Historical review of lighthouse design under wind load: the Ile Vierge lighthouse

Abstract

The purpose of the study presented here is to describe the design method used by engineers in the nineteenth and early twentieth centuries to size lighthouse structures and to compare them with current European standards. The historical information presented here is derived from two sources in particular: the archives of the Ile Vierge lighthouse, which was built at the northern tip of Brittany between 1897 and 1902, and the scientific journals, books and courses available at that time. Firstly, the article describes the structure of the Ile Vierge lighthouse, which is the tallest stone lighthouse in Europe. The wind load acting on lighthouses and chimneys was formulated in France by L. Fresnel in 1825. Fresnel's work is compared to W. J. M. Rankine's theory used in the UK. The safety coefficients applied with respect to the stability of the towers in France and the UK in the nineteenth-century are compared. On the occasion of the construction of the Ile Vierge lighthouse, the masonry strength under wind loads led to a discussion among engineers of the French lighthouse authorities. They also worried about the risk of excessive oscillations of the towers, which could cause a dysfunction of the lamp. Thirdly, the standard wind action defined in Eurocode 1 is applied to the Ile Vierge lighthouse. Calculation results are given. A comparative analysis of the ancient and modern methods is presented. Overall, this historical research shows that the designers of lighthouses in the nineteenth-century had the same objectives as today: to build strong, durable structures in which deformations under loads are compatible with serviceability. This article is part of the theme issue ‘Environmental loading of heritage structures’.