Cyclic Pull-Out Push-In Shear-Lag Model for Post-installed Anchor-Infill Assembly

A cyclic piecewise linear shear-lag material model representing the local bond behavior of the post-installed anchor-infill assembly used for simulating its cyclic pull-out push-in response is presented. The anchor-infill assembly is such that used in various strengthening techniques to strengthen reinforced concrete structures. The properties of the infill material used for installing post-installed anchor-infill assembly are characterized by a nonlinear interface between the surrounding concrete and the anchor. A new type of anchor-infill assembly is introduced in which the infill material is divided into two layers for the purpose of providing a larger failure path length resulting in increase of the energy absorption capacity. The cyclic response is divided into two categories, namely the one with indentation and the one without indentation, where indentation represents concrete crushing at the base of drilled hole used for installing anchor bar. Each cycle is further subdivided into six paths of elastic loading followed by de-bonding in pull-out direction, unloading, reloading, de-bonding in push-in direction and unloading again. The stiffness degradation upon de-bonding and stiffness recovery upon reloading due to the lateral pressure effect and Poisson’s effect is incorporated in the form of stiffness and constant shear force update at the beginning of each loading path. Rules are formulated to plot the cyclic response, by a trial and error approach, to suit the presented material model. The sequential conceptual diagram showing the development of global cyclic load–displacement response of the anchor-infill assembly is also presented. Finally, the response of the anchor-infill assembly is plotted using thefinite element method under three different support conditions and comparisons are made with the results of numerical rules and good agreement is found. The effectiveness of the proposed two-layer model is also confirmed by comparing its cyclic pull-out push-in response with that of single-interface model, and it is found that the energy absorption capacity increases by 24 % and the failure path length increases by 80 %.