Composite double-bridge Kralupy

Special bridge project near Kralupy, Czech Republic, consists of 2 bridges (main bridge and ramp) that are connected on 1st intermediate pier of the main bridge. The main bridge is double-composite bridge of 4 spans 101+147+75+55 m (total superstructure length is 373,75 m) The bridge has width varying between 16,6 m to 18,35 m. On the 1st intermediate support of the main bridge is connected in the perpendicular direction 306,125 m long ramp with 6 spans 50,425+55+50+45+42+40+23 m and width 11,35 m. Both bridges create an unprecedented junction. The model was created for basic design and expected construction beyond year 2020.

The main bridge is of steel box cross-section with varying height and with top concrete slab and also bottom concrete slab in the vicinity of supports. This structural system is called "double composite" and provides greater stiffness than a continuous composite bridge without the bottom slab. The bottom slab is also very cheap to do, as its formwork is directly the steel box girder. The bottom concrete slab provides needed stiffness during the construction process, which is planned to be the free cantilever erection from both intermediate piers adjacent to the main span of the bridge.

The ramp is traditional multi-span composite bridge with double I cross section and with constant height. The erection method chosen for the ramp is incremental launching of completed steel structure from its abutment and after welding to the main bridge, the concrete deck is casted. Both bridges have specifically designed shape of piers.

This was our first big project in SCIA Engineer when we started modelling in Excel parametrically, instead of starting directly in the software as we had been doing before. Both bridges are in a significant longitudinal inclination and they have very repetitive geometry. The main bridge has the box cross section with parabolically varying height and with evenly distributed transverse braces. Bridges were defined in Excel (1d and 2d elements and supports) and imported by Table Input. The model was in its first stage after 2 days, when we already had preliminary results. Additional parts of the model were added manually - details of the junction, the lookout platform above the 2nd adjacent pier of the main bridge, details of the bearings of the main bridge, the piers and foundations. Piers were aproximated by column elements with arbitrary shape and are heavily reinforced. Load cases were inputted manually with repetitive traffic loads being composed also in Excel. 

Reference: Created exclusively for VPU DECO, 4/2017, www.vpupraha.cz