| With the continuous acceleration of urban construction,high-rise and super-high-rise buildings in China are showing a blowout development,and concrete-filled steel tubes are widely used in high-rise buildings as an excellent structural system.The continuous improvement of building height and span will make ordinary concrete-filled steel tube members unable to meet the structural system bearing capacity and related performance design requirements.Therefore,scholars from various countries meet the needs of actual projects by arranging steel structures with different composite-sectional forms in steel tubes to form composite steel tube concrete structures with steel distribution.However,if the cross-section steel distribution form is too complicated,there will often be practical problems such as difficulty in pouring and vibrating,and the quality of engineering cannot be guaranteed.The emergence of self-compacting concrete fundamentally solves this engineering and technical problem,which makes the steel tube concrete structure with composite steel distribution have good application prospects.This thesis relies on the China Resources East Super High-rise Project(Guangxi’s tallest building,403 meters),and chose to distribute C60 super high-rise self-compacting concrete at the same time.Based on the advantage that self-compacting concrete is not affected by the complexity of the section,the axial experiment of 33 composite steel self-reinforced concrete composite column specimens(24 square steel tube specimens and 9 circular steel tube specimens)was designed and accomplished,the destruction process of each specimen in the axial experiment and the destruction form after loading were observed,the load-displacement curve of each specimen was obtained.The influence of various design parameters((steel form;aspect ratio;steel pipe wall thickness;steel ratio)on the mechanical properties such as ultimate bearing capacity,peak displacement,initial stiffness,ductility and dissipation of the specimen is analyzed.The test results show that the ultra-high pumping high-strength self-secret concrete used in experiment has great operating performance,the compactness is well.In the three-layer composite steel distribution form,specimens the steel ratio is17.9% and section combines square steel tube 、 circular steel tube and I beam has the best performance.In the double-layer composite steel distribution form,specimens the steel ratio is9.3%and section combines square steel tube 、 circular steel tube has the best performance.And with the increase of the wall thickness of the circular steel tube,the ultimate bearing capacity,initial axial compression stiffness and ductility of the specimens in the form of composite steel are significantly improved.The load capacity of the specimen combined square steel tube andspiral rib may decrease sharply during the loading process,and the ductility is worse,so attention should be paid to the actual engineering application.Based on the experiment value,a new type of axial bearing capacity formula of axial performance of self-compacting concrete composite column with composite-sectioned steel was derived by referring to the specification and the previous experiment results of the research group.The results show that:Among all three formulas,the calculated value of bearing capacity based on the calculation formula of "arch effect" constraint of bearing is the most coincident with the experimental value.The calculation methods based on the calculation formula of the steel reinforcement constraint combination are all based on the existing specifications.The calculation is more convenient when applied in actual engineering. |
