Vulnerability Assessment of Light Houses

Abstract

Lighthouses are the road signs of the ocean. They guide sailors through dangerous waters. Each lighthouse design is based on the land it is built on, its purpose, and the technology available. The Geometry of the towers can be round, square, octagonal, or conical in shape. These towers need to be in operation 24x7, guiding the ships coming towards the coast. However, during recent 2001 Bhuj earthquake these light houses got affected. In this report, a study has been carried out to find out the damage of three typical light houses namely Navadra, Kachchigadh and Dwaraka point. Primarily, the above light houses have analyzed and designed as per Indian standards. These light houses are modeled using 2D Applied Element Method (AEM) to perform damage analysis. In addition to this other methods have been used to calculate the response of port building including soil-structureinteraction (Annexure of Light House). Pushover analysis is done to get base shear vs roof displacement of building using displacement control method. Using energy dissipation approach, damage is quantified at every displacement level and normalized to 1. It means when D=0 then building will not experience any damage and if D=1 means it is complete collapse. The damage states of the structure were defined as no damage (D<0.2), slight damage (D<0.4), Moderate damage (D<0.6), severe damage (D<0.8) and complete collapse (D>0.8). A fragility curve has been developed to quantify the damage to light houses with respect to different peak ground accelerations. Based on the fragility analysis of port building the following recommendations are drawn. • Typical light house at Navadra (Octogonal Geometry) will experience at damage of 0.21 when subjected to PGA of 0.218g at KHF Mandvi and the same light house if located at Jodiya (0.377g) will experience damage of 0.4. If this light house situated at KMF Jhangi (0.396g) it will be damaged upto 0.47. • In case of Kachchigadh light house (Hexagonal Geometry) at Navadra will experience at damage of 0.18 when subjected to PGA of 0.218g at KHF Mandvi and the same light house if located at Jodiya (0.377g) will experience damage of 0.34. If this light house situated at KMF Jhangi (0.396g) it will be damaged upto 0.37. • And in case of Dwarka point light house (Square Geometry) located at Navadra will experience at damage of 0.21 when subjected to PGA of 0.218g at KHF Mandvi and the same light house if located at Jodiya (0.377g) will experience damage of 0.4. If this light house situated at KMF Jhangi (0.396g) it will be damaged upto 0.47.