Fengtai Bridge (Sichuan) – Prestressed Structure
Sichuan Fengtai Bridge (Suining) – Prestressed Engineering Case Study
The Fengtai Bridge in Suining, Sichuan Province, is a key infrastructure project and a crucial node of the city’s middle ring road. The main bridge is a prestressed concrete continuous girder bridge with a total length of 1,075.27 m and a width of 33.8 m, designed as a dual-direction six-lane first-class highway. The superstructure consists of a single-box, double-cell variable-height continuous beam, featuring three span arrangements: (43.67+68+43.67) m, (51+2×68+51) m, and (51+72+72+51+42.6) m. The piers are double-limbed vase-shaped columns with capping beams.
Prestressing technology was extensively applied to achieve a long-span, lightweight structure while maintaining structural rigidity and crack resistance, and to accommodate the variable cross‑section depth and complex stress distribution of the continuous girder.
| Construction Challenge | Description | Prestressed Solution |
|---|---|---|
| Large‑span continuous girder Long-span & variable cross‑section depth | The main span of up to 72 m and the continuous variation of the cross‑section depth result in complex internal forces, including high bending moments and shear forces at the supports. | Use bonded post‑tensioning with a combination of longitudinal, transverse, and vertical tendons; the longitudinal tendons are arranged in a parabolic profile to align with the bending moment envelope, effectively balancing the internal forces. |
| Complex tendon placement Tendons in single-box double-cell girder | The single-box double-cell girder has a narrow interior space, making tendon installation and grouting difficult. | Pre‑fabricate tendon assemblies; use plastic corrugated ducts for enhanced strength and sealing; pre‑install grouting pipes and vents; adopt a high‑performance grout to ensure complete filling. |
| Pier-cracking prevention Double-limbed vase-shaped piers | The double-limbed vase-shaped piers are prone to tensile cracking due to temperature gradients and shrinkage effects. | Install prestressed vertical steel bars inside the pier shafts; impose pre‑compression stress to counteract tensile forces from shrinkage and temperature, effectively controlling cracking. |
| Grouting quality control High risk of voids during grouting | The curved ducts and the variable-depth girder make it difficult to completely fill the grout, leading to corrosion risks. | Adopt vacuum‑assisted grouting with a high‑performance, corrosion‑inhibited grout; use transparent hoses for venting to visually ensure the grout is fully filled. |
| Long‑term deflection Creep and shrinkage control | Continuous rigid‑frame bridges are prone to long‑term creep and shrinkage, which can affect the long‑term smoothness of the bridge deck. | Specify low‑relaxation steel strands (≤2.5% at 1000 h); increase the number of reinforcement bars in the compression zone; implement a strict curing system to reduce the creep effect. |
| Corrosion protection River‑crossing structure in a humid environment | The bridge is located over the Fujiang River, where high humidity and seasonal flooding increase the risk of corrosion to the prestressing system. | Use epoxy‑coated steel strands and corrosion‑inhibited grout; strengthen the waterproofing and anti-corrosion treatment of the anchorage zone. |
Successfully achieved large‑span structural integrity, pier crack control, and enhanced durability
✅ Achievements & Summary
Through the application of advanced post‑tensioning technology:
· Achieved a 72 m main span with a lightweight, single-box double-cell variable‑height continuous girder, reducing structural self‑weight.
· Effective crack control in the double‑limb vase‑shaped piers via vertical prestressing bars.
· Zero‑void grouting ensured through vacuum‑assisted grouting and corrosion‑inhibited grout.
· Enhanced durability with low‑relaxation strands, epoxy‑coated steel, and corrosion‑inhibited grout, providing a 100‑year design life.
The Sichuan Fengtai Bridge demonstrates how advanced prestressing technology enables the construction of long‑span, lightweight continuous girder bridges that are safe, durable, and cost‑effective.
