SAFI Sample Projects. Design of a Steel Structure. SAFI Quality Software Inc. 3393, chemin Sainte-Foy Ste-Foy, Quebec, G1X 1S7 Canada

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1 SAFI Sample Projects Design of a Steel Structure SAFI Quality Software Inc. 3393, chemin Sainte-Foy Ste-Foy, Quebec, G1X 1S7 Canada Contact: Rachik Elmaraghy, P.Eng., M.A.Sc. Tel.: Fax: Internet Site: info@safi.com

2 Design of a Steel Structure Description This example describes the edition and analysis of a small two-storey building. The verification of the elements resistance is also presented at the end of the document. The height of the storeys is 3.6 meters. The spacing of the columns is 7.5 meters between axes A, B, C and D. The spacing of the columns between axes 1, 2, 3 and 4 is 6.0 meters. The first floor spans on three bays only (from axis 1 through axis 3). Creating the project 1. To create a new file when SAFI is already running, use the New command from the File menu. 2. Select the folder in which to save the file and enter the name of that file. Then, click on the Save button. 3. The General Options dialog box is automatically displayed. You may adjust the general parameters of the project. These parameters can also be modified later. For this example, select 3D in the Analysis mode section.

3 Design of a Steel Structure 2 Creating the geometry Editing the construction lines The first thing to do when creating a new model is to define the grids according to the requirements of the model. To define the working grid, select the Grid Options command from the View menu or click on the button from the Edition toolbar. SAFI allows to use multiple edition grids at the same time. To make a grid visible on screen and allow to use this grid for the edition of the geometry, check the Show this grid option box for the desired grid.

4 Design of a Steel Structure 3 Modify the parameters of the grid according to the requirements of the actual model. First, change the plane of the grid to obtain a horizontal grid (plane X-Z). Change the name of the grid to Base. As described earlier, the columns along the X direction are evenly spaced at 7500 mm so click on the Create regular lines button in the Lines along axis "x" section, specify the spacing at 7500 mm in the Spacing field and set the Number of divisions to 3 (which will give three divisions and thus four lines). Repeat this operation for the lines in the Z direction (the spacing is 7000 mm and the number of divisions is 3). The new grid is not in the same plane as the original one. Click on the Top View button ( ) from the Camera toolbar (Top View command from the View Camera menu). Notice that the global axes are displayed in the bottom left corner of the screen. The Y axis should now head out of the screen. To adjust the size and position of the model to the dimensions of the screen, use the Fit to Screen command ( ) from the Camera toolbar (Fit to Screen command from the View Camera menu).

5 Design of a Steel Structure 4 Editing the geometry When the grid is properly defined, the geometry may be quickly created. The model may be created in different ways depending on your preferences and work methods. The easiest way is to use the graphical edition commands along with the grids. The model may also be created using tables. Note that the grid is not required when editing the geometry by means of tables. The grid is yet a good locating system. Step 1: Creating the joints at the base In a 3D building model, it is better to position the joint corresponding to the base of the columns first. Activate the Add ( ) command from the Edit Joint menu (this command is also accessible from the Edition toolbar). Using this command, it is possible to create joints one at a time by clicking at the intersection of the grid lines. It is also possible to create an array of joints on an area of the grid. To create an array of joint, press the left button of the mouse (keep it pressed) at a point located outside the bottom left

6 Design of a Steel Structure 5 corner of the grid and drag a window up to the top right corner of the grid. Release the mouse button to create the array of joints. A joint will be created at each intersections of the grid lines.

7 Design of a Steel Structure 6 Step 2: Creating the columns Click on the Isometric View ( ) button from the Camera toolbar to view the model in 3D. Then, adjust the size and position of the display with the Fit to Screen command.( ). Select the joints of the base by using the Select All command from the Edit Selection menu. This command is also accessible from the Edition toolbar ( ). Open the Extrude dialog box from the Edit Operations sub-menu (this command can also be found from the Edition toolbar ). Fill the dialog box as shown below and click on the Extrude button from this dialog box. The result should look like the image below.

