Steel structures are ideally suitable for impact loads because they have high toughness value.

Toughness:
Toughness is a material property that measures its ability to absorb energy and deform plastically before fracturing. It is an important characteristic when considering the behavior of a material under impact or dynamic loads.

Impact Loads:
Impact loads are sudden and short-duration loads that occur when a structure experiences a collision or a sudden application of force. These loads can result in high-stress concentrations and deformation, which can lead to structural failure if the material is not able to absorb and distribute the energy effectively.

Why Steel Structures are Suitable for Impact Loads:
Steel structures are known for their exceptional toughness, making them highly suitable for impact loads. This is due to the following reasons:

1. Ductility:
Steel has high ductility, meaning it can undergo significant deformation before failure. When subjected to impact loads, steel is able to absorb energy by deforming plastically. This helps to prevent sudden brittle failure and allows the material to distribute the applied force over a larger area.

2. High Yield Strength:
Steel has a high yield strength, which is the point at which permanent deformation begins. This means that even under high impact loads, steel can withstand significant stress without undergoing plastic deformation. The high yield strength of steel allows it to resist deformation and maintain its structural integrity.

3. High Fatigue Strength:
Fatigue strength refers to a material's ability to withstand cyclic loading without failing. Steel exhibits high fatigue strength, making it resistant to cracking and failure under repeated impact loads. This property ensures the long-term durability and reliability of steel structures subjected to dynamic loading conditions.

4. Excellent Fracture Toughness:
Fracture toughness is a measure of a material's resistance to crack propagation. Steel has excellent fracture toughness, which means it can resist the propagation of cracks caused by impact loads. This property helps to prevent catastrophic failure and ensures the safety of steel structures.

In conclusion, steel structures are ideally suitable for impact loads due to their high toughness value. The combination of ductility, high yield strength, high fatigue strength, and excellent fracture toughness makes steel an excellent choice for applications where impact loads are anticipated.