a construction worker guides a huge steel I-beam as it's lowered by a crane into position. The worker signals with hand gestures while the beam slowly descends toward its mounting points. The massive beam connects two concrete support pillars, forming the main structural framework. As the beam settles into place, it becomes the primary support that will hold the bridge deck above. Other workers nearby secure safety cables and prepare welding equipment for the final installation. A supervisor points upward checking the beam's alignment with the overall bridge structure. a large iron or steel beam being used in the construction of a bridge