TY JOUR TI Reconstruction of cantilever stone staircases in the architecture of St. Petersburg. Part 3: how to calculate a straight flight staircase with plane treads KW stone structures KW cantilever staircases KW hanging stairs KW inspection KW reconstruction KW restoration KW verification calculations KW calculation examples JO Proceedings of Petersburg Transport University AU Weber, M.D. AU Kuznecov, A.V. PY 2026 IS 23 PB FSBEI HE "Emperor Alexander I St. Petersburg State Transport University"