Contact Artefacts please if you have any comments or more information regarding this record.	Menu Home Upfront Now Up Books Towns Structures People Firms Lexicon		Railway Bridge over the Imvani River iMvani district, Eastern Cape CAPE GOVERNMENT RAILWAYS: Architect

Date: c1890 Type: Railway Bridge Status: Extant   Click to view map Coordinates: Alt: 994m

Near the hamlet of Imvani a solitary lattice girder bridge crosses the Imvani River, a minor tributary of the Black Kei. A railway bridge, it has a single span of approximately 30 m long, is about 4,5 m wide and is supported on concrete abutments. The western and eastern approaches to the bridge are flanked by two low concrete balustrade walls which are an extension of the north and south faces of the abutment. Of interest is that immediately to the north is another pair of abutments, of an earlier date, made of large hammer dressed stones, built for a similar span but with a much lower elevation above the riverbed. The stone abutments mark the original alignment of a branch Railway Line - from the mainline between East London and Queenstown - constructed up to St. Marks by the Cape Government Railways (CGR) in the early 1890's. The existing concrete abutments and the existing bridge mark a minor change to the alignment at an elevated grade. It might be that existing lattice girder bridge was relocated a short distance downstream onto the concrete abutments, but this is conjecture. The elevated and relocated bridge was probably implemented after the great floods experienced in the Eastern Cape in 1917. A large rusty metal signboard at the western approach warned pedestrians not to cross the bridge. Now much obscured by rust, the last two lines of the Afrikaans text state that: Oortreders sal vervolg word (Offenders will be prosecuted) This lattice girders of this bridge can be described as a double-lattice web with multiple triangulations. A double-lattice web has two sets of parallel web bars joined by paired diagonal bars connected to the top and bottom chords. In this bridge each of the lattice girders has a total of 12 triangulations. The bridge is a type which has become known in South Africa as a ‘half-through’ bridge with the railway lines supported on the lower chord. In a 'full-through' bridge the two lattice girders would have been higher than the train and would have had their top (compression) chords braced over the width of the bridge to prevent buckling. The pair of lattice girders are fabricated from heavy steel sections rivetted together. Thirteen substantial transverse beams are supported on the two lowest chords - which in turn support two fabricated linear U-beams, bridged at intervals with substantial flat plates which supported the timber sleepers. Provision was made for pedestrian walkways on either side of the rails. Each walkway was formed of four closely spaced T-sections spanning between the transverse beams and rivetted in place. The ends of the T-sections were stamped by the boiler makers with a matching code to facilitate the installation on site. A manufacturer's plate was not found. It is however likely that the bridge was fabricated in the workshops of the CGR - possibly in East London. The steel component parts would presumably have all been transported to the site via the already constructed railway line. In the 1940's a major replanning and realignment of the mainline railway route between East London and Queenstown was undertaken and it is likely that this branch railway line was then decommissioned - making the bridge over the Imvani river redundant. The bridge has however fortunately survived as a layer of the development of the railway system in this part of South Africa. Fortunately the bridge is not easily accessible and has remained intact without the theft of any components. The farmer has mounted beehives on top of the bridge girders which are clearly a disincentive to metal thieves. The original line of the eastern approach to the bridge bisects the farm Douglas and remains as a memory of the original alignment between the irrigated fields. The gentle curve on the western side towards the modern Imvani station is a similar situation. Remnants of the original stone ballast remain on both sides of the bridge, but none of the sleepers or railway lines. The mainline railway line approaches the newer Imvani station a short distance to the west, passing below the N6 in a north-easterly direction. As in the rest of South Africa this railway line has had the overhead copper bus bars stolen and is currently only useable by diesel locomotives. William Martinson April 2023