1) Dr.-Ing., Professor, University of Applied Sciences Lübeck, Germany,


Supplementary injection anchors are used for transferring tensile-forces that cannot be transmitted by the masonry itself or for new connections. They basically consist of a tensile element – usually reinforcing steel or threaded rods – inserted into a slightly larger borehole and grouted with cement. The solid plug of injection material transfers the tensile forces. Assuming successful grouting, considerable tensile forces can be transferred at short bond lengths. Supplementary Injection Anchors have been utilized since the 1920s and are applied within a core philosophy of minimum intervention.

Design recommendations for injection anchors have been developed since 1998. The bond strength of injection anchors depends on the properties of the existing materials and the injection technology. If the anchors relate to structural safety, then field pull-out tests are required to ensure quality: Recent surveys from Auckland, New Zealand, revealed numerous cases where anchors between brick masonry and timber diaphragms have failed prematurely at the 2010/2011 earthquakes. Based on the results of about 650 pull-out tests in laboratory and in-situ in Karlsruhe and in Lübeck, the paper is investigating the performance of injection anchors inside masonry and the evaluation of bond strength in field pull-out tests.


Keywords: restoration, repair, injection anchor, performance, pull-out test, in-field test