Structural Engineering

Measuring elasticity in aluminum bars helps civil engineers connect force, stress, and strain to the way a material changes shape. Because each civil engineering structure is unique and costly to reproduce, engineers depend on analytical models instead of full-scale testing for every design. These simplified models help check that strength and stiffness limits are not exceeded.

To build those models, engineers need two things. They need theories that describe how structures respond to loads.

Steel strength can vary widely, and this lesson focuses on how that shows up in stress-strain behavior. Stress is the force applied to a material, and strain is the change in shape or length that results. The study compares two steels that represent the range often seen in civil engineering applications.

The two examples are a very mild, hot rolled steel and a harder, cold rolled steel. Hot rolled steel is formed at high temperature, while cold rolled steel is processed differently to produce...

Aluminum is a widely used metal with a strong strength-to-weight ratio, corrosion resistance, and easy fabrication. It is also non-magnetic and has high thermal and electrical conductivity. These properties help explain why aluminum appears in so many products and structures.

Aluminum is found in everyday items such as soda cans and airplane components. It is especially useful when alloyed with one or more common elements. Alloys are metal mixtures, and they expand aluminum’s role in...

Charpy V-notch testing helps measure how steel handles impact before it fractures. It is a simple way to estimate a material's toughness, or its ability to absorb energy when hit suddenly. In civil engineering, this test is used to judge how likely a steel is to fail in a brittle way.

Brittle fracture is one of the most dangerous kinds of structural failure. It can happen suddenly and with little warning. The material does not bend much first, much like a bone fracture. These failures are more...

Rockwell hardness testing measures how much a material resists indentation. It is a simple and relatively inexpensive mechanical test, so engineers use it often when they need useful data quickly. It is also less destructive than tensile testing, which makes it practical for many samples.

Hardness is a material property that describes how much plastic deformation, or permanent yield, happens when a known force is applied. Hardness tests are empirical, which means the results come from measured...

Slender steel members can fail by buckling when they are placed in compression. In civil engineering, this failure mode matters because steel structures are often designed to be strong, economical, and fast to build.

Steel members are useful in civil works because the material has high strength and many parts can be prefabricated before they reach the job site. That helps reduce material use, simplify fabrication, and speed up construction. Compared with reinforced concrete structures, the...

Earthquake testing of structural models helps engineers understand how buildings may behave during ground shaking. Earthquakes remain a major hazard around the world. Damage can affect large regions and lead to heavy loss of life, as seen in the 2005 Banda Aceh earthquake in Indonesia.

The number and strength of earthquakes are not increasing, but the risk to buildings is. Rapid, unregulated growth in seismically active areas, including the Circum-Pacific "belt of fire," raises that risk.

Metal fatigue in bridges and other structures develops when repeated loads weaken metal over time. The Silver Bridge collapse in Point Pleasant, West Virginia, in 1967 brought this problem into focus. The eyebar-chain suspension bridge over the Ohio River failed during evening rush hour, and 46 people died.

The collapse began with a single eyebar that had a small 0.1-inch defect. Repeated loading made that defect grow until it reached a critical length. The eyebar then failed in a brittle way,...

Polymer materials are used in civil structures, from soft sealants to rigid pipes in water and wastewater systems. A polymer is a molecule made of repeating subunits. The word comes from Greek, where "poly" means many and "-mer" means basic unit. These repeating units are called monomers, and the structure of the polymer helps determine its properties.

Polymers are grouped into three main categories: plastics, elastomers, and rigid rod polymers. Plastics include thermosets and thermoplastics.

Fiber-reinforced polymeric materials, or FRP materials, are composite materials made of long fibers embedded in a polymer resin. The fibers are arranged in aligned, parallel directions. This gives the material orthotropic behavior, which means it responds differently depending on the direction of the load.

Along the fiber direction, FRP is very strong and stiff. Across the fibers, it is much weaker because the resin carries most of the load in that direction. A common unidirectional form is...

Concrete and asphalt both rely on aggregates, which are the sand- and rock-like particles mixed into the material. Concrete is a composite made of cement, water, air, coarse aggregate, and fine aggregate. Fine aggregates are usually sands, while coarse aggregates are natural or crushed rocks. Chemical admixtures may also be added to change specific properties, such as making concrete more fluid during casting.

Asphaltic mixes also contain coarse and fine aggregates, along with asphalts,...

Concrete mix design and fresh concrete tests are used to check whether a batch is workable and ready to place. Concrete has two phases. One phase is the cement paste, which includes cement, water, and air. The other phase is the aggregate portion, which includes coarse and fine aggregates.

Designing a concrete mix involves two key goals. The fresh mix must be easy to cast into forms, even when the forms contain steel reinforcement. In this stage, concrete rheology, or how the material flows,...

Concrete strength tests after hardening show how cured concrete performs once it has set. Concrete goes through two main stages in construction. The first stage is batching, transporting, and casting fresh concrete. At that time, the material is viscous, and workability and finishability are the main performance goals.

The second stage begins soon after the concrete is placed in the form. Hydration starts, and the concrete begins to set and harden. This process is complex, and not every phase...

Concrete tension behavior is important because cracking often begins when concrete is pulled apart or combined with shear. A previous lab on concrete in compression showed that concrete can carry very large compressive stresses, but the failures did not occur as pure compression failures. Instead, they formed along shear planes, where tensile forces were highest.

This experiment focuses on how hardened concrete behaves in tension and why its maximum tensile strength matters. Tension and shear...

Wood is a common building material used in construction. It is renewable and sustainable, and it also has strong visual appeal. More buildings are likely made with wood than with any other structural material today.

Many wood structures are single-family homes. Wood framing is also used in larger apartment buildings, as well as in commercial and industrial buildings. Its wide use comes from both cost and appearance. Wood buildings can often be built with little equipment, which helps keep...