Numerical Investigation Into Prestressed Stayed Steel Box Section Columns Under Eccentric Loading

As a basic component of prestressed steel structure,prestressed stayed steel column can significantly enhance the bearing capacity of ordinary slender columns under compression.In addition,the slender stay also makes the components lightweight and beautiful,enriching the architectural performance of ordinary compression columns.However,in the past,when prestressed stayed steel columns were studied or applied,the cross-sections of steel columns and crossarms were mostly circular.In fact,the box cross-sections also met the stability of symmetry and the principal axis direction of the cross-section,and were easy to connect with other members.In this paper,the overall stability of box-section prestressed stayed steel columns under eccentric compression is studied by theoretical analysis and the numerical analysis method that verified by model tests.Firstly,this paper has summarized the theoretical analysis methods,test methods and results of typical prestressed stayed steel columns,and verifies the correctness of the finite element simulation method used mostly in this paper.On this basis,through a large number of ABAQUS finite element simulation calculations,the stability performance of eccentrically loaded prestressed stayed steel box section columns with single-layer and double-layer crossarms is analyzed,and the effects of eccentricity,slenderness ratio,initial prestress,the initial geometric imperfection,stay stiffness and transverse crossarm stiffness on the bearing capacity of prestressed stayed column are discussed,and the factors affecting the stability bearing capacity of eccentrically loaded prestressed stayed column are obtained.The qualitative analysis results show the difference of stability bearing capacity between axially compressed and eccentrically compressed prestressed stayed column.At the same time,the reduction factor of ultimate bearing capacity of eccentricity,slenderness ratio and ratio of crossarm length to column length is proposed to quantify the reduction ratio of bearing capacity under eccentric compression to that under axial compression,which can provide reference for future engineering design and application.The main results are as follows:In this paper,it is found that the bearing capacity of axially and eccentrically loaded steel columns is significantly increased by the introduction of crossarms and prestressed stays.The bearing capacity of eccentrically loaded single-layer prestressed stayed column increases with the increase of initial prestress,but the post-buckling behavior tends to be unstable due to the larger initial prestress.Compared with the state of axial compression,the bearing capacity of eccentrically loaded prestressed stayed column is more sensitive to the change of initial prestress.Single-layer prestressed stayed column are more sensitive to initial imperfections,and the bearing capacity of prestressed stayed column decreases with the increase of initial geometric imperfections.The relationship curve between ultimate bearing capacity and initial imperfection decreases linearly.When eccentricity increases from 0 to 0.5,the change rate of ultimate load value is faster,and the change rate of ultimate load value is slower when eccentricity is greater than 0.5.Increasing load eccentricity and slenderness ratio will decrease the bearing capacity,and the ultimate bearing capacity will decrease linearly with the increase of eccentricity and slenderness ratio.There are essential differences between the influence of the length of crossarm and the diameter of stay on the stability of eccentrically loaded prestressed stayed column and that of axially loaded steel columns.For axially loaded prestressed stayed column,when the critical buckling mode is anti-symmetric,the effect of increasing the length of crossarm and diameter of stay on the buckling load and strength is very weak;for eccentrically loaded prestressed stayed column,even if the anti-symmetric buckling occurs,the buckling strength can be enhanced by increasing the length of crossarm and diameter of stay.The factors affecting the bearing capacity of eccentrically loaded double-layer prestressed stayed steel box section columns are analyzed.These factors include load eccentricity,crossarm length,stay diameter,etc.The results show that the increase of load eccentricity decreases the bearing capacity of double-layer prestressed stayed column,while the increase of the length of crossarms and the diameter of stays will enhance the bearing capacity of prestressed stayed column,which is affected by eccentricity and compressive state.For axially compressed double-layer prestressed stayed column,when the length of crossarm and diameter of stay are small,the symmetrical mode buckling of the prestressed stayed column occurs.Increasing the length or diameter of the crossarm can greatly increase the bearing capacity,but when the anti-symmetrical mode buckling occurs,the increase of the length of crossarm and diameter of stay has no significant effect on the bearing capacity.For eccentrically loaded double-layer prestressed stayed column,even if the anti-symmetric modal buckling occurs,the effect of the length of crossarm and diameter of stay on improving the bearing capacity can not be ignored.Based on the analysis of factors affecting the bearing capacity of single-layer and double-layer prestressed stayed steel box section columns under eccentric compression,the formula for calculating the reduction factor of bearing capacity considering the influence of eccentric load is fitted.It can be used to estimate the ultimate bearing capacity reduction factor of eccentrically loaded prestressed stayed column compared with axially loaded columns when the ratio of length of crossarms to column length a/L,slenderness ratio and load eccentricity are given.The empirical calculation shows that the fitting formula is accurate and can be used as a reference for the design of eccentrically loadedprestressed stayed steel box section columns.In this paper,finite element numerical simulation is used to study the stability of single-layer and double-layer prestressed stayed steel box section columns.The effects of eccentricity,slenderness ratio,initial prestress,the initial geometric imperfection,stay stiffness and crossarm stiffness on the stability of eccentrically loaded prestressed stayed column are analyzed,and the reduction factor of bearing capacity considering the influence of eccentric load is proposed.The research results can provide reference for engineering design and practical application of prestressed stayed steel columns.