Esijännitellyn

Esijännitellyn is a Finnish term that translates to "prestressed" in English, commonly used in civil engineering and construction. It refers to a method of strengthening concrete or other materials by introducing internal stresses that counteract the stresses that will be experienced during service. This is typically achieved by stretching high-strength steel tendons or cables before or during the concrete pour, and then anchoring them once the concrete has gained sufficient strength.

There are two main types of prestressing: pre-tensioning and post-tensioning. Pre-tensioning involves stretching the tendons before the concrete is cast. Once the concrete hardens around the tendons, the tension is released, transferring the stress to the concrete. Post-tensioning, on the other hand, involves casting the concrete with ducts for the tendons. After the concrete has hardened, the tendons are threaded through the ducts, stretched, and then anchored against the concrete.

Prestressed concrete offers several advantages over conventional reinforced concrete. It allows for longer spans, thinner structural elements, and improved resistance to cracking under load. This makes it a valuable technique for constructing bridges, high-rise buildings, and other large-scale structures where durability and efficiency are paramount. The controlled internal stresses help to distribute loads more effectively, enhancing the structural integrity and lifespan of the construction.