cross-sectional stress distribution and development of the three,the development process of elastic plastic strain,and the bearing of the three.The difference in capacity,the bearing capacity of the double-row-hole castellated beam,the force process,the failure form,and the change law of equivalent bending stiffness under different design parameters,and the relevant design parameter value suggestions are given.The calculation formula for the bending deflection of the single-row castellated beam is given to evaluate the accuracy of the calculation of the bending deflection of the double-row castellated beam,and combined with numerical simulation,a simplified calculation formula for the deflection of the double-row castellated beam suitable for engineering is given.The research results show that compared with the single-row castellated beams with the same expansion ratio,the two-row castellated beams are basically the same in the stress process and failure mode.There is a certain reduction in the rigidity of the double-row castellated beams,but The ultimate bearing capacity has been improved to a certain extent,and the double-row hole castellated beam can effectively alleviate the stress concentration at the foot of the hexagonal hole.Through the finite element numerical simulation of the double-row castellated beam under different design parameters,it is concluded that:(1)As the opening rate increases,its bending stiffness and ultimate bearing capacity show a significant downward trend,when the opening rate reaches 75%When the web produces a large buckling deformation,the opening ratio should be between 60%and 70%in comprehensive consideration;(2)With the decrease of the web height-to-thickness ratio,the flexural rigidity of the castellated beam shows an upward trend,and its relative The change of the ultimate bearing capacity of solid web beams is not obvious,but the buckling deformation of the web is obviously relieved.Therefore,comprehensive consideration is given to controlling the height-to-thickness ratio of the web to not less than 100;(3)With the increase in the spacing between the upper and lower rows of the web,the The flexural rigidity and ultimate bearing capacity both show a downward trend.For double-row castellated beams,the ratio S/H between the upper and lower rows of holes S and the beam height H should not be less than 1/20.The theoretical calculation formula for the deflection of the single-row castellated beam still has high accuracy when calculating the bending deflection of the double-row castellated beam.The calculation formula for the deflection of the double-row castellated beam combining the finite element method and the practical estimation method is proposed in this thesis.The calculation method is relatively simple and can be applied to engineering practice. |
