Keywords: prestressed bridges, structural design, evolutive construction.

The present paper describes the design, construction and analysis of the new viaduct over the river Palancia for the motorway A-23 Sagunto-Somport (stretch Variant of Viver, Castellón, Spain). The viaduct is a two-way double deck structure of 11.80 m width each way. The length of the viaduct is 504 m distributed in nine spans of 60-90-60+6x49 m length. The viaduct's deck is split in two parts by a joint that separates the main three-span viaduct from the access six-span viaduct. The viaduct is a box-girder prestressed concrete structure sustained by piers with rectangular hollow-sections. The main viaduct has 60-90-60 m span-lengths and has a variable depth cross-section. The depth of the section is 4.50 m at piers and 2.85 m at mid-span and abutments. The access viaduct has 6x49 m span-lengths and a constant depth of 2.85 m. The construction of the main viaduct follows a singular sequence of evolutive uncoupled stages built with a truss flexible shoring system. Stages 1 and 2 are uncoupled and symmetric. They include the lateral 60 m span plus a cantilever of 24 m into the main span of 90 m of length. Stage 3 closes the 42 m gap between stages 1 and 2 and closes the main span of 90 m. The bridge was designed in accordance to the Spanish IAP-98 loading code and the EHE structural concrete code [1,2]. The piers of the main viaduct have been the object of structural optimization reported in a recent publication [3].

Prestressing for stages 1 and 2 are seven cable families whose layout is typical of a beam plus a cantilever. Prestressing for stage 3 is only for positive bending and the layout goes along the bottom flange of the cross-section. Stage 3 cables are anchored in wedges inside the cross-section. Some of the cables of stage 3 are common to stages 1 and 2, so that the construction joints are in compression in all cases. This construction sequence has several advantages. Firstly, stages 1 and 2 are symmetric and disconnected, so that they can be built simultaneously and hence there is repetition and reduction of the building time. Secondly, the length of stage 3 can be adjusted so the bending diagram of the whole bridge is similar to that of a would-be bridge built in one go. This significantly reduces the redistribution of bending moments due to creep, which enables savings in prestressing of the deck. Thirdly, the critical sections at the pier and mid-span are quite close their anchorage. The analysis of the bridge requires a nonlinear step-by-step verification of the deck following the construction sequence of the deck under a flexible shoring. The analysis showed that the deck cracked unless a partial prestressing of the cross-section (bottom part) was included. It also showed a detachment of the deck from the shoring system in the 24 m cantilevers due to prestressing. The six-span access viaduct is constructed using a typical span-by-span sequence with joints at 9.80 m along cantilevers beyond the piers. It is finally concluded that this procedure of construction is suitable for main span lengths up to a 100 m.

1

M. Fomento, "IAP-98: Code about the actions to be considered for the design of road bridges (in Spanish)", M. Fomento, Madrid, 1998.

2

M. Fomento, "EHE: Code of Structural Concrete (in Spanish)", M. Fomento, Madrid, 1998.

3

F.J. Martinez, F. González-Vidosa, A. Hospitaler, V. Yepes, "Heuristic optimization of RC bridge piers with rectangular hollow sections", Computers and Structures, 88(5-6), 375-386, 2010.

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