Horizontal Stiffener in a Plate Girder

In a plate girder, a horizontal stiffener is provided to safeguard against compression buckling of the web plate. Let's understand the concept in detail:

Plate Girder
A plate girder is a built-up structural member that consists of a web plate (vertical plate) and two flange plates (horizontal plates) welded together. It is commonly used in the construction of bridges and buildings to support heavy loads.

Compression Buckling
Compression buckling is a phenomenon that occurs when a slender member, such as a plate, columns, or beams, is subjected to compressive forces. These forces cause the member to deform laterally, leading to instability and potential failure.

Purpose of Horizontal Stiffener
The primary purpose of a horizontal stiffener in a plate girder is to prevent compression buckling of the web plate. It provides additional support to the web plate, increasing its resistance to buckling under compressive loads.

Working Principle
When a plate girder is subjected to compressive forces, the web plate tends to buckle due to its slenderness. The horizontal stiffener is attached to the web plate at regular intervals along its length. These stiffeners help in distributing the compressive forces evenly and prevent buckling.

Role of Horizontal Stiffener
The horizontal stiffener performs the following functions to safeguard against compression buckling:

1. Increased Moment of Inertia: By attaching the stiffeners to the web plate, the effective moment of inertia of the plate girder increases. This increase in moment of inertia enhances the girder's resistance to compression buckling.

2. Stabilizing the Web Plate: The stiffeners act as braces, providing lateral support to the web plate. They help in maintaining the stability of the plate girder by preventing lateral deformation and buckling.

3. Reduced Effective Length: The stiffeners divide the web plate into smaller sections, reducing its effective length. This reduction in effective length decreases the slenderness ratio of the web plate, thereby enhancing its resistance to buckling.

Conclusion
In conclusion, horizontal stiffeners are provided in a plate girder to safeguard against compression buckling of the web plate. They increase the girder's resistance to buckling by increasing the moment of inertia, stabilizing the web plate, and reducing its effective length. By effectively distributing the compressive forces, horizontal stiffeners ensure the structural stability and safety of plate girders under heavy loads.