INFLUENCE OF SPECIMEN GEOMETRY ON ANCHOR BEHAVIOR IN SEISMIC CRACK MOVEMENT TESTS

It is generally acknowledged that one of the most critical test to capture the behavior of a post-installed fastener under seismic action is the so-called “seismic crack movement test”, which consists in applying a constant load to a single fastener installed in a crack subjected to opening and full closing cycles. The paper presents numerical simulations and experimental results of crack movement tests on large size post-installed anchors which show a strong influence of the geometry of the concrete specimen in which the anchor is installed. As first assessment, the intrinsic limit of applicability of a concrete specimen unable to allow a full theoretical development of a concrete cone is put in evidence. By comparing results of seismic crack movement tests using two different specimens, it is noticed how splitting force generated by the anchor affects the restoring of zero crack opening when increasing the number of cycles. Increasing the size of concrete element has a beneficial effect: the drift between crack opening measured at the top of concrete element and at the embedment depth is limited, limiting the effects of bending induced in the concrete specimen. Such difference also affects the anchor’s performance in residual pull–out test, where the possibility of developing a full concrete cone needs to be preserved while avoiding strut and tie mechanisms. To improve the regularity of the crack plane, a feedback control using the crack opening measure is used and discussed. The results are compared with systems using an open loop control.