ANALYSIS AND DESIGN OF STRUCTURES USING STAAD ANALYSIS AND DESIGN OF STRUCTURES USING STAAD Course material for Design engineers of ISGEC Heavy Engineering A-7, Sector-63, Noida, U.P, India S.Kanthimathinathan Tiruchy Engineering Consultancy House 1/1-A- Nariyan Street, Srirangam, Tiruchy-620006 Date 25-06-2012 / R00 Page 1 of 24
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ANALYSIS AND DESIGN OF STRUCTURES USING STAAD
ANALYSIS AND DESIGN
OF
STRUCTURES USING STAAD
Course material for Design engineers of
ISGEC Heavy Engineering
A-7, Sector-63, Noida, U.P, India
S.Kanthimathinathan
Tiruchy Engineering Consultancy House
1/1-A- Nariyan Street, Srirangam, Tiruchy-620006
Date 25-06-2012 / R00 Page 1 of 24
ANALYSIS AND DESIGN OF STRUCTURES USING STAAD
TABLE OF CONTENTS
S.NO CONTENTS PAGE NO
1.0 INTRODUCTION 02
2.0 STEPS INVOLVED 3
3.0 STARTING STAAD 03
4.0 CONCRETE DESIGN 04
5.0 USER PROVIDED TABLE 7
6.0 PRIMARY LOAD CASES 10
7.0 LOAD COMBINATION FOR BEAMS 11
8.0 LOAD COMBINATION FOR COLUMNS & FOUNDATION 12
9.0 DESIGN PARAMETERS 14
10.0 DESIGN GROUP SPECIFICATION 15
11.0 STEEL STRUCTURE DESIGN 15
1.0 Introduction
Structures can be analysed as a 2D-frame (or) 3D-frame.Using manual methods for analysis take longer time and lengthy calculations are involved. Due to the use of computer, repetitive calculation can be carried out accurately and with speed. One such popular computer software for structure engineering application is STAAD-Pro. This package is user friendly, easy to understand, use and interpret the output from the analysis and design of structures. 3D models of large structures can be created and analysed with ease resulting in optimal design with saving in time. Many trials can be made with ease. The analysis can be made for different load combinations which will take more time if done manually.In this course material an attempt is made to explain how to use the software package STAAD Pro effectively and correctly to the advantage of structural engineers. Tips for practicing engineer are given.
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ANALYSIS AND DESIGN OF STRUCTURES USING STAAD
2.0 Steps involved
Important steps involved in the analysis are
1. Model creation, declaring member property & end conditions and application of load. 2. Analysis and Design3. Output generation and interpreting the results.
2.1 Model creation
This includes modeling (geometry), giving property of members, material constants, support condition, loads and its combination.
2.2 Analysis and design
STAAD Pro will check the syntax (commands) and the data required for analysis and design. If there is any error, the error message will be displayed. Once the input is acceptable, the analysis will be performed based on the given parameters and output is generated.
2.3 Output generation and interpreting the results
The user can not take the output as correct unless the same is verified.
Reading the output is in post processing which includes the following:
• Tables and graphical output, upon verification; if needed the input may have to be edited for its correctness.
3.0 Starting STAAD Pro
Method – 1
Start
↓
All Programs
↓
STAAD Pro 2007 V8i
Method – 2 Double click on the icon which will enter into STAAD Pro package.
3.1 How to create the file
File
↓
New
(or)
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ANALYSIS AND DESIGN OF STRUCTURES USING STAAD
• Click on new structure in the file toolbar• Dialog box will be displayed• At one time STAAD Pro can operate on one file only• Specify the file name
3.1.1 Example
Let us say the structure name is called Mill building for a MM Power plant, Your file name can be MMPL-MILL 1.Givig the serial number at the end of the file will help you in identifying the last used file.
3.2 Folder
Specify folder in which you want ot save the file.
Example: D:\staad\ MMPL-MILL 1
3.3 Structure Type
• Space - 3D wire frame model and loads are applied on any plane.• Plane - 2D wire frame model with loads on the same plane. In this model load can not be applied in
perpendicular of the plane in which model is created.• Floor – 2D structure in global X and Z direction.• Truss – Plane frame (2D) having members carrying axial load only. In this, all the members are declared as
truss. No moment is carried / applied.
3.5 Units:
Units are Imperial (foot, inch, Kips etc) & Metric (m, mm, KN etc)
During installing the software, the default system is specified. However while creating the input, the units can be changed.
5.1 User Provided Table Specification for steel structures
5.1.1 Purpose:
User can create and use any steel section (Build-up section) by using this commend.
