Ingenieria Estructural

Finite Element Structural Analysis on an Excel Spreadsheet
Course No: S04-003 Credit: 4 PDH

Richard Campbell, P.E., S.E.

Continuing Education and Development, Inc. 9 Greyridge Farm Court Stony Point, NY 10980 P: (877) 322-5800 F: (877) 322-4774 info@cedengineering.com

FINITE ELEMENT STRUCTURAL ANALYSIS ON AN EXCEL SPREADSHEET
INTRODUCTION Finite Element (FE) software is an essentialtool for most structural design engineers, and at the cost of most commercial FE software, it had better be essential. The commercial FE software used by many engineering firms will provide you with more computer-output than you could read in a month and more than you can understand in a year. Commercial programs are great for impressing clients, and great for performing extensive analysis whenreally needed. But in design of frame-type structures, rarely is all that power and output really needed. Spreadsheet based FE analysis differs from conventional FE analysis as follows: Spreadsheet-based Finite Element Conventional Finite Element Data, equations, results on one Huge amounts of data & equations spreadsheet Formulas are all on one spreadsheet Complex “black box” algorithms Complextheory, beyond average user Calculation steps and intermediate calculation results all on one spreadsheet Spreadsheets are best for handling huge Commercial software is best for handling amounts of data and equations complex algorithms and complex theory Commercial software is expensive but The FE spreadsheet is free and most needed. engineers already have the software necessary for spreadsheets.Understanding FE theory allows the user to in many cases forego commercial software and use more basic software, such as the FE spreadsheet. In 10 years of private practice, I have relied almost exclusively on a FE spreadsheet for analyzing frame-type structures. That spreadsheet is presented in this course as a teaching tool and as a practical, effective design tool. The spreadsheet is limited to2-dimensional frames of about 50 nodes, but if a problem is within that range it is easier to use, easier to understand, easier to port, easier to check and much less expensive than commercial programs. In 25 years of engineering, I have never seen a design that was flawed because the designer failed to generate enough computer output. I have never seen a structure that was inadequate because thedesigner didn’t use enough nodes in his analysis model. I have never seen an analysis that was erroneous because there weren’t enough digits to the right of the decimal point. For most frame-type structure problems, use of commercial FE software results in too much output, too many nodes, and too many insignificant digits. When you buy a new car, you go for a drive before you read the owners manual.In a similar fashion, in this course you will download and use the FE spreadsheet before you learn the underlying theory. Since theory is easier to understand as an explanation of a tool we can use than as a hypothesis of one we could create, we will first learn how to use the FE spreadsheet, then use theory to explain how it works.

Section 1: Description of the Finite Element Spreadsheet: Twospreadsheet workbooks in Microsoft Excel format are provided for download as a part of this course. They are both FE spreadsheets; one is a training sheet with just 5 nodes and 5 members, the other is a sheet for practical use with 16 nodes and 37 members. Each workbook consists of three sheets: 1. a documentation sheet, 2. a FE analysis sheet, 3. a plot sheet. 1. The documentation sheet gives anoverview of the structure of the FE spreadsheet and a list of the basic underlying assumptions. 2. The FE analysis sheet provides all the formulas and calculations to solve frame-type 2D static problem. Required inputs are: • node coordinates, • member node-to-node connectivity, • member properties, • support conditions, • and loadings. Calculated output (on the same sheet) is: • support...