Refined Simulation Research On Mechanical Properties Of Static And Dynamic Bond Between Corroded Steel Bars And Concrete

Sufficient bond strength between steel bars and concrete in the structure is the premise for the two materials to be stressed and deformed harmoniously.Studying the bond properties between steel bars and concrete is the basis for analyzing the mechanical properties of reinforced concrete structures and components.Reinforced concrete structures in corrosive environment tend to corrode during the service life,and the structures may also be subjected to extreme dynamic loads such as explosions and impacts.Such environmental corrosion and dynamic load effects will significantly change the bond properties between steel bars and concrete,including bond failure mode,bond strength and peak slip.In order to evaluate the bond performance and failure mechanism of the(rusted)ribbed steel bar-concrete bond interface,a refined simulation model and method that can reflect the(rusted)ribbed steel bar-concrete bond interface interaction was established in this thesis.On the basis of good agreement with the existing test results,the influence laws of restraint effect,strain rate effect and corrosion effect(corrosion level)on bond properties were systematically analyzed,and a bond stress-slip constitutive relationship model which can reflect the combined influence of corrosion and strain rate was established.The main research contents are summarized as follows:1.Considering the heterogeneity of concrete mesoscopic components,a threedimensional mesoscopic numerical model was established to study the cracking behavior of protective layer caused by non-uniform corrosion expansion of steel bar.The effects of corrosion mode,aggregate distribution position,bar diameter and thickness of concrete protective layer on the cracking and failure mechanism of protective layer were analyzed,and the distribution law of corrosion expansion pressure caused by corrosion of steel rebar was clarified.2.Combined with the geometric characteristics of the surface of ribbed rebar and the heterogeneity of mesoscopic components of concrete,and considering the friction and mechanical interaction between steel bar and concrete,a two-dimensional and a three-dimensional refined analysis model and method for the study of the bond performance between ribbed steel bar and concrete were established,and the influence laws and mechanisms of stirrup coefficient,protective layer thickness,rebar diameter,concrete strength grade and strain rate effect on the bond performance were revealed.3.Combined with the geometric characteristics of corroded steel bar,a two-stage refined numerical analysis model and method for analysis of the static and dynamic bond performance between corroded steel bar and concrete was established.The influence laws and mechanisms of corrosion level and strain rate were analyzed.The quantitative relationships between static/dynamic bond strength,peak slip and corrosion level and strain rate were obtained.The bond stress-slip constitutive relationships considering the combined effects of corrosion level and strain rate was established.4.Based on the established bond stress-slip relationship between corroded steel bar and concrete,taking the reinforced concrete column damaged by eccentric pressure as an example,the influence of corrosion on the mechanical properties of components was analyzed from the perspective of numerical simulation,and the accuracy and reliability of the proposed bond stress-slip model were verified.