Tekla Structures
Analysis Manual
Product version 14.0
April 2008
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Contents
Preface ...7
Audience ... 7
Additional help resources ... 7
Conventions used in this guide ... 8
Related guides ... 9
1
Getting Started with Analysis... 11
1.1
Basics ... 11
Following through structural analysis... 13
Members, elements, and nodes... 13
1.2
Determining member properties ... 14
Member analysis type ... 15
Member axis location ... 17
Analysis member offsets... 17
Analysis properties of plates ... 18
Spanning ... 19
Loading ... 20
Analysis offsets of plates ... 21
Analysis properties of components ... 22
Analysis properties of slab components... 23
Analyzing composite beams ... 24
Viewing analysis results ... 24
Manual method - limitations ... 25
Support conditions ... 25
Defining support conditions... 25
Design information ... 27
Properties of intermediate members... 28
Defining buckling lengths (columns) ... 28
Effective buckling length ... 28
Kmode options ... 29
1.3
Fine-tuning analysis models ... 30
Adding intermediate nodes ... 33
Using rigid links... 34
A closer look at the analysis model ... 36
Objects ... 36
Nodes connecting members and elements ... 36
Loads in analysis... 37
Load modeling code ... 38
Analysis method ... 39
2
Loads... 41
2.1
Basics... 41
Automatic loads and load groups ... 42
2.2
Grouping loads... 42
Load group properties ... 42
Load group compatibility ... 43
Working with load groups ... 44
Checking loads and load groups ... 44
Changing the load group ... 44
Importing and exporting load groups ... 45
2.3
Load types and properties... 45
Load types... 45
Load forms ... 47
Load magnitude... 47
Temperature loads and strain ... 48
2.4
Distributing loads... 48
Attaching loads to parts or locations ... 48
Applying loads to parts ... 49
Loaded length or area ... 50
Modifying load distribution... 50
2.5
Working with loads... 52
Changing loaded length or area ... 52
Scaling loads in model views ... 53
Defining varying wind loads... 53
2.6
Load reference... 54
3
Analysis and Design ... 57
3.1
Analysis model geometry... 57
Creating rules to define analysis model geometry ... 58
Modifying analysis model geometry ... 59
Connecting or disconnecting parts in analysis ... 60
Defining analysis connections of parts ... 60
3.2
Analysis model properties... 64
Objects in an analysis model ... 65
Analysis model filter ... 66
Member axis... 66
Member end connectivity ... 67
Defining nodes ... 67
Model merging with analysis applications... 68
Analysis method... 69
Seismic analysis... 69
Modal analysis ... 70
Design codes and methods... 71
Design properties ... 71
Contents of STAAD.Pro results files and reports... 71
3.3
Load combination ... 72
Load combination properties... 72
Load combination factors... 73
Load combination types ... 73
Creating load combinations... 75
Automatic load combination... 75
Automatically including loads in combinations... 76
Manual load combination ... 77
3.4
Working with analysis and design models... 77
Checking objects contained in an analysis model... 78
Adding or removing analysis objects... 78
Showing analysis models and support conditions in model views... 78
Analysis model status ... 81
Running analysis... 81
Viewing analysis results... 82
Preface
Tekla Structures includes complete documentation in an accessible help system. Our online help is a detailed guide to Tekla Structures concepts, tools, commands, and features, with plenty of examples. The documentation is also available in PDF format.
Topics in the Preface are:
•
Audience (p. 7)•
Additional help resources (p. 7)•
Conventions used in this guide (p. 8)•
Related guides (p. 9)Audience
This guide is aimed at structural engineers, detailers and designers who model, analyze, and design concrete and steel structures.
We assume that you are familiar with the processes of structural engineering.
Additional help resources
The following resources also provide information about Tekla Structures:
Web site http://www.tekla.com
E-mail Contact your local helpdesk via e-mail:
Area office E-mail address
China [email protected] Finland [email protected]
If you believe you have discovered a problem with this software, please report it to your Tekla Structures Reseller using the maintenance request form provided at Help > Tekla on the Web > Maintenance request....
Please send any comments or suggestions about Tekla Structures documentation to [email protected].
Tekla Extranet Anyone with a current maintenance contract can use Tekla Extranet. Register now to get free access to our online discussion forums, hints & tips, software downloads, tutorials, and more. To register, go to https://extranet.tekla.com. You can also access Tekla Extranet from Tekla Structures by clicking Help > Online Support > Tekla Extranet.
Conventions used in this guide
Typefaces We use different typefaces for different items in this guide. In most cases the meaning is obvious from the context. If you are not sure what a certain typeface represents, you can check it here.
Noteboxes We use several types of noteboxes, marked by different icons. Their functions are shown below: France [email protected]
Germany [email protected] Japan [email protected] Malaysia [email protected] Middle East [email protected] Sweden [email protected] UK [email protected] US [email protected] Area office E-mail address
Convention Usage
Bold Bold indicates the names of keyboard keys. Bold is also used for general emphasis in text.
Arial bold Any text that you see in the user interface appears in Arial bold. Items such as window and dialog box titles, field and button names, combo box options, and list box items are displayed in this typeface.
Italic bold New terms are in italic bold when they appear in the current context for the first time.
Monospace Extracts of Tekla Structures’s program code, HTML, or other mate-rial that you would normally edit in a text editor, appears in mono-spaced font.
Filenames and folder paths appear in monospace.
Related guides
Tekla Structures includes a comprehensive help system in a series of online books. You will also receive a printed installation guide with your Tekla Structures installation DVD.
•
Modeling ManualHow to create a physical model.
•
Analysis ManualHow to create loads and run structural analysis.
•
Detailing ManualHow to create reinforcement, connections, and details.
•
Drawing ManualHow to create and edit drawings.
•
System ManualCovers advanced features and how to maintain the Tekla Structures environment.
•
TplEd User’s GuideHow to create and edit report and drawing templates.
