Influence Lines Structural Analysis

A structure, for exemple a bridge, is be subjected to static and moving load. Static loads have a unique position on the structure so their effect have a unique value. We mean by effect( a bending moment, shear force, a support reaction, and so on ). The position of moving load varies along the structure, the effect of those loads varies in function of this position.

The engineer responsible for the design of structural elements and the justification of their internal and external stability must determine the position of the loads giving the most unfavorable effect.

This effect, can be the maximum value, is the case for example for the value of the support reaction used for design of spread foundation. The maximum soil pressure corresponds to the maximum of support reaction so we should look for the position of the vehicle which gives the maximum value of this reaction.

As it may be the minimum value, this is the case, for example, with the study of the sliding stability this same foundation where the value of the vertical reaction has a stabilizing effect.

Then, the most unfavorable conditions in sliding correspond to the position of the vehicle which gives the minimum value of this support reaction.

The influence lines are the means allowing the engineer to meet the objective of designing all elements of a structure especially a bridge in the most unfavorable situations.

This course will allow you to acquire theoretical bases on influence lines, the way in which influence lines are used to calculate effect of real loads and to practice the determination and use of influence lines.

This course is subdivided into three parts:

The first part is devoted to the theoretical aspects of influence lines. It introduces, defines and explains how to use influence lines to determine the effect of moving loads on a structure.

the second part contains examples of determining and using influence lines for typical structures.

the last part is dedicated to the use of SAP 2000 software for the study of structures under moving loads.

Finally, it should be noted that assimilation of influence lines is essential for any civil engineer. I hope that this course provides you with the basics relating to this important subject and that it will be useful for you in your professional career. I wish you good learning.