STAAD Pro – An introduction

This is an introduction to STAAD software, which is a structural engineering software widely used for the design of multistoreyed buildings

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Abstract

STAAD Pro is a comprehensive structural engineering software that addresses all aspects of structural engineering including model devolopment, verification, analyis, design and review of results. It includes advanced dynamic analysis and push over analysis for wind load and earthquake load.

STADD Pro

Review: STAAD Pro is a comprehensive structural engineering software that addresses all aspects of structural engineering including model devolopment, verification, analyis, design and review of results. It includes advanced dynamic analysis and push over analysis for wind load and earthquake load.

Types of structure:

image image image image image image image

PLANE
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SPACE
image image image

TRUSS
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FLOOR

 

Getting started with STAAD Pro.

      In STAAD Pro we can analyze the structures in 2D and 3D, for the conveinience of modelling and defining the structure for analysis, STAAD uses different templates for 2D and 3D structures. In STAAD we use the following types of structures.

        • Space structures
        • Plane structures
        • Floor structures
        • Truss structures

All the structures are shown in the above figure. Space structures consists of 3 dimensions and structure will have 6 degrees of freedom(6 D.O.F). i.e. 3 rotational and 3 translational.

      The plane sturctures can be considered for any one plane. Forces are considered parallel to the surface of plane or in the surface of the plane.

Eg: In XY plane, Fx, Fy & Mz

      For the design of horizontal members like slabs, floors etc. the floor structure is used. It is a 2-D or 3-D structure in which horizontal movement cannot be considered.

      For the structures only the axial force are considered and there is no bending.

Starting the program

      STAAD Pro can be started from the programs menu in windows or from the desktop Icon (If available). Every time you start the programme a new dialogue box will pop up. The box consists of types of structure of space, plane, floor and truss. Select the appropriate structure to be worked out, file name and location to be saved. The length and force units should be specified to be used in the drawing. After this step the STAAD Pro interface appears.

      In the central area there is a white space with some grids, this is the drawing area showing the whole structure. We can model our structure and assign the load in this interface. In the left part there are so many “tab” which is called page control. Different processes of STAAD Pro like modeling, analysis, post analysis, design can be accessed within these “tab”. To the right there are different window available. Options for different tabs in page control are accessed in this area. By default usually snap and grid settings is shown in the window.  
 

GRID

      Perpendicular construction lines which can be used as an aid to modeling the structure is called GRID or grid lines. Grid lines are usually set to a default value by the program when it starts, but of course we can change the density of grid lines in the snap/grid settings window. It is recommended to draw only the required grid lines to draw our structure to accurately model the structure without any confusion. We can change the no: of grid lines in X, Y & Z directions and spacing in each axes. We can have multiple grid systems in different names also.

GUI of STAAD

      STAAD Pro has got a versatile Graphical User Interface (GUI) integrated into the program for the easy modeling, post analysis and print options. The interface is fully developed and well documented; various editing commands are available within this GUI. Some of the features and commonly used editing commands are discussed.

INSERT NODE: You can add nodes to the structure using this method.

ADD BEAM: Add beam method is used to draw beam in structure. Beam refers not only beams, but all the linear structures (beams, columns, and truss members).

ADD SOLID: Used to draw solids in structure

ADD PLATES, SURFACES: Add laminar surfaces to the model.

TRANSLATIONAL REPEAT: Create an array in the specified axis at desired spacing

CIRCULAR REPEAT: Create a polar array around an axis at desired spacing.

MOVE: Move an entity from one place to other

ROTATE: Rotate an entity around an axis

MIRROR: Make a mirrored copy of a single or group objects.

SPLIT BEAM: This method can be used to split a beam into number of beams, three options are there

    1. Add new point at a given distance or to divide the beam at a given proportion
    2. Add a midpoint to the beam
    3. Add a number of points

Structure wizard

      Templates of some structures are come packed with STAAD Pro. and we can use these templates by using structure wizard. We can select a template and give the necessary details to model the structure easily. If unequal beams are to be drawn, select the pick icon (…) on the side and give required data values. Transfer model icon will transfer the model to the STAAD interface. You have to specify the coordinates which the structure is to be placed then.

3-D rendering

      You can view a 3-D rendering of the structure for a better visualization of what you modeled. Loading arrangements can be also seen and better understand to pull out errors if any. 3-D rendering can be view by selecting viewà3-D Rendering

Assignment methods

      Every attributes we define in STAAD should be assigned to the corresponding members or nodes or plates for the analysis and design. For example supports created must be assigned to nodes where supports are needed, loads defined must be assigned as member load or nodal load wherever applicable, the post analysis results we needed must be assigned for each members and so that only results of that members are displayed in STAAD Output.

      There are 4 different assign methods commonly used in STAAD they are:

        1. Assign to selected
        2. Assign to view
        3. Use cursor to assign
        4. Assign to edit list

Assign to selected: Some of the beams or nodes are selected initially and the property is assigned to that selected members

Assign to view: property is assigned to all the relevant members in the view.

Use the cursor to assign: we can select our members by clicking on the members

Assign to edit list: node numbers or beam numbers are entered in the text box separated with space in which properties are assigned to the members in the list only.

