Technical reference manual v8i

STAAD.Pro
V8i (SELECTseries 1)
Technical Reference Manual
DAA037780-1/0002
Last updated: 23 June 2010

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Technical Reference Manual — i
End User License Agreement
To view the End User License Agreement for this product, review: eula_
en.pdf.
ii — STAAD.Pro
Table of Contents
Introduction 1
Section 1 General Description 3
1.1 Introduction 4
1.2 Input Generation 5
1.3 Types of Structures 5
1.4 Unit Systems 6
1.5 Structure Geometry and Coordinate Systems 6
1.6 Finite Element Information 18
1.7 Member Properties 34
1.8 Member/ Element Release 43
1.9 Truss/Tension/Compression - Only Members 43
1.10 Tension, Compression - Only Springs 44
1.11 Cable Members 44
1.12 Member Offsets 47
1.13 Material Constants 48
1.14 Supports 48
1.15 Master/Slave Joints 49

1.16 Loads 49
1.17 Load Generator 57
1.18 Analysis Facilities 60
1.19 Member End Forces 82
1.20 Multiple Analyses 88
1.21 Steel, Concrete, Timber Design 89
1.22 Footing Design 89
1.23 Printing Facilities 89
1.24 Plotting Facilities 89
1.25 Miscellaneous Facilities 89
1.26 Post Processing Facilities 90
Section 2 American Steel Design 91
Technical Reference Manual — iii
2.1 Design Operations 92
2.2 Member Properties 92
2.3 Allowables per AISC Code 96
2.4 Design Parameters 100
2.5 Code Checking 108
2.6 Member Selection 109
2.7 Truss Members 110
2.8 Unsymmetric Sections 110
2.9 Composite Beam Design as per AISC-ASD 110
2.10 Plate Girders 112
2.11 Tabulated Results of Steel Design 113
2.12 Weld Design 116
2.13 Steel Design per AASHTO Specifications 119
2.14 Steel Design per AISC/LRFD Specification 154
2.15 Design per American Cold Formed Steel Code 170
2.16 Castellated Beams 177
2.17 Steel Design per the AISC Unified 360-05 Steel Design Spec-

ification 188
Section 3 American Concrete Design 197
3.1 Design Operations 198
3.2 Section Types for Concrete Design 198
3.3 Member Dimensions 199
3.4 Design Parameters 199
3.5 Slenderness Effects and Analysis Consideration 203
3.6 Beam Design 204
3.7 Column Design 209
3.8 Designing elements, shear walls, slabs 214
Section 4 American Timber Design 227
4.1 Timber Design 227
4.2 Design Operations 239
4.3 Input Specification 242
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4.4 Code Checking 243
4.5 Orientation of Lamination 243
4.6 Member Selection 244
Section 5 Commands and Input Instructions 251
5.1 Command Language Conventions 253
5.2 Problem Initiation And Title 259
5.3 Unit Specification 260
5.4 Input/Output Width Specification 262
5.5 Set Command Specification 262
5.6 Separator Command 270
5.7 Page New Command 270
5.8 Page Length/Eject Command 271
5.9 Ignore Specifications 271
5.10 No Design Specification 272
5.11 Joint Coordinates Specification 272

5.12 Member Incidences Specification 276
5.13 Elements and Surfaces 279
5.14 Plate Element Mesh Generation 285
5.15 Redefinition of Joint and Member Numbers 292
5.16 Entities as single objects 293
5.17 Rotation of Structure Geometry 298
5.18 Inactive/Delete Specification 299
5.19 User Steel Table Specification 300
5.20 Member Property Specification 309
5.21 Element/Surface Property Specification 338
5.22 Member/Element Releases 340
5.23 Member Truss/Cable/Tension/Compression Specification 345
5.24 Element Plane Stress and Ignore Inplane Rotation Specifications
352
5.25 Member Offset Specification 353
5.26 Specifying and Assigning Material Constants 355
Technical Reference Manual — v
5.27 Support Specifications 375
5.28 Master/Slave Specification 390
5.29 Draw Specifications 392
5.30 Miscellaneous Settings for Dynamic Analysis 392
5.31 Definition of Load Systems 394
5.32 Loading Specifications 484
5.33 Reference Load Cases - Application 573
5.34 Frequency Calculation 574
5.35 Load Combination Specification 576
5.36 Calculation of Problem Statistics 579
5.37 Analysis Specification 579
5.38 Change Specification 610
5.39 Load List Specification 611

