Wu Zhi Qiao Bailey Bridge
Jul 22, 2022
Wu Zhi Qiao Project
Wuzhiqiao Charity Project (Bridge to China) promotes sustainable rural development and improves people's livelihood through the establishment of pedestrian bridges, green buildings, students' experiential learning and community livelihood improvement projects.
The work of the project is mainly completed by volunteers who are professionals, as well as a team of university staff and university students in the Mainland and Hong Kong. When constructing temporary bridges, ecological dwellings and other small village facilities, the project focuses on the concept of environmentally friendly construction. The volunteer team works closely with local villagers to teach the villagers the knowledge of construction techniques and materials used, so that they can carry out maintenance and protection work in the future.
Design of Wu Zhi Qiao Bailey
Wuzhi Bailey Bridge is a light pedestrian bridge, which is a prefabricated steel bridge: the main force-bearing member Bailey frame, the secondary force-bearing member steel beams, bridge decks and other related supporting members and connecting bolts, pins. It is assembled; it has the advantages of simple structure, standardized prefabricated components, controllable cost, only relying on manpower and small machinery for construction, and fast construction speed. Wuzhi Bailey Bridge can be used as a pedestrian bridge for all kinds of rural areas and mountainous areas.
Wuzhi Bailey Bridge, as a rural bridge, in principle only provides passage for people and common agricultural livestock, and is not suitable for the passage of motor vehicles and various agricultural machinery. In the currently designed and adopted plan of the endless Bailey bridge, the center-to-center distance between the two horizontal Bailey frames has two specifications of 1.30m and 1.50m (the net widths are 1.25m and 1.45m respectively). The latter width specification is more suitable for areas with livestock passing needs. In principle, the net width of Wuzhi Bailey Bridge should not be greater than 1.50m, to prevent any possible illegal behavior of motor vehicles and agricultural machinery on the bridge, which may cause unsafe load conditions beyond the structural design expectations.
General requirements
1. The elevation of the bottom of the Wuzhi Bailey Bridge should be at least 0.5m above the height of the highest water level in the past 10-20 years to prevent the dead wood and rocks washed down by the flood during the summer flood season from damaging the bridge structure;
2. The single span of the Wuzhi Bailey Bridge should not be larger than 16m (8 sections) to ensure that the stability of the structure meets the requirements;
3. The net width of the bridge deck of Wuzhi Bailey Bridge should not be greater than 1.50m to ensure that the bridge structure is only used for the passage of people and animals;
4. The bridge deck of Wuzhi Bailey Bridge needs to consider factors such as anti-skid, convenient passage of people and animals, and convenient installation. The design selection is made according to the actual use requirements, and the structure of the bridge deck is not considered in the calculation model;
5. Structural design and calculation can be modeled and analyzed according to beam elements, and the hinged or semi-rigid effects of nodes can be ignored. Therefore, the maximum deflection limit of the structure under the action of the full-span constant + live load standard value is preferably taken as a single-span. 1/500 of ;
6. During the buckling stability check calculation, the ultimate load factor of the first-order buckling live load of the overall structure shall not be less than 4.0;
7. The slenderness ratio of compression members (including diagonal braces that may be compressed) shall not be greater than 100, and the maximum slenderness ratio of other members shall not be greater than 130;
8. The vertical vibration frequency of the structure should be greater than 3Hz to ensure pedestrian comfort;
9. The force-bearing members such as berets and beams should use general hot-rolled steel sections to ensure section strength, toughness and local stability;
10. The construction of factory components should be operated in strict accordance with the specifications, the welds should meet the design requirements, and the burrs and welding slag produced by cutting and welding of steel should be dealt with after completion.
Grinding and finishing;
11. After all holes and sleeves are processed and passed the inspection, they should be coated with industrial vaseline or solid lubricating oil immediately, and the truss pins and bolts should be coated withrust oil, other components should be rusted by sandblasting, and treated with surface galvanized or inorganic zinc-rich paint to increase the rust resistance of structural steel;
12. The holes on each component must be welded first and then drilled. The wall of each hole must be perpendicular to the surface of the rod to form a cylindrical hole. The finish of the hole wall must meet the design and construction requirements.
Bolts, nuts, washers and pins used in structural connections shall meet national standards;
13. During the assembly process of Bailey bridge, the wind-resistant tie rod needs to be fully tensioned by adjusting the turnbuckle bolts;
14. Due to the deviation of the local bending axis of the member, the deviation value shall not exceed the following ranges:
(1) The section bar of each stress member (Bailey frame and beam) is 1/1000 of the length of each bar; the deviation of the beam between the elevation and the plane is absolute
The value shall not exceed 2mm;
(2) The plane deviation of the bridge deck shall not exceed 1/1000 of the length, and the deviation on the facade shall not exceed 2mm;
(3) The diagonal bracing and the wind-resistant tie rod are 1.5/1000 of the length of the rod;
Materials and Properties
The steel used for Bailey bridge should be Q235 steel and Q345 steel, and their quality should conform to the current "Carbon Structural Steel" (GB/T700) and "Low Alloy High Strength Structural Steel" (GB/T1591) respectively. The selection of steel grades requires Considering the local minimum temperature in winter at the bridge point, it is recommended to select the steel grade of B or above.
After the structure is completed, the surface of the structural steel needs to be treated with inorganic zinc-rich paint. The quality of the zinc-rich paint used must comply with the current "Zinc-rich Primer" (HG/T 3668), and with appropriate intermediate paint and topcoat, the quality must meet the current requirements. Specifications, such as "Epoxy Mic Iron Intermediate Paint" (HG/T 4340), "Solvent-Based Polyurethane Coatings (Two-Component)" (HG/T 2454), etc. The selection and matching of coatings should ensure that the coatings have a maximum anti-corrosion life of the structure. 10+ years
Bailey frame connecting pins should be forged or rolled steel with high-quality carbon structural steel, and its material should conform to the current "High-quality Carbon Structural Steel" (GB/T699). The bolted connection of Bailey bridge is not used as the main force-bearing member, and ordinary bolts can be used. The ordinary bolts should comply with the current "Hexagon Head Bolts Class C" (GB/T5780) and "Hexagon Head Bolts" (GB/T5782), and high-strength bolts can also be used. Bolts instead.
As the major supplier of Wu Zhi Qiao Bailey Bridge project，ZhenJiang Great Wall group strictly follow the above design requirements and provide great technical support for the project.
“Thanks to Zhenjiang Great Wall Heavy Industry Co., Ltd. for putting forward many pertinent suggestions for our Wuzhi Bailey BridgeThe proposal enables students to perform physical assembly tests in their factories, and can further optimize the endless Bailey bridge for mass production.”