•
SymEd User’s GuideHow to use the SymEd graphical interface to manipulate symbols.
A tip might introduce a shortcut, or suggest alternative ways of doing things. A tip never contains information that is absolutely necessary.
A note draws attention to details that you might easily overlook. It can also point you to other information in this guide that you might find useful.
You should always read very important notes and warnings, like this one. They will help you avoid making serious mistakes, or wasting your time.
This symbol indicates advanced or highly technical information that is usually of interest only to advanced or technically-oriented readers. You are never required to understand this kind of information.
•
Installation Troubleshooting Guide1
Getting Started with
Analysis
Introduction This chapter explains how to prepare a Tekla Structures model for structural analysis and design. It includes a general description of the principles of analysis and design and discusses the theoretical basis of the analysis method used in Tekla Structures. This chapter also explains what is included in the analysis model, and how it is included. You will also learn how to define support conditions for parts.
Audience This chapter is for engineers and designers who run structural analysis on concrete and steel structures.
Assumed background
We assume that you have read Parts in the Modeling Manual and created parts.
Contents This chapter is divided into the following sections:
•
Basics (p. 11)•
Determining member properties (p. 14)•
Analysis information and settings (p. 36)1.1 Basics
In this section This section presents the basic vocabulary and concepts we use to describe structural analysis in Tekla Structures. The illustrations below show the analysis concepts and procedures.
Physical model A physical model includes the parts you have created using the Model Editor, and information related to them. Each part in the physical model exists in the completed structure.
Load model The load model contains information about loads and load groups. It also contains information about the building code Tekla Structures uses in load combination. To create a load model, see
Loads (p. 41).
Analysis model Tekla Structures generates an analysis model of the physical and load models when you run structural analysis. Tekla Structures does the following in order to generate the analysis model:
•
Creates nodes and analysis members and elements of the physical parts•
Determines the support conditions for nodes•
Determines the connectivity between the members and nodes•
Distributes loads to members and elementsThe analysis model also includes load combinations.
Analysis application
Tekla Structures links with a number of analysis applications and also supports import and export with them in several formats. The analysis application you use to run structural analysis uses data from the analysis model to generate analysis results.
For more information on the analysis applications that you can use with Tekla Structures, visit Tekla Extranet at https://extranet.tekla.com. You can also access Tekla Extranet from Tekla Structures at Help > Online Support > Tekla Extranet.
Parts Loads
Physical and load models Node
Loads
Analysis member Analysis model
Following through structural analysis
Before analysis Carry out the following steps before you run structural analysis in Tekla Structures:
1. Create the main load-bearing parts to form the physical model. See Parts in the Modeling Manual. There is no need to detail or create connections at this stage.
2. Set the support conditions for parts and connections, as well as other analysis properties for individual members. See Determining member properties (p. 14).
3. Create the load model. See Loads (p. 41).
4. Define the analysis geometry settings and modify the geometry if needed. See Analysis model geometry (p. 57) and Modifying analysis model geometry (p. 59).
5. Create a new analysis model and define its properties. See Analysis model properties (p.
64).
6. Create load combinations.
7. Check the analysis model in a Tekla Structures model view. See Showing analysis models and support conditions in model views (p. 78) and Checking objects contained in an analysis model (p. 78).
8. Check the analysis parts and modify their properties if needed. See Analysis part properties (p. 61).
Now you are ready to run the analysis.
See also The following sections discuss the theoretical basis of the analysis method used in Tekla Structures. They also explain what is included in the analysis model, and how it is included.
•
Members, elements, and nodes (p. 13)•
A closer look at the analysis model (p. 36)•
Loads in analysis (p. 37)•
Load modeling code (p. 38)•
Analysis method (p. 39)Members, elements, and nodes
Members Every physical part (beam or column) that you select to include in the analysis model produces one or more analysis members. A single physical part produces several members if the part intersects with other parts. Tekla Structures splits the part at the intersection points of the member axes.
Tekla Structures analyzes parts using properties in the profile and mate-rial catalogs, including user-defined properties. If there are no profile or analysis properties in the catalog, Tekla Structures calculates them using the profile dimensions in the model.
To create accurate analysis models, make sure that connected parts have common reference points, for example, at grid line intersections.
Elements Tekla Structures splits the plates, slabs, and panels that you include in the analysis model into
analysis elements, based on their analysis properties and the parts connected to them.
Nodes Nodes connect analysis members and elements. Tekla Structures creates nodes at:
•
The ends of members•
The intersection points of member axes•
The corners of elementsThe following properties affect the exact location of nodes:
•
Part profiles, i.e. neutral axis and orientation•
Part reference lines (see Part location in the Modeling Manual)•
Location of member axes (see Member axis location (p. 17) and Member axis (p. 66)•
Location and shape of elements (see Analysis properties of plates (p. 18))•
Node definition method (p. 67)To force members to meet in the analysis model, Tekla Structures may need to merge nodes, shift or extend member axes, create rigid links between nodes, ignore minor members, etc.
For more information on where and how Tekla Structures creates nodes, members, and elements, see A closer look at the analysis model (p. 36).
1.2 Determining member properties
You can define analysis properties for individual parts, or for an entire analysis model. This section describes the properties of the individual analysis members. To define these, use the
Analysis, Loading, Composite, Start releases, End releases, and Design tabs in the part properties dialog boxes, or the Analysis tab in the connection and detail dialog boxes.
The methods used to create a physical model affect the analysis model. Because of this, you may need to try different modeling methods and analysis model properties in order to create an accurate analysis model of a complex physical model.
For more information on using common properties for the parts in an analysis model, see
Analysis model properties (p. 64).
Member analysis type
Use the Analysis tab in the part properties dialog boxes to define how Tekla Structures handles individual members in the analysis. The following table lists the options.
You can have Tekla Structures show the member analysis type of parts using different colors in the physical model. The Color column lists these colors.
