Research On The Safety Of Bailey Bridge in Bangladesh
Aug 15, 2022
This paper analyzes the safe traffic capacity of the Bailey Bridge in Bangladesh Sewage Treatment Plant, determines the potential safety hazards of the existing Bailey Bridge, and proposes measures and countermeasures to ensure safety.
Basic dimensions of Bailey bridge
| Superstructure | The total span is 30.6m, the width of the bridge deck is 3.36m.The total width of the inner side is 3.82m; the total width of the outer side of the bridge is 5.12m |
| Berry frame | The length of a single beret is 3.05m and the height is 1.34m.There are 20 berets in total, 10 on each side of the deck |
| Pile | 9 reinforced concrete piles per abutment |
| Caps | The thickness of the cap on the upper part of the pile is 900mm, the width is 6m, and the vertical direction of the river is 5.3m |
Materials for Bailey Bridge
The yield strength of the steel is 550MPa, the tensile design strength is 275MPa, and the shear strength is 208MPa. The pile body and the abutments are made of C25 and C30 concrete, respectively.
Design Traffic Load
The design traffic load adopts AASHTO HS20-44. 20 ton semi-trailer.Trailer load, axle load is 145kN. The design concentrated load is 80kN, the design shear load is 110kN, and the lane load is 9.35kN/m
Current status and Follow-up planning
At present, due to the needs of engineering construction, transportation of building materials and large-scale machinery and equipment, etc.Vehicles need to pass through the bridge, and the maximum load has reached 100 tons. At the same time, the bridge is the only passageway, the traffic density is high. Especially at night when heavy vehicles pass frequently.
The test of bridge operation is huge. According to the short-term and long-term regional planning of Dhaka City, it is planned to build the area into a new urban area. At present, there are many construction projects such as houses and roads in this area, and building materials transportation vehicles significantly increased. Vehicles that are expected to be likely to pass in the near or long term will include a large number of heavy-duty vehicles transport trucks, with an average load of about 50 tons.
Measures to Improve the Service Life of Existing Bailey Bridges
The normal design life of the bridge is generally 50 years. Due to the insufficient stiffness of the Bailey bridge, the measures to be taken if the bridge continues to be used safely are as follows:
①If a member of the same type is added to the upper and lower parts of the Bailey Bridge, according to the analysis, the maximum displacement of the bridge deck will be reduced by 23% under normal load. Under abnormal load, the maximum bending stress of the member can be controlled at 246MPa.
②If two members of the same type are added to the upper part of the Bailey bridge, and one member of the same type is added to the lower part, the bridge will meet the traffic capacity of abnormal vehicle loads;
③The above design is designed to meet the load of 20 tons. If the normal load of 50 tons is passed, according to the calculation, it is necessary to add piers in the middle of the bridge to convert the bridge into a double simply supported beam or a continuous beam, but the bridges on both sides of the existing bridge need to be checked and verified. table carrying capacity
Conclusion:
(1) The existing Bailey bridge has good overload capacity, but due to its own stiffness
Insufficient, large and irrecoverable deformation has been produced under the action of overload.
(2) The truss on the inner side of Bailey bridge bears more load than the outer side.
(3) Considering the local reports of crashes of the Bailey Bridge every year, and considering the need for the bridge to exceed the originally designed traffic capacity, the most thorough and safe solution is finally adopted, that is, the existing bridge superstructure is replaced. For reinforced concrete bridges, completely solve the problem of insufficient traffic capacity of existing bridges
