supervisión y evaluación que permitan ajustar las modalidades de su oper ación o decidir sobre su cancelación
3.11. P rocurar que sea el medio más eficaz y eficiente pa ra alcanzar los objetivos y metas que se pr etenden
Create this model by applying the modeling techniques that have been presented up to this point.
Figure 2. 200
Tips:
• Open Dataset 2_COMBINED.std.
• Create connection between cross members at intersection. • Translational Repeat once in the Z direction at Z = 15 feet {4.5
meters}.
• Link steps, open base.
• Delete the horizontal beam that connects the cross-braces at their intersection points.
• Use arrow keys to rotate model to match the figure above. • Click File | Save As, and name the model MY EXERCISE 2. • Click File | Close to return to the Start Page.
Property Assignment
The following topics are included in this module.
3.1 Steel Design Model Geometry ... 2
3.2 Working with Groups ... 4
3.3 Assigning Member Properties ... 11
3.4 Member Beta Angle ... 32
3.5 Assigning Member Specifications ... 45
3.6 Assigning Supports ... 60
3.7 Assigning Loads... 69
3.8 The Material Page ... 85
3.1 Steel Design Model Geometry
This section uses the model shown below to demonstrate the assignment of member properties, material constants, supports, and loads to the structure.
Figure 3. 1
• There is one aspect of the model geometry that should be reviewed before proceeding.
• This model was created using the Mirror command. • In the Mirror dialog, an option called Mirror Member
Orientation was left unselected.
• If the Mirror Member Orientation feature is turned on, the program attempts to mirror the member orientation, in addition to the member geometry, as shown below:
Figure 3. 2
• The implications of this selection will be explained in detail later in this section.
3.2 Working with Groups
• Open the file named Dataset 3_1.std.
• When working with structural models, it sometimes helps to cluster a set of entities under a single umbrella for ease of handling the data associated with those entities.
For example, one may wish to have all the principal rafters of a warehouse structure made of a common structural section such as a C10x15 channel.
If there are many rafters, it helps to be able to refer to all of them as a group, rather than working with all of the rafter members individually
• This process of clustering is referred to in STAAD.Pro as the formation of groups.
• This can save a lot of time when assigning attributes to members of the structure.
STAAD.Pro allows properties to be assigned to a group using a single instruction, rather than having to repeatedly select the individual members in order to assign various properties to them.
For instance, in the STEEL DESIGN example project, the bottom chord of the truss consists of eight members. If we cluster these members into a group, we will not have to select eight members individually in order to assign properties to them.
Similarly, assigning group names to the members comprising the top chord, the two columns, and the truss webs will make the process of assigning data to these members a lot easier.
Creating New Views is another method of filtering STAAD.Pro entities, as presented in a different module.
However, creating Groups has an advantage over creating a new view, because groups actually become part of the STAAD.Pro input file.
• Groups remain part of the model after the current STAAD.Pro session is closed. So, if you provide your input file to another STAAD.Pro user, they will be able to use the groups you created.
• Four groups will be created for the STEEL DESIGN example: Group name Description
_BOTC Truss bottom chord
_TOPC Truss top chord
_COL Columns
_WEB Truss webs
• Click Tools | Create New Group…. The Define Group Name dialog opens.
• STAAD.Pro group names must start with an underscore character (refer to Section 5.16 of the Technical Reference manual for additional information on forming group names). • However, if the underscore is not entered manually in the
Define Group Name dialog, STAAD.Pro will add it
automatically when the dialog is closed.
• Choose the Beam option in the Select Type list.
A common mistake is to leave the Select Type option set to
Node, when the intent is to group beams.
• The Create Group dialog lists the group names that are currently available to assign to (or associate to) members in the model. Currently, the only available group name is _BOTC.
• In the Assign methods category, there are three options available to associate group names with members. See the commentary below for a description of each option:
• Associate to View – associates the highlighted group name with all of the members in the view.