Some analysis properties of parts are user-defined attributes. For more information, see Fine-tuning analysis models (p. 30).
Option Description Color
Default Member can take any type of load. Columns, beams, and braces are modeled as beam members. Slabs and panels are modeled as shell elements. Temperature load is available only for beam members.
Light gray
Beam Member can take any load, including temperature.
For more information on members with the Truss, Tension only, or Compression only setting, see A closer look at the analysis model (p. 36).
To have Tekla Structures indicate the member analysis type of parts in an object group using colors:
1. Click View > Representation > Object Representation.... 2. Select the object group.
3. In the Color column, select Color by analysis type. 4. Click Modify.
Shell Member can take any load, except temperature. Use to analyze slabs, panels, and plates.
Magenta
Ignore Member ignored in the analysis. Red
Truss Member can only take axial forces, not bending or torsion moments, or shear forces. Usually used for brace members.
Green
Truss - Tension only
Member can only take tensile axial forces, not moments or shear forces. If this member goes into compression, it is ignored in the analysis.
Cyan
Truss - Compres-sion only
Member can only take compressive axial forces, not moments or shear forces. If this member goes into tension, it is ignored in the analysis.
Yellow
Rigid diaphragm Only applies to contour plates and concrete slabs parallel to the global xy plane.
Nodes that belong to a part matching the filter will be connected with rigid links which together affect displacement. For example, you can use column_filter to connect only column nodes to rigid diaphragms.
Blue
Shear wall For rectangular concrete panels and concrete slabs using design codes ACI and BS 8110 only.
Tekla Structures analyzes the concrete panel or slab as a shear wall that does not take any direct loads.
Gray
Plate Same as Shell but plate, membrane, or mat foundation elements are used in the analysis application.
Aqua
Membrane Lime
Mat foundation Pink
The analysis application that you use may not support all options.
For more information on object representation and object groups, see Object representation settings and Object groups in the Modeling Manual.
Member axis location
The locations of the member axes of parts define where the analysis members actually meet, and their length in the analysis model. They also affect where Tekla Structures creates nodes. See
Members, elements, and nodes (p. 13) and A closer look at the analysis model (p. 36). Use the Analysis tab in the part properties dialog boxes to define the member axis location of individual parts for analysis purposes. The options are:
Tekla Structures uses the options above for each part when you select the Model default option for the member axis location in the analysis model properties. See Member axis (p. 66).
Analysis member offsets
Use offsets at the ends of analysis members to shorten or lengthen members in their local x directions, for analysis purposes and to take the eccentricity effects into account.
For example, if a beam only actually spans the clear distance between two supporting columns, you can use offsets to only include the clear distance in the analysis, instead of the distance between the center points of the columns.
Another example is an eccentric connection between a precast concrete column and beam. To take the eccentricity of the load from the beam into account, use the analysis offsets of the beam.
Option Description
Neutral axis The neutral axis is the member axis for this part. The location of the member axis changes if the profile of the part changes.
Reference axis The part reference line is the member axis for this part. See also Part location in the Modeling Manual.
Reference axis (eccentricity by neutral axis)
The part reference line is the member axis for this part. The location of the neutral axis defines axis eccentricity.
If you select the Neutral axis option, Tekla Structures takes the part loca-tion and end offsets into account when it creates nodes. See End offsets in the Modeling Manual. If you select either of the Reference axis
Use the Analysis tab in the part properties or connection dialog boxes to define the offset at each end of a member. The options are:
Analysis properties of plates
When creating an analysis model, Tekla Structures creates analysis elements for contour plates, concrete slabs, and concrete panels.
Use the Analysis, Spanning, and Loading tabs in the appropriate part properties dialog boxes to define how Tekla Structures creates analysis elements.
The analysis properties of plates are:
Option Description
Manual Works like end offsets for parts in the physical model. Enter a positive or negative value in the Dx
field. See also End offsets in the Modeling Manual.
Automatic Dx The offset is the distance between the intersection of the parts’ neutral axes and the intersection of the edges of the parts.
Longitudinal member offset
Only applies to connection members and details. Works like the Manual option and a value in the Dx
Spanning
Use the plate spanning properties to define which parts carry loads from plates in slab-to-beam connections and wall-to-column connections:
Property Description
Type See Member analysis type (p. 15). Set to Shell to create elements in the analysis model.
Plane The plane of the plate on which Tekla Structures creates the elements. The options are:
•
Top plane•
Middle plane•
Bottom plane•
Left plane•
Right plane•
Middle plane (of left/right)The reference points of connected parts must also be in this plane.
Element size The approximate dimensions of the elements, in the local x and y directions of the plate. For triangular elements, the approximate dimensions of the bounding box around each element.
Holes The approximate dimensions of the elements around openings.
Some analysis properties of parts are user-defined attributes. For more information, see Fine-tuning analysis models (p. 30).
The spanning settings of the plate determine the spanning of the load. The spanning setting of the load does not affect a load applied to a plate (see also Modifying load distribution (p. 50)).
Loading
The loading properties allow you to include concrete slabs as loads in the analysis model. The loading properties are:
Property Description
Spanning The options are:
Single spanning plates carry loads in the direction of the primary axis. Beams or columns parallel to the spanning direction are not connected to the plate, and will not carry the load from plate.
Double spanning plates carry loads along the primary and secondary axes. Beams or columns in both directions will carry the load from plate.
Primary axis direc-tion
Define the direction of the primary axis in one of the following ways:
•
Enter 1 in the axis field which is parallel to the primary axis direction.•
Click Parallel to part, and then select the beam in the model that is parallel to the direction.•
Click Perpendicular to part, and then selectthe beam in the model that is perpendicular to the direction.
Show direction on selected members
A red line indicates the primary spanning direction of the plate carrying the load.
