[Popular Science] | An Article To Understand! What Is The Difference between Pre-tensioning And Post-tensioning in Bridge Construction?

【Introduction】  

Are you curious about how the concrete girders of viaducts and highways are made of “steel”? The secret is in the “prestressing technology”! Today, we take you to reveal the bridge community's two “internal cultivation method” - pre-tensioning method VS post-tensioning method, 3 minutes to see the difference between them!

❷Post-tensioning: “Threading the Needle” for Bridges

Applicable scenario: T-shaped/I-shaped girder bridges (large span, high girder body)  

Core logic: first pour concrete and leave apertures, then thread the tendons and tension them, and then rely on the anchorage to “lock” the prestressing force!

Construction of four parts:  

1️⃣ Buried pipe shaping: pre-buried metal bellows when pouring the beam, reserving the “meridian channel”;  

2️⃣ Threading the reinforcement and pulling the bow: after the concrete reaches the standard, put in the stranded wire, and vigorously tension it with a jack;  

3️⃣ Anchor sealing: the strand is fastened with a special anchorage, and the internal force is injected into the beam instantly;  

4️⃣ Grouting and sealing: the aperture is filled with mud to prevent rust, and finally the end concrete is poured to “seal the sword”.

Technical Highlight:  

Reinforcing steel alignment! Partially curved to the end of the beam, specializing in the support area “shear disobedience”;  

Curve reinforcement to avoid tensioning the top of the beam “cracked emoji”, the distribution of internal forces more scientific.

Advantages: flexible response to large span, specializing in a variety of complex forces! But the site construction is slightly troublesome.