Research On Mechanical Behavior And Design Method Of Slanted Column Supporting Conjoined Structure

With the development of construction techniques and design methods,Slanted column transformation has been commomly used in both high-rise buildings and largespan space structures.The supporting oblique column arranged under the conjoined structure can bridge large barriers such as rivers and highways.Besides,this kind of structure has a clear load path and evenly distributed stiffness.So the slanted column supporting conjoined structure has a good outfit and is subject to a reasonable structure form.At present,there are many researches and applications on the structure of the slanted column.However,few researches and application have been conducted on the slanted column supporting the connected structure.In this paper,the typical representative π-shaped slant-column-beam substructure was extracted from various types of oblique column conversion structures.After figuring out the mechanical properties of the substructure,the substructure was then substituted into the slanted column supporting conjoinde structure.By changing the key parameters,the mechanical behaviour of the overall structure when was studied.Finally,the characteristics of the performance of the structure are summarized and design suggestions were proposed..The main work is as follows:1.The calculation diagram of the slanted column was extracted from the π-shaped substructure.According to the force balance condition of the joint and the lateral stiffness of the column calculated by the D method,a formula calculating the vertical and horizontal displacement of the slanted column under the vertical load was derived.Thus,the vertical stiffness of the slanted column and the horizontal force on the surrounding structure can be calculated.Compared with the results of finite element analysis,the formula can be applied to the slanted column angle range up to 40 ° ~ 125 °,and the calculation error is less than 8%.2.Regarding the force balance of the joints and the deformation of the surrounding members,the formula for calculating the lateral stiffness is reasoned.Then the expression of the correction coefficient of the anti-side stiffness of the slanted column was obtained by numerical fitting.Combining the formula with the coefficient,the lateral stiffness of the column of which slanted inclined angle within 40°~125° can be calculated,and the calculation error is less than within 10% in the normal structure.3.Through the displacement method and the equilibrium method,the lateral elastic buckling equation and the buckling equation without lateral displacement with π-shaped substructure under concentrated vertical load were derived.Then based on the negative stiffness theory,the calculation formula of the lateral elastic buckling load of the slanted column was derived,and the calculation formula of the calculated length coefficient of the slanted column with lateral displacement instability was derived;there is the formula for calculating the length coefficient when the vertical column is not laterally unstable in the code.Some parameters in the formula have been amended,and the length coefficient formula of the beam in the π-shaped substructure was obtained which is under the action of concentrated load,and then the elastic buckling load of the π-shaped substructure without lateral displacement was found.4.Under vertical load,the apex of the slanted column is going to exert relative horizontal displacement and relative vertical displacement upon the surrounding members,and then the secondary internal force is generated between the surrounding members and the inclined column.The smaller the slanted angle,the number of layers,the slanted column and the intermediate beam,the larger the secondary internal force generated by the apex of the slanted column to the surrounding members.5.The lateral stiffness of the slanted column is related not only to the characteristics of the members such as the inclination angle,the height of the slanted column and the cross-section of the slanted column,but also closely related to the peripheral members such as the line stiffness of the column at the top of beam,the number of upper floors,the line rigidity of the upper floor beam,and the line rigidity of the upper column.The lateral stiffness of the slanted column decreases with the increase of the line stiffness of the upper column,and increases with the increase of other parameters refeered ahead;and the smaller of the inclination angle(the angle with the horizontal plane),the faster of the lateral stiffness of the slanted column increases.Therefore,there is generally no weak layer due to the inclined arrangement of the layered columns.And it is recommended that the layered columns be arranged slantedly in both the x and y directions to enhance the seismic resistance and torsion resistance of the structure.6.The lateral stiffness of the inclined column is composed of three parts: the first part is the bending rigidity of the slanted column itself,the second part is the horizontal component of the axial force of the slanted column,and the third part is horizontal force produced by the rotation of the top end of the slanted column.The three factors of the slanted column crossing layer number,the inclination angle and the upper connected layer number will affect the axial force of the slanted column to affect the lateral stiffness of the slanted column.When slightly slanted(60°<α<120°),the lateral stiffness of the slanted column generally increases by 50%~200% compared with the straight column;and when the slanted column passes through multiple layers,the inclination angle is small(α<60°)and the number of upper conjoined layers are big,the anti-side stiffness of the inclined column may increase several times to ten times or more with respect to the straight column,and the ratio the lateral stiffness of the slanted column accounts for the total side stiffness is also increased.Therefore,when the earthquake happen,the shear force distributed to the inclined column according to the stiffness also increases synchronously.If necessary,the end of the inclined column can be hinged or even a damper can be added or weaken the rigidity of the beam on the upper floor,thereby controlling the seismic shear force of the slanted column within a reasonable range.7.Under the uniform vertical load,parametric analysis of the stability performance of the inclined column supporting conjoined structure were conducted.The results show that: the symmetric inclined arrangement of the penetrating column is beneficial to improve the stability bearing capacity of the structure;the overall instability problem of the inclined column connected structure under the uniform vertical load is not prominent.Usually,the stability of the structure can be checked by checking the local components.8.Compared with the conversion form of the big beam conversion,the truss conversion,the hollow truss conversion,the span advantage of the inclined column is obvious,the seismic stiffness is distributed uniformly,the material utilization is sufficient,,so the inclined column should be preferred.