Analysis offsets of plates
You can define analysis offsets for individual corners of contour plates, concrete slabs, and concrete panels in the global x, y, and z directions. Use the Analysis offsets tab in the part’s user-defined attributes dialog box. It includes Node offset fields for 12 corners.
To define analysis offsets for a plate:
1. Run the analysis, or create an analysis model.
2. Click Tools > Inquire > Object and select the plate in the model to query its corner points. Property Description
Generate self weight load
The analysis model includes the part weight, for example a deck, as a load even if the part is not otherwise included in the analysis model.
If the part is included in the analysis model, so is its self-weight. The option No works only with the analysis types Ignore and Rigid diaphragm. List boxes for
addi-tional loads
Enter slab live load or additional self-weight (screed, services) using three additional loads with load group name and magnitude. The directions of these loads follow the direction of the load group to which they belong.
Part names Use this filter to ensure that area load from a slab is transferred to the correct parts, for example, beams supporting the slab. Typically you would enter the beam name as the filter value.
Use continuous structure load distri-bution
Use to assign most of the load to the middle supports on continuous structures.
The Inquire Object dialog box opens, listing the corner indices and coordinates:
3. Double-click the plate in the model to open its properties dialog box.
4. On the Attributes tab, click the User-defined attributes... button to open the attributes dialog box.
5. On the Analysis offsets tab, enter the x, y, and z offsets of each corner in the appropriate field, according to the index of the corner. Use the current length units and separate the x, y, and z values with spaces.
6. Click Modify.
Analysis properties of components
Use the Analysis tab in the connection or detail dialog boxes to define how Tekla Structures handles connections and details in the analysis.
The analysis properties of connections and details are:
You can also modify analysis model geometry by moving analysis part handles. See Modifying analysis model geometry (p. 59).
Analysis properties of slab components
Use the Analysis tab in the Slab generation with polygon plate (61) and Slab generation with points (62) dialog boxes to define the analysis properties of parts created using these
components.
The following table lists the analysis properties of slab components. The option you select in the
Analysis type list box limits the other properties you can define (see the Only use for column). Property Description
Use analysis restraints
Set to Yes to use the analysis properties of the connection or detail in the analysis, instead of the analysis properties of the parts in the connection. You must also select Yes in the Member end release method by connection list box in the
Analysis Model Properties dialog box when you create the analysis model. See Member end connectivity (p. 67).
Member selection Use to associate the analysis properties with each connection part (Primary, 1. secondary, 2. secondary, etc.).
Restraint combina-tion
See Support conditions (p. 25) and Defining support conditions (p. 25).
Support condition Longitudinal member offset
See Analysis member offsets (p. 17).
Analysis profile Tekla Structures uses this profile in the analysis, instead of the one in the physical model, in order to take the stiffness of the connection or detail into account.
Analysis profile length
This means that in the analysis, Tekla Structures overrides the profile of the part in the physical model, for this length.
Property Description
Only use for
Analysis type How Tekla Structures analyzes the slabs.
•
Ignore: Slabs are not analyzed.•
Beam: Analyze each slab as a beam.•
Plate: Analyze each slab as a plate.•
Rigid diaphragm: Analyze slabs as arigid diaphragm.
See also Member analysis type (p. 15).
Beam axis The location of the beam axis. See also
Member axis location (p. 17).
Analyzing composite beams
Composite beams consist of a beam and studs, with a concrete slab on top of the beam. You can define the analysis properties of the slabs in composite beams, and define the width of the slab manually or automatically.
To define the properties of the concrete slab in a composite beam: 1. Open the Beam Properties dialog box and go to the Composite tab. 2. Select the Composite beam option in the Composite beam list box. 3. Select a Material and enter the Thickness of the slab.
4. To define the effective slab width:
•
Manual method: Select the To the left from the beam and/or To the right of the beam radio button and enter a value in the field next to these buttons. See also Manual method - limitations (p. 25).•
Automatic method: For the left and right side, select the Automatic, half of span length divided by radio button and enter a value in the field next to these buttons. When you run the analysis, Tekla Structures calculates the effective slab width by dividing the span length of the beam by the value you enter.Viewing analysis results
To view the analysis results for composite beams, right-click the beam and select Inquire on the pop-up menu. The analysis results include:
•
Element and node IDs•
Effective width•
Slab thickness•
Slab materialRestraints The support conditions of beam ends. The options are Pinned and Fixed.
Beam
Plate plane The plane on which to create the elements and nodes. If you select Top plane, Tekla Structures creates the elements on the top surface of the slab.
Plate
Element type The shape of the elements. Plate
Element size x and y: The approximate dimensions of the elements, in the local x and y direction of the slab. For triangular elements, the approxi-mate dimensions of the bounding box around each element.
Holes: The approximate size of the elements around openings.
Plate
Filter Nodes that belong to a part matching the filter will be connected to the rigid diaphragm. For example, you can use
column_filter to connect only column nodes to rigid diaphragms. Rigid diaphragm Property Description Only use for
•
Concrete strength•
Rib width and height•
Stud diameter and lengthManual method - limitations
•
Effective width cannot exceed the distance to the nearest beam.•
Effective width cannot be more than half the distance to the nearest composite beam.•
If there is no beam on either side of the composite beam, the slab width is zero. Use theAutomatic composite beam option to have Tekla Structures calculate the slab width.
Support conditions
In structural analysis, the stresses and deflections of a part depend on how it is supported by, or connected to, other parts. You normally use restraints or springs to model connections. These determine how analysis members move, deflect, warp, deform, etc., in relation to each other, or to nodes.
Member ends and nodes have degrees of freedom (DOF) in three directions. The displacement of a member end can be free or fixed, and the rotation can be pinned or fixed. If the degree of connectivity is between free, or pinned, and fixed, use springs with different elastic constants to model them.
Tekla Structures uses part, connection, or detail properties to determine how to connect members in the analysis model. To define the member end conditions, use the Start releases
and End releases tabs in the part properties dialog boxes. The connection and detail dialog boxes have Analysis tabs.
