Structures with Daniel Frangus & Mihai Suta of Campbell Reith

Structural Engineering in the Built Environment: Materials, Loads, and the Art of Support

When we move through towns and cities, it's easy to admire the towering buildings, sweeping bridges, and elegant public spaces — but behind every structure lies the discipline of structural engineering. It’s the science (and art) of making sure the built environment safely stands, resists forces, and endures over time. The fundamentals of structural engineering, from classic materials to the forces acting on structures, and how this all connects to modern, sustainable design.

Understanding Structural Loading

Every structure, whether a sculpture in a park or a skyscraper, must withstand loads — forces that act upon it. These come in different forms:

• Point loads: concentrated at a single point (like a column or a statue).

• Uniformly distributed loads (UDLs): spread evenly across a surface (like the weight of a green roof or a floor slab).

Structural engineers use different design cases to test the safety of a structure:

• Ultimate Limit State (ULS): ensures a structure won't collapse.

• Serviceability Limit State (SLS): ensures it functions well without excessive movement, cracking, or vibration.

Material Eras and Their Legacy

Over time, structural materials evolved — each with strengths, weaknesses, and environmental considerations:

• Cast Iron (1800–1900)

Used for drainpipes, framing, and decorative features.

Pros: recyclable, easy to cast.

Cons: prone to rust and fire hazards.

• Steel (1900–Present)

Ideal for long spans, trusses, and complex framing.

Pros: stronger than iron, adaptable.

Cons: thermal expansion, corrosion risk, requires fire protection.

• Concrete (1800–Present)

Versatile for frames, foundations, and retaining walls.

Pros: cast into complex shapes, durable.

Cons: heavy, weak in tension, requires steel reinforcement which can rust.

• Masonry/Stone (1800–Present)

Historically vital for wall panels, clay pipes.

Pros: durable, doesn’t corrode.

Cons: heavy and rigid, limiting design flexibility.

• Timber (1700–Present)

Still widely used for beams, rafters, and sustainable building systems.

Pros: natural, renewable, lightweight. Innovations like Glulam (glued laminated timber) and Cross Laminated Timber (CLT) have made it even more viable, controlling imperfections and improving performance.

Key Structural Components and Behaviours

• Columns: take vertical (axial) loads and sometimes bending

• Beams: resist bending, shear, and occasionally axial loads

• Trusses: a framework of tension and compression members

• Braced structures: resist lateral forces like wind

• Transfer elements: redistribute loads, especially above open spaces

End conditions matter too; in-ended, fixed, or roller-supported — affecting how loads transfer.

Foundations and Landscape Integration

The interaction between structures and landscapes is vital. The soil beneath a structure affects how it behaves:

• Soil bearing capacity

• Settlement potential

• Water table levels

• Contamination risks

For challenging conditions:

• Deep foundations like piles bypass weak surface soils

• Heave protection materials prevent ground movement damage

• Avoid large trees near clay soils as they can cause desiccation (drying out), leading to ground shrinkage

Retaining Walls and Earth Retention Systems

To hold back soil or create level changes:-

• Gravity walls: use mass to resist soil pressure

• Cantilever walls: rely on weight and footing for balance

• Anchored walls: reinforced with cables or rods

• Crib walls: timber or concrete cells filled with soil/stone

• Reinforced soil systems and soil nailing stabilize slopes

• Embedded retaining walls (continuous piled, secant piled, diaphragm, king post, or sheet piled) offer deeper, structural solutions

Sustainable and Net Zero Structural Design

Modern design demands sustainability:

• Steel, timber, and masonry can be recycled or repurposed

• Locally sourced materials reduce embodied carbon

• Concrete’s carbon footprint is a concern, but innovations like low-carbon mixes and better reinforcement systems are emerging

• Net zero design is about reducing operational and embodied energy, managing resources, and ensuring buildings support both people and the planet

Final Thoughts

Structural engineering isn’t just about holding things up — it’s about harmonising structure, landscape, and community needs. From ancient stone walls to cutting-edge CLT towers, the principles remain the same: understanding forces, choosing the right materials, and designing for safety, performance, and longevity.