Material Characteristics of Steel, Concrete, Masonry, and Timber

Material Characteristics of Steel

Strength and Ductility

Steel is prized in structural design for its high tensile and compressive strength. One of the most exam-relevant features of steel is its ductility—its ability to undergo significant deformation before failure.

• Yield strength (F_y): 36 ksi to 50 ksi (e.g., ASTM A36 or A992)
• Young’s Modulus (E): ~29,000 ksi
• Poisson’s Ratio: ~0.3

Behavior Under Load

Steel is homogeneous and isotropic. It exhibits linear elastic behavior up to yield, followed by plastic deformation.

Corrosion and Fire

Steel is susceptible to corrosion and loses strength rapidly in fire conditions.

Exam Tip: Know how temperature affects steel and understand the stress-strain curve for mild steel.

Material Characteristics of Concrete

Strength and Brittleness

Concrete has high compressive strength but low tensile strength, which is why it is reinforced with steel.

• Compressive strength (f’_c): 3,000 to 6,000 psi
• Tensile strength: 10–15% of f’_c
• Modulus of Elasticity (E_c): E_c = 57,000 √f’_c
• Poisson’s Ratio: ~0.2

Creep and Shrinkage

Concrete undergoes creep and shrinkage over time, which can lead to long-term deformation.

Durability and Fire Resistance

Concrete is durable and fire-resistant but must be detailed correctly to prevent corrosion of reinforcement.

Exam Tip: Be familiar with ACI assumptions in flexural design (e.g., strain compatibility and Whitney’s stress block).

Material Characteristics of Masonry

Composition and Types

Masonry consists of individual units bonded with mortar. It can be unreinforced (URM) or reinforced (RM).

Strength and Behavior

Masonry is strong in compression but weak in tension and shear.

• Compressive strength (f’_m): 1,500 to 3,000 psi
• Modulus of Elasticity (E_m): 700–1,000 × f’_m
• Flexural tensile strength: direction-dependent

Durability and Fire Resistance

Masonry is durable and fire-resistant, but detailing is important to avoid moisture damage.

Exam Tip: Know ASD and SD approaches. Understand the behavior of reinforced vs. unreinforced walls.

Material Characteristics of Timber (Wood)

Natural Material with Variability

Timber is an anisotropic material with properties that vary based on grain, species, and moisture content.

• Modulus of Elasticity (E): 1–2 million psi
• Strongest: parallel to grain
• Weakest: perpendicular to grain

Design Considerations

Design values are adjusted using modification factors:

• C_D: Load duration factor
• C_F: Size factor
• C_r: Repetitive member factor

Fire and Decay

Timber chars predictably in fire and is susceptible to decay if not properly protected.

Exam Tip: Know how to apply NDS equations and factors in wood design.

Summary Table

Final Exam Tips

1. Memorize common material properties. You’ll often need approximate values.
2. Understand failure modes. Ductile vs. brittle behavior is key.
3. Practice code-based problems. Especially from ACI, NDS, and AISC.
4. Review behavior under combined loading. Like bending + axial.
5. Study time effects. Such as creep in concrete and load duration in timber.

By mastering these core concepts, you’ll not only be ready for the exam—you’ll be a better engineer in the field.

Ready to test your knowledge? Try practice problems on concrete beam capacity, column buckling, or shear in timber joists. Real-world scenarios are the best prep!

Let us know if there is anything we can do to help you prepare for the exam.