Experimental Research On Bond Properties Of Prefabricated Composite-sectioned Concrete Filled Steel Tubular With Bars

Prefabricated composite-sectioned concrete filled stainless steel tubular column is connected by grouting.After the column is installed,the superfine grouting material will be poured into the prefabricated hole and then assembled with another column,thereby a vertically continuous prefabricated composite-sectioned concrete filled stainless steel tubular column has been done.Prefabricated composite-sectioned concrete filled stainless steel tubular column has many advantages which it is the standard factory production,and itself is the formwork.It complies with the national policy which the development of the green buildings and the prefabricated building will be speeded up.As a new prefabricated structure,mechanical properties of prefabricated composite-sectioned concrete filled stainless steel tubular column need to be researched.The research content of this paper is the grouting and intercalation connection of prefabricated composite-sectioned concrete filled stainless steel tubular columns,and 24 sets of 196 steel bars were designed.The pull-out test was used to systematically study differences in the bonding and anchoring performance between anchor steel bars,and grouting materials and composite-sectioned concrete filled stainless steel tubular columns which have the different anchorage lengths,different diameters of steel bar,different strengths of concrete,different types of stiffening ribs,different forms and diameters of prefabricated holes,different grouting material strengths,different thicknesses of outer steel tube,and different sizes of inner steel tube.Analysis of the experimental results shows:(1)The larger the diameter of the steel bar,the greater the maximum tensile force it can withstand,but the average bond stress of steel bars of different diameters is basically the same.(2)When the performance of grouting material is better than that of concrete,the larger the preformed hole diameter is,the better the anchorage performance of the steel is.However,if the diameter of the preformed hole is sufficient,the diameter and form of the prefabricated hole will not affect the maximum tensile force and average bond stress of the steel reinforcement,however,the reinforcement in the spiral hole is better than the anchorage ductility of the round hole.(3)In the scope of this test,the strength of the concrete has little effect on the maximum tensile force of the steel bar,but the greater the concrete strength,the greater the average bond stress of the steel bar.(4)The shorter the anchorage length,the greater the average bond stress to the steel bars.(5)In the scope of this test,the form of stiffeners,the thickness of the outer steel tube,the size of the inner steel tube and the strength of the grouting material have little effect on the maximum tensile force and the average bond stress of the steel bar.And the stress mechanism of anchoring steel bars are analyzed,which could be divided into eights phases.At the same time,the distribution law of stress along the anchorage length and the distribution law of the bond stress along the anchorage length under different anchoring conditions were analyzed.The recommended value of the anchor bar and the diameter of prefabricated hole is given.