hướng dẫn sử dụng phần mềm cast

Overview In this document, the task of designing a double corbel is completed to illustrate how the CAST Design Tool (Version 0.9.10) can be used for the design of D- (Discontinuity) Regions. Following a brief introduction and description of the CAST graphical user interface, a step-by-step solution is presented. In order to describe many of the important features of this program, complete details are provided with associated images from CAST. The completion of this exercise and thus familiarization with CAST is estimated to take 60 minutes. Introduction Figure 1 describes the geometry and loadings for the double corbel structure being considered. The thickness of the corbel is 600 mm. The concrete strength is 35 MPa, and the yield strength of reinforcement is taken as 420 MPa. The corbel supports an ultimate vertical force of 1000 kN and an ultimate horizontal force of 100 kN at each end and two ultimate point loads of 3000 kN in the supporting column region. Bearing plates of 150 mm length x 600 mm width x 25 mm thick are provided at each end of the corbel. Figure 2 shows the selected strut-and-tie model for this structure. The design will be completed to meet ACI 318-02 Appendix A requirements. Figure 1 The Geometry and the Loadings of the Corbel under Consideration Figure 2 Strut-and-Tie Model Employed in this Corbel Design CAST Window Creation/modification of the structure’s geometry and strut-and-tie model, execution of the truss analysis, and stress checks using CAST Design Tool are all done through the CAST Graphical User Interface (GUI). The CAST GUI that appears on your screen will look similar to Figure 3. This interface consists of several components as labeled in Figure 3. Please familiarize yourself with the names of these interface components as they will be used throughout this handout. Figure 3 A Typical CAST Window (Click here to view a larger image) Notes: • The screen shown in this handout may look slightly different from your computer’s screen due to different toolbar positions and different settings of screen resolution and fonts. • In addition, several terminologies used in CAST Design Tool are explained below:  D-Region Boundary: o A closed, non-intersecting polygon that defines the geometry of the structure. o There are two types of D-Region Boundaries: Outer Boundary (Perimeter) and Inner Boundary (for openings). o You are allowed to create only one Outer Boundary, but you can create as many Inner Boundaries as you want. o Because there is only one Outer Boundary that should exist in your model and the region inside the Outer Boundary represents the concrete continuum, you are not allowed to copy, cut, or remove it from your model once you create it. However, you are surely allowed to change the positions of the Boundary Corners. You are also allowed to add and remove Boundary Corners as you wish.  D-Region Boundary Corner: o Intersection of two Boundary Edges.  D-Region Boundary Edge: o Line connecting two Boundary Corners. o Place for STM Nodes that possess Bearing Plates, Point Loads, or Point Supports.  Strut-and-Tie Model: o Internal truss in the D-Region. o Consists of STM Elements interconnected at STM Nodes.  STM Element: o Component of Strut-and-Tie Model. o STM Elements can be in the form of Struts (compressive STM Elements) or Ties (tensile STM Elements). o STM Elements have Effective Widths, representing the extent of idealized compressive stress fields (for Struts) or tensile stress fields (for Ties).  STM Node: o Component of Strut-and-Tie Model. o Place where one or more STM Elements meet, also called a nodal zone. o There is only one STM Element allowed to frame into an STM Node having Bearing Plates, Point Loads, or Point Supports.  Stabilizer: o STM Element whose member force is zero. o Stabilizers are not included in the nodal zone construction. o Stabilizers are required to avoid ill-conditioned structure stiffness matrix in truss analysis. o You must always create a stable Strut-and-Tie Model; Stabilizers are identified by CAST during truss analysis. o See Q & A #4 for more detail about Stabilizers. Getting Started In this section, we start the program, set the units, create a new model file, define project description, define general properties, setup Guidelines, and save the model in a file. 1.1 Click Start menu of the Windows operating system, point to Programs, point to CAST, and then click CAST. This starts the CAST program. A CAST window followed by the CAST splash screen then appears. After this, if the Tip of the Day dialog box like the one shown in Figure 4 is displayed, close it by clicking the OK