Padma Multipurpose Bridge Project

Table 6-3: Comparison of concrete extradosed and steel truss bridgesView of SuperstructureConcrete Extradosed BridgeSteel Truss BridgeDescriptionTechnical RobustnessStructural EfficiencyA prestressed concrete extradosed bridge with both roadand rail are located on the same upper deck. Rail track islocated at the centre while two road carriage ways arelocated on both sides. Associated facilities such as gasand cable lines are located at the bottom of the deck.According to FS, length of the bridge is 5.58 m with spanlengths varying from 60 m to 180m and total piers are44. But for the purpose of the comparison with the steelbridge, the length of the bridge is considered as 6.15 kmand all quantities and estimates are extrapolatedaccordingly.Structurally less efficient.Two carriageways, rail envelops and major services areprovided in the upper deck level with a resultant overallwidth of With a deck width of 33.5m. A wider structure isless structurally efficient solution and generally leads towide pier column.A composite steel truss bridge with the road on the upper leveland the rail at the lower level. Rail line is located on the centre ofthe lower deck while associated facilities such as gas and cablelines are located on the lower deck on either side of the rail line.The lower deck is steel, while the upper deck is concrete. Totallength of the bridge is 6.15 km with a span length of 150 m andtotal piers of 41. The span length is 150m and overall depth is13.6m, the span-to-depth ratio is 11, which is typical for steel trussstructure. The truss depth of 13.6m is more than adequate inaccommodating the vertical clearance in the railway envelopeStructurally more efficient.A two level structure provides the opportunity for a more compactcross section solution. With overall width of only 22.5 m, it can beconsidered a more efficient deck structure.Superstructure Concrete structure Lower level steel structure and upper level concrete structure.Substructure Concrete box type pier. Tubular steel pier.6-12