CC BY
13
УДК 624.21
J. STUDNICKA, DrSc., Professor
T. ROTTER, CSC., Associate Professor, CTUPrague
RECENT STEEL BRIDGES IN CZECH REPUBLIC
Short information is given about several new steel bridges opened for traffic in small Central Europe’s country, in Czech Republic.
Steel bridges are not used in Czech Republic very frequently. Concrete bridges are dominant with approximately 80% amount of newly built structures. Steel is chosen only for bigger spans and where special circumstances are advantageous for this high strength material; for example in undermined areas, when rebuild bridge has weak supports, when very small height is remaining and so on.
Approximate consumption of steel for bridges is 5 000 t per year in whole annual production of 200 000 t steel structures in Czech Republic. In spite of this fact several interesting structures were finished during last five years. We will try to introduce them in this paper to Russia readers which are familiar with much bigger and heavier bridge structures in their very large and spacious country.
1. Marian Bridge in Usti
Two span cable-stayed road bridge with spans 120 + 60 m with unique shape leading across Labe River was finished in 1998 and was many times awarded (internationally e.g. by ECCS in 1999) and also has been cited in different journals and books.
Everybody can see that bridge with missing back stay is not example of strongly effective structure and feel that architectural demands overbalanced mechanical and static reasons. In spite of this new bridge serves more than five years without problems and became itself landmark of town.
Longer span of bridge is designed as all steel structure with central box girder, wide cantilevers and orthotropic deck. Upper flange of box girder serves like footpath, Fig. 1. Altogether 15 pairs of cables were used for reducing of bending moments in main girder. Short span has composite steel and concrete structure because of self weight was very useful on this side. Two parts of the inclined steel pylon are carefully shaped and hollow section of them is stiffened strongly on inner side. Cables were prestressed from pylon side.
The main girder of bridge was erected on right bank of river and pushed across river with help of temporary support in river bed. Finished bridge is shown on Fig. 2.
11.0 m________________________I 4.2m_1_____________11.0 m
____________________26.2m_________________________
Fig. 1. Cross section of steel span of Marian Bridge
Fig. 2. Cable-stayed Marian Bridge in Usti
2. Long Bridge in Ceske Budejovice
So called Long Bridge in regional capital of south Bohemia has two continuous 47 m spans shaped also by architect, Fig.3. Steel and concrete composite deck is supported by semi trussed main girders with cables inside upper tube chords. Three traffic lanes are on the bridge.
Fig. 3. Long Bridge in Ceske Budejovice
The bridge across Vltava River replaced more than 100 years old narrow bridge. The old bridge was in the first stage moved during one day upstream to parallel position with temporary supports in river and both sides. New bridge was erected on the old supports. Traffic was shifted to new bridge in one day break. Bridges successfully resisted during the enormous flooding in 2002.
3. Highway bridge across Labe River near town Lysa
The highway bridge on local road across Labe River near small town Lysa has span of arch 128 m. Composite steel and concrete bridge deck is made of concrete slab with thickness 200 mm and steel transverse girders only, stringers are not used. Distance of transverse girders is 3 m. Shear connection for composite action is fulfilled by perforated band which is welded to upper flange of steel girders. Dimension of arch is 1.4x0.9 m; main girders are 2.2 m high. Width of bridge is 12 m + 2x2 m footpaths. Tie rods are made from tubes. Bridge view is on Fig. 4.
4. Bridge for Prague underground railway
The underground (metro) line B is crossing small lake in the Prague suburb named Stodulky. The crossing is realized by continuous composite steel and concrete bridge with spans 30 + 7x45 + 30 m. The main box girder is encased in concrete mainly from fire resistance reasons but composite action is used for bending resistance too, of course. Shear connectors connecting concrete encasement with steel girder are automatically welded studs with diameter 20 mm. Dimensions of box girder are 2x3 m and wide cantilevers supports two railway tracks in gravel ballast. Because Moscow made metro coaches need to be in dry atmosphere during service the whole superstructure is wrapped by weather resist steel envelope, see Fig 5.
Fig. 5. Bridge for metro in Prague
5. Railway bridge in Ceska Trebova
Important bridge on European corridor line Berlin - Prague - Wien (designed for velocity 160 km/h) was built like two girders composite steel and concrete continuous beam. Two tracks are supported by superstructure with two main girders, see Fig. 6. Distance of two girders is 5.3 m and height of girders is 2.75 m for span of 44 m. The continuous beam from S355 is used. Flanges of width 1100 mm have thickness to 96 mm; web thickness is 22 to 26 mm.