8 Design of a Steel Structure 7 Step 3: Creating the beams of the first floor To ease the edition, it is better to display only the joints of the first floor (Y=3600 mm). First, click on the Front View ( ) button from the Camera toolbar. To keep only the joints of the first floor visible, select them by using the Select by Window command from the Edition toolbar and the activate the View/Hide command ( ) from the Camera toolbar. At this point, only the joints of the first floor should be visible as shown on the image below. When a joint is selected, it is drawn as a large blue point. Selected members are drawn as a thick line. To create the beams of first floor, you may create the links between the joints one at a time or create them in one operation in the same way the base joints were created. To create the members all at once, you must first adjust the elevation of the grid to Y = 3600 mm. To modify the elevation of the grid, click on the button from the Edition toolbar. Change the Y coordinate of the grid as shown below, click on the Set button and then on the Close button. The grid should now be positioned at the same level than the visible joints. Activate the Top View ( ) command from the Camera toolbar to view the model from the top. Activate the Add command from the Edit Member menu (this command is also accessible from the Edition

9 Design of a Steel Structure 8 toolbar ). Create the members by dragging a window around the joints to connect them. For example, drag a window around the joints located on line 1 (one) between lines A and D to connect nodes A1 and B1, nodes B1 and C1 and finally nodes C1 and D1. Repeat the same procedure to create the remaining beams. Activate the isometric view ( ) and deactivate the mask by clicking on the View/Hide command. The structure should now look like the image below.

10 Design of a Steel Structure 9 Step 4: Creating the beams of the second floor By repeating the method described above, you can quickly create the beams of the second floor. Select the joints of the second floor and hide the rest of the structure. Move the grid at Y=7200 mm and create the members. The image below shows the beams of the second floor once created. Activate the isometric view ( ) and deactivate the mask by clicking on the View/Hide command. The structure should now look like the image below.

11 Design of a Steel Structure 10 Step 5: Creating the floors The floors in this example will be simulated by a slab supported by joists. SAFI allows for three type of surfaces (two way slabs, one way slabs, and slab with joists) which can have three or four sides. Using the technique described in step 3, keep only the members of the first floor visible. Then, use the top view to ease the edition of the floors. To create a floor, use the Add ( ) command from the Edit Surface sub-menu (this command is also accessible from the Edition toolbar). To create a floor, simply click on the four joints that will define the four corners of the floor. Remember that the loads acting on the floors will be distributed on the members located on the perimeter of the surface. Thus, to distribute the loads on all the members of the first floor, three surfaces are required. Click consecutively on the joints located at A3, B3, B1, A1 to create the first floor. The order in which the joints are selected will determine the connectivity of the floor which has an influence on the layout of the trusses. The surfaces can be edited, when required, by the Edit Surface ( ) command from the Edit Surface sub-menu. When the first surface is created, a dialog box is opened allowing you to define the default parameters of the load surfaces. To define the surface as a slab with trusses, adjust the values of the dialog box as shown below.

12 Design of a Steel Structure 11 From the same dialog box, you may activate the diaphragm effect generated by the steel deck and/or slab. To activate the diaphragm, click on the Diaphragm tab.

13 Design of a Steel Structure 12 The stiffness of the diaphragm may be approximated by determining an equivalent plate thickness. Click on the button to define a plate element. Complete the information of the plate as shown below and click on the OK button. Back in the diaphragm tab, complete the information for the diaphragm as shown below and click on the OK button. The first surface is now completely defined. As it is the first surface created in the model, the parameters of this surface will be used as the default parameters for the new surfaces created. To create the other surfaces of the first floor, click on the four joints of the second and third surface. The result of these operations are shown in the image below.

14 Design of a Steel Structure 13 Use the same approach to define the surfaces at the roof level. After deactivating the View/Hide command, select the beams of the roof and reactivate the View/Hide command. Before creating the surfaces, modify the default parameters of the surfaces by using the Default parameters command from the Edit Surface sub-menu.