• Associate to Selected Geometry – associates the
highlighted group name with all of the currently selected members. (Currently “grayed out” because no members are selected.)
• Associate to List – associates the highlighted group name with all of the members whose numbers are entered in the
List field.
• The goal is now to associate the group name _BOTC with the bottom chord members of the truss.
• Leave the Create Group dialog open, then click Select | Beams Parallel To | X from the main menu.
The bottom chord members (and only the bottom chord members) will be selected.
• Notice that the Associate to Selected Geometry radio button in the Create Group dialog is now active.
• Click the Associate button at the bottom of the Create Group dialog.
STAAD.Pro associates the bottom chord members with the group named _BOTC.
It also displays the member numbers in the List field and changes the 1:_BOTC listing in the Create Group dialog to say
(Beam Assigned), implying that the group name has been assigned to at least some beams in the model.
• Click the Create button in the Create Group dialog again. • Choose the Beam option in the Select Type list.
• Enter TOPC (this time, without the leading underscore) in the
Group Name field, and click OK .
• Note that STAAD.Pro automatically inserted the required leading underscore in _TOPC in the Create Group dialog. • Click inside the Main Window to deselect all members. • Hold the Control (Ctrl) key and click the top chord members
one at a time using the Beams Cursor to select them.
Due to the inclined orientation of these members, there is no easier method to select them.
2:_TOPC (Beam Unassigned) is currently highlighted in the
Create Group dialog by default.
The Assignment Method is set to Associate to Selected
Geometry by default.
• Click the Associate button.
The top chord members are assigned to the _TOPC group, and their member numbers appear in the List field.
• Click the Create button.
• Choose the Beam option in the Select Type list. • Enter _COL in the Group Name field.
• Click OK.
• Click the Create button.
• Enter _WEB in the Group Name field. • Click OK.
Note that the list of group names in the Create Group dialog provides an indication as to which type of elements can be included in each group. (All four of our groups can only be assigned to beams.)
Also note that the list of group names in the Create Group dialog provides an indication as to which of the group names have been assigned to at least some members in the model and which group names are currently unassigned.
The group names _COL and _WEB remain unassigned at this time.
• Click on _COL.
• Click on the column at the left side of the model, then press and hold Control (Ctrl) and click on the column at the right side of the model .
• Choose the Associate to Selected Geometry Assign Method, and then click Associate .
The remaining members are the truss webs.
They could be selected using the tedious method of clicking on them one at a time. A more efficient method would be to use the groups we have created to select all of the members in the three existing groups, and then use an Inverse Selection command to select the remaining members not included in the three existing groups.
• Click Select | By Group Name….
• Click on all three group names in the Select Groups dialog. Note that STAAD.Pro allows more than one group to be selected without having to hold down any keys.
• Click Close.
The top chord, bottom chord and columns will be highlighted in the Main Window indicating that they are all selected. • Click Select | By Inverse | Inverse Beam Selection.
The selection is inverted so only the truss web members are selected.
• Click the _WEB group in the Create Group dialog.
• The Assign Method defaults to Associate to Selected Geometry. • Click Associate.
The webs are now assigned to the _WEB group. • Select _BOTC and click on the Highlight button. The
members of the selected group should be highlighted in the Main Window.
• Verify by selecting each group name one at a time and clicking Highlight .
If no members are highlighted after selecting a group name and clicking the Highlight button, check to make sure that the group is indicated as a Beam group type in the list of groups in the Create Group dialog.
If any of the groups accidentally got created as Node type groups, they will need to be deleted and recreated as Beam type groups, before the members of this model can be correctly assigned their group name.
• If any members were unintentionally omitted from a group, they can be added to the group using the Create Group dialog, or they can be added to the list in the Input File using the STAAD.Pro Editor.
• If, later on, a member is removed from the model, and if that member was part of one of the defined groups, STAAD.Pro will remove the member number from the group automatically.