button. Figure 4 The Tip of the Day Dialog Box 1.2 Select the active unit you want to work with from the Active Unit of Measure combo box (seeFigure 5) located in the Standard toolbar. Since our design problem is given in SI unit, select SI Unit. Figure 5 The Active Unit of Measure Combo Box Note:You can change the units at any time; CAST will handle all the conversion automatically 1.3 Click the button (or select New from the File menu). CAST responds by displaying the Define Project Description dialog box shown in Figure 6. In this dialog box: • Change the Project Name text box to Double Corbel. • Provide a name in the Designer text box. In our case, assume that the designers are Sabrina and Julius, so type in Sabrina & Julius. • Change the Date text box to current date, let say 4/2/2002. • Enter any important notes in the Notes text box. In our case, type in Example for CAST Tutorial. • Click the OK button to confirm the input and close the window. Figure 6 The Define Project Description Dialog Box Note: The Define Project Description dialog box can be later displayed for editing by clickingProject Description from the Define menu (or by pressing Ctrl+D key combination). Alternatively, it can be displayed by clicking the button from the Defining toolbar. 1.4 CAST will then display the Define General Properties dialog box shown in Figure 7. This dialog box allows us to define the thickness of the structure under consideration, the concrete cylinder strength, and the steel yield strength. • Type in 600 in the D-Region Thickness text box. • Type in 35 in the Concrete Cylinder Strength, f'c text box. • Leave the Concrete Tensile Strength, f'ct text box blank. • Type in 420 in the Non-Prestressed Reinforcement Yield Strength, fy text box. • Click the OK button to confirm the input and close the window. Figure 7 The Define General Properties Dialog Box Note: • The Define General Properties dialog box can be later displayed for editing by clickingGeneral Properties from the Define menu (or by pressing Ctrl+T key combination). Alternatively, it can be displayed by clicking the button from the Defining toolbar. 1.5 Now, we will create Guidelines to help determine the geometry of the model. To do this, clickGuidelines from the Construct menu. CAST will display the Construct Guidelines dialog box shown in Figure 8. In this dialog box: • Check the Glue Boundary Corners or STM Nodes to Guidelines checkbox to turn on this option. If this option is on, it lets you edit D-Region Boundary Corners and/or STM Node locations by simply editing the Guidelines. • Check the Snap Boundary Corners or STM Nodes to Guidelines checkbox to turn on this option. If this option is on, a D-Region Boundary Corner or an STM Node drawn or moved near a vertical and horizontal Guideline will snap to it. This option guarantees that new generated Boundary Corners or STM Nodes will be precisely placed on Vertical and Horizontal Guidelines as well as at the intersection of Vertical and Horizontal Guidelines. This option can also be activated from the Snapping toolbar: when on and when off. • Select the type of the Guidelines we want to add/move/delete. Let’s begin with the Vertical Guidelines by clicking on the text box of the Distance from Y-Axis frame located in theVertical Guidelines frame. • Add Vertical Guidelines. In our case, we need twelve Vertical Guidelines, i.e., at location X=-1000, X=-910, X=-900, X=-500, X=-250, X=0, X=125, X=250, X=500, X=900, X=910, X=1000. Enter each number in the text box of the Distance from Y-Axis frame located in the Vertical Guidelines frame followed by clicking the Add button. • After completing Vertical Guideline locations, do the same for Horizontal Guidelines. In our case, we need six Horizontal Guidelines, i.e., at location Y=-600, Y=0, Y=400, Y=900, Y=1000, Y=1500. Enter each number in the text box of the Distance from X- Axis frame located in the Horizontal Guidelines frame followed by clicking the Add button. • Press the OK button to confirm the input and close the window. Figure 8 The Construct Guidelines Dialog Box. Notes: • Guidelines are lines that we create to help us determine the geometry of the model. The Boundary Corners and STM Nodes of our structural model are usually located at intersections of Vertical and Horizontal Guidelines. • We can later display the Construct Guidelines dialog box for editing by clickingGuidelines from the Construct menu (or by pressing Shift+F3 key combination or by clicking the button from the Standard toolbar). • When a Guideline is visible on a display window, the Construct Guidelines dialog box can also be displayed by double clicking on the Guideline. • If you want to change a Guideline location (a Vertical Guideline for example):  Select the Guideline location you want to change from the list box in the Defined Locations frame.  