The analysis properties of a member determine the degrees of freedom for each end of a main part or member. The first end of a part has a yellow handle, the second end has a magenta handle. See also Part location in the Modeling Manual.
Defining support conditions
Parts Use the Start releases and End releases tabs in the part properties dialog boxes to define support conditions. The Start releases tab relates to the first part end (yellow handle), the End releases tab to the second part end (magenta handle).
Plates To define the support conditions of contour plates, concrete slabs, and concrete panels, use the
Supported list box in the Analysis Part Properties dialog box.
Connections and details
Use the Analysis tab in the connection or detail dialog boxes to define the support conditions for the members and node in a connection. Use the Member selection list box to associate the support conditions with each connection part (Primary, 1. secondary, 2. secondary, etc.).
Support conditions
Tekla Structures includes four predefined combinations for member ends, and an option for user-defined settings. The predefined combinations (the first four in the following table) automatically set the appropriate support conditions and degrees of freedom. The combinations are:
The support conditions of a member end can be:
Displacements and rotations
’U’ denotes translational degrees of freedom (displacement). ’R’ denotes rotational degrees of freedom (rotation). Define the degrees of freedom in the global coordinate system. The options are: Combinatio n Support condition Translational DOFs Rotational DOFs
Supported Fixed Fixed
Supported Fixed Pinned
Connected Fixed Fixed
Connected Fixed Pinned
Use this option to define your own settings for the supports and connections at member ends. You can use springs and almost any combination of degrees of freedom.
To ensure that the part remains stable, and that all loads applied to it pass through to the other structures, avoid using combinations with too many degrees of freedom.
Option Description
Connected Member end is connected to an intermediate analysis node (another part). Indicate degrees of freedom for the node.
Supported Member end is the ulti-mate support for a super-structure (for example, the foot of a column in a frame).
Indicate degrees of freedom for the support.
Option More information
Free Only applies to translational degrees of freedom.
Design information
Use the Design tab in the part properties dialog boxes to view and modify the design properties of individual parts in an analysis model. Design properties are properties which can vary, according to the design code and the material of the main part (for example, design settings, factors, and limits).
The properties you see when you first open the dialog box are the properties that apply to the entire analysis model you have selected in the Analysis & Design Models dialog box. See also
Design codes and methods (p. 71).
To set different design properties for specific parts, modify the values in the appropriate part properties dialog box.
Fixed
Spring Enter translational and rotational spring constants. The units Tekla Structures uses depend on the program’s unit settings. See Units and decimals in the Modeling Manual.
Partial release Only applies to rotational degrees of freedom. Use to specify the degree of connectivity, if it is between fixed and pinned. Enter a value between 0 (fixed) and 1 (pinned).
For example, if the analysis model contains parts with different material grades, define the most common material grade using the analysis model properties. Then change the material grade of specific parts using the appropriate part properties dialog box.
To omit individual members from the design check when you run the analysis, set the following properties to No:
•
Steel parts: Check design - Enable design check of member•
Concrete parts: Calculate required area - Enable design check of memberProperties of intermediate members
When creating an analysis model, Tekla Structures may need to produce more than one analysis member for each physical part. This can result in intermediate members and member ends. Tekla Structures determines the analysis properties of intermediate members as follows: 1. The member analysis type and member axis location of the analysis members are the same
as of the original part.
2. The analysis offsets of the part ends apply to the corresponding analysis member ends. Intermediate member ends do not have analysis offsets.
3. The support conditions of all intermediate member ends are Connected. The translational and rotational degrees of freedom are all Fixed. This reflects the nature of the physical part, which is a continuous length.
4. The effective buckling length of each analysis member is K*L. K is the length factor for buckling. L is length, a value described by the Kmode design property. For more information, see Defining buckling lengths (columns) (p. 28).
5. The other design properties are the same for the analysis members as for the original part.
Defining buckling lengths (columns)
Tekla Structures allows you to define buckling lengths for column segments, which represent the building levels. Tekla Structures automatically divides columns into segments at the point where a support in the buckling direction exists, or where the column profile changes.
Effective buckling length
Effective buckling length is K*L, where K is the length factor and L is the buckling length. To calculate a part’s effective buckling length:
1. Open the part properties dialog box and go to the Design tab.
2. Select an option for Kmode. For more information about the available options, see Kmode options (p. 29).
3. Enter one or more values in the K - Length factor for buckling field. The number of values you can enter depends on the option you selected in the Kmode field. For multiple values:
•
Enter a value for each column segment starting with the lowest segment, and•
Use spaces to separate multiple values:•
You can also use multiplication to repeat factors, for example, 3*2.00. 4. Go to the L - Buckling length field:•
To automatically calculate length values, leave the fields blank.•
To override one or more length values, enter values in the relevant buckling length fields. The number of values you need to enter depends on the option you selected in the Kmode field. You can use multiplication to repeat buckling lengths, for example, 3*4000.5. Create the analysis model and use the Tools > Inquire > Object command on a part. The
Inquire Object dialog box opens and displays the member number and the effective buckling length for each segment:
Kmode options
Use the Kmode options to define how Tekla Structures calculates buckling lengths. The options are:
Option Description
Physical member L is the length of the column.
Column segment L is the length of one column segment.
Column segment, multiple values
L is the length of one column segment with user-defined factors and lengths for each column segment.
Analytical member L is the length of the member in the analysis model.
Analytical member, multiple values
L is the length of the member in the analysis model with user-defined factors and lengths for each member.
1.3 Fine-tuning analysis models
Several properties and user-defined attributes enable you to control how Tekla Structures creates analysis models.
To modify the user-defined attributes, open the part properties dialog box and click the User-defined attributes... button to open the attributes dialog box.
