Wednesday, May 26, 2010


ETABS and Primavera Project Planner Tutorials and Topics coming soon this week


Sunday, May 16, 2010

Design and Analysis of Truss Using Staad Pro

Analysis and Design of Truss using Staad Pro

The above figure shows a truss from several truss supposed to cover certain area.As shown the truss has a cantilever part ,its span equals 4 meters.The proposed truss depth is 3 m.The loads are shown as concentrated on tuss joints.The values of its load case are shown .
Use all the data you take in steel course to design and analyze steel truss.

Main Steps Of Modeling Truss in STAAD PRO

  • Entering Job information
  • Building model geometry
  • Defining member properties ,sections
  • Assigning Loads(Load Cases and combination)
  • Defining Pre-Analysis Print out,analysis type and Post-Analysis print out
  • Defining Design Requirements
Note :To see the image clearly click the image.
How to Start Staad Pro
The Pic below shows how to start Staad Pro
Click the picture to enlarge

In New File select
  1. Truss
  2. Units (here KN and mm in this example)

The staad Graphical interface will appear as shown in below picture

1-Entering Job Information

2-Building Model (structure) Geometry

  • Defining Truss Geometry
One of the methods that you can construction lines and then draw on these lines the truss members
Noting that the no. of construction lines is excluding Ist line..

After clicking Snap Node/Beam ,use the mouse and connect between nodes created at the intersections of construction lines

How to see Diagram Labels(Nodes Numbers,Beam Numbers etc)

Node and beam labels are a way of identifying the entities we have drawn on the screen, and very useful when dealing with the output results

3. Defining member properties, sections
  • Property
In which we can define or choose sections properties of the members of the truss.
  • Spec.:
In which we can define or choose members’ specifications.
  • Support:
In which we can define the supports properties (restraints).
  • Load:
In which we can define the applied loads, load cases, load combinations.
  • Material
In which we can define the material properties (ex. E, density, etc.)

Assume Preliminary Sections:

Using The Canadian Steel Tables
All Top and Bot chords are one size L 55*55*3
All Diagonals and verticals are one size L 45 * 45* 3

Assigning the sections created to the model


By clicking on the support icon the shown window will appear. We have to create new kinds of supports

Use the mouse and click on the nodes according to its support type as shown below

4. Defining Loads
The creation and assignment of load cases involves the following two steps:
1. First, we will be creating all 3-load cases.
2. Then, we will be assigning them to the respective members/nodes

For example
Dead Load Case can be Load Case No.1

Live Load Case can be Load Case No. 2 and Wind Load is the Case No.3

Also, we can define load combinations according to required.
For example, we can create a load combination

1.25 D.L. + 1.5 L.L + 0.8 W.L.

and In Dead Load Create the Self weight as

In each Load Case Creat the Nodal Loads on truss as specified before.Make sure of the direction of forces acording to global coordinates

After Creating the commond of (Perform Analysis-Check);We have to assign the members that want to be this type of analysis for it.

Click Assign and then use the cursor and choose all the members,thus all the members should be highlighted as shown below.

To add the Pre-Print Commond click" Define Commands"

For example here we have choosen to print the support reactions,member forces,joint displacements

Post Print Commands
  • Support reactions
  • Analysis results
  • Member Forces
  • Max Forces
Add which property you need and then use cursor to ASSIGN to which member in the truss
6-Defining Design Requirements

1. To Specify steel design parameters,go to Design/Steel page from the left side of the screen.Make sure that under the Current Code selections on the top right hand side ,Canadian is selected.
There are many Design Commands in the STAAD Design subroutine.Here,we will use only to Check Code,regarding adequacy of members.

7-Analysis & Viewing Results

STAAD Performs Analysis and Design simultaneously. In order to Perform Analysis and Design,select the Run Analysis option from the Analyze menu

When you select the Run Analysis option from the Analyze menu,the following dialog box appears.We are presented with the choice of 2 engines.the STAAD engine and the STARDYNE Advanced Analysis engine.The STARDYNE Analysis engine is suitable for advanced problems such as Buckling Analysis,ModaL Extraction using various method ,etc
STAAD engine is suitable for this tutorial. Click on th Run Analysis button.
The soloving process is shown in pop up screen.

Visualization of Some Results

Generally,in any program ,try to make some checks about the shapes of defletions,BMD,SFD.Also check the level of reactions. Just to make sure that there is no significant nput error.
Viewing The OutPut File
During the analysis process,STAAD creates an Output file .This file provides important information on whether the analysis was performed properly.
For example,if STAAD.Pro encounters an instability problem during the nalysis process,it will be reported in the output file.
Alternatively ,we can select the File/View/Output File/STAAD Output option from the top menu.
The Output File
Its name is <>
As shown for example ,below are the results of the steel design check.
The End..


