Research On Mechanic Behavior Of UHPFRC Encased Steel Composite Member

As the height of super high-rise structures is getting higher and higher,the proportion of the structural self-weight that affects the structural design is getting larger and larger.In order to support the self-weight of the superstructure,the cross-sectional area of the columns at the bottom is getting larger.In order to reduce the section area of the component,the actual project uses high-strength concrete instead of traditional ordinary concrete.However,high-strength concrete has brought about a series of problems such as high requirements for the ratio of hoop,difficulty in lashing,high cost of construction,and difficulty in guaranteeing the quality of the pouring.In recent years,some scholars have added steel fibers to the cement matrix to suppress the bursting of high-strength concrete,thereby improving the deformation capacity of the concrete and achieving the full-section plastic stress distribution.Therefore,this paper proposes a new type of section steel-UHPFRC composite column cross-section.This combined structure uses ultra-high-strength concrete mixed with high-strength steel fibers to achieve ultrahigh ultimate load carrying capacity.The required stirrups ratio is low,and even stirrups are not required.At the same time,the section core is placed with steel to avoid sudden failure of the combined column and improve the ductility of the combined column after peak failure.1)Investigate the bond-slip performance of ultra-high-performance concrete and section steel,that is,study the problem of the combined effect of ultra-high-performance concrete and section steel,and conduct a section-shaped steel core push-out test on 12 section steel-ultra high-performance concrete columns.Test column failure mode,crack distribution,etc.Based on the collected load data,profile slip data,and profile strain data,the concrete types(general concrete,high-strength concrete,ultra-high-performance concrete),fiber content,anchor length,The influence of the lateral hooping rate and the thickness of the concrete protective layer on the bonding performance of the steel-concrete,the calculation method of the characteristic bonding strength of the steel-ultra-highperformance concrete,and the distribution mechanism of the bonding stress along the anchor length were explored.;2)The mechanical properties of the composite steel-ultra-highperformance concrete composite structure under axial compression are the most basic mechanical performance of the composite steel-ultra-high-performance concrete composite structure.The mechanical properties of this new composite structure can be initially verified.The ultra-high performance concrete composite column is subjected to an axial compression test to observe the failure mode,crack conditions,analysis of the collected load data,loading end displacement data,material strain data,etc.of the composite structural column during the test,and explore the type of concrete(ordinary concrete,High-strength concrete,ultrahigh-performance concrete),fiber content,and lateral coupling ratio on the axial compressive performance of steel ultra-high-performance concrete composite columns;...