5.40 Load Envelope 613
5.41 Section Specification 613
5.42 Print Specifications 615
5.43 Stress/Force Output Printing for Surface Entities 620
5.44 Printing Section Displacements for Members 622
5.45 Printing the Force Envelope 624
5.46 Post Analysis Printer Plot Specifications 625
5.47 Size Specification 625
5.48 Steel and Aluminum Design Specifications 626
5.49 Group Specification 632
5.50 Steel and Aluminum Take Off Specification 634
5.51 Timber Design Specifications 635
5.52 Concrete Design Specifications for beams, columns and plate ele-
ments 637
5.53 Footing Design Specifications 641
5.54 Shear Wall Design 641
5.55 End Run Specification 644
Index 645
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Index of Commands 653
A, B 653
C 653
D 653
E 653
F 653
G 653
H 654
I 654
J, K 654
L 654

M 654
N 654
O 654
P 654
Q, R 655
S 655
T 655
U, V, W, X, Y, Z 655
Technical Support 657
Technical Reference Manual — vii

Introduction
Section 1 of the manual contains a general description of the analysis and
design facilities available in the STAAD engine.
Specific information on steel, concrete, and timber design is available in
Sections 2, 3, and 4 of this manual, respectively.
Detailed STAAD engine STD file command formats and other specific user
information is presented in Section 5.
Technical Reference Manual — 1
Introduction
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Introduction
Section 1
General Description
1.1 Introduction 4
1.2 Input Generation 5
1.3 Types of Structures 5
1.4 Unit Systems 6
1.5 Structure Geometry and Coordinate Systems 6
1.6 Finite Element Information 18

1.7 Member Properties 34
1.8 Member/ Element Release 43
1.9 Truss/Tension/Compression - Only Members 43
1.10 Tension, Compression - Only Springs 44
1.11 Cable Members 44
1.12 Member Offsets 47
1.13 Material Constants 48
1.14 Supports 48
Technical Reference Manual — 3
1.15 Master/Slave Joints 49
1.16 Loads 49
1.17 Load Generator 57
1.18 Analysis Facilities 60
1.19 Member End Forces 82
1.20 Multiple Analyses 88
1.21 Steel, Concrete, Timber Design 89
1.22 Footing Design 89
1.23 Printing Facilities 89
1.24 Plotting Facilities 89
1.25 Miscellaneous Facilities 89
1.26 Post Processing Facilities 90
1.1 Introduction
The STAAD.Pro 2007 Graphical User Interface (GUI) is normally used to
create all input specifications and all output reports and displays (See the
Graphical Environment manual). These structural modeling and analysis input
specifications are stored in a text file with extension “.STD”. When the GUI
does a File Open to start a session with an existing model, it gets all of its
information from the STD file. A user may edit/create this STD file and have
the GUI and the analysis engine both reflect the changes.
The STD file is processed by the STAAD analysis “engine” to produce results

