Short Answer:

The different types of loads on beams are classified based on how they act on the beam and how they are distributed. The main types are point load (concentrated load), uniformly distributed load (UDL), uniformly varying load (UVL), moment load, and combined loads. Each type of load causes bending and shear forces in different ways along the beam length.

In simple words, loads on beams are the external forces or weights applied to the beam, which create internal stresses and deflection. These loads can be applied at specific points, distributed evenly, or vary along the length of the beam. Understanding different load types is essential for safe and effective beam design.

Detailed Explanation :

Types of Loads on Beams

A load on a beam is an external force or weight applied to it, which causes bending, shear, and deflection. Beams are designed to resist these loads safely without excessive deformation or failure. The type, magnitude, and distribution of loads determine how internal forces are developed in the beam.

Loads can be applied vertically, horizontally, or at an angle, but in most engineering applications, vertical transverse loads are the most common. The loads are generally classified according to their manner of application and distribution along the beam’s length.

The main types of loads acting on beams are as follows:

1. Point Load (Concentrated Load)

A point load or concentrated load is a load that acts at a specific point or over a very small area of the beam. It is usually represented by a downward arrow showing the load magnitude and direction.

In practice, no load is perfectly concentrated, but when the area of load application is very small compared to the beam’s length, it is considered a point load.

Example: The weight of a machine or a pillar resting at a single point on a beam.

Effect:

• Produces a sudden change in shear force.
• Creates a triangular bending moment diagram between the supports.
• Maximum bending moment occurs directly below the point of load.

Mathematically, if a load  acts at a distance  from the left support on a simply supported beam of span :

where  and  are reactions at supports A and B.

2. Uniformly Distributed Load (UDL)

A uniformly distributed load is spread evenly over a portion or the entire length of the beam, with constant intensity (force per unit length). It is usually expressed in N/m or kN/m.

Example:
The weight of a floor slab or the self-weight of the beam itself.

Effect:

• Shear force varies linearly along the beam.
• Bending moment forms a parabolic curve along the length.

If a simply supported beam of length  carries a UDL of intensity  (N/m):

• Reaction at each support:

• Maximum bending moment at the center:

The UDL causes the beam to bend smoothly with maximum deflection at the midspan.

3. Uniformly Varying Load (UVL)

A uniformly varying load is one that changes gradually in intensity along the beam’s length, forming a linear variation. It can be triangular (increasing or decreasing) or trapezoidal depending on the variation pattern.

Example:
Wind pressure on walls, water pressure on a dam gate, or loads on tapered beams.

Effect:

• Shear force varies parabolically.
• Bending moment forms a cubic curve.

For a triangular load (starting from zero to a maximum value  over span ):

• Equivalent point load =
• Acts at a distance  from the larger end (where the load intensity is maximum).

If the load decreases linearly from  to zero, the resultant force acts at a distance  from the smaller end.

4. Moment Load (Couple or Torque Load)

A moment load is not a force but a twisting or turning effect applied directly to a beam. It causes a bending moment at a specific point without introducing shear force. It is represented by a curved arrow and measured in N·m or kN·m.

Example:

• A torque applied by a motor shaft.
• A couple acting on a beam due to external forces.

Effect:

• Creates a sudden change in the bending moment diagram, but the shear force diagram remains unaffected.
• Causes rotation or twisting at the point of application.

5. Combined Loads

In real structures, beams are rarely subjected to a single type of load. They often experience a combination of loads, such as point loads plus UDL, or UDL plus moments.

Example:

• A bridge beam carrying vehicles (point loads) along with its own weight (UDL).
• A crane beam subjected to load and torque simultaneously.

Effect:

• The shear force and bending moment distribution become more complex.
• Requires superposition of effects from each load type for analysis.

The principle of superposition is applied to calculate total deflection, bending moment, and shear force in such cases.

6. Dynamic or Moving Loads (Special Type)

Dynamic loads vary with time or position. These include impact loads and moving loads (like vehicles on bridges). They produce changing shear and bending moments along the beam.

Example:
Trains or trucks moving over bridge girders, cranes lifting and releasing loads, or vibration in machinery frames.

Dynamic analysis is required for such beams to ensure that resonance or fatigue does not occur.

Importance of Load Types in Beam Design

• Load type determines beam size and material: Heavy distributed loads may require steel or reinforced concrete beams, while lighter point loads can be supported by wood or aluminum.
• Bending and shear analysis: Each load type produces different bending moment and shear force diagrams that help in safe design.
• Deflection control: The shape of the load affects beam deflection; UDL causes smoother deflection, while point loads cause sharper bends.
• Safety and stability: Understanding load patterns ensures that beams do not fail under varying loading conditions.

Hence, load classification is the foundation of beam analysis and design in structural and mechanical engineering.

Conclusion

In conclusion, the different types of loads on beams include point load, uniformly distributed load, uniformly varying load, moment load, and combined loads. Each load type affects the beam differently in terms of shear force, bending moment, and deflection. Correct identification and analysis of loads are crucial for designing strong, stable, and durable structures. Beams must always be designed considering real-life load combinations for maximum safety and performance.