Design Recommendations For Injection Anchors As Supplementary Reinforcement Of Historic Masonry


A research project at Karlsruhe University has been investigating the loadbearing characteristics of supplementary injection anchors as a repair method in historic masonry.  Such anchors are necessary for carrying tensile forces, or for new connections.  They basically consist of a tensile element, usually steel, inserted into the slightly larger borehole, and the annulus is grouted with cement. The solid plug of injection material transfers the tensile forces to the masonry.  Because of the present lack of codes dealing with admissible bond stresses, there is an uncertainty in the design of injection anchors.  Complementary standards for concrete should not be applied unless they are considerably reduced.  If the anchors relate  to structural safety, then field pull-out tests are required  by the Local Authority.  Design recommendations for injection anchors, based on the results of 500 pull-out tests in the laboratory and in-situ are given.  One relevant  factor is the strength of the injected mortar plug developed  from the source grouting suspension and the water absorption  capacity of the surrounding masonry.  Other parameters that have to be taken into account are appearance of bed or cross  joints and conditions of restraint to free transverse deformations.  5 refs.

Primary author(s): Gigla B, Wenzel F

                            Lubeck,Fachhochschule, Karlsruhe,University

Source: 12th IB2MaC. Twelfth Int.Brick/Block Masonry Conf. Proc.

            Madrid,25-28 June 2000,p.691-706

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