Prestressed beam Concrete || Brigde Construction Strength #construction #structuralengineering

Added: 2026-06-03

[00:00:00]Why are prefabricated beams hollow inside? Are [music] they cheaper or weaker? Let's understand why. In the past, engineers used solid [music] concrete or stone beams to build bridges. These beams were extremely heavy, which made them very [music] difficult to transport and lift with cranes. Over time, as trucks and heavy traffic [music] passed over them, cracks often appeared at the bottom of the beams. Sometimes, the beams even broke.

[00:00:22]Later, [music] engineers studied the problem carefully and discovered something important. The top and bottom parts of the beam carry most [music] of the stress, while the middle part experiences very little stress and does not contribute much to the beam's strength. So, they decided to make the middle section hollow. [music] This made the beams much lighter and saved a significant amount of material.

[00:00:41]Engineers also left empty spaces near the bottom inside the beam.

[00:00:45]High-strength steel cables, called tendons or steel strands, [music] are placed inside these tubes. These cables are stretched very tightly using special machines before the concrete is poured.

[00:00:54]The stretched steel cables act like powerful rubber bands. They constantly try to shrink [music] back to their original length. This creates a strong built-in compression force throughout the beam. Congratulations, [music] you've learned about prestressed concrete.