Note that STAAD.Pro also allows groups of plate or solid elements to be created. However, these options weren’t offered in the list box of the Define Group Name dialog, because they only appear if the model contains plates or solids.
• Click the Close button to dismiss the Create Group dialog. • A copy of this model is already saved in this state in the
dataset, and is named Dataset 3_2.std. • Click File | Close to return to the Start Page. • Click No when asked if you want to save.
3.3 Assigning Member Properties
• Open the file named Dataset 3_2.std.
• Click the General page tab in the Page Control area. Note that the general progression is to work from top to bottom of the Page Control area to complete the steel design example.
• The General page has five sub-pages: • Property
• Spec • Support
• Load & Definition • Material
• The Property sub-page will be active or “in focus,” when the
General tab is selected.
• The Data Area on the right side now contains a dialog labeled
Properties - Whole Structure (referred to from here on as the Properties dialog).
Note: if the Properties dialog is ever closed, it can be recalled by clicking on the Property sub-page of the General page. • The Properties dialog is used to assign properties: cross
section, modulus of elasticity, Poisson’s ratio, density, and thermal coefficient for steel, concrete or aluminum members. • Standard cross sections can be chosen from tables or custom
sections can be defined.
• The following standard sections from the American steel table database will be used in the current model:
• Assigning properties is a two-step process. First, pick the sections/materials to assign to the structure. The program maintains the list of these sections in the Properties dialog. Then, use the list to assign the sections/materials to selected members.
• Click the Section Database button in the Properties dialog. • Note the tabs across the top of the Section Profile Tables
dialog for access to section tables for different materials. • Steel - provides access to a list of steel tables of more than
fifteen different countries.
• Coldformed Steel - provides access to a list of tables from various manufacturers of cold-formed steel products. • Timber - provides access to an extensive list of wood
sections comprised of various combinations of species, grades, and sawn lumber sizes. Also includes properties for Glued-Laminated material.
• Aluminum - provides access to the American Aluminum table.
The American - W Shape table from the Steel tab is active by default.
• Click American Steel Joist, and note that many common joist designations are available.
Columns Wide flange: W 18 x 35
Bottom chord Channel: C 12 x 30
Top chord Rectangular HSS: 7 in. x 4 in. x 3/16 in.
Click on any of the other country names to see the libraries that are available for use with international codes.
• Click American | W Shape.
• Scroll down through the shapes listed in the Select Beam category, and click on W18x35 .
• Note the radio buttons on the right side of the dialog under the
Type Specification heading.
• ST specifies a single section from the standard table. • T is used to indicate a T-shaped section formed by cutting
through the middle of the web of a standard W section. • CM is used to specify a composite section comprised of a
concrete slab on top of a wide flange steel shape. When this radio button is selected, the CT, FC and CW edit boxes become active.
• CT is the thickness of the concrete • FC is the strength of the concrete
• CW is the width of the concrete (as defined by code,
not the width of the beam – see Technical Reference
manual Section 5.20.1, Note 1, p. 5-64).
• Three more radio buttons allow the specification of top and/or bottom cover plates.
• Information on all these specifications is available in Section 5.20.1 of the Technical Reference manual.
• Make sure the ST radio button is selected.
• Below the Select Beam list is the View Table button. This button accesses a section properties table for the section type selected (in this case, the American W-Shapes).
• Below the View Table button is the Material checkbox. This checkbox is toggled on by default. When it is on, default material constants such as the Modulus of Elasticity (E), density, Poisson’s ratio and the coefficient of thermal expansion (alpha) are also assigned to the members, in addition to the selected section properties.
• Material constants are determined based on the material selected in the Material list. The Material list is currently set to STEEL based on the selection of a W18x35 from the Steel tab.
• Section 5.26.2 of the Technical Reference manual provides standard values assigned if the Material checkbox is toggled on.
