Buckling Capacity Analysis Of Axially Compressed Prestressed Stayed Steel Columns With Additional Stay Systems

China is in the period of rapid development of modernization and urbanization.With the development of society and the continuous innovation of science and technology,the form requirements of structure in building engineering are becoming more and more diversified.The prestressed steel structure system using steel as the main building material is widely used in modern construction engineering due to its characteristics such as good rigidity and toughness,convenient construction,material saving,rich modeling,and beautiful and novel forms.Prestressed stayed steel columns are the basic components of a class of prestressed steel structures.They conform to the new construction concept of"low-carbon economy"and"green building"advocated at the same time.Has received extensive attention and research.In this paper,a new type of additional stay prestressed crossarm steel column with pre-stressed stays laid between the strut layers is taken as the research object.Firstly,the common form,working principle,stability theory and finite element analysis method of prestressed stayed steel column are introduced,and the feasibility of the finite element analysis method used in this paper is verified by the comparison of the experimental results and the finite element analysis.On this basis,the ABAQUS finite element analysis was used to study the overall stability performance of the prestressed steel column system with additional stays under different connection methods of the crossarm and the central column.The effects of different factors such as strut length,stay diameter,initial prestressing level,and initial defects on the bearing capacity of the prestressed stayed steel column with additional stay systems were discussed.An optimal stay arrangement scheme for this type of prestressed stayed steel column with additional stay systems is given,and the theoretical optimal initial prestress calculation method for the plane prestressed stayed steel column with additional stay systems is derived based on the minimum deformation assumption,with a view to designing such structures provide evidence.Firstly,the critical load and buckling modes of the structure are analyzed.The Prestressed stayed steel column usually has two forms:symmetric buckling mode and antisymmetric buckling mode.The first-order buckling modes of the prestressed stayed steel column with additional stay systems are all symmetrical buckling modes.When the crossarm length is small or the stay diameter is small,the buckling mode of the structure is mode1,and as the stay diameter and the length of the crossarm increase,the buckling mode of the structure gradually changes from mode1 to mode3.When the stay diameter is small,the effect of increasing the length of the crossarm on the critical buckling load of the structure is obvious;as the stay diameter increases,increasing the length of the crossarm can increase the critical buckling load of the structure first and then decrease.The magnitude of the increase also gradually decreased.When the stay diameter reaches8.0mm,increasing the length of the crossarm does not effectively increase the critical buckling load of the structure,and even reduces the critical buckling load of the structure slightly.In addition,it is found through research that such structures can ignore the role of related buckling in buckling analysis.The influence of the prestressed stayed steel column with additional stay systems on the stability of the structure when the diameter of the stay and the length of the crossarm are changed is analyzed.Increasing the crossarm length and stay diameter has no effect on the initial stiffness of the structure,but it will affect the post-buckling stiffness of the structure.The larger the stay diameter,the greater the impact.When the stay diameter is fixed,the ultimate bearing capacity of the structure can be increased by increasing the strut length,but the effect is more significant when the ratio of crossarm length to central column is less than 0.1.When the ratio of crossarm length to central column is greater than 0.1,the effect of increasing crossarm length on the ultimate bearing capacity of the structure becomes smaller.The larger the stay diameter is,the lower the lifting effect of increasing brace on the ultimate bearing capacity is.In addition,the longer the crossarm,the larger the corresponding axial compression displacement and the larger the deformation degree.When the crossarm is short,increasing the stay diameter can significantly improve the buckling load of the structure,and when the strut is long,increasing the stay diameter can also improve the bearing capacity of the structure,but the lifting range is reduced.The increase of stay diameter and crossarm length has more effect on the bearing capacity of rigid connection structure than that of hinged connection structure.The initial prestressing levels of the structure in the two connection methods were studied.The bearing capacity of the prestressed stayed steel column with additional stay systems increases with the increase of the initial prestress.When the stay diameter is small,the initial prestress level has a small effect on the stiffness of the structure.As the stay diameter increases,the effect of the initial prestress on the stiffness of the structure gradually increases,especially the initial stiffness of the structure.In contrast,the post-buckling performance of prestressed steel columns with crossarm hinges is more sensitive to the magnitude of the initial prestress value,but when the crossarm hinges or rigid with the column,the initial prestress value affects the initial stiffness of the structure the same.Increasing the initial prestressing force can improve the bearing capacity of the structure,but an excessively high initial prestressing level will have a negative effect on the structure.In most cases,when T_i/T_opt reaches 7 initial prestress value,the lifting effect on the bearing capacity of the structure begins to decrease.The initial imperfection of the structure in the two connection modes were studied.The initial flaw value does not affect the initial stiffness of the structure.In contrast,the post-buckling performance of prestressed steel columns hinged with crossarm is more sensitive to the size of initial imperfection.When the initial imperfection value is changed from L/200 to L/1000,the reduction of the initial imperfection value significantly improves the ultimate bearing capacity of the prestressed stayed steel column.After the initial imperfection value is less than L/1000,the ultimate bearing capacity of the prestressed stayed steel column increases and decreases,which indicates that the larger the stay diameter in the post-buckling stage,the smaller the initial imperfection value,and the faster the load decreases with the axial displacement.At the same time,the optimization of the stay diameter of such structures is discussed.When the stay diameter of the prestressed stayed steel column with additional stay is small,it is not necessary to change the stay diameter of the structure,but the bearing capacity of the structure can be increased by appropriately increasing the diameter of the stay between the crossarm layers.The increase of the stay diameter should not exceed the original stay diameter.Twice.When the structure stay diameter is moderate,the material can be fully utilized without changing the stay diameter.When the diameter of the structure stay is large,the diameter of the stay laid between the strut layers can be appropriately reduced,which can ensure the sufficient bearing capacity of the structure and save the amount of material.This paper provides a reference for the design of prestressed stayed steel column with additional stay systems.