Result

   After analysis STAAD gives 3 options for the user. User can

  1. Stay in modeling mode – user can continue the modeling of structure.
  2. Go to post processing mode – View the analysis results in graphical format
  3. View output file – View the results of analysis in written format

Post processing mode: This mode helps the user to visualize the shear force, bending moment and other stress resultant developed at the members, i.e. we can see the SFD, BMD, Elastic curve etc of the whole structure or of individual members.

Output file: Each analysis carried out in STAAD will produce a text document containing all the inputs, outputs and other information that user selected when modeling the structure. This is stored in a file named “filename.anl”

Design

      Design in STAAD supports more than 10 codes. INDIAN standard codes(Concrete and steel) are also supported, Limit state method is used for the design.

Design of concrete sections

      After the analysis the design can be done simply by just giving the design commands. Although you have to set the parameters for design in the design tab. CODE CHECK is the most usually used parameter used as we are giving the section sizes.

Default steel strength is Fe415 and concrete grade is M30. For altering the parameters

Click design tab, click define parametersà FC – change the value

Define parametersà FE – change value

Design of steel sections

      Design of steel sections can be more economically done by adding new commands to the design. Select optimum command for design can be effectively used to design economical sections. The above command will select an optimum size for all members using a procedure consisting of multiple cycles of analysis as well as iteration on section sizes until an overall structure least weight is obtained.

Take off command will calculate the whole weight of the structure and amount of material needed.

If only CHECK CODE command is activated the results of design will give an indication and a suggestion of alternate section to replace the “to be failed”  section.

STAAD editor

      We can model, define attributes and assign it to the model using STAAD GUI but there is a built in command line interface to these things. It is known as STAAD EDITOR. STAAD Editor is a command line interface for developing models and all other STAAD input by typing some commands collectively called STAAD language. The STAAD Editor will produce a *.std file which is recognized by the STAAD engine and it will create the model from that file.

      Although the STAAD input can be created through the Modeling mode, it is important to understand the command language. With the knowledge of this language, it is easy to understand the problem and add or comment data as necessary. The general sequence in which the commands should appear in an input file should ideally follow the same sequence in which they are presented in this section. The commands are executed in the sequence entered.

      STAAD commands have a particular syntax in which the STAAD engine can understand and failing to follow will give syntax error. Some common syntax for the basic operations are described.

      A sample STAAD editor commands to create and analyze a simple overhanging beam is shown below.

STAAD PLANE

START JOB INFORMATION

ENGINEER DATE 07-Nov-10

END JOB INFORMATION

INPUT WIDTH 79

UNIT METER KN

JOINT COORDINATES

1 0 0 0; 3 6 0 0; 4 9 0 0; 5 3 0 0;

MEMBER INCIDENCES

1 1 5; 3 3 4; 4 5 3;

DEFINE MATERIAL START

ISOTROPIC CONCRETE

E 2.17185e+007

POISSON 0.17

DENSITY 23.5616

ALPHA 1e-005

DAMP 0.05

END DEFINE MATERIAL

CONSTANTS

MATERIAL CONCRETE ALL

MEMBER PROPERTY AMERICAN

1 3 4 PRIS YD 0.6 ZD 0.3

SUPPORTS

1 PINNED

3 FIXED BUT FX FZ MX MY MZ

LOAD 1

JOINT LOAD

4 FY -12

PERFORM ANALYSIS PRINT ALL

FINISH

      STAAD and FINISH — STAAD refers to the starting of STAAD input, FINISH refers to the end of STAAD input. STAAD engine executes only the commands between these two commands.

      STAAD PLANE — All STAAD commands are started with the type of the structure. In this it is a PLANE structure.

      START JOB INFORMATION, END JOB INFORMATION – Between these it is job information constitutes the detail of model like date, engineer, and other particulars.

      INPUT WIDTH – These commands may be used to specify the width(s) of the lines of output file(s). This is a customization facility that may be used to improve the presentation quality of the run documents.

      UNIT METER KN – Specifies the unit as meter and KN.

      JOINT CORDINATES – Below which it is Joint numbers and coordinates. Syntax is as follows.

JOINT NUMBER image CORDINATES (X  Y  Z) image image image 

 

      MEMBER INCIDENCES – Below which it is member definitions. Syntax is as follows.

      MEMBER NUMBER image image NODES NUMBER WHICH SHOULD BE CONNECTED BY THE BEAM image image 

 
 

      DEFINE MATERIAL START – Definition of material begins here. Many physical attributes of ISOTROPIC CONCRETE are defined between START and FINISH.

      CONSTANTS – Assigning of materials and sections starts here. CONCRETE is assigned to all members, member numbers (1 3 4) followed by the type of sections (PRIS) and its size is given (YD .6 ZD .3).

      SUPPORTS – Node number (3) followed by type of support (FIXED BUT) and fixity if any (FX FZ MX MY MZ).

      LOAD – Follows the name of load case. Load type and its value

2 UNI GY -4 0 3

      In above command 2 is the member number to which load is to be given, UNI denotes UNIFORM LOAD, GY denotes load is in the GLOBAL Y direction, -4 is the value of UDL, 0 3 is the length through which load is assigned.

      PERFORM ANALYSIS – Analysis is carried out

      PRINT ALL — All analysis results for all members all printed on to output file.

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