A multimodal study of pinning selection for restoration of a historic statue

• Join repair is simulated to analyze six pin materials for marble sculpture repair.
• Substrate failure modes in compression and tension nearly sync for fiberglass pin.
• Stiff materials cause substrate tension failure long before compression failure.
• The simulations are validated using uniaxial compression tests of mock repairs.

Current practices for repair of fractured stone architecture and monuments rely on drilling into the substrate and installing metal pins, providing component alignment and resisting shear and tensile stresses. Adhesives such as acrylic resin may reinforce the pins at the interface with the stone. This research studies failure modes in the repaired areas of the statue Adam (Tullio Lombardo c. 1490–95) to ensure the artwork's longevity. Six materials as pins were investigated to repair fractured Carrara marble specimens. Furthermore, the results of finite element simulations were correlated with experiments on pinned join repairs. The simulations and experiments concluded that fiberglass pins outperformed metal pins. The fiberglass pins provided maximum strength to withstand the static forces of the repaired sculpture, without damaging the substrate before pin failure. From the simulation results, a ranking of the pin materials quantified the overall efficiency of the system. The ratio of join displacements at the tension stress limit to the compression stress limit in Carrara marble indicates the join performance, where 1.0 represents equal strength in tension and compression. The fiberglass pin achieves a ratio of about 0.80, from which we conclude that sudden join failure may be prevented, a desirable trait for monumental conservation.

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