15 Design of a Steel Structure 14 Change the default number of trusses to 11 and click OK. Once this is done, add the surfaces as shown below. Surface A1, A2, D2, D1 Surface A2, A3, D3, D2 Surface A3, A4, D4, D3 The image below shows the structure as it should be when all the floors are defined. Step 6: Creating the walls While floors can be defined to distribute pressure loads to the surrounding beams and simulate the diaphragm effect of slab and/or steel deck, wall may be defined to distribute the wind loads acting on the wall surface to the columns of the building. SAFI does not make a distinction between walls and floors, load surfaces are all treated the same way without considerations for their orientation. The walls may be created with the same method used to create the floors (see step 5). Unlike the floors for which the diaphragm effect is considered, the walls will be used only to distribute the wind loads, their plane stiffness will not be considered. To lateral stability of the building will be

16 Design of a Steel Structure 15 provided later by means of bracings. The wind loads will be transferred only to the columns, the surfaces will thus need to be defined as one way surfaces. To modify the default parameters of the surfaces, use the Default parameters ( ) command from the Edit Surface sub-menu. Change the Surface Type to One Way Distribution. Click on the Diaphragm tab and deactivate the diaphragm effect (uncheck the Enable Diaphragm option). Click OK when this is done. Finally, add the surfaces on the walls. The image below shows on which wall to add the surfaces. Step 7: Creating the vertical bracings To ease the creation of the bracings, it is better to hide a portion of the structure. From a top view, select the members of the perimeter of the building. To make a selection in multiple steps, hold down the SHIFT key while selecting.

17 Design of a Steel Structure 16 Activate the View/Hide command, and switch back to an isometric view. To create the bracings, use the Add command ( ) from the Edit Member sub-menu. The bracings should be created on the outer faces of the building as shown below. Assigning support conditions To assign support conditions are other attributes such as section shapes, loads, imposed displacements, etc., you must first select the elements of the model to which you want to assign these attributes. Here, the support conditions will be assigned to all the joints located at the base of the columns. First, display the model from the front by using the Front View ( ) command from the Camera toolbar. Then, select the joints at the base of the columns using the Select by Window command from the Edition toolbar. Press the left button of the mouse, make a window around the base joints and release the mouse button to select the joints. When the base joints are selected, the support conditions may be assigned to them. Activate the Joint Attributes command from the Edit Joint sub-menu or click on the Joint Attributes

18 Design of a Steel Structure 17 button ( ) from the Edition toolbar. From the dialog box displayed, specify the support conditions as shown below. In addition to restraining the movement along the X, Y et Z axes, the rotation around the vertical Y axis must also be restrained in order to prevent the columns from rotating around their longitudinal axis. Click OK when this is done. A symbol representing the support conditions defined should appear on the selected joints. Assigning member properties (sections, end releases,...) For this example, we will assign three different section shapes from the CISC database. One section to the columns (HSS152x152x6.4), one section for the beams (W360x45) and one section for the bracings (L127x127x6.4). We will see later in this chapter how to verify the resistance and how to optimize the sections according to the requirements of a given design code.

19 Design of a Steel Structure 18 From a front view, select the beams of the first floor and the beams of the roof. Then, activate the Member Attributes command from the Edit Member sub-menu or click on the Member Attributes button ( ) from the Edition toolbar. For the moment, no section is defined in the current model. To define a standard section, click on the button above the section list. In the menu that appears, select the Section Libraries command.

20 Design of a Steel Structure 19 The dialog box displayed allows to add a standard section or any section stored in a user defined library to the current model. The default material (STEEL) is a G40.21M-350W steel. This material may be modified at any time using the Materials command from the Tables menu. Select a W360x45, in the Section name list and then click on the Add button and the Close button. Back in the Member Attributes dialog box, select this section in the section list. The beams will be considered hinged according to their strong axis (MZ) and their weak axis (MY) at both ends (node I and node j). Check the four corresponding option boxes.

