LENGTHY SERVICE

Gisborne Herald, Volume LXVI, Issue 20067, 13 October 1939, Page 6

LENGTHY SERVICE

KAITARATAHI BRIDGE TWO TYPES COMPARED DEMOLITION of the old FINE NEW STRUCTURE After serving the travelling public for over 40 years the old one-way wooden bridge over the Waipaoa River at Kaitaratahi has been replaced by a modern composite structure of the plate girder span type. Tenders have been called for the demolition of the old bridge. Although the two bridges are of almost the same length, the new one has been built on an angle so as to obviate the right-angled bends on to the approaches and to improve the visibility. The old bridge was made up of four 80ft. spans, two of 70ft., one of 12ft. and the smallest of Bft., and they were all timber-truss spans. In the new structure there are six 90ft. plate-girder spans. Speaking to-day of the work that had been done in tile construction of the old bridge, the district engineer, Mr. O. G. Thornton, said that it was i credit to its builder. The piles were of totara and the piers and trusses of kauri. The joints of the trusses had decayed and for the past two or three years loads on the bridge had to be limited. In 1928 the structure was condemned for a time and it was understood that it had lived its life then, but at a small expense various repairs were made that were calculated to extend its usefulness for another few years New Bridge Higher Explaining the reason for the extra height of the new bridge, which was built sft higher at the approaches and 3ft. higher in the centre than the older one, Mr. Thornton said that it was accounted for by three reasons. Measurements were taken at the railway bridge in the vicinity and it was found that erosion and silting in the Dast 30 years had reduced the capacity under that bridge by one-third. The decking had to be raised slightly so as to keep it well above high flood level and the danger of too great pressure from flood waters. In the modern bridge there were no overhead trusses and all the strengthening was under the decking, and the higher level was also partly to conform with the new construction of the highway. The new bridge was twice the width of the old one and has pedestrian refuges l'or the safety of children making the crossing while on the way to and from school. Children would be able to take refuge in those positions in the event of stock being driven on to the bridge, particularly if there was a stampede of cattle while the bridge was in use by pedestrians. It was called a composite bridge because it had pile foundations, reinforced concrete piers, reinforced concrete decking, and Australian hardwood handrails. Obstacles for Contractor As if objecting to being spanned hy a new and modern structure, the Waipaoa River placed many obstacles in the way of the contractors, the Williamson Construction Company, Christchurch, and traffic was forced to use the old bridge for an extra period. High freshes and floods in the river caused the major trouble and work had to be delayed on several occasions while equipment that was on the river bed in connection with the construction work was retrieved from the lower reaches. The«incursion of silt into various mechanical appliances further held up work while the apparatus was being overhauled for service again. It was found difficult to drive the piles into the fine sand and shingle that made up the bed of the river, and. as a precaution against the scouring of flood-waters, steel sheathing was driven to act as an apron around the piles in the main piers. The new bridge was opened for the use of traffic recently and has been recognised as a great improvement by those who use the main highway continuously.