You can also modify several properties on the Analysis and Analysis (2) tabs of the attributes dialog box:
Use the analysis model geometry settings and analysis properties of parts to define how Tekla Structures creates analysis models. See Analysis model geometry (p. 57) and Analysis part properties (p. 61).
Attribute Description Options/Values
Node offsets Moves the part in the analysis model when members do not meet and are not connected.
Consider longitu-dinal model offsets
Controls the member longitu-dinal offsets.
Auto (default) uses the Dx end offset if it extends the beam, or if it shortens the beam and there is a node near the shortened posi-tion.
None
Extending only uses the Dx end offset when it extends the beam, and ignores it when it shortens the beam.
Always No. of split nodes Use to create additional nodes or
analyze a beam as straight segments, for example, a curved beam.
See also Adding intermediate nodes (p. 33).
Enter the number of nodes.
Split distances To define additional nodes in the member, enter distances from the part starting point to the node. See also Adding intermediate nodes (p. 33).
Enter distances, separated by spaces, for example:
1000 1500 3000
Curved beam by straight segments
Use to analyze a curved beam as straight segments.
Yes No Node merge
distance
Merges nodes within the distance specified into a single node. For example, use this to force truss-type analysis members to meet in the analysis model. The Keep axis attribute over-rides this attribute.
Distance
Design group (opti-mization)
Defines which design group the part belongs to. Used in optimi-zation.
Member level (z) Sets the same z coordinate for all nodes.
Enter a value for the z coordi-nate.
Profile Analysis part profile.
You can use different analysis profiles at the start and end of parts if the analysis application you use supports it.
Select a profile from the profile catalog.
To use different profiles at part ends, enter two profiles separated by a pipe character, for example: HEA120|HEA140
Connect to (part IDs)
Forces or disables connections between the analysis members you specify.
Works with the Connect exclu-sively attribute.
To enable connections, enter the part ID’s, separated by spaces. To prevent connection, enter negative part ID’s, separated by spaces.
Connect exclusively Select Yes to connect the part only to the parts defined by the
Connect to (part IDs) attribute.
Keep axis Select Yes to fix the location of member axis so that Tekla Struc-tures does not shift the axis when it makes members meet in the analysis model.
For example, use this with the
Node merge distance attribute to force truss-type members to meet in the analysis model. Overrides the Node merge distance attribute.
Rigid link Enables or disables rigid links at the start, mid, and end points of parts.
Use with the Force to centric connection option in the Anal-ysis Model Properties dialog box to specify which parts to use rigid links.
See also Using rigid links (p.
34).
For each point: 0 = disable 1 = enable For example:
•
0 = no rigid links•
100 = rigid link at start point•
111 = rigid links at start,mid, and end point
•
001 = rigid link at end pointPinned rigid link (to part names)
Connects the part using pinned rigid links to the parts you specify.
Enter the part names, separated by spaces, commas, or semico-lons. You can also use wildcards (see Using wildcards in the Modeling Manual).
Thickness Analysis plate thickness.
Minimum hole size (to consider)
Use to ignore small openings in plates in the analysis.
Enter the size of the bounding box around the opening.
Short cantilever limit (to remove)
Use to ignore short plate cantile-vers in the analysis.
Enter a cantilever length.
Mesh point IDs (add/ remove)
Use to exclude nodes from or include nodes in plate element meshes.
Only nodes created because of connected members or loads can be excluded.
To include nodes, enter the point ID’s, separated by spaces. To exclude nodes, enter negative point ID’s.
For example: 1203 -1205 -1206
See also To find out how to create user-defined attributes, see Adding properties in the System Manual.
Adding intermediate nodes
Sometimes intermediate nodes are needed along a member, for example in frequency analysis. To create additional nodes, use the following user-defined attributes on the Analysis tab of the part properties dialog box:
•
No. of split nodesEnter the number of nodes. Tekla Structures gives equal spacing to added nodes.
•
Split distancesEnter the distance values from the part starting point. Tekla Structures adds nodes using these distances:
Simple plate Select Yes to create a simpler analysis model of plates, where cuts and openings are not consid-ered.
Trim plate connec-tions
Select No to connect plates using rigid links, without moving nodes.
Select Yes to connect plates by moving plate nodes, instead of using rigid links.
Supported Use to define supports for plates and beams.
You can create supports for the bottom edge of a wall, for all edge nodes of a slab, or for all nodes of a beam. For walls the bottom edge can be inclined.
Simply: only translations are fixed
Fully: both translations and rota-tions are fixed
Some attributes are only available if you select the Extended clash check checkbox in the Analysis Model Properties dialog box. They are:
•
Rigid link•
Node merge distance•
Connect to (part IDs)•
Connect exclusively•
Keep axisFor more information on the Extended clash check, see Creating common nodes (p. 37).
Using rigid links
You can enable or disable rigid links using the Node definition method (p. 67) in the entire analysis model. You can override this setting in specific places:
•
If Node definition is Force to centric connection, rigid links are generally not used, but it is possible to force rigid links in specific places.•
If Node definition is Use rigid links, rigid links are used, but it is possible to prevent the use of rigid links in specific places.The value of the attribute is a three-digit number of 1’s and/or 0’s.
•
1 = rigid link enabled•
0 = rigid link disabledThe first digit is the setting for the part start point, the second digit is the setting for all intermediate points between the start and end point, and the third digit is setting for the part end point.
A rigid link is created at a connection between two members if:
•
An eccentric connection exists.•
Rigid links are enabled for both parts, either as an analysis model property or user-defined attribute of parts.Example 1 The node definition method of the analysis model is Force to centric connection. If the Rigid link attribute is not set, there will be no rigid link. To create the rigid link, use the following values of the user-defined attribute Rigid link:
Example 2 The node definition method of the analysis model is Use rigid links. If the Rigid link attribute is not set, there will be rigid links. To disable rigid link between two members, set the attribute for one part only:
If you are merging nodes of two parts, and you have set the Keep axis
attribute to Yes for both parts, Tekla Structures creates a rigid link.
