Safety analysis of a cultural heritage structure has been performed. After a making a detail account of past alterations, damage and present state, a 3D numerical model of a typical bay of the structure had been prepared in GID (ver. 8). To implement a realistic behaviour of material, a nonlinear material model so called tension compression distributed damage model has been utilized. Analysis has been performed in COMET. The results include analysis both for gravity load and seismic load. An overall assessment of the ultimate vertical load carrying capacity (although a little realistic but gives a sense of safety psychologically) and structural behaviour at an earthquake demand displacement has been done to explain the safety condition of the structure.