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Abstract

The purpose of this thesis is to investigate the effect of stereotomy on the mechanical behavior of stone cantilever staircase. Due to time restraint and unforeseen circumstances of the academic year, the focus of this thesis is on the influence of cross sectional area differences on behaviors such as bending moment, torsional moment and shear values. Cantilever staircases are often repaired and preserved incorrectly due to the lack of proper understanding of their mechanical behavior. Furthermore, current literature reveals remaining misunderstanding of how they behave, prompting the motivation for this thesis. The thesis investigates whether there is a spectrum of behavior from unrebated to rebated staircase and from rectangular to triangular, and whether the efficiency of the structure increases with this change. The straight cantilever staircases of four different geometries are modeled using 3DEC distinct element modeling software from Itasca Consulting Group Inc. and the mechanical behaviors are compared across the four staircases. Triangular cross section has not yet been modeled in literature, despite being the majority of stone cantilever constructions. Fiber-optic sensors are installed on the spiral cantilever staircase at the Museum of the City of New York. Empirical strain data collected from fiber-optic sensors on active loading of a cantilever staircase have not been done in previous studies. The results of this thesis show that the rebate adds significant advantage in reducing torsional moment. In agreement with literature, the results show that torsional moment is the dominant actor on unrebated forms. Rebated forms are predominantly dictated by bending moment. However, rebate perpendicular to the soffit actually demonstrated an increase in torsion, making it less efficient than right-angled rebate.