Wednesday, May 12, 2010

Symbolic expressions,variable precision and exact arithmatic in MATLAB

Symbolic Expressions, Variable Precision, and Exact Arithmetic

As we have noted,MATLAB uses floating point arithmetic for its calculations.
Using theSymbolic Math Toolbox,you can also do exact arithmetic with symbolic expressions. Consider the following example:

>> cos(pi/2)
ans =

The answer is written in floating point format and means 6.1232×10-17 .
However, we know that cos(p/2) is really equal to 0. The inaccuracy is due
to the fact that typing pi in MATLAB gives an approximation to pi accurate
to about 15 digits, not its exact value. To compute an exact answer, instead
of an approximate answer, we must create an exact symbolic representation
of p/2 by typing sym(’pi/2’). Now let’s take the cosine of the symbolic
representation of p/2:
>> cos(sym(’pi/2’))
ans =
This is the expected answer.
The quotes around pi/2 in sym(’pi/2’) create a string consisting of the
characters pi/2 and prevent MATLAB from evaluating pi/2 as a floating
point number.The command sym converts the string to asymbolic expression.
The commands sym and syms are closely related. In fact, syms x is equiv-
alent to x = sym(’x’). The command syms has a lasting effect on its argu-
ment (it declares it to be symbolic from now on), while sym has only a tempo-
rary effect unless you assign the output to a variable, as in x = sym(’x’).
Here is how to add 1/2 and 1/3 symbolically:

>> sym(’1/2’) + sym(’1/3’)
ans =

Finally,you can also dovariable-precision arithmetic with vpa.For example,
to print 50 digits of 2, type

>> vpa(’sqrt(2)’, 50)
ans =


MATLAB Basics Algebra

Using MATLAB’s Symbolic MathToolbox, you can carry out algebraic
or symbolic calculations such as factoring polynomials or solving algebraic
equations. Type help symbolic to make sure that the Symbolic Math Tool-
box is installed on your system.
To perform symbolic computations, you must use syms to declare the vari-
ables you plan to use to be symbolic variables.
Consider the following series of commands:
>> syms x y
>> (x - y)*(x - y)ˆ2
ans =
>> expand(ans)
ans =
>> factor(ans)
ans =

Notice that symbolic output is left-justified, while numeric output is
indented. This feature is often useful in distinguishing symbolic output
from numerical output.

Although MATLAB makes minor simplifications to the expressions you
type, it does not make major changes unless you tell it to. The command ex-
pand told MATLAB to multiply out the expression, and factor forced MAT-
LAB to restore it to factored form.
MATLAB has a command called simplify, which you can sometimes use
to express a formula as simply as possible. For example,

>> simplify((xˆ3 - yˆ3)/(x - y))
ans =
MATLAB has a more robust command, called simple, that sometimes does
a better job than simplify. Try both commands on the trigonometric
expression sin(x)*cos(y) + cos(x)*sin(y) to compare — you’ll have
to read the online help for simple to completely understand the answer.


MATLAB BASICS(input & output)

Input and Output
You input commands to MATLAB in the MATLAB Command Window. MAT-
LAB returns output in two ways: Typically, text or numerical output is re-
turned in the same Command Window, but graphical output appears in a
separate graphics window. A sample screen, with both a MATLAB Desktop
and a graphics window, labeled Figure No. 1, is shown in Figure 2–1.
Togeneratethisscreenonyourcomputer,firsttype1/2 + 1/3.Thentype
ezplot(’xˆ3 - x’). While MATLAB is working, it may display a “wait” symbol — for example,
an hourglass appears on many operating systems. Or it may give no visual
evidence until it is finished with its calculation.
As we have just seen, you can use MATLAB to do arithmetic as you would a
calculator.You can use “+” to add, “-” to subtract , “*” to multiply, “/” to divide,and “ˆ” to exponentiate.
For example,
>> 3ˆ2 - (5 + 4)/2 + 6*3
ans =
MATLAB prints the answer and assigns the value to a variable called ans.
If you want to perform further calculations with the answer, you can use the
variable ans rather than retype the answer. For example, you can compute
the sum of the square and the square root of the previous answer as follows:

>> ansˆ2 + sqrt(ans)
ans =

Observe that MATLAB assigns a new value to ans witheachcalculation.
of your choosing.
For example,

>> u = cos(10)

>> v = sin(10)
>> uˆ2 + vˆ2
ans =

MATLAB uses double-precision floating point arithmetic,which is accurate
to approximately 15 digits;however,MATLAB displays only 5 digits by default.
To display more digits, type format long. Then all subsequent numerical
output will have 15 digits displayed. Type format short to return to 5-digit
MATLAB differs from a calculator in that it can do exact arithmetic. For
example,it can add the fractions 1/2 and 1/3 symbolically to obtain the correct
fraction 5/6.
We discuss how to do this in the section Symbolic Expressions,
Variable Precision, and Exact Arithmetic Post

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