engleski

Design and construction of Mirna viaduct

The Mirna viaduct crosses the Mirna River valley on Nova Vas – Višnjan section of the Istrian “ Y” west leg state road. The construction of the viaduct started in 2002 and it was opened for traffic in June 2005. The overall viaduct length is 1, 378.03 m, with spans L=51.07+15x66.491+70.096+2x50.069+63.087+42.558+30, 542=1354.86 m. The ground plan alignment of the viaduct is in constant curvature of 4, 005.5 m. The vertical grade line alignment is in uniform concave curvature of 17, 500.0 m, following the terrain profile to limit the height of viaduct columns. The overall width of the viaduct deck without cornices is 10.10 m. The relatively slender continuous superstructure comprises two main steel 2, 750.0 mm deep plate girders spaced at 5, 500.0 mm, cross beams in frame action and a concrete 25.0 cm deep deck plate in composite action with main girders. A relatively unusual structural bearing layout was adopted, with longitudinally fixed bearings on 13 middle piers, made possible by the low horizontal stiffness of friction steel pile foundations in adverse soil conditions. The superstructure is longitudinally restrained at both abutments by viscous dampers. All viaduct piers are very slender of H shaped cross section, comprising a 30.0 cm web and two 35.0 cm flanges extending in the direction of the bridge axis, with varying height 13.45÷40.026 m. Shallow spread foundations are utilized on the solid rock of Mirna valley slopes. All piers in the valley are founded on long driven steel friction piles. Piers were constructed in climbing formwork in 5.0 m long segments with high precision because of their extreme slenderness. The erection of the superstructure was executed by longitudinal launching of steel grillages from both abutments. Concreting of the deck plate was executed on temporary formwork, in strictly prescribed order. A short review of design and construction of the Mirna viaduct is presented in the paper.

Bridge design; Composite Superstructure; Steel piles

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