Evaluation of Flat Jack Test Method Effectiveness for Masonry Structural Investigations

Abstract

Flat jack testing method is one of the most commonly used techniques for the structural assessment of existing masonry structures. Single and double flat jack are commonly adopted to evaluate the acting normal stress, or the compressive behaviour of masonry material. Test procedures are codified by international standards (e.g. A.S.T.M D4729-87; C1196-04; C1197-04, R.I.L.E.M TC 177–MDT D.4; R.I.L.E.M. TC 177–MDT D.5), which provide the preliminary calibration of an experimental coefficient (km), which determination influences significantly the reliability of the test. This paper presents the result of an experimental study on the calibration of km coefficient for flat jacks. The problem is investigated by several tests carried out at DISMAT Laboratory in Canicattì (Italy). Different types of flat jacks made by different manufacturers are considered, and two calibration methods are adopted in order to relate the pressure values of the flat jack with those of the hydraulic press and obtaining the coefficient km. Results of this investigation highlighted the influence of materials used and production technology for the flat jacks for obtaining reliable results from the tests on masonry structures.