Types of structural beams

So, what's the definition of a structural beam?

Structural beams play a critical role in the construction of numerous buildings, bridges, and other structures, serving as indispensable elements. These beams are horizontal members that offer stability and support to the structure. Typically, they are constructed with sturdy and long-lasting materials, including steel or concrete, and engineered to withstand a diverse array of loads and forces. Structural beams act as conduits, transferring loads from the structure's floors or roof to its supporting walls or columns.

What are the different types of beams

There are 5 types of beams commonly used in structural design:

1. Simply supported Beams
2. Continuous Beams
3. Fixed Beams
4. Cantilever Beams

Simply supported beams

A beam that stretches across a solitary distance connecting two supports is known as a simple beam. One of its ends is backed up by a pinned support, whereas the other end is supported by a roller support. Simple beams are the fundamental type of beams that exist. They are comparatively easy to design and build.

Continuous beams

A beam which stretches across numerous distances between supports is referred to as a continuous beam. These beams are more intricate than simple beams and demand meticulous analysis.

An example of a continuous beam is a beam used on a multi-story building. It spans multiple distances between supports, such as columns or walls, and is able to carry the weight of the floors.

Fixed end connection beams

These beams are supported at both ends with fixed supports and are unable to rotate or deflect under load.

An example of a fixed beam is a beam that is used to support the weight of a roadway on a bridge. The beam is supported at both ends by concrete piers, and is not allowed to rotate or deflect under the weight of the roadway and the vehicles that travel on it.

Cantilevers

These beams are supported on one end with a fixed support and have a free end that extends beyond the support. They are used to support loads that extend beyond the support.

An example of a cantilever beam is a balcony that extends out from the side of a building, supported on one end by a structural wall and with the other end unsupported.

The types of beam supports

Supports are used to transfer loads and forces from the beam to the structure. There are different types of external beam supports:

1. Fixed Supports
2. Pinned Supports
3. Roller Supports

Fixed Supports

Fixed supports are acknowledged as rigid supports since they do not permit any kind of rotational or translational movement. These supports have the ability to withstand horizontal, vertical, and moment loads, making them an incredibly robust and stable form of beam support through their reaction forces.

Fixed supports typically have end plate or flanges which sit outside the area of the main beam member itself. 

Pinned supports

Pinned supports allow rotational movement but do not not allow translational movement. Pinned supports are able to resist horizontal and vertical loads, but cannot resist moments due to there being no lever arm.

A pinned support is more common than a fixed support and they can be seen in most hinged connections used on your cupboards and doors, whereby rotation of the join is permitted but no translational movement is allows. The hinge prevents and resists horizontal and vertical forces but allows for rotation.

Roller supports

Roller supports enable rotational and translational motion of the beam in a single direction. These supports can endure either vertical or horizontal loads, but not both, depending on their orientation. They are not capable of resisting moment loads.

A bridge deck is an example of where roller supports are commonly used to allow for expansion and contraction resulting from temperature variations. Even though the movement during expansion and contraction is generally minimal, it can accumulate over time and lead to difficulties if the movement is not accounted for. Roller supports enable this motion by permitting the bridge deck to rotate and move in one direction only.

Spring supports

Spring supports provide similar conditions to pinned supports, they resist horizontal and vertical forces whilst providing zero rotational or moment resistance. The difference between pinned supports and spring supports is that spring supports provide a horizontal and vertical resistance proportional to the displacement of the support. The resistance force is proportional to the displacement and is governed by a coefficient known as the hookes spring constant.

F = -kx 

Here are some spring constants for common materials:

• Steel: 80-300 N/m
• Stainless steel: 40-300 N/m
• Copper: 12-90 N/m
• Brass: 30-80 N/m
• Bronze: 70-200 N/m
• Aluminum: 10-70 N/m
• Titanium: 80-200 N/m

Note that these values are approximate and can vary depending on the specific alloy of the metal, as well as other factors such as the manufacturing process and the size and shape of the spring. Additionally, it's worth noting that Hooke's Law is only valid for small deformations of the spring, and for larger deformations, the spring may behave differently.

Try our free structural beam calculator to run beam analysis and produce shear and bending moment diagrams here.