21 Design of a Steel Structure 20 Make sure the Change Section Shape option is checked and click OK to assign these parameters to the selected beams. The button above the section list displays the dimensions and properties of the selected section shape in the list. To assign the section to the bracings, you must first select them by using the Select by Window command. To simplify this task, you may hide a portion of the structure as described in step 7. Press the SHIFT key on the keyboard to make the selection of the bracing in multiple steps. The CTRL key allows to add or remove a member to the selection while the SHIFT key always add to the current selection. While maintaining the SHIFT key pressed, successively click on each member of the bracings. When you have selected all bracings, assign a L127x127x6.4 by the using the Member Attributes command as shown above. Also assign hinges at both ends of these members. To assign the HSS152x152x6.4 to the columns, you must first select them. To quickly select the columns, you may use the Special Selection command ( ) from the Edit Selection sub-menu. In this dialog box, select Y Dir. in the Direction list, and click on the Select button. When this is done, click on the Close button. Once again by using the Member Attributes command, assign a HSS152x152x6.4 section to the columns. Note that no hinges are defined for the columns of the building. Assigning loads Step 1: Creating the basic loads The basic loads are families of loads acting on the structure. The different basic load types are typically the dead loads, the live loads, the snow loads, the wind loads, etc. To edit the basic loads, activate the Basic Loads command from the Tables menu. Fill this dialog box as shown below and click OK.

22 Design of a Steel Structure 21 All loads added to a given basic load will have the same factor for a given load combination (see next step). Note that new basic loads may be added at any time. Step 2: Creating the load combinations The load combinations are used to factor the various loads defined. For the current example, we will create two load combinations Dead Live Snow Dead Live Snow Wind Select the Load Combinations command ( ) from the Tables menu. For the moment, no load combination is defined. To create a load combination, click on the button in the upper right corner of the dialog box. Enter the factor associated with each basic load in the table. To rename a load combination, double-click on the tab label or use the button. Click a second time on the button to create a second load combination and specify the corresponding factors.

23 Step 3: Adding the dead loads In this example, the dead loads are composed of loads of two natures. Design of a Steel Structure 22

24 Design of a Steel Structure 23 The first load added to the model is the gravity load which takes into account the self weight of each element of the model. To define this load, select the Gravity Load command from the Tables General Loads sub-menu. To define the gravity load, first select 1 - Dead in the Basic Load list and specify the direction of the gravity (-1.0 along the Y axis). The image above shows this dialog box filled with the correct information. The second dead load is a pressure load of -2.5 kpa (2.5 kn/m 2 ) applied to the floors. To define this load, first select the floors of the building. Then, click on the Surface Loads command from the Edit Loads menu. This command is also accessible from the Assign Loads( ) command of the Edition toolbar. Each tab of this dialog box is divided into two parts. The upper part is common to all tabs, it allows to select the basic load into which the loads will be added. This part also contains shortcuts to the basic loads, load combinations and load tables dialog boxes. The second part of the dialog box allows to specify the various parameters required to properly define a load.

25 Design of a Steel Structure 24 Click on the Pressure tab to display the input data for the surface loads and the select 1 - Dead in the Basic Load list. Fill the data as shown below and click on the Add button to assign this load to the selected surfaces. The pressure is defined negative to indicate that the pressure is acting along the negative Y direction (downward). The pressure P1 is constant on the whole surface. Click on the Close button. The pressure load just defined should be visible on screen. Step 4: Creating the live, snow and wind loads Select the Graphic Options command from the View menu. In this dialog box, click on the Loads tab and uncheck the dead load (Dead) in the Basic Load list. This will allow to validate the new loads more easily as they are added to the model.

26 Design of a Steel Structure 25 Select the surfaces on the first floor to add a live pressure load of -4.8 kn/m 2. Then, on the Surface Loads command from the Edit Loads menu. Fill the information as described below (pay attention to the basic load selected), click on Add and then click on Close.

27 Design of a Steel Structure 26 Select the members of the second floor (roof) to add a snow load of -3.2 kn/m 2. Then, on the Surface Loads command from the Edit Loads menu. Fill the information as shown below (pay attention to the basic load selected), click on Add and then click on Close. Finally, select the surfaces located along the A axis (left wall) to define a wind pressure of 1.1 kn/m 2 along the X direction. Then, on the Surface Loads command from the Edit Loads menu. Fill the information as shown below (pay attention to the basic load selected), click on Add and then click on Close.

