Analysis of the stress and deformation states in the vertical flat-jack test

35 Performing a realistic assessment of unreinforced masonry structures involves designing and executing 36 appropriate experimental tests on masonry components for determining the material model parameters 37 to be used in structural analysis. Considering recent developments in which inverse analysis was used 38 as calibration framework, a vertical flat-jack test is investigated in this paper. Two simplified models 39 are described for the analysis of the stress state in the masonry due to the pressure transferred by the 40 flat-jack. Furthermore, with the aim of designing the sensor setup for the test, a POD analysis on the 41 deformation state of the structure is carried out, highlighting the basic deformation modes which 42 govern the response. The results show that high stresses and local modes can occur in the proximity 43 of the flat-jack, and thus local use of FRP reinforcement is recommended to avoid undesired brittle 44 crack propagation which may prevent accurate calibration of mortar joint mechanical characteristics. 45