The Compressive Strength of Steel

What is compressive strength?

Compressive strength is a material’s capacity to withstand the pressure of a force that pushes, squeezes, or compresses it. If a building has a low compressive strength, it is more likely to buckle and fail under pressure.

That's why it’s crucial to ensure a blast resistant building is made of a material with high compressive strength, like steel.

When an explosion occurs, it produces a blast wave that moves outward at supersonic speed. The blast wave can cause devastating structural damage to buildings that cannot withstand the compressive force. More importantly, when a structure fails, it can cause casualties from the immediate collapse and any resulting shrapnel.  

Below, we’ll look at the compressive strength of steel and how that makes it an ideal material for blast resistant buildings.

How is Compressive Strength Measured?

Compressive strength measures how much load a material can bear. We can gauge a material’s compressive strength by performing a test in which a force is exerted downward on top of an object and upward from the bottom (thereby compressing it). The compressive strength measurement is determined by dividing the force it took to get the material to deform by the cross-sectional surface area of the object.

A compressive strength measurement ultimately gives us the amount of force it will take to cause your material to fail and is noted in one of two ways: pounds per square inch (psi) or Megapascals (MPa). In the US, psi is the most common measurement of compressive strength. (Note that 1 pascal =  0.00014503773800722 psi, making 1 MPa = 145.03773773 psi.)

HOW MUCH COMPRESSIVE STRENGTH DOES A BLAST RESISTANT BUILDING NEED?

Because blast resistant buildings are designed to withstand significant pressure, they are constructed of materials with high psi levels. Features such as doors and other fixtures which can fail and become projectiles during blasts should also be made of materials that can withstand blast pressure.

A residential house can be destroyed by an explosion with an overpressure of 2-3 psi and cause severe casualties from flying debris. At 5 psi, we can expect most buildings to collapse, and by the time we get to 20 psi, the blast would be enough to destroy even the most robust structures.  

However, no industry regulations dictate the strength ratings for blast resistant buildings. The closest thing we have are recommended practices (RP) from the American Petroleum Institute (API). These are referred to as API RP 752 and 753. They’re designed to ensure that the design, construction, installation, and maintenance of both temporary and permanent structures in hazardous areas are safe for occupants, including blast resistant buildings. When choosing a blast resistant building, it's crucial to ensure it is API RP 752/753 compliant.

How Blast Resistant Building Companies Use Compressive Strength to Ensure Buildings Are Safe

Blast resistant building companies test the load-bearing abilities of their structures, foundations, and load-bearing pillars. It's essential to know the compressive strength limit of building materials, how long they can withstand pressure, and the specific way in which they fail at their upper limit. Do they bend, deform, crack, or shatter in a way that endangers human life?

But while it’s critical to assess the amount of compression that building materials can withstand, the safety of a building is also dependent on how it responds to other related forces. That’s because an explosion can be followed by tremors, fire, or shock waves. So, compressive strength is part of a more extensive set of equations that include shear strength and tensile strength.

This is why blast resistant building companies must conduct comprehensive blast tests.

Why Steel is the Best Option

There’s no denying steel's superior strength compared to other materials. Its strength-to-weight ratio is eight times stronger than concrete, another popular blast resistant building material. Steel also has superior tensile and shear strength, though exact measurements depend on its composition.

Steel is the strongest common building material, making it ideal for blast resistant buildings. Hot-rolled structural steel is the most resilient, measuring roughly 50,000 psi for both tension and compression strength. Most structural steel has a compressive strength of approximately 25,000 psi. By comparison, the compressive strength for concrete is typically around 4,000 psi. (However, it can be higher if it is reinforced with steel.)

Understanding Compressive Strength

When choosing a blast resistant building material, it's crucial to understand compressive strength and its role in helping a building withstand both explosions and their immediate aftermath.

The compressive strength of steel makes it the most reliable material for blast resistant buildings, allowing anyone at or near the blast site the best chance of being protected from the blast wave or projectiles caused by an explosion. Steel is more likely to bend than break and withstands both accidental and intentional detonations without catastrophic structural failure.

Saving lives is RedGuard’s priority. Reach out today to speak with our team about your blast resistant building needs.