28 Design of a Steel Structure 27 Verifying the input data Before executing the analysis of the model, it is of good practice to perform a quick verification of the input data. SAFI has multiple tools to verify and help to correct the model. One of these tools is the Verify Input Data command ( ) from the Analysis menu. This command verifies simple instabilities, double or orphan joints, missing member attributes, etc. Running the analysis We are now ready to run the analysis of the structure. All analysis, verification and design commands are located at the same place to ease the analysis operations. To display the analysis dialog box, use the Run command from the Analysis menu. This command can also be found on the Main toolbar ( ).

29 Design of a Steel Structure 28 The analysis and design options available depend on the modules installed on your computer. To run the static analysis, select static linear in the list Analysis list and click on the Run button. Verifying the results Once the structure is analyzed, you need to verify that the results are correct and that they correspond to what you expected. The post-processing commands are available from the Analysis menu or from the Results bar which can be displayed using the View/Hide results bar command ( ) from the Analysis menu.

30 Design of a Steel Structure 29 The Results bar contains six sections (Analysis, Frequencies, Dynamic, etc.) containing three to four buttons each. Each section allows to view the results for a specific type of analysis. The button allows to define the results which will be shown for the entire structure (or the visible part if the View/Hide Selection command is activated). The checkbox at the left of this button allows to toggle the display of these results on and off. The button allows to view the numerical results in tables. Some filters may be applied to these results to reduce the quantity of data displayed and ease their interpretation. When this button is clicked, a menu showing the available results is displayed. The button allows to view the results by means of charts along with the numerical values. These charts may be customized, printed or transferred to other applications. When this button is clicked, a menu showing the available results is displayed. Only the results which can be plotted are available here. In the current example, the static analysis has been made. Thus, the results are available only for the commands of the Analysis section of the results bar. The button allows to define which results of the static analysis should be presented graphically. Let's start by displaying the internal deformations of the members. Click on the button from the Analysis section of the Results toolbar to open the static analysis results dialog box.

31 Design of a Steel Structure 30 In this dialog box, check the Internal option located in the Deformations section and click OK. Then, check the option box at the left of button. You should see the internal deformations on the screen corresponding to the first load combination. It may be difficult to view the results when the entire structure is visible. Many operations can be made to ease the visualization of the results. You may use the Rotate command from the Camera toolbar to change the angle of view of the structure. To ease the use of this command, click on the right button of the mouse to display the contextual menu for this command. In this menu, select the Restrain to Y Screen Axis command. This option allows to rotate the view of the structure around the screen vertical axis only. You may also use the various commands from the Graphic Options dialog box (found in the View menu). The Visualization tab allow to display or hide any type of element of the structure. The Text tab allows to specify if the numerical values of the displayed results are visible or hidden. (Joint Text Results and Member Text Results). The Text Properties tab allows to change the size and the position of the texts as well as the font. The Scale tab allows to enlarge or reduce the drawing scale of the results curves (Axial, Shear, Torsion, Bending, Stresses, Displacements, etc.). For example, a displacement scale of 10 mm/m means that a displacement of 10 mm will be displayed on screen as 1 m. In this particular case, the real scale is 1000 mm/m. In most cases, this scale is not practical as the displacements appear too small on the screen. For this example, a value of 50 mm/m gives interesting results. Finally, it is possible to hide a part of the structure by using the View/Hide command ( conjunction with the selection commands. ) in

32 Design of a Steel Structure 31 To view the results for the second load combination, click on the Combinations command in the lower part of the Results bar. Check the load combination for which you want to view the results and click OK. It is also possible to view the numerical results for the entire structure or a part of the structure through tables. Click on the button in the Analysis section of the Results bar. When the button is clicked, a menu is displayed allowing to select which type of results to view. Choose Joint Displacements in this menu. When the command is activated, you are allowed to define some filters to apply to these results which will reduce the amount of data displayed.

33 Design of a Steel Structure 32 Select All structure in the Elements list and All Load Combinations in the Load Combinations list. Then, click on OK to display the joint displacements for all joints and all load combinations. Certain analysis results may be viewed through charts. Click on the button in the Analysis section of the Results bar. When this button is clicked, a menu is displayed which allows to select the type of results to display.