Concrete deck thickness is between 250 to 400 mm. Prestress were not used. Stud shear connectors with diameter 20 mm were used. Cylindrical strength of concrete was 30 MPa.
Bridge was pushed from one side during erection. Bridge was open for traffic in 2002.
Fig. 6. Railway bridge in Ceska Trebova
6. Highway bridge in Ostrava
Almost half kilometer long highway bridge in Ostrava across Odra River was just finished, Fig. 7. Bridge is built in undermined area with very big supports declines expected. Spans of continuous beam are 50 + 90 + 99 + 90 + 72 m. The main box girder is used for both directions of highway.
Main box girder has width 6.9 m and height 3.55 m. Steel box is connected by 22 mm stud connectors with 0.5 m thick concrete deck which is prestressed both in transverse and longitudinal directions. Concrete with cylindrical strength 30 MPa was used. Longitudinal prestressing is realized by free cables inside box girder. Thickness of steel plates is between 35-70 mm, web thickness is 18-35 mm. Weight of steel structure is 4300 t.
Bridge was pushed from one side during erection. Bridge was finished in 2003 as part of highway Ostrava - Brno.
Fig. 7. Composite steel and concrete highway bridge in Ostrava
7. Footbridge in Prague
Relatively small footbridge on south side of Czech capital is famous mainly like town gate because bridge goes across main highway connecting the second biggest Czech town Brno with Prague. Every visitor coming to Prague by car can see this welcoming arch, Fig. 8.
Steel arch has span 59 m. Rise of an arch is 26 m. Two inclined steel arches supports very shallow steel box girder of height 650 mm with orthotropic deck. Width of beam is 3 m.
Bridge was opened in 1995.
Fig. 8. Footbridge in Prague - Sporilov
8. Footbridge in Mlada Boleslav
Footbridge connecting car factory Skoda with railway station is composed from concrete deck and steel “tree like” supports. Spans of bridge are not too long (approx. 20 m) and width of bridge is 2.5 m only. Vertical and horizontal forces to supports are not too big and tubes 324x36 are therefore enough for lower part of pylons. Basic tubes are splitted into four branches in steel cast joints which are welded on both sides.
Very slender deck (200 to 400 mm) from concrete C30/37 is not prestressed. The length of bridge is 191 m. Axis of bridge is curved in both planes, Fig. 9.
Fig. 9. Footbridge in Skoda factory in Mlada Boleslav
9. Bridge on Prague Beltway (design)
Prague is capital of Czech Republic and with 1.5 million habitants and historical City with narrow streets is every day almost collapsed under traffic. Round beltway is necessary to canalized through traffic outside of town. East and west parts of this vital beltway exist now but two big bridges across Vltava River are still missing. On south of Prague big concrete bridges are just before the start of construction and on north part (district Suchdol) big steel bridge is under planning nowadays.
In 1998 was public competition with approximately 30 designs and the winner was design of Authors of this paper. Now design work with winner idea continues and perhaps in 2006 erection of bridge will start.
Double deck steel and concrete bridge (4 lanes in each direction) is supported by steel arch with span 170 m. Fig. 10. Main frame girder of length 470 m is also from steel but bridge deck is composite steel and concrete with steel cross girders and steel plate 10 mm thick connected by studs with 95 mm thick concrete deck.
Consumption of steel (S355 and S460) is expected approximately 9500 t.
Fig. 10. Highway bridge in Prague (design)
Acknowledgement
Bridges are in Czech Republic owned by government and state is also only one client for planning, design and erection of new bridges. Designs of bridges are very carefully checked by state Authorities. Both Authors of this paper are University teachers and serve to state Authorities in the field of bridge checking and improvements for long time.
Research in bridge engineering is supported by Ministry of Education (grant J04/98/210000001) and Ministry of Transport. Support is gratefully acknowledged.
ДЖ. СТУДНИКА, Т. РОТЕР
СОВРЕМЕННЫЕ СТАЛЬНЫЕ МОСТЫ В ЧЕШСКОЙ РЕСПУБЛИКЕ
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