Experimental Study On The Bonding Performance Of Non-standard Coated Steel Bars And Concrete

The non-standard coated steel bar is a new type of steel bar developed by the Institute of Metal Research of the Chinese Academy of Sciences for marine corrosion environments.The non-standard steel bar uses a method of heightening the rib to increase the bite area of the steel bar and the concrete,thereby making up for the increase in the traditional standard steel bar.After oxygen coating,the friction resistance and adsorption force are reduced.The coating on the surface of the non-standard coated steel bar can well separate the steel bar from the external environment,so it has very good corrosion resistance and is suitable for heavy corrosion environments such as the ocean.In addition,the non-standard coated steel bar also has an excellent comprehensive Performance and energy saving and environmental protection,in the 21 st century,the rapid development of the construction industry has a very large application prospect.As a new type of steel bar,whether the bonding and anchoring performance of non-standard coated steel bar and concrete can guarantee the cooperative work of steel bar and concrete has become a key question for its application in engineering.Based on the central drawing method,an experimental study on the bonding performance of non-standard coated steel bars and concrete,as well as the bonding strength and bonding reliability of steel bars was carried out.According to the test method standards or test procedures related to the central drawing method,45 non-standard steel central drawing test pieces and 36 ordinary steel comparison test pieces were designed,from the bonding mechanism,bonding stress distribution,and affecting bonding.The main factors of performance,anchoring reliability analysis and other aspects were tested and compared,and the anchorage performance of non-standard coated steel bars and ordinary steel bars and concrete was compared and analyzed.The influences of steel bar diameter,protective layer thickness,concrete strength,anchoring length and other factors on the anchorage performance of non-standard coating and concrete were studied.The results show that within a certain range,the bonding limit load of the steel bar increases with the thickness of the concrete protective layer of the test piece;the larger the diameter of the steel bar,the larger the bonding limit load of the steel bar and the smaller the bonding strength;When the strength of concrete is increased,the bond strength of non-standard coated steel bars and concrete increases,and the degree of violent destruction of the specimen increases;as the bond length increases,the splitting strength and bond strength increase first and then Decreasing trend.Based on the statistical analysis of the pull-out test results,a calculation formula for the bond strength of non-standard coated steel bars and concrete was proposed,and the reliability analysis was carried out using the center point method.Anchor length calculation formula.The method of making pull-out test pieces through the method of affixing strain gauges in the grooves of the steel bars was tested,and the strain changes of the steel bars at different anchoring positions during the loading process were measured to obtain stress distribution data,and the local adhesion of non-standard coated steel bars and concrete was studied Junction performance,bonding stress distribution,and the basic relationship between bonding stress and slip.The research shows that within the range of anchoring length,the non-standard coated steel bars have uneven strain components,and two peaks appear near the loading end and the free end.The basic relationship between bond stress and slip presents a cubic function change law.To reflect the influence of slip and anchorage position,the bond-slip constitutive relationship can be described as the bond-slip basic relationship function Φ(s)and the position function φ(x)in the form τ(s,x)=Φ(s)φ(x).