34 Design of a Steel Structure 33 Select the Internal Forces command from this menu. Once this command is activated, click on a member of the structure. The internal forces in the selected member will be displayed in a dialog box. In the Diagram list, select Moment Z to view the distribution of the bending moment according to the strong axis for the load combination selected in the Load Combination list. When the mouse pointer is moved over the chart, the numerical results corresponding to this position on the beam are highlighted in the table. The buttons in the left part of the dialog box allow to customize the charts, to print the table, to print the chart or to copy the chart to the clipboard for use with other applications such as a word processor. Printing the report After the analysis is performed and the validation of the results is made, the analysis report may be printed. The report generator allows to customize the data to print in the report. To open the report generator, use the Generate Report command ( ) from the Analysis menu. This command is also accessible from the Main toolbar.

35 Design of a Steel Structure 34 The report generator is made of a certain number of tabs depending on the modules installed: the Model tab for the input data, the Analysis tab for the analysis results and seven other tabs for the input data and results of the design modules. The first tab (Model) contains two parts. The upper part is a tree list of the data that can be included or excluded from the report by checking or unchecking the appropriate branches. The et markers allow to expand or collapse a branch of the list. If a base branch is unchecked, all items contained in that branch will be automatically excluded from the report. The lower part of this tab allow to specify a range of elements, load combinations, basic load and time (for seismic and/or dynamic analysis) which will be used to determine which data to print in the report. The Analysis tab (and all other tabs) is made of a tree list only. This list works the same way as the tree list in the Model tab. When the desired options are selected, click on the Generate button. At this time, you are prompted to provide a name for the report file. It is also possible to specify the report format. Four report formats are available: SAFI Report (default), Microsoft Excel Worksheet, Microsoft Access database and ASCII file (unformatted text). Enter a file name and click on Save. When the report is generated, it is automatically displayed. The SAFI Report contains a table of content which allows to quickly access individual tables. It is also possible to open a full section of

36 Design of a Steel Structure 35 the report by selecting the All item in the list (All Analysis Results for example). The image below shows a preview of the analysis report for the current example. Assigning steel parameters Design code The various design codes handled by SAFI have all their own characteristics. Thus, it is important to select the design code which will be used to make the verification of the limit states before specifying any parameters required by that code. For example, the Canadian and American codes use only one bending coefficient (w2 or Cb) while the European code uses three coefficients (c1, c2 and c3). The program will allow you to specify only the parameters required by the selected code. Activate the Parameters command from the Applications Steel sub-menu or the Codes command from the Analysis menu. In the Steel tab of this dialog box, select the CAN/CSA-S16-01code.

37 Design of a Steel Structure 36 Effective area in tension of the bracings The steel module of SAFI can make the verification of the tensile resistance of the structural elements subjected to tensile forces. By default, the program considers that the effective area in tension of a section is equal to the gross area of the section. To perform an accurate verification of the members in tension, it is necessary to specify the net area of the members which take into account the area reduction due to the bolts holes and/or connection plates. In the current example, the effective area will be specified for the members of the bracings. Select these members by using the selection by window command (Select command from the Edition Selection sub-menu). To ease the selection of these members, you may use the Overlapping Area option which allows to select elements inside a window and also the elements crossing that window (Selection Options command from the Edit menu). Note that the members may be selected in multiple steps by using the CTRL and SHIFT keys which allows to add and remove members to the current selection. When all the bracings are selected, activate the Member Attributes command from the Edit Member sub-menu. The dialog box opened contains at least two tabs (e.g. the General tab and the Steel tab). Click on the Steel tab to access the parameters of the steel module.

38 Design of a Steel Structure 37 At the bottom of the dialog box, specify a ratio of 0.75 (75%) as the ratio of the gross area. (Change Net Area in Tension field). The effective area in tension will be taken as the gross area multiplied by this ratio. Click OK when done.