The Guideline location value will appear in the text box of the Distance from Y- Axisframe. Edit the value in this text box.  Click the Modify button in the Vertical Guidelines frame.  Click the OK button to confirm the change and close the window. • To delete a defined Guideline (a Vertical Guideline for example):  Select the Guideline location you want to delete from the list box in the Defined Locations frame.  Click the Delete button in the Vertical Guidelines frame.  Click the OK button to confirm the deletion and close the window. The screen will then refresh and will look similar to Figure 9. Figure 9 CAST Window after Step 1.5 (Click here to view a larger image) Notes: • We can have multiple display windows to view our structural model at the same time. To add a new display window, click the Window menu, point to New Window, and click on one of the Load Condition names listed. To arrange the positions of the display windows, select one of the four options available (Tile Horizontally/Tile Vertically/Cascade/Arrange Icons) from the Window menu. • We can hide/display the Guidelines of the active display window by clicking Show Guidelines from the View menu (or by pressing F3 key). Similarly, we can hide/display the axes shown in an active display window by choosing Show Axes from the View menu (or by pressing F4 key). • In addition to Guidelines, CAST also provides Grid Points to help us determine the geometry of our model. To setup Grid Points, select Grid Points from the Construct menu (or press Shift+F2 key combination). The Construct Grid Points dialog box similar to Figure 10 will then appear on the screen. In this dialog box, we can:  Set the horizontal or vertical interval of Grid Points by entering the horizontal or vertical text box in the Grid Point Interval frame.  If you want to store the specified horizontal or vertical Grid Point interval in file to be used for the next opening of CAST, click the Save As Defaults button. The Grid Point interval will be stored in CAST.INI.  Check the Snap Boundary Corners or STM Nodes to Grid Points checkbox to turn on this option. If this option is turned on, a D- Region Boundary Corner and/or STM Node drawn or moved near a Grid Point will snap to it. This option guarantees that new generated D-Region Boundary Corners and/or STM Nodes will be precisely placed at the grid points. This option can also be activated from the Snappingtoolbar: when on and when off. Figure 10 The Construct Grid Points Dialog Box 1.6 Although you have not finished creating the model, you should save your work at this early stage. To save the model for the first time, do the following: • Select Save As or Save from the File menu (or use Ctrl+S key combination, or click the button from the Standard toolbar). CAST responds by displaying the Save As dialog box shown in Figure 11. • Change the directory to your working directory. In this case, assume that the working directory is c:\CAST\Files. • Provide a file name in the File name text box. In this case, assume that the file name isDCorbel. CAST will then automatically build an extension of .CST to the file name. • Click the Save button. It is also a good idea to save your work from time to time because you will have to do the unsaved work again if your PC system collapses before you save your work. To save your work, select Savefrom the File menu (or use Ctrl+S key combination, or click the button from the Standardtoolbar). Figure 11 The Save As Dialog Box Constructing the Model In this section, we construct the D-Region Boundaries and the Strut-and-Tie Model. After that, we define and assign Bearing Plates (if any), Point Loads, and Point Supports. 2.1 We will use the Guidelines constructed in Step 1.5 to help us create our D-Region Boundaries. If you do not see the Guidelines on the screen, click Show Guidelines from the View menu. This creates a rectangle surrounding the icon next to it and works as a toggle to turn on/off the Guidelines. Make sure that the Snap Boundary Corners or STM Nodes to Guidelines button located in the Snapping toolbar is on by clicking it: when on and when off. Click then the button (or click the Construct menu and then click Outer Boundary) to switch to the Draw mode. Next, create the D-Region Boundary by placing the Boundary Corners at the Guideline intersections as follows: • Click on the intersection of Guideline X=-1000 and Guideline Y=1000 • Click on the intersection of Guideline X=-500 and [...]