• If the Material checkbox is toggled off, the material constant values can be assigned later using Commands | Material
Constants.
• Leave the Material checkbox toggled on and the material set to
STEEL. This will associate steel material properties with the
W18x35 once it is added to the list of available sections. • Click Add.
W18x35 appears as an available section in the Properties dialog.
• Click on the Channel tab.
• Scroll down to the C12 sections, and click on C12X30. • Leave the Type Specification set to ST (Single Section from
Table) .
• There are also options to specify Double Channels in the Back- to-Back and Front-to-Front configuration.
The Material checkbox is checked by default, and the material list is set to STEEL.
• Click the Add button. The C12X30 section is added to the list of sections in the Properties dialog.
• Click on the HSS Rectangle tab.
This example problem requires a 7 in. x 4 in. x 3/16 in. rectangular hollow structural section (HSS7x4x3/16). In STAAD.Pro nomenclature, this will be listed as
HSST7x4x0.188, with the wall thickness being a decimal value instead of a fraction.
• Scroll through the list of HSS sections and click on HSST7X4X0.188 .
The Material checkbox should remain checked, and the material list should be set to STEEL.
• Click the Add button. The section is added to the list in the
Properties dialog.
• Click the Angle tab.
• The following figure, from the Technical Reference manual (Section 2.2.1) illustrates how angles are specified in STAAD.Pro
Figure 3. 3
• The angle code L is followed by numbers representing the length of the longer leg in tenths of an inch, the length of the shorter leg in tenths of an inch, and the thickness of the steel in sixteenths of an inch.
• Therefore, the 3 in. x 3 in. x ½ in. angle section for the truss webs would be specified as L30308.
• Click on L30308 to highlight it.
• Leave the Type Specification set to ST (Single Section from Table) .
The Material checkbox should remain checked, and the material list should be set to STEEL.
• Click the Add button. The L30308 section is added to the list of sections in the Properties dialog.
• Click the Close button to dismiss the Section Profile Tables dialog.
• The Values button in the Properties dialog accesses a table listing only the sections that appear in the Properties dialog and their properties.
This table is provided for quick reference only. Properties may not be edited in this table.
• Click the Define button in the Properties dialog.
• The Property dialog includes various types of cross sections, including: • Circle • Rectangle • Tee • Trapezoidal • General • Tapered I • Tapered Tube • Assign Profile
• Each page contains a schematic representation of the cross section and fields to parametrically define the cross section dimensions.
• The General tab can be used to define the cross section dimensions of any irregular-shaped section.
• Tapered I and Tapered Tubes are for creating sections whose dimensions vary from one end of the member to the other. • The Assign Profile tab provides a way to specify only a
category of cross section, either Angle, Double Angle, Beam,
Column or Channel.
Based on the profile that is selected, STAAD.Pro assigns a hard-coded section size without any attempt to design or optimize the section. It just provides a starting point for analysis.
• The Material checkbox and associated list provide a connection between section properties and materials. • Click Close to dismiss the Property dialog.
• Click the Materials… button in the Properties dialog. • The Materials dialog lists the currently defined materials and
their values for modulus of elasticity E, Poisson’s ratio, density, and alpha coefficient.
Materials are defined in another area of the program. The values cannot be edited in this table, but the dialog provides access to the table for convenient viewing.
• Click the X in the upper right corner of the Materials window to close it.
• The Thickness button can be used to assign thickness to surfaces or plates if the model contains any.
• Click the User Table… button.
The User Table button provides access to user-defined section properties tables, if any exist.
• A warning box pops up indicating that no user tables were found, and offering to create one.
• Click Yes to the warning box.
• Click the New Table button on the Create User Provided
Table dialog.
• The Select Section Type list is used to define the section type:
wide flange, channel, angle, etc…
• The External Table checkbox is unchecked, so the new table will be specific to (and contained within) the current model. If it is checked, the new table will be available for use on future