39 Design of a Steel Structure 38 Flexural buckling support The steel module of SAFI can make the verification of the bending and compression-bending resistance and stability of the structural elements subjected to bending moments. By default, the program considers that the members are supported against flexural buckling at their two ends and that for the top flange (positive moment) and at the bottom flange (negative moment). In the current example, it is reasonable to consider that the beams to which the trusses are attached are supported at their top flange at each connection with the trusses. As the spacing of the trusses is different at the first floor than at the roof, the operation must be made in two steps. First, select the members of the first floor to which the trusses are attached using the selection by window command (Select command from the Edit Selection sub-menu).

40 Design of a Steel Structure 39 Beams of the first floor with intermediate lateral supports When the beams of the first floor are selected, activate the Member Attributes command from the Edit Member sub-menu. The Steel tab of this dialog box should already be active. If it is not, click on it to activate it. In the Change Top Flange Support area, select Discontinuous in the Lateral Support Type list and specify a length of 2000 mm between the supports in the Unbraced Length field. This length corresponds to the spacing of the trusses of the first floor.

41 Design of a Steel Structure 40 Click on OK when done. Repeat the same operation for the beams of the roof. The unbraced length for these beams should be 1875 mm. This length corresponds to the spacing of the trusses at the roof level. Beams of the roof with intermediate lateral supports We will also consider that the floor and roof slab provides a continuous lateral support to the top flange of the outer beams parallel to the trusses. The two following images shows the beams to which continuous lateral supports will be assigned. Beams of the first floor (mezzanine) with continuous lateral supports

42 Design of a Steel Structure 41 Beams of the second floor (roof) with continuous lateral supports Select these beams and activate the Member Attributes command from the Edit Member submenu. In the Steel tab, specify the parameters as shown below.

43 Design of a Steel Structure 42 Design The program has some tools to determine the optimal section shapes for each member of the structure. However, for practical reasons, it is often better to optimize the section shapes for groups of elements instead of each element separately. In addition, to allow for the numerical computations, a continuous column or beam must be cut at the intersection with other elements of the structure. Thus, a continuous beam will be modeled by a certain number of member which can't logically be optimized separately (a continuous beam is made of only one section shape). In this case the concept of groups is mandatory. Design groups To create a group of members, you must first select the members of that group using the various selection commands and save that group using the Define Group command of the Edit Selection sub-menu. The only parameter required to define the group is a name allowing to subsequently refer to that group. Let's first create a group for the bracings. By using the selection commands, select the members of the bracings as shown below. Note that the members may be selected in multiple steps by using the CTRL and SHIFT keys which allows to add and remove members to the current selection. When the bracings are selected, activate the Define Group command from the Edit Selection sub-menu. When the command is activated, a dialog box is displayed allowing you to assign a name to the group of members selected.

44 Design of a Steel Structure 43 Type Bracings in the Selection Group Name and click on the OK button. The member group is now saved and may be recovered at any time using the Fetch Group command of the Edit Selection sub-menu. Repeat this process for the other groups of members presented below. Inner beams of the mezzanine (group Mezzanine (inside)) Outer beams of the mezzanine (group Mezzanine (outside))

45 Design of a Steel Structure 44 Other beams of the mezzanine (group Mezzanine (others)) Inner beams of the roof (group Roof (inside).)

46 Design of a Steel Structure 45 Outer beams of the roof (group Roof (outside)) Other beams of the roof (group Roof (others))

47 Design of a Steel Structure 46 Columns (group Columns) Optimization When the design groups are created, the optimization of the section shapes can be made. Activate the Design command from the Applications Steel sub-menu.

48 Design of a Steel Structure 47 In the upper part of the dialog box, check the Auto Assign Sections option. This option allows to automatically assign the optimized sections to the members of the groups. It is thus possible, by disabling this option, to optimize the sections of the model without losing control on the model. If this option is not enabled, the sections may be manually assigned using the Assign button found in the design summary at the right of the dialog box. For this example, we will consider that the selected section shapes are suitable. Also check the Force Convergence option which forces the optimization module to repeat the optimization cycles until the full convergence is reached. In the Group Name list, select the Mezzanine (inside) group which contains the inner beams of the mezzanine. Select 1 - STEEL in the Material list, CISC in the Section Library list and W in the Section Type list (a W section in the CISC database corresponds to an IPE in the European database). Click on the button in the upper right part of the dialog box to create a new tab which will be used to specify the optimization parameters for the Mezzanine (outside) group. When a tab is added, you have the possibility to copy the parameters of the current tab in the new one. Click Yes to copy the current tab in the new one. All the parameters are copied except the design group. In this new tab, select the Mezzanine (outside) in the Group Name list. Repeat this procedure for the other beam groups.