that are stored in several files with extensions such as ANL, BMD, TMH, etc.
The ANL text file contains the printable output as created by the
specifications in this manual. The other files contain the results
(displacements, member/element forces, mode shapes, section
forces/moments/displacements, etc.) that are used by the GUI in post
processing mode.
This section of the manual contains a general description of the analysis and
design facilities available in the STAAD engine. Specific information on steel,
concrete, and timber design is available in Sections 2, 3, and 4 of this manual,
respectively. Detailed STAAD engine STD file command formats and other
specific user information is presented in Section 5.
The objective of this section is to familiarize the user with the basic principles
involved in the implementation of the various analysis/design facilities
offered by the STAAD engine. As a general rule, the sequence in which the
4 — STAAD.Pro
facilities are discussed follows the recommended sequence of their usage in the
STD input file.
1.2 Input Generation
The GUI (or user) communicates with the STAAD analysis engine through the
STD input file. That input file is a text file consisting of a series of commands
which are executed sequentially. The commands contain either instructions or
data pertaining to analysis and/or design. The elements and conventions of the
STAAD command language are described in Section 5 of this manual.
The STAAD input file can be created through a text editor or the GUI
Modeling facility. In general, any text editor may be utilized to edit/create the
STD input file. The GUI Modeling facility creates the input file through an
interactive menu-driven graphics oriented procedure.
1.3 Types of Structures
A STRUCTURE can be defined as an assemblage of elements. STAAD is capable
of analyzing and designing structures consisting of both frame, plate/shell and

solid elements. Almost any type of structure can be analyzed by STAAD.
A SPACE structure, which is a three dimensional framed structure with loads
applied in any plane, is the most general.
A PLANE structure is bound by a global X-Y coordinate system with loads in
the same plane.
A TRUSS structure consists of truss members which can have only axial
member forces and no bending in the members.
A FLOOR structure is a two or three dimensional structure having no
horizontal (global X or Z) movement of the structure [FX, FZ & MY are
restrained at every joint]. The floor framing (in global X-Z plane) of a building
is an ideal example of a FLOOR structure. Columns can also be modeled with
the floor in a FLOOR structure as long as the structure has no horizontal
loading. If there is any horizontal load, it must be analyzed as a SPACE
structure.
Specification of the correct structure type reduces the number of equations to
be solved during the analysis. This results in a faster and more economic
solution for the user. The degrees of freedom associated with frame elements
of different types of structures is illustrated in Figure 1.1.
Technical Reference Manual — 5
Figure 1.1 - Degrees of freedom in each type of Structure
1.4 Unit Systems
you is allowed to input data and request output in almost all commonly used
engineering unit systems including MKS, SI and FPS. In the input file, the user
may change units as many times as required. Mix and match between length
and force units from different unit systems is also allowed. The input-unit for
angles (or rotations) is degrees. However, in JOINT DISPLACEMENT output,
the rotations are provided in radians. For all output, the units are clearly
specified by the program.
1.5 Structure Geometry and Coordinate Sys-
tems

A structure is an assembly of individual components such as beams, columns,
slabs, plates etc In STAAD, frame elements and plate elements may be used
to model the structural components. Typically, modeling of the structure
geometry consists of two steps:
A.
Identification and description of joints or nodes.
B.
Modeling of members or elements through specification of connectivity
(incidences) between joints.
In general, the term MEMBER will be used to refer to frame elements and the
term ELEMENT will be used to refer to plate/shell and solid elements.
6 — STAAD.Pro
Connectivity for MEMBERs may be provided through the MEMBER
INCIDENCE command while connectivity for ELEMENTs may be provided
through the ELEMENT INCIDENCE command.
STAAD uses two types of coordinate systems to define the structure geometry
and loading patterns. The GLOBAL coordinate system is an arbitrary
coordinate system in space which is utilized to specify the overall geometry &
loading pattern of the structure. A LOCAL coordinate system is associated with
each member (or element) and is utilized in MEMBER END FORCE output or
local load specification.
See "5.11 Joint Coordinates Specification " on page 272
1.5.1 Global Coordinate System
The following coordinate systems are available for specification of the
structure geometry.
1. Conventional Cartesian Coordinate System: This coordinate system (Fig.
1.2) is a rectangular coordinate system (X, Y, Z) which follows the
orthogonal right hand rule. This coordinate system may be used to define
the joint locations and loading directions. The translational degrees of
freedom are denoted by u

