Application of plate girders in steel construction

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1. Plate Girders “A plate girder is a type of beam built from plates of steel that are either bolted or welded together.” The plate girders are typically I-beams made up from separate structural steel plates which are welded or, bolted or riveted together to form the deep vertical web with a pair of angles each edge to act as compression and tension flanges.

2. History and background of plate girders Plate girders became popular in the late 1800's, when they were used in construction of railroad bridges. By 1950's welded plate girders replaced riveted and bolted plate girders. The purpose of the plate girder is to build a beam that is larger than anything that can be built by a steel mill or factory.

3. The size and shape of the girder allows builders to construct structures that are much longer and heavier duty. Plate girders are usually prefabricated and the length limit is frequently set by the mode of transportation.

4. Applications of plate girders Plate girders are usually used to construct bridges that are suitable for short to medium spans and may support railroads, highways, or other traffic. Some of the most commonly used girder bridges are: Box Girder Bridge Beam Bridge Multi- Girder Composite Bridges Half-Through Plate Girder Bridges

5. Box girder bridges Box girders are a particular form of plate girder, with two webs joined by common top and bottom flanges. The box girder normally comprises either prestressed concrete, structural steel, or a composite of steel and reinforced concrete.

6. Box girder bridges (continued) Advantages Offer better resistance to torsion. Gives excellent appearance and durability. larger girders can be constructed.

7. Box girder bridges (continued) San Francisco–Oakland Bay Bridge, aka Bay Bridge, California, USA

8. Box girder bridges (continued) Main materials are Steel & concrete Total length is 4.46 miles (7.18 km) Width is 96.24m Height is 526 ft (160 m)

9. Crane Bridge Runway Girder Crane bridge girder is a special type of plate girder used to support the crane loads. Crane runway girders provided in a perpendicular direction to the crane bridge at the ends may also be the plate girders.

10. C. B. R. Girder (continued) Usage of Crane bridge Girders has allowed the engineers to deal efficiently with higher loads. Some of the important features of C.B.Gs are: Limit the applied stress range to acceptable levels. Avoid unexpected restraints at the attachments and supports Avoid stress concentrations at critical locations Avoid eccentricities due to rail misalignment or crane travel Minimize residual stresses

11. Beam Bridges A beam or girder bridge is the simplest kind of bridge. A beam bridge consists of a horizontal beam that is supported at each end by piers. The weight of the beam pushes straight down on the piers.

12. Beam Bridges (continued) Beam bridges rarely span more than 250 feet. This doesn't mean beam bridges aren't used to cross great distances it only means that there may be a series of beam bridges joined together, creating what's known as a  "continuous span."

13. Beam bridge (cont) Esplanade Riel Bridge, Winnipeg, Canada Pedestrian bridge Designer : Colin Douglas Stewart and Étienne Gaboury 197 meters (646 ft) long & 7m wide

14. Multi-girder composite bridges 'Composite' means that the steel structure of a bridge is fixed to the concrete structure of the deck so that the steel and concrete act together, so reducing deflections and increasing strength One of the most commonly used for medium span bridges. Multi-girder construction is used for single spans and for continuous multiple spans. Effectively used where construction depth is limited.

15. M-g-c bridges (continued) The girders are braced together at supports and at some intermediate positions Generally taken into account, where short piers are to be used. Use of multi-girders allow the designer free to choose the thickness of web and size of flange accordingly.

16. M-g-c bridges (continued) River Eden Bridge Three span multi-girder bridge Main span of 64 m, with 34m side spans 1351t capacity

17. M-g-c bridges (continued) Surtees Bridge, at river Tees, United Kingdom 150m of total span 3 no of spans, 2 piers in water About 2000t capacity

18. Half through plate girder bridges A bridge provides a running surface for the traffic that crosses it and to ensure minimum interface issues. The traffic runs on top of the bridge structure.

19. Half through P.G.B (continued) Provide best solution for small and medium span bridges. More commonly seen in railway bridges and footbridges.

20. Half through P.G.B (continued) Preferred, where there is minimum clearance level above the ground, river, road or the railway below. In half through configuration of girder bridge, the traffic is only partially inside the structural envelope.

21. Half through P.G.B (continued) Common solution for pedestrian and cycle-way bridges. The footway/cycle-way is relatively narrow and a stiffened steel plate deck can easily span between open web main girders on either side.

22. Half Through Plate Girder Bridges

23. Bridges using plate girders

24. Advantages of using plate girders in steel construction There are number of advantages of using plate girders in bridge construction or other structures, some of which are as follows: Possessing the features of structure is simple. Provides Convenient Transport. Speedy erection. Heavy loading capacity, Great stability and long fatigue life. Being capable of an alternative span, loading capacity.

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