49 Design of a Steel Structure 48 Finally, create a tab for the columns (group Columns) and select a HS (square) section type. For this example, the bracings will not be optimized.

50 Design of a Steel Structure 49 When all groups are defined, click on the Optimize button to launch the optimization of the structure. After the optimization is made, click on the View Report button to display a summary report of the selected selections. This report also presents, at the end, the total weight of the structure including the members that have not been optimized (in the present case, the bracings). Click on OK to close the optimization module dialog box. Verification of the limit states The optimization performs, at each cycle, the verification of all limit states in order to select the best section shape. However, the results of these verifications are not stored. Thus, it is necessary to execute the analysis with the steel verification to obtain the numerical values of these limit states. Activate the Verification command from the Applications Steel sub-menu. This command quickly performs the analysis using predefined options. When the command is activated, you are prompted to save the file. Click Yes to save the model and run the analysis. Results and report The results of the limit states verification may be consulted in three different ways, each having specific uses. The results can be first presented for the whole structure (or the visible part if the

51 Design of a Steel Structure 50 View/Hide Selection command from the View menu is active) by the means of color charts. This method is useful to have a rough estimate of the limit states for each member of the model and to spot the critical areas. It is also possible to view the numerical results of the limit states through tables. This method is convenient to quickly obtain the numerical values of each limit states for the whole or part of the structure. These tables also present the main analysis results used to compute the limit states. These two methods are fast and require a low amount of manipulations. However, they present the results of the last analysis only and do not allow to store the results in a permanent manner. The analysis reports, as though longer to generate, allow to keep permanent copies of the steel verification results in different file formats (SAFI Report, Excel Worksheet, etc.). Global results To display the results of the limit states computations directly on the members of the structure, use the Options command from the Analysis Global Curves Steel sub-menu. In the dialog box, select the type of results you want to see and click OK. To display these results, activate the Display command from the Analysis Global Curves Steel sub-menu. These results may be viewed for one or several load combinations. When more than one load combination is selected, the results displayed correspond to the maximum for these load combinations. To specify the load combinations for which to display the results, use the Combinations command from the Analysis Global Curves sub-menu.

52 Design of a Steel Structure 51 Select all load combinations and click on the OK button. To view the results for only a part of the structure, select the members for which you want to see the results and activate the View/Hide Selection command from the View menu. Maximum limit states (Roof) Maximum limit states (Mezzanine) Maximum limit states (Columns)

53 Design of a Steel Structure 52 Numerical results To consult the numerical values of the limit states, use the command in the Analysis Numerical Results Steel which corresponds to the type of results you want. When one of these command is activated, a dialog box allowing to filter the content of the table is opened. It is possible to display the results for the whole structure or only for the selected members of the model (Elements list). It is also possible to view the results for a specific load combination or for all load combinations (Load Combinations list). If a certain filter is grayed in the filter dialog box, it means that this filter is not applicable to the type of results requested.

54 Design of a Steel Structure 53 Analysis report Limit States Summary for some members of the model To store the limit states results in an external file, it is required to generate a report. To do so, use the Generate Report command from the Analysis menu. When the command is activated, the report manager is opened. This dialog box contains a certain number of tabs depending on the modules installed on your computer. For this example (and for the design of steel structures in general), only the Model, Analysis and Steel tabs are useful. In each of these tabs, select the parts you want to see in the report. It is possible, here also, to generate the report for the whole or a part of the model by using the edition field (which allow to specify a range of elements or a range of load combinations) and

55 Design of a Steel Structure 54 the Selection Groups list which allow to print the report for the currently selected elements or predefined groups (including the design groups). Example of steel verification report