ENGR218, Statics/Mechanics of Materials

Project 1:  Stress Analysis of Wind Turbine Tower Base

A 750 kW wind turbine is the focus of this project. You are required to carry out an analysis of the axial stresses generated at the base of the tower. Stresses are to be calculated for the maximum allowable wind speed, 25 m/s. The important geometry is described below, along with masses of the key components (tower, nacelle, rotor and blades). The total rotor diameter, D_rotor, is 47.5 m.

The analysis will be carried out in sections, finishing with determination of axial stress due to combined axial loading and bending. A detailed description of what is required is presented over the page. 

Schematic of Turbine:

Requirements:

The analysis has been broken into several parts, and associated with the relevant portion of the lecture notes. For each section of the assignment you must present your findings clearly, significant marks being awarded for quality of presentation. For Section A, numerical results have been provided, as these are required for the following sections.

SECTION A, Calculation of Internal Forces:

Draw a complete free body diagram of the wind turbine above AA. Calculate the values of the internal forces and moments at section AA.

SECTION B, Calculation of Stress due to Axial Loading:

Calculate the axial stress distribution generated by the axial internal force acting on the tower base (section AA). Show diagrammatically the stress distribution, and state values of axial stress at points a, b, and c.

SECTION C, Calculation of Stress due to Bending:

Calculate the axial stress distribution generated by bending alone on the tower base. Show diagrammatically the stress distribution, and state values of axial stress at points a, b, and c. THINK VERY CAREFULLY about your findings. Should you expect tensile or compressive stresses at a, b, and c.

SECTION D, Calculation of Total Axial Stress:

Calculate the total axial stress distribution generated by axial loading and bending on the tower base. Show diagrammatically the stress distribution, and state values of axial stress at points a, b, and c. Also, calculate how far the neutral axis has been displaced from the centre line of the X-section, and in which direction.

SECTION E, Calculation of Transverse Shear Stress:

Calculate the transverse shear stress distribution generated by the shear internal force acting on the tower base (section AA). Show diagrammatically the stress distribution, and state values of axial stress at points a, b, and c.

You MUST SHOW ALL WORK used to find your stated solution,

and any relevant assumptions must be stated.

Assessment:

• Your mark for this assignment will contribute 5% of the total course mark.
• Also note that 30% of your mark for this assignment will be allocated to quality of presentation. However, this does not mean your assignment needs to look excessively pretty, or necessarily be typed up using a word processor. It should be:
• Neat and tidy,
• well commented,
• 
  and well organised (i.e. organised into appropriate sections, and the marker should be able to find your results very easily).