1
, u
2
, u
3
and the rotational degrees of freedom
are denoted by u
4
, u
5
& u
6
.
2. Cylindrical Coordinate System: In this coordinate system, (Fig. 1.3) the X
and Y coordinates of the conventional cartesian system are replaced by R
(radius) and Ø (angle in degrees). The Z coordinate is identical to the Z
coordinate of the cartesian system and its positive direction is
determined by the right hand rule.
3.
Reverse Cylindrical Coordinate System: This is a cylindrical type
coordinate system (Fig. 1.4) where the R- Ø plane corresponds to the X-Z
plane of the cartesian system. The right hand rule is followed to
determine the positive direction of the Y axis.
Technical Reference Manual — 7
Figure 1.2 : Cartesian (Rectangular) Coordinate System
Figure 1.3 : Cylindrical Coordinate System
Figure 1.4 : Reverse Cylindrical Coordinate System
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1.5.2 Local Coordinate System
A local coordinate system is associated with each member. Each axis of the

local orthogonal coordinate system is also based on the right hand rule. Fig. 1.5
shows a beam member with start joint 'i' and end joint 'j'. The positive
direction of the local x-axis is determined by joining 'i' to 'j' and projecting it in
the same direction. The right hand rule may be applied to obtain the positive
directions of the local y and z axes. The local y and z-axes coincide with the
axes of the two principal moments of inertia. Note that the local coordinate
system is always rectangular.
A wide range of cross-sectional shapes may be specified for analysis. These
include rolled steel shapes, user specified prismatic shapes etc Fig. 1.6 shows
local axis system(s) for these shapes.
Figure 1.5a
Technical Reference Manual — 9
Figure 1.5b
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Figure 1.6a - Local axis system for various cross sections when global Y axis
is vertical.
Note: The local x-axis of the above sections is going into the paper
Technical Reference Manual — 11
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Figure 1.6b - Local axis system for various cross sections when global Z axis
is vertical (SET Z UP is specified).
1.5.3 Relationship Between Global & Local Coordinates
Since the input (see Section 5.26.1) for member loads can be provided in the
local and global coordinate system and the output for member-end-forces is
printed in the local coordinate system, it is important to know the relationship
between the local and global coordinate systems. This relationship is defined
by an angle measured in the following specified way. This angle will be defined
as the beta (b) angle. For offset members the beta angle/reference point
specifications are based on the offset position of the local axis, not the joint
positions.

Beta Angle
When the local x-axis is parallel to the global Vertical axis, as in the case of a
column in a structure, the beta angle is the angle through which the local z-axis
(or local Y for SET Z UP) has been rotated about the local x-axis from a
position of being parallel and in the same positive direction of the global Z-
axis (global Y axis for SET Z UP).
When the local x-axis is not parallel to the global Vertical axis, the beta angle
is the angle through which the local coordinate system has been rotated about
the local x-axis from a position of having the local z-axis (or local Y for SET Z
UP) parallel to the global X-Z plane (or global X-Y plane for SET Z UP)and the
local y-axis (or local z for SET Z UP) in the same positive direction as the
global vertical axis. Figure 1.7 details the positions for beta equals 0 degrees or
90 degrees. When providing member loads in the local member axis, it is
helpful to refer to this figure for a quick determination of the local axis system.
Reference Point
An alternative to providing the member orientation is to input the coordinates
(or a joint number) which will be a reference point located in the member x-y
plane (x-z plane for SET Z UP) but not on the axis of the member. From the
location of the reference point, the program automatically calculates the
orientation of the member x-y plane (x-z plane for SET Z UP).
Technical Reference Manual — 13
Reference Vector
This is yet another way to specify the member orientation. In the reference
point method described above, the X,Y,Z coordinates of the point are in the
global axis system. In a reference vector, the X,Y,Z coordinates are specified
with respect to the local axis system of the member corresponding to the
BETA 0 condition.
A direction vector is created by the program as explained in section 5.26.2 of
this manual. The program then calculates the Beta Angle using this vector.
14 — STAAD.Pro

Figure 1.8
Figure 1.9
Technical Reference Manual — 15