For this beam, type in 010. (Rigid link is wanted in mid beam.) For this brace, type in 100. (Rigid link is wanted at beam start point.)
1.4 Analysis information and settings
This section generally discusses the analysis process and describes analysis settings.
A closer look at the analysis model
This section gives detailed information on how Tekla Structures creates analysis models of physical models.
Objects
Tekla Structures ignores the following objects in the analysis, even if you have included them in the analysis model (see Objects in an analysis model (p. 65)):
•
Parts and loads that are filtered out (see Analysis model filter (p. 66))•
Component objects (minor parts, bolts, reinforcing bars, etc.)•
Parts with the Ignore setting (see Member analysis type (p. 15))Truss members Tekla Structures does not split members with the Truss, Tension only, or Compression only
setting (truss members) when two or more truss members intersect with a normal member or with another truss member.
To force truss member nodes to meet at the same point, use the user-defined attributes Node merge distance and Keep axis. For more information on user-defined attributes, see Fine-tuning analysis models (p. 30).
Nodes connecting members and elements
Tekla Structures first creates analysis nodes:
•
On member axes at the ends of parts•
At the intersection points of member axesFor this beam, type in 101. (No rigid link is created for intermediate nodes.)
The methods used to create a physical model affect the analysis model. Because of this, you may need to try different modeling methods and analysis model properties in order to create an accurate analysis model of a complex physical model.
•
At the corners of elementsTekla Structures then checks if the analysis members have common nodes.
Creating common nodes
To force Tekla Structures to find parts that clash and create common nodes for them, select
Extended clash check checkbox in the Analysis Model Properties dialog box.
If the end points of the parts are within 10 mm of each other, Tekla Structures moves the nodes in the following order:
1. Horizontal parts 2. Other parts
Vertical parts and parts that have the user-defined attribute Keep axis set to Yes do not move. Also, supported nodes are not moved.
If the part end points are not within 10 mm of each other, Tekla Structures extends each part’s bounding box by 1 mm to find parts that clash.
Other methods Tekla Structures also creates common nodes for members if:
•
A connection exists between the members.•
The user-defined attribute Connect to (part IDs) forces the parts to meet.See also
•
For more information on user-defined attributes, see Fine-tuning analysis models (p. 30).•
For more information on the nodes, see Defining nodes (p. 67).Element nodes This is how Tekla Structures creates nodes when plates connect with other parts:
Loads in analysis
These are the principles that Tekla Structures follows when it processes loads in the physical model to create analysis model loads.
You define which loads are included in the analysis model. Tekla Structures applies these loads to members, based on the part name filtering criteria and each load’s bounding box. See
Applying loads to parts (p. 49).
Point loads Point loads are transferred to the node that is generated from the member to which the load is applied to, and that is nearest to the location of the load, or to a member. Only one load can correspond to each physical load.
Line loads A line load is transferred to members that are inside the bounding box of the line load, and whose part names match the part name filtering criteria of the load. The load must have a perpendicular component to the part to be applied to the part. If several members receive the load, the load is distributed based on the length of each member.
Area and uniform loads
Area loads are decomposed to line loads. These decomposed loads are then applied to members. Members inside the bounding box of the load and whose names match the part name criteria receive the load. The area load is divided among the members so that the load applied to the member is proportional to the projection length of the member to the load plane. The resultant of the line loads is the same as the resultant of the original area load.
Connected part Action
Beam Tekla Structures splits the beam and creates nodes in it at the element corners.
Column Tekla Structures creates a node at the column. Another plate Tekla Structures creates the analysis elements so that
the plates have common nodes on the edges of the plates.
Nodal load Tekla Structures binds loads to nodes or members in the analysis model. A load is a nodal load if:
•
It is between two nodes and the distance to the nearest node is less than 110 mm.•
It is not between two nodes (even outside the member) but inside the bounding box and meets the part name filtering criteria.Nodal loads do not cause parts to bend.
Member load If a load does not meet the criteria for the nodal load, it is a member load. Member loads cause parts to bend.
Other loads Temperature loads are like line loads which affect an entire member. The left, right, top, and bottom surfaces of the member a temperature load affects define the direction of the load.
Load modeling code
Use the Options dialog box to determine the building code and safety factors Tekla Structures uses in load combination.
1. Click Tools > Options > Options... > Load modeling. 2. Go to the Current code tab.
3. Select the code in the Load modeling code list box.
4. Change load combination factors on the appropriate tab if needed:
5. Click OK.
Tab Description More information
Current code The code to follow in analysis and load combination.
Eurocode The partial safety factors in limit states and reduction factors, for the Eurocode, based on load group types.
Load combination factors (p. 73)
British The partial safety factors in limit states, for the British code, based on load group types.
AISC (US) The partial safety factors in limit states, for the US code, based on load group types.
UBC (US) Uniform building code, Amer-ican code.
CM66 (F) The partial safety factors in limit states, for the French code for steel structures, based on load group types.
BAEL91 (F) The partial safety factors in limit states, for the French code for concrete structures, based on load group types.
IBC (US) International building code. American code.
ACI American Concrete Institute publication 318.
Analysis method
You can use either the linear (first order), or non-linear (second order, P-delta), analysis method in Tekla Structures. The non-linear method considers the non-linear nature of the geometry. This takes into account major deflections, but not the non-linear nature of materials. Tekla Structures treats materials as linear. See also Analysis method (p. 69).
If you have to change the code during a project, you will also need to change the load group types and check load combinations.
2
Loads
Introduction Once you have modeled physical structures by creating parts you can start adding loads. In Tekla Structures, you can create point loads, line loads, area loads with uniform or variable
distribution. You can also model temperature, wind, and seismic loads. Either attach loads to specific parts or to locations.
In this chapter This chapter explains how to create and group loads. It also includes a general description of load groups, load types, and load properties. The online help contains step-by-step instructions for all load commands.
