Girder Cross Section

Materials Used

■ Steel: SM490–520

■ Concrete:

    - Slab, top: 27MPa

    - Lower casing: 45MPa

■ PC Strand:

    - SWPC 7B 15.2, Fpy = 190MPa

■ Steel: SM490–520

■ Concrete:

    - Slab, top: 27MPa

    - Lower casing: 40MPa

Method Overview

A composite method that combines a pre-compressed concrete panel with an I-girder. It introduces prestress in phases to compensate for long-term loss, ensuring full composite action by correcting the camber difference between the girder and panel.

Prestress is applied to the I-girder through pre-flexion loading, then concrete is cast and released, introducing compressive prestress into the lower flange concrete to create a composite girder.

Advantages & Disadvantages

- Full prestressing prevents tensile cracks in lower casing concrete

- No need for production bed installation, fast construction, and environmentally friendly (no waste)

- Partial prestressing may cause cracks in lower casing, increasing maintenance cost

- Long-term storage after compression can lead to significant prestress loss

Cost-Effectiveness
(35M)

Uses less steel (main cost driver), and the simplified process allows mass production in a short time, making it cost-effective despite being a composite structure.
(Monthly production: 20–25 units)

Requires more steel during the preflexion process. Additional 7-day curing process for compressive prestressing raises overall cost.
(Monthly production: 8–12 units)