Structural Engineering: Introduction to Qualitative Analysis
In this course a qualitative analysis will be performed of 9 simple determinate structures. Qualitative analysis in structural engineering refers to drawings of bending moment diagrams, shear force diagrams, axial force diagrams and deflected shapes without the use of any calculation (be it equilibrium equations or energy theorems).
Prior knowledge required
This is an entry level course. Thus no prior knowledge of qualitative analysis is required. However, students should understand what are bending moments and deflected shapes.
This course is essentially divided into three parts.
The first part of the course is just an introduction and there is an important lecture that discusses the tools that are used when performing qualitative analysis of structures.
The second part of the course deals with performing the qualitative analysis of beam structures. These beams range from the most simplest forms, such as simply supported beams to continuous beams having hinges.
The third part of the course deals with performing qualitative analysis of determinate frame structures. In this part of the course special attention is paid to the horizontal reactions of frame structures.
Many undergraduate structural analysis subjects at universities involve number-crunching to determine bending moments and deflected shapes of beams and frames. Many students perform these calculations mindlessly and do not pay attention to the actual behavior of the structure. The result is that students leave university without having the skill to sketch a deflected shape of some of the most moderately simple beams and frames. The aim of this course is to arm those students with this very necessary skill required as a structural engineer.
This course can also aid structural engineers who use software excessively to qualitatively verify the results from their analysis.
Confidently sketch deflected shapes and bending moment diagrams of determinate beams and frames without performing any calculations or using a structural analysis software.
Introcuction to Course
In this lecture the instructor defines qualitative structural analysis. He discusses the difference between quantitative and qualitative structural analysis as well as the importance of structural intuition. The aims and learning outcomes of the course are also covered.
In this lecture the instructor briefly discusses the techniques used for a successful understanding and implementation of qualitative analysis.
Examples of Beams
In this example the instructor performs a qualitative analysis of a simply supported beam. This is a perfect example that can be used to describe the qualitative analysis process.
In this examples the instructor does a continuously cantilevered beam. An important learning outcome is the portion of the beam that remains straight when drawing the deflected shape. This is due to a lack of curvature.
In this example the instructor does a continuous beam that has a through-pins. An important learning outcome is understanding how the through-pins influences the deflected shape and bending moment diagrams.
In this example the instructor does a fixed ended beam that has 2 through-pins. The beams is symmetrical. An important learning outcome is identifying the determinacy of the structure and understanding how the through-pin influences the deflected shape and bending moment diagrams. The symmetrical nature of the beam is also taken into account.
Examples of Frames
In this example the instructor goes through a cantilevered frame. An important learning outcome is the fact that axial deformation of the beam is assumed to be so small as to be ignored.
In this example the instructor goes through another cantilevered frame. The frame in this case sway and attention is giving to the beam column joint. An important learning outcome is that the joint maintains it's 90 degree angle when drawing the deflected shape.
In this example the instructor goes through a pinned-pinned frame. The critical learning outcome occurs when the instructor describes how there has to be horizontal reactions despite the fact that there is no horizontal loading.
In this example the instructor goes through a pinned-pinned frame. However this frame has through-pins at the beam-column connection. An important learning outcome is how this can be reduced to a simple pinned-pinned beam. There is also rotation at the beam-column joint. That means the a 90 degree angle does not have to be maintained.
In this example the instructor goes through a frame that is pinned at one support and has a roller at the other. An important learning outcome is how the amplified deflected shape maintains its 90 degree angle and the columns remain straight due to the absence of a shear force.