5.1.2 Syntax:
START USER TABLE
TABLE i1 (fn)
Section-type
Section-name
Property-spec
END
Where,
• i1 = table number (1 to 99).• Section-type =a steel section name including: WIDE FLANGE, CHANNEL, ANGLE, DOUBLE
ANGLE, TEE, PIPE, TUBE, GENERAL, I-SECTION & PRISMATIC.• Section-name = any user designated section name, use 1 to 12 characters. First three characters
of Pipes and Tubes must be PIP and TUB respectively. Only alphanumeric characters and digits are allowed for defining section names. (Blank spaces, asterisks, question marks, colon, semi-colon etc. are not permitted.)
• Property-spec = Properties for the section. The requirements are different for each section type as follows. Shear areas AY and AZ must be provided to ensure proper shear stress or shear strength calculations during design.
Note:The default length units for properties are the current units. If UNIT command is entered within the User Table in the input file then those units become the current units. However, a UNIT command on an external file only affects that file and has no effect on the units in subsequent input file commands. The user may specify the desired length unit by using the UNIT command as the first command in the table (see example).
5.2 Various formats used for creating user tables:
Formats are
(a) Wide Flange – Used to create Rolled I section, Plate formed I Section & Channel
(b) General – Used to create Double I section, Double Channel, Box & Plus I section.
(c) Prismatic – Used to create Channel & Box section
(a) I section – Used to create Rolled I section & Tapered I section
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ANALYSIS AND DESIGN OF STRUCTURES USING STAAD
5.2.1Wide Flange:
1) AX = Cross section area
2) D = Depth of the section
3) TW = Thickness of web
4) WF = Width of the flange
5) TF = Thickness of flange
6) IZ = Moment of inertia about local z-axis (usually strong axis)
7) IY = Moment of inertia about local y-axis
8) IX = Torsional constant
9) AY = Shear area in local y-axis. If zero, shear deformation is ignored in the analysis.
10) AZ = same as above except in local z-axis.
5.2.2General
The following cross-sectional properties should be used for this section-type. Note that this facility allows the user to specify a built-up or unconventional Steel Section.
1) AX = Cross section area.
2) D = Depth of the section.
3) TD = Thickness associated with section element parallel to depth (usually web). To be used to check depth/thickness ratio.
4) B = Width of the section.
5) TB = Thickness associated with section element parallel to flange. To be used to check width/thickness ratio.
6) IZ = Moment of inertia about local z-axis.
7) IY = Moment of inertia about local y-axis.
8) IX = Torsional Constant.
9) SZ = Section modulus about local z-axis.
10) SY = Section modulus about local y-axis.
11) AY = Shear area for shear parallel to local y-axis.
12) AZ = Shear area for shear parallel to local z-axis.
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ANALYSIS AND DESIGN OF STRUCTURES USING STAAD
14) PY = Plastic modulus about local y-axis.
15) HSS = Warping constant for lateral torsional buckling calculations.
16) DEE = Depth of web.
Note: Properties PZ, PY, HSS and DEE must be provided for code checking/member selection per plastic and limit state based codes (AISC LRFD, British, French, German and Scandinavian codes). For codes based on allowable stress design (AISC-ASD, AASHTO, Indian codes), zero values may be provided for these properties.
5.2.3 I section:
This section type may be used to specify a generalized I-shaped section. The cross-sectional properties required are listed below. This facility can be utilized to specify tapered I-shapes.
1) DWW = Depth of section at start node.
2) TWW = Thickness of web.
3) DWW1= Depth of section at end node.
4) BFF = Width of top flange.
5) TFF = Thickness of top flange.
6) BFF1 = Width of bottom flange.
7) TFF1 = Thickness of bottom flange.
8) AYF = Shear area for shear parallel to Y-axis.
9) AZF = Shear area for shear parallel to Z-axis.
10) XIF = Torsional constant ( IX or J)
Note:
1) DWW should never be less than DWW1. The user should provide the member incidences accordingly.
2) The user is allowed the following options for the values AYF, AZF and XIF.
a) If positive values are provided, they are used directly by the program.
b) If zero is provided, the program calculates the properties using the following formula.
AYF = D x TWW (where D =Depth at section under consideration)
AZF = 0.66 ((BFF x TFF) + (BFF1 x TFF1))
XIF = 1/3 ((BFF x TFF3) + (DEE x TWW3) + (BFF1 x TFF13)) (where DEE = Depth of web of section)
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ANALYSIS AND DESIGN OF STRUCTURES USING STAAD
c) If negative values are provided, they are applied as factors on the corresponding value(s) calculated by the program using the above formula. The factor applied is always the absolute of the value provided, i.e. if the user provides the value of XIF as -1.3, then the program will multiply the value of XIF, calculated by the above formula, by a factor of 1.3.
5.2.4 Prismatic
The property-spec for the PRISMATIC section-type is as follows -
1) AX= Cross-section area
2) IZ = Moment of inertia about the local z-axis
3) IY = Moment of inertia about the local y-axis
4) IX = Torsional constant
5) AY= Shear area for shear parallel to local y-axis.
