Pre-tensioning

Pre-tensioning, in construction, is a technique used to improve the tensile strength of concrete elements by applying compressive stress before the concrete hardens. This is achieved by stretching steel tendons within a mold, then casting concrete around them. Once the concrete has cured, the tendons are released, transferring the tensile force to the concrete, creating internal compression. This counteracts tensile stresses that the concrete will experience under load, leading to increased load-bearing capacity, reduced cracking, and greater durability, particularly for structures like bridges and precast concrete beams.

Pre-tensioning meaning with examples

• Engineers employed pre-tensioning to manufacture the long-span bridge girders, enhancing their strength and allowing for greater distances between supports. The carefully calculated pre-stress minimized deflection under heavy traffic loads and ensured the structure's longevity.
• The construction company chose pre-tensioning for the concrete floor slabs of the high-rise building. The resulting pre-stressed slabs, significantly thinner than conventionally reinforced slabs, reduced the overall building weight and allowed for greater design flexibility.
• The precast concrete beams, created through pre-tensioning, were quickly assembled on-site for the new warehouse project. The factory-controlled environment ensured quality, while the pre-stressed elements provided the required strength and durability for industrial loads.
• During the failure investigation of the parking garage, the analysis revealed that insufficient pre-tensioning resulted in premature cracking and eventual structural degradation, emphasizing the need for meticulous quality control.
• For the railway sleepers, pre-tensioning was deemed critical. This process endowed them with high resistance to flexure, enabling them to handle the substantial repetitive stresses imposed by the trains moving over them.