Context 146 - September 2016

C O N T E X T 1 4 6 : S E P T E M B E R 2 0 1 6 45 Intrusive investigation, which could only take place after the contractor had been appointed in late 2012, revealed several serious hidden defects and some significant variations from the 1898 design. At ninth floor level, the bearings of the two upper pairs of RSJs were found to be much more badly corroded than those for the two lower pairs, because the builder had left the ends exposed to the weather.The same two pairs of RSJs were found to be of considerably smaller section size than the 1898 drawing specified. At eighth-floor level, severe cracking was found in the south-west corner masonry.This was caused by corrosion where the ends of one of the upper pairs of RSJ sections, also found to have been left exposed. Although the amount of corrosion on the top flange was sufficient to have jacked up the masonry, causing the severe cracking, the loss of section was fortunately insignificant to the RSJs’ integrity. At fourth- to seventh-floor levels, severe corrosion of the top flanges of the closely-spaced, small-section secondary RSJs was found when the water tanks were removed. This was probably caused by condensation occurring where the cast iron of the tanks had been in contact with the secondary RSJs.The four larger primary RSJs were (perhaps surprisingly) found to be in good condition, even where their bearings had been revealed by trial opening-up in the masonry. IAN ANDREW Conserving Ruchill Hospital water tower The requirement to restore the severely decayed, Category A listed, hilltop Victorian water tower at the former Ruchill hospital, Glasgow, set a challenge to its structural engineers. In 2009 WYG was invited by Colliers International (agent for Scottish Enterprise) to assess the remaining dozen buildings at the closed Ruchill Hospital in Glasgow. All were listed and in very bad condition. Sadly, all but one were razed to the ground in 2013.The building that was spared this fate was the Category A listed, 10-storey Victorian water tower, standing foursquare on the hill top at the centre of the site. A condition of demolition of the other buildings was that the tower would be restored to its original condition. It was important to establish how the diminishing upper parts of the tower had been assembled and what materials had been used. Outwardly it was clear that the tower was primarily a gravity masonry structure, resisting wind loading and supporting four large water tanks on the middle floors. By around 1900 structural steel was available, so the eighth- and ninth-floor structures incorporated grillages of four pairs of RSJ sections, arranged two-above-two to support the inset tower wall masonry – as the tower reduces in plan size through these floors, before terminating in a copper-clad timber cupola. The cupola is restrained to the ninth floor by four vertical iron tension rods. The design and specification for stabilising and repair- ing the tower structure were prepared in 2011 with only the knowledge gained in 2009 from visual inspection and study of the original construction drawing of 1898. The completed tower from the south west, after restoration