A long horizontally curved, post-tensioned concrete highway bridge, continuous over 12 spans. is described. Particular emphasis is placed on a number of original and unorthodox design concepts which make the structure unique. ~3 a~t l c l e . ' presente la description d'une l o n g~~e poutre d e pont en beton pricontrainte par post-tension, continue sur 12 travees et courbee hot-izontalement. Les auteurs mettent en relief un certain nombre de details d e conception inhabituels qui font de cet ouvrage une structure originale et unique.[Traduit par la Revue]A bridge deck is normally prevented from moving horizontally by fixing it to one or more of the intermediate piers. Joints are left at the abutments to permit expansion and contraction. This is a convenient arrangement for most straight bridges in normal cir&mstances. The present structure, however, is quite sharply curved and there is a need to avoid the massive type of piers required to resist horizontal forces imposed by a deck over 40 ft (12.2 m ) above ground level. From these considerations the novel structural form described in this paper was evolved.No expansion joints are provided in the structure. The deck is anchored at both abutments and is free to slide in any direction at all the intermediate piers, so that contraction or expansion is accommodated by flexing of the curved deck in the horizontal plane. Slight changes in curvature are sufficient to reduce the induced forces, due to environmental loadings, to a level which can be resisted by the abutments and the transverse flexural stiffness of the deck. Lateral forces, due to wind, centrifugal, and earthquake loading, can also be accommodated by bending of the deck and by compressive and tensile axial stresses similar to those that occur in an arch.Only four torque-resisting supports are provided in the structure. These are located at each abutment and at two of the intermediate piers, resulting in a maximum torque-span of 778 ft (237 m). The torque-span is defined as the distance between adjacent torque-resisting supports. The use of such a long torquespan is made feasible by the provision of single column supports, which are placed eccentrically to the longitudinal centerline of the deck. The eccentricity is determined to effectively balance the torsional moments induced in the deck by dead load and longitudinal prestressing.The structure is located in the Highway 420/QEW interchange at Niagara Falls, Ontario. Construction commenced in February, 1972, and the structure was completed -9 months later. The general contractor on the project was C.A. Pitts, Engineering Construction Ltd., Toronto.
Description of StructureThe structure is shown in Fig. 1 and is a 12 span, continuous, post-tensioned concrete highway bridge forming the third level of the interchange. The deck has a horizontally curved alignment, the radius of curvature of which varies from 3820 ft ( 11 65 m ) to 71 6 ft (21 8 m), and a vertical alignment on a 600 ft (183 m) vertical curve. The span lengths range from a minimum of 100 ft...
