General Information
Figure 1 shows a suspension bridge that is used by motorcycles, bicycles and pedestrians.
| Type | Single-span suspension bridge |
| Main span | ≅ 90 m |
| Deck width | ≅ 1.5 m |
| Deck width to main span ratio | ≅ 1:60 |
| Pylon | Reinforced concrete (A-type, longitudinal) |
| Girder | Steel truss |
Steel Truss Girder
Figure 2 shows a schematic three-dimensional view of a steel truss girder sector.
The truss is made of L-sections and consists of zig-zag diagonals, verticals, cross members, and cross braces. The verticals, cross members and braces are placed each zig-zag period. The hanger cables are connected to the upper chords over the verticals by welded U-bars. Figure 3 shows the truss viewed from below.
Over the cross members are placed three timber stringers, and the deck consists of timber planks.
Figure 4 shows a side view of a bridge sector on shore 1.
A horizontal member made of an L-section connects a vertical with a diagonal (on one side and shore 1 only). The same region is used for the chord-to-chord connection, which consists of an additional (overlapping) L-section fixed by bolts and nuts.
Figure 5 shows a side view of a bridge sector on shore 2.
A deformed bottom chord is noticeable, and the vertical clearance h ≅ 2 m. Figure 6 shows the deformed bottom chord.
A new bottom chord made of an L-section with a smaller size is welded next to (on both sides) the deformed bottom chord. The overlapping regions are marked by the double yellow arrows.
How does the new bottom chord affect the stiffness of the truss?