... Guideline X=900 and Guideline Y=1000 This step creates STM Element ID E16 Figure 15 CAST Window Showing an STM Element and Guideline Locations (Click here to view a larger image) Up to this point, we have finished drawing the geometry of the Strut-and-Tie Model Figure 16 shows how the CAST window should look like now Figure 16 CAST Window after Step 2.2 (Click here to view a larger image) Notes: When we... the Thickness text box Click the OK button to confirm the input and close the window After this stage, the CAST window will look similar to Figure 19 Figure 17 CAST Window Showing Selected STM Nodes (Click here to view a larger image) Figure 18 The Assign Bearing Plates Dialog Box Figure 19 CAST Window After Step 2.3 (Click here to view a larger image) Notes: • You are only allowed to assign bearing... confirm the input and close the window At this stage, we have finished assigning Point Loads and Point Supports to the STM Nodes.Figure 21 shows how the CAST window should look like now Figure 20 The Assign Boundary Conditions Dialog Box Figure 21 CAST Window after Step 2.4 (Click here to view a larger image) Notes: You may assign Point Loads to STM Nodes that are located on D-Region Boundaries (Outer... the Strut-and-Tie Model used in this design is statically determinate Figure 29 The Assign Relative Stiffnesses and Widths Dialog Box The CAST window now should look like Figure 30 At this stage we have completed the model and are ready to analyze the model Figure 30 CAST Window after Step 4.5 (Click here to view a larger image) Checking Stresses After defining the properties of STM Elements and Nodes,... which is not stable, an error message indicating that excessive loss of accuracy occurred during the process will show up To fix this problem, please follow suggestions described in Q & A #9 Figure 23 CAST Window after Analysis is Performed (Click here to view a larger image) Defining and Assigning Properties In this section, we define Strut/Tie/Node Property Types based on the forces we obtained from... define two Concrete Strut Types in this step: Prismatic Strutand BottleShaped Click the button from the Defining toolbar Alternatively, click theDefine menu, point to Strut Types, and click Concrete Struts CAST will then display the Define Concrete Strut Types dialog box as shown in Figure 24 In this dialog box, do the following: • Change the Name text box located in the Type List frame to Prismatic Strut... to use built-in Strut Types, please see the notes in Step 4.4 Click the Define menu, point to Tie Types, and click NonPrestressed Reinforcement Tie Types (or click the button from the Defining toolbar) CAST will then display the Define Non-Prestressed Reinforcement Tie Types dialog box as shown in Figure 25 In this dialog box: • • • • Change the Name text box located in the Type List frame to Main Tie... Boundary This last step can also be accomplished by simply clicking the right button of your mouse Up to this point, we have finished drawing the geometry of the structure as shown in Figure 12 Figure 12 CAST Window after Step 2.1 (Click here to view a larger image) Notes: • You can create openings within the D-Region, if any, in the same manner as you create the Outer • • • • • Boundary, except that you... analysis progress shown in Figure 22 then appears After the analysis is completed, the forces for each STM Element and the corresponding Stress Ratios are shown in the display window (Figure 31) Figure 31 CAST Window after Step 5.1 (Click here to view a larger image) 5.2 What we need to do now is to check if stresses in the STM Elements and Nodes are within allowable limits Our design is acceptable because... the Boundaries If this were not the case, you must go back to redefine the Widths of STM Elements and Nodes as described in Step 4.5 and checked the stresses again Displaying Model and Analysis Results CAST program provides two ways to view the model and the results o displays and tabular displays Graphical Displays ; We can have a different type of graphical displa Each window may also have its own . Windows operating system, point to Programs, point to CAST, and then click CAST. This starts the CAST program. A CAST window followed by the CAST splash screen then appears. After this, if the. Design CAST Window Creation/modification of the structure’s geometry and strut-and-tie model, execution of the truss analysis, and stress checks using CAST Design Tool are all done through the CAST. the CAST window will look similar to Figure 19. Figure 17 CAST Window Showing Selected STM Nodes (Click here to view a larger image) Figure 18 The Assign Bearing Plates Dialog Box Figure 19 CAST