3. Earthquake Deformation/Disintegration Mechanism of Masonry Walls

      Since the Hyogoken-Nambu Earthquake in 1995, a range of earthquake-proofing measures has been promoted for a host of structures on the assumption of a future large-scale earthquake. However, it is not yet possible to evaluate the stability of railway masonry walls because their behavior under earthquake conditions is unclear. The Railway Technical Research Institute (RTRI) therefore conducted a shaking table experiment using a model masonry wall to clarify its mechanism of disintegration from seismic forces.
      With hard ground, the experiment showed that subsidence of the back cobblestones on the rear side is caused by the forward displacement of masonry due to inertial force, with increasing deformation leading to final breakdown (overturning mode). Conversely, with soft ground breakdown is caused by the lower part of the masonry wall being pushed forward (slip mode).
      By considering the above modes, prevention of masonry deformation/breakdown under earthquake conditions becomes possible through countermeasures to control the subsidence of back cobblestones or to reinforce horizontal resistance forces in the foundation ground.

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