Objects include beams, columns, slabs, decks, walls, links, tendons, and other joint, frame and shell objects. To draw, the program must be in Draw Mode, which is activated by clicking one of the draw buttons on the toolbar or using a Draw menu command. In Draw Mode, the left mouse button is used to draw and edit objects, and the right mouse button is used to query the properties of those objects.
As frame objects are drawn, frame properties can be assigned simultaneously. Shell objects may be assigned floor properties, wall properties, or defined as openings when drawn. After an object has been drawn, the object may be selected and loads may be assigned to it, or existing assignments can be modified.
Draw Mode and Select Mode are mutually exclusive. No other operations can be performed when the program is in Draw Mode. View User's Guide Select Selection is used to identify those objects to which the next operation will apply.
Certain editing, assigning, printing and displaying operations require prior selection of an object. To select, the program must be in Select Mode, which is activated by clicking one of the select buttons on the toolbar.
Alternatively, selecting any action from the Select menu puts the program into Select Mode. Many different types of selection are available, including selecting individual objects, drawing a window around objects, and selecting by property type. In Select Mode, the left mouse button is used to select objects, and the right mouse button is used to query the properties of those objects. Assign Certain assignments may be made when drawing an object, such as assigning a structural property when drawing a frame object.
However, additional assignments, or changes to assignments, may be made to one or more objects that were selected immediately before using the Assign menu command. Assignment operations include properties, restraints, loads and group names. The first time an analysis is to be run, chose Set Load Cases to Run from the Analyze menu and select which cases are to be run.
Once load cases have been selected, use Run Analysis from the Analyze menu, or click the Run Analysis button on the toolbar to run the analysis. Any cases that have been run already do not need to be run again. If a load case that requires results from another case is chosen, the prerequisite case will be run first if it has not been already.
The program saves the data, then checks and analyzes the model. During the checking and analysis phases, messages from the analysis engine appear in a monitor window. When the analysis is complete, a deformed shape will be displayed. No other ETABS operations may be performed while the analysis is proceeding and the monitor window is present on the screen.
However, other Windows applications can be run during this time. Display The Display menu commands are used to view the model and the results of the analysis. Graphical and tabular displays are available in this program. Display items may be chosen from the Display menu or accessed using toolbar buttons. Each window may also have its own view orientation and display options. Undeformed geometry, loads and analysis results can all be displayed. Details of the displayed results can be obtained by clicking on an object with the right mouse button.
Choose a table to be viewed and then right click. If objects are selected prior to using the commands, certain tables will only be available for the selected objects. If no objects are selected, the tables produced are for Display User's Guide the entire model. Tabular data can also be printed using the Create Report commands available on the File menu.
Design After an analysis has been completed, frames, composite beams and columns, joists, shear walls, slabs, and steel connections can be designed with respect to design code requirements.
Design may be performed for the given design combinations by choosing the appropriate Design menu command. Graphical displays of design parameters are available.
Tabular design information can also be printed using commands from the File menu. Detailing The Detailing menu provides control over the organization and layout of schematic construction documents. Items such as drawing size and layout, section cuts, column schedules, beam framing plans, shear wall reinforcement, composite slab reinforcing layouts, general notes, cover sheets and so on may be specified.
This menu is typically accessed after analysis and design are complete. The drawing sheets and views generated may be displayed by selecting the Detailing tab in the Model Explorer. Tools The Tools menu provides access to user or third-party developed plugins that allow for customization of the program.
Display units, colors, the graphics mode, tolerances, and whether multiple towers are allowed can be specified here. Help The program Help is available from this menu. Documentation and verification manuals in PDF format are accessed through the Help menu as well. Options Chapter 3 Basic Modes, Drawing Tools, Mouse Pointers Objective This chapter briefly describes the two modes of user operation for the program, identifies the drawing tools, and describes how the appearance of the mouse pointer changes for various operations.
