Restoration of Cast Iron and Wrought Iron Structures – Case Study: The Restoration of the Orangery at Hof ter Borght in Westmeerbeek (Belgium)

The structural restoration of the heavily degraded combined wrought iron and cast iron orangery of the castle Hof ter Borght at Westmeerbeek, Belgium, proved to be a challenge. This paper presents the problems encountered and the suggested interventions. The assessment of the condition of the construction was difficult because of the very extensive plant growth in and on the orangery, which had broken nearly all the glass panels of the roof and walls and covered most of the wrought iron and cast iron elements. During the disassembly of the structure, the weakened connections between several elements suffered unavoidable additional damage. Microscopical and chemical analyses indicated wrought iron and cast iron of low quality for several elements, exhibiting impurities and air pockets. The mechanical characteristics of the historical wrought iron and cast iron were determined by tensile and compression testing. A finite element model of the orangery is used to analyse the stresses in the structure, assuming an intact structure at first. Secondly, additional modern steel elements are added to support the weakened structure, along with the strengthening of the connections themselves. Several options for reinforcement of the cast iron connections are suggested and compared, ranging from recasting entire elements to bolted steel overlapping plates. Furthermore, the feasibility of local epoxy polymer filling for column feet anchorage and other epoxy prothesis applications for cast iron connections is assessed.