Edinburgh Napier University

  For the development of innovative connections for the restoration of the integrity of structural elements of ancient stone temples, it is imperative, among others, to understand the reasons of the ‘pull-out’ phenomenon. Pull-out can be defined as the gradual or abrupt removal of the reinforcing bars from the body of the structural member, without prior failure of neither the marble nor the bars. An analytic solution is not yet available and in this context, a combined experimental and numerical analysis was undertaken in an effort to enlighten the failure mechanisms activated during the phenomenon. The experimental part included a series of pull-out tests with prismatic specimens made from Dionysos marble in which threaded metallic bars were planted in drilled holes. The adhesion between the marble and the bar was achieved using a suitable cementitious material. The criterion adopted for the design of the connections is to avoid completely the failure of marble. The parameters studied included the depth and the pitch of the thread of the reinforcing bars. The experimental set-up comprising suitable supporting and measuring systems was improvised, given the absence of a standard, relevant to this particular problem. Based on the experimental results, a design criterion is introduced allowing for a predefined amount of slip between the reinforcing bar–cement interface and the marble body. In addition, a numerical model is developed, calibrated on the basis of the experimental results. It is concluded that the form of the thread influences considerably the carrying capacity: denser pitches lead to higher ultimate load and energy consumption while the coarser ones favour parasitic bending effects and a flexible behaviour. In addition, the medium depth for each pitch leads to a stiffer and stronger behaviour.