Effect of Moving Loads on Indeterminate Trusses An indeterminate truss is a structure with multiple degrees of freedom, meaning it has the ability to rotate...
An indeterminate truss is a structure with multiple degrees of freedom, meaning it has the ability to rotate freely about multiple axes. This makes it particularly susceptible to the effects of moving loads, which are forces applied to the structure that cause it to deform and rotate.
In this chapter, we will explore the effect of moving loads on indeterminate trusses and how these loads affect the structure's behavior. We will focus on the concept of influence lines, which are graphical representations of the external forces that cause the truss to deform and calculate the internal forces and displacements within the structure.
Key Concepts:
Indeterminate Truss: A structure with multiple degrees of freedom, meaning it can rotate about multiple axes.
Moving Load: A force applied to the structure that causes it to deform and rotate.
Influence Line: A graphical representation of the external forces that cause the truss to deform.
Internal Forces and Displacements: The forces and moments acting within the truss, and the resulting changes in its deformation.
Analysis:
When a moving load is applied to an indeterminate truss, it creates additional forces and moments within the structure. These external loads can cause the truss to deform in a variety of ways, depending on its geometry and material properties.
Influence lines are a powerful tool for analyzing the effect of moving loads on indeterminate trusses. By plotting the external forces and calculating the internal forces and displacements, engineers can determine the behavior of the structure and predict its response under different loading conditions.
Examples:
A cantilever truss subjected to a moving load will have an influence line that extends from the fixed end to the free end of the truss. This line represents the force and moment that will cause the truss to rotate about its fixed end.
A frame with multiple columns subjected to a moving load will have multiple influence lines. These lines will intersect at a point called the centroid, which represents the point of maximum deformation.
A truss with a fixed end and two hinged ends will have an influence line that extends from the fixed end to the two hinged ends. This line represents the force and moment that will cause the truss to rotate about the fixed end.
Conclusion:
Moving loads have a significant effect on indeterminate trusses, causing them to deform and rotate in various ways. By understanding the concept of influence lines and analyzing the external forces and internal forces within the truss, engineers can predict its behavior and ensure its safety under different loading conditions