Red Seal Ironworker (Structural/Ornamental) Practice Exam

What happens to steel structures during temperature changes?

1. They become more rigid

2. They can cause expansion and contraction, potentially leading to stress and deformation

3. They absorb heat and become lighter

4. They remain unchanged regardless of temperature

The correct answer is: They can cause expansion and contraction, potentially leading to stress and deformation

Steel structures are subjected to expansion and contraction as temperatures fluctuate. When temperatures increase, steel expands, and when the temperatures decrease, it contracts. This phenomenon occurs because the atomic structure of steel changes in response to thermal energy; the atoms move more vigorously at higher temperatures, leading to an increase in the material's overall dimensions. This expansion and contraction can result in significant stress, particularly if the steel is constrained by other structural elements or connections that do not allow for movement. Over time, these stresses can lead to deformation, strain, or even structural failure if the design does not account for thermal effects. Engineers must carefully consider thermal expansion and contraction in their designs, making provisions such as expansion joints to accommodate these changes, thereby ensuring the integrity and safety of the structure. The other choices do not accurately represent the behavior of steel under temperature changes. While steel does not become more rigid as temperatures change, it can actually become more ductile when heated, and it certainly does not absorb heat and become lighter; the mass of the material remains constant regardless of temperature. Motion of atoms due to temperature changes is a critical factor in determining the physical response of steel structures.