Girder Cross Section

Materials Used

■ Steel: SM490–520

■ Concrete:

    - Slab, upper: 27MPa

    - Lower casing: 45~48MPa

■ PC Strand:

    - SWPC 7B 15.2, Fpy = 190MPa

■ Steel: SM490

■ Concrete:

    - Slab, upper: 27MPa

    - Lower casing: 40MPa

■ PC Strand:

    - Unbonded, mono 15.2, Fpy = 190MPa

Method Overview

A composite method using approx. 80% of the Preflexion load compared to the traditional method to induce elastic recovery in the steel I-girder and introduce initial prestress to the lower flange concrete. Additional prestress is applied using unbonded strands.

A method that enhances eccentric efficiency by integrating steel plates on the upper flange, reducing girder height. Prestress is applied at different construction stages by unifying the continuity point with steel plates + rebar + prestressing material.

Advantages & Disadvantages

- Long-term storage after compressive prestress in the lower flange may cause excessive prestress loss

- Full prestressing design ensures high crack resistance

- Wide flange makes it less suitable for curved bridges compared to PSC beams

- Full prestressing design ensures high crack resistance

Cost-Effectiveness
(35M)

High steel consumption and separate 7-day concrete curing for compressive prestressing in preflexion process increase construction cost.

Slightly less steel is required than traditional Preflex methods, but additional processes offset cost savings.

High steel consumption and separate 7-day curing for compressive prestressing in preflexion process raise construction cost.
(Monthly production: 8–12 units)

Standard

L = 35m, B = 24.3m, 10 girder rows
Design Load: DB-24