Select or Draw The two distinct modes in this program are the select mode and the draw mode. By default, the program is in select mode. Chapter 6 describes the various methods for selecting points, lines, and areas in a model. The names of the commands are assumed to explain the actions that will be accomplished. The mouse pointer indicates which mode is enabled. In select mode, the pointer is the Normal Select Pointer. If the default settings are being used, the mouse pointer will look like this.
In draw mode, the mouse pointer is the Alternate Select pointer. Note that while in draw mode, if the mouse pointer is moved over the toolbar buttons or the menus, the pointer temporarily changes to the se- Select or Draw User's Guide lection pointer. If during this time one of the menus or toolbar buttons is not clicked, the mouse pointer reverts to the draw mode pointer when it is moved back into the display window. The appearance of the mouse pointers for those actions depends on the mouse pointer properties you specify.
Structural objects are placed relative to the grid system. Create the Basic Grid System Begin creating the grid system by starting the program. The Start Page will be displayed as shown in Figure These units determine what units are associated with each piece of input data, and what units are used to display model output.
These units may be inconsistent for different items, i. To review the display units hold the mouse cursor over the information icon. Also on the Model Initialization form are drop-down lists for selecting the steel section database, the steel design code, and the concrete design code to use when creating and designing the model.
The New Model Quick Templates form is used to specify horizontal grid line spacing, story data, and template data. Template models provide a quick, easy way of starting a model. They automatically add structural objects with appropriate properties to the model. We highly recommend that you start your models using templates whenever possible.
Specify the number of grid lines in the X and Y directions and a uniform spacing for those lines. Note that the uniform spacing in the X and Y directions can be different. This option defines a grid system for the global coordinate system only. Click the Grid Labels button to control how the grids are labeled.
Define nonuniformly spaced grid lines in the X and Y directions for the global coordinate system. After choosing this option, click the Edit Grid Data button to edit the grid system.
This may allow for easier identification of specific locations in the model. The program provides default names for each story level for example, Story1, Story2 and so on and assumptions for story level similarity.
Enter values in the Story Data form to define your own story names, story levels of non-uniform height and customized story similarity. Story level "similarity" can be significant, e.
The splice data identifies which stories contain steel column splices and the height of the splices - splice data is not applicable to concrete columns. For more information about the Story Data form, refer to the Editing chapter of this manual. Story level similarity can also be significant to composite beam and steel joist design.
In many cases it is the simplest, most convenient and quickest way to start a model. The New Model templates are shown below: Objective User's Guide Note that the templates consist of two for steel buildings and four for concrete buildings, as well as a button for creating grids only and a button for starting a blank model, both of which add no structural objects to the model. Choose any of the templates by left clicking its associated button. When one of the template buttons is chosen, the Structural Geometry and Properties form will appear for that template, as shown in Figure The Structural Geometry and Properties form typically contains areas for specifying structure data and loads.
Note: This form will not display if the Grid Only or Blank buttons are chosen since no structural objects are defined. Figure Structural Geometry and Properties Once all structure and load data have been entered, click the OK button to close the form and return to the New Model Quick Templates form. Also, beams are modeled as line elements in this program.
Thus, slabs with out-of-plane bending capability span from center-of-beam to center-of-beam in the program model. The number of view windows can be changed using the Windows List button.
Note that the Plan View is active in Figure When the window is active, the display title tab is highlighted. Set a view active by clicking anywhere in the view window. The following sections will show how to define additional properties or review program defaults.
Figure Define Materials form The Define Materials form allows for the both the review of existing materials, as well as the definition of new properties. When the Add New Material Property form appears as shown in Figure , select a material from the Material Type drop-down list and then a Standard and Grade from their respective drop-down lists.
Click the OK button on the Material Property Data form to return to the Define Materials form, where additional materials may be defined or reviewed. Click the OK button on the Define Materials form when finished with materials. The Frame Properties form allows for the definition of new sections as well as the review of existing sections. To make steel frame sections