6) AZ= Shear area for shear parallel to local z-axis.
7) YD= Depth of the section in the direction of the local y-axis.
8) ZD= Depth of the section in the direction of the local z-axis.
6.0 Primary load cases :
Load case 1 ( Self.Wt + Dead load )
Load case 2 (Impose load)
Load case 3 (Equipment dead load)
Load case 4 (Equipment live load)
Load case 5 (Wind load +X)
Load case 6 (Wind load -X)
Load case 7 (Wind load +Z)
Load case 8 (Wind load -Z)
Load case 9 (Seismic load +X)
Load case 10 (Seismic load -X)
Load case 11 (Seismic load +Z)
Load case 12 (Seismic load -Z)
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ANALYSIS AND DESIGN OF STRUCTURES USING STAAD
7.0 Combination load case for Beams (Working Stress Method ):
Note: Load combinations 126 to 133 are with 50% I.L on platforms. This is applicable only where there are more than 10 floors. If the floors are equal to or less than 10; the reduction shall be as in clause 3.2 of IS:875 part 2.Also refer appendix-A of IS:875 part 2.
9.0 Design Parameters :
Parameter name
Description Default value
BEAM0.0 = Design only for end moments and those location specified at by section commend.1.0 = Calculate the section forces at 12 points along the beam, design at each inter
mediate location and report the critical location where ratio is maximum.
0
FYLD Yield strength of steel 250
MAIN Allowable kl/r for the slenderness calculation for structural members (Refer IS:800 1984, Table-3.1)
180
LZ & LYLength in local Z & Y-axis to calculate slenderness ratio. (Recommended to provide taking into account the lateral restraint of compression flange with respect to axis)
Member length
UNLUnsupported length to calculate allowable bending stress
Member length
DJ1 Joint no. denoting starting point for calculation of “Deflection length”
(Recommended when the real beam is divided into number of member in staad)
DJ2 Joint no. denoting end point for calculation of “Deflection length”
(Recommended when the real beam is divided into number of member in staad)
DFF Deflection length / Max. allowable local deflection
(Refer IS:800 1984 , Cl-3.13)
RATIO Permissible value of actual to allowable stresses (Recommended value is 0.85 to 0.9 depending upon the accuracy of loads applied)
1
TRACK 0.0 = Suppress critical member stress1.0 = Print all critical member stress2.0 = Print expanded output. If there is deflection check, that also print the governing
load case number for deflection check . (Recommend 2.0 after modeling & analysis is perfected)
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ANALYSIS AND DESIGN OF STRUCTURES USING STAAD
10.0 Design group specification:
10.1 Group:
This command may be used to group members together for analysis and provide optimized steel design. Grouping is based on the span , End condition, Load, Unsupported length & interchangeability etc.
10.2 Select:
STAAD will select member (member size) based on the design parameter and code. The selection is done using the results of the final analysis until the least weight size is obtained.
10.2.1 Syntax
SELECT ( Member memb list / all / member group name)
GROUP pro-spec MEMBER memb list
pro-spec = (ax/sz/sy)
10.2.2 Example:
SELECT ALL
GROUPSZ MEMB 1 3 7 TO 10
Note: In this example, the member 1, 3, 7 to 10 are assigned the same properties based on which of these members has the largest section modulus.
11. An example of steel structure design
STAAD SPACE
START JOB INFORMATION * Used to provide job description.
ENGINEER DATE 23-Jun-12 * It is not mandatory.
JOB NAME Rcc building * only for internal reference.
JOB CLIENT Abc
JOB NO 102
JOB REV 00
ENGINEER NAME xxx
CHECKER NAME yyy
APPROVED NAME zzz
CHECKER DATE 25-Jun-12
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ANALYSIS AND DESIGN OF STRUCTURES USING STAAD
APPROVED DATE 27-Jun-12
END JOB INFORMATION
INPUT WIDTH 79
UNIT METER MTON * Used to provided unit for dimension & load.
JOINT COORDINATES *It is used to create node or joint for modeling. (Node no x-coordinate
y-coordinate z-coordinate). Node number need not to be in order.
START GROUP DEFINATION *It is user defined function. User can select the selected elements (Node/Member/Floor) from the model depending on the requirement. Further input can be provided based on this group name.
START USER TABLE *User can create build up section property table depending upon the requirement but using the formats as in 5.2.1, 5.2.2, 5.2.3 &5.2.4.
TABLE 1 *User provided table serial number. Each table has different table serial number or identification number which shall be used while declaring property.
UNIT CM MTON *Note change in unit.This is applicable only Inside UPT.
WIDE FLANGE *Format of the table.
ISMB400 *Identification of property name which will used in member property.