16.21 | Spring 2005 | Undergraduate

Techniques for Structural Analysis and Design


Lec # Topics key dates
Part 1: Review of the Equations of Linear Elasticity
1 Introduction  

Stress at a Point

Stress Tensor and the Cauchy Formula

Transformation of Stress Components

Principal Stresses and Principal Planes

Equations of Motion

Symmetry of the Stress Tensor



Strain at a Point

Transformation of Stress Components

Compatibility Conditions


Thermodynamic Principles
The First Law of Thermodynamics: Energy Equation

The Second Law of Thermodynamics


Constitutive Equations
Generalized Hooke’s Law

Strain Energy Density Function

Elastic Symmetry

Thermoelastic Constitutive Equations


Boundary Value Problems of Elasticity
Summary of Equations

Classification of Boundary Value Problems

Existence and Uniqueness of Solutions

Assignment 1 due
Part 2: Energy and Variational Principles

Preliminary Concepts

Work and Energy

Strain and Complementary Strain Energy

Virtual Work


Concepts of Calculus of Variations
Concept of a Functional

The Variational Operator

The First Variation of a Functional

Extremum of a Functional

The Euler Equations

Natural and Essential Boundary Conditions

A More General Functional

Minimization with Linear Equality Constraints

Assignment 2 due in lecture 11

Virtual Work and Energy Principles
Principle of Virtual Displacements

Unit Dummy Displacement Method

Principle of Total Potential Energy

Principle of Virtual Forces and Complementary Potential 

Unit Dummy Load Method

Assignment 3 due in lecture 14

Energy Theorems of Structural Mechanics
Castigliano’s First Theorem

Castigliano’s Second Theorem

Betti’s and Maxwell’s Reciprocity Theorems

16 Some Preliminaries  

The Ritz Method

Description of the Method

Matrix Form of the Ritz Equations

One Dimensional Examples

Assignment 4 due in lecture 17
19 Weighted Residual Methods
A Brief Description of Galerkin, Least-squares and Collocation Methods
Assignment 5 due

Formulation of the Displacement Based Finite Element Method

General Derivation of Finite Element Equilibrium Equations

Imposition of Displacement Boundary Conditions

Generalized Coordinate Models for Specific Problems

Lumping of Structure Properties and Loads


Convergence of Analysis Results
Definition of Convergence

Properties of the Finite Element Solution

Rate of Convergence

Calculation of Stresses and the Assessment of Error

24 Isoparametric Derivation of Bar Element Stiffness Matrix  

Formulation of Continuum Elements

Quadrilateral Elements

Triangular Elements

Convergence Considerations

Element Matrices in Global Coordinate System

Assignment 6 due in lecture 25

Formulation of Structural Elements
Beam Elements and Axisymmetric Shell Elements

Plate and Shell Elements

Assignment 7 due in lecture 28
30 Numerical Integration  
31 Direct Solution of Linear System of Equations  

Types of Structural Failure

Yield Stress and Ultimate Stress

Maximum Normal Stress Theory

Tresca Condition, Hydraulic Stress, von Mises Criterion, Distortion Energy Interpretation

Graphical Representation of Failure Regions

Extension to Orthotropic Materials, Hill Criterion, Hoffman Criterion

Nature of Failure Criteria, Functional Forms

General Failure Analysis Procedure

Application to Pressure Tank

Assignment 8 due in lecture 33

Fracture Mechanics
Description of Phenomena and Importance

Energy Approach to Crack Growth, Energy Consumed by Crack Growth, Griffith’s Experiment and Formula

Definition of Stress Intensity Factor

Stresses at Crack Tip, Mode I, II and III Cracks

Solutions of Linear Elastic Fracture Mechanics, Geometry Effects

Combined Loading; Material Selection Example

Assignment 9 due in lecture 36

Term Project due in lecture 36


Fatigue and Longevity
Terminology, SN Diagrams, Goodman Diagrams

Effects of R Value, Stress Concentrations

Ground-Air-Ground Cycle, Miner’s Rule

Micromechanical Effects

Paris’ Law

Fatigue Life Prediction

R Effects and Forman’s Law, Sequencing Effects

Approach to Design for Longevity

Material Selection Example


Course Info

As Taught In
Spring 2005
Learning Resource Types
Problem Sets
Exams with Solutions
Lecture Notes