Why do steel bars overlap?

Generally speaking, the cost of lap joint is lower than that of welding or mechanical connection, and the construction is faster, so as long as lap joint is allowed, it is generally reinforced lap joint.

In the process of reinforced concrete structure construction, in order to ensure the continuity of reinforcement force and reliable transmission of force.

For the convenience of transportation, all steel bars except wire rods are supplied in 6m or 9m. Wire rod can be supplied in large length, but there is also a length limit for secondary transportation on site. It's hard to imagine transporting 80-meter-long steel bars from underground to the 20th floor. Therefore, there will inevitably be overlapping or welding places in the project.