Assumed background
We assume that you have created a Tekla Structures model and have a basic understanding of modeling.
Contents This chapter is divided into the following sections:
•
Basics (p. 41)•
Grouping loads (p. 42)•
Load types and properties (p. 45)•
Distributing loads (p. 48)•
Working with loads (p. 52)•
Load reference (p. 54)2.1 Basics
This section presents some Tekla Structures vocabulary and concepts to help you start to model loads.
Load model A load model is the portion of the Tekla Structures model that includes all loads, together with the load group and building code information related to them. Each load in a load model has to belong to a load group. Each load can only belong to one load group. A load group can contain one or more loads.
Load group A load group is a set of loads that are treated alike during load combination. Load groups should contain loads caused by the same action and to which you want to refer collectively. Tekla Structures assumes that all loads in a group:
•
Have the same partial safety and other combination factors•
Have the same action direction•
Occur at the same time and all togetherSee Grouping loads (p. 42) and Load combination (p. 72).
You need to create load groups because the same action can cause different types of loads, for example, point loads and area loads. See Load types (p. 45). You can include as many loads as you like in a load group, of any load type.
Working with loads
In Tekla Structures, you can attach each load to a part for modeling purposes. You can also create floating loads that are bound to locations rather than parts. See Attaching loads to parts or locations (p. 48).
Use the load’s bounding box and part name filter to define which parts carry the load. See
Applying loads to parts (p. 49).
Automatic loads and load groups
Self-weight Tekla Structures automatically calculates the self-weight of structural parts using the density of the material and the dimensions of the part.
To automatically include the self-weight of parts in load combinations, select the Include self-weight checkbox when you create load combinations. See Creating load combinations (p. 75).
Wind loads Use the Wind load generator (28) tool to define the effects of wind on a structure.
Seismic loads To automatically include seismic loads in the x and y directions in load combinations: 1. Define the code to follow in the seismic analysis.
2. Define the load groups to include in the seismic analysis and their factors. For more information, see Seismic analysis (p. 69).
See also Load combination types (p. 73)
Attaching loads to parts or locations (p. 48)
2.2 Grouping loads
Load groups should contain loads caused by the same action and to which you want to refer collectively. Tekla Structures assumes that all loads in a group:
•
Have the same partial safety and other combination factors•
Have the same action direction•
Occur at the same time and all togetherLoad group properties
To define the properties of a load group, click the Load groups icon on the Loads and Analysis
toolbar to open the Load Groups dialog box. The properties are:
Current When you apply loads in the model, Tekla Structures applies the Current load group. You can only define one load group as Current.
Name Each load group must have a unique name. Use load group names to define the visibility and selectability of loads. For example, you can select, modify, or hide loads based on their load group. See Filter in the Modeling Manual.
Type The type of a load group is the type of action that causes the loads.
Actions causing loads are building code specific. See Load modeling code (p. 38). Most building codes use some or all of the following actions and load group types:
•
Permanent, dead, and/or prestressing loads•
Live, imposed, traffic, and/or crane loads•
Snow loads•
Wind loads•
Temperature loads•
Accidental and/or earthquake loads•
Imperfection loadsDirection The direction of a load group is the global direction of the action that causes the loads. Individual loads in a load group retain their own magnitudes in the global or local x, y, and z directions. See also Load magnitude (p. 47).
Load group direction affects which loads Tekla Structures combines in load combination:
•
z direction groups are combined with both x and y direction groups.•
x or y direction groups are not combined with each other.Color Use different colors for different load groups.
Load group compatibility
When Tekla Structures creates load combinations for structural analysis, it follows the building code you select in Tools > Options > Options... > Load modeling. See Load modeling code
(p. 38) and Load combination (p. 72).
To accurately combine loads which have the same load group type, you need to identify which load groups:
•
Can occur at the same time (are compatible)•
Exclude each other (are incompatible)To define load group compatibility, click Load groups icon on the Loads and Analysis toolbar to open the Load Groups dialog box. Enter numbers to indicate compatibility.
Compatibility Compatible load groups can act together or separately. They can actually be one single loading, for example, a live loading that needs to be split in parts acting on different spans of a continuous beam. Tekla Structures then includes none, one, several, or all of the compatible load groups in a load combination.
Incompatibility Incompatible load groups always exclude each other. They cannot occur at the same time. For example, a wind loading from the x direction is incompatible with a wind loading from the y
Tekla Structures automatically determines and applies the self-weight of parts. See Automatic loads and load groups (p. 42).
direction. In load combination Tekla Structures only takes into account one load group in an incompatible grouping at a time.
Working with load groups
Use the Load groups dialog box to view, define, modify, and delete load groups. For example, this is where you set load group properties and indicate load group compatibility.
Click the Load groups icon on the Loads and Analysis toolbar to open the dialog box:
Checking loads and load groups
To find out which load group a load belongs to, select the load in the model and click the Load groups by loads button. Tekla Structures highlights the load group in the dialog box.
To find out which loads belong to a load group, select the load group in the dialog box and click the Loads by load groups button. The associated loads are highlighted in the model.
If you have many loads in the model, you can show the group name and magnitude in the model view by right-clicking a load and selecting Inquire from the pop-up menu. If you have already run the analysis, Tekla Structures also highlights the parts that carry this load.
Changing the load group
To move a load to a different load group, select the load in the model, then select a load group in the dialog box and click the Change load group button.
Tekla Structures automatically applies basic compatibility facts, such as self-weight being compatible with all other loads, or live loads being compatible with wind load.
Tekla Structures does not combine loads in the x direction with those in the y direction.
Compatibility indicators are all 0 by default. It indicates that Tekla Struc-tures combines the load groups as defined in the building code.
Load group types vary according to the code defined in Tools > Options > Options... > Load modeling. If you have to change the code during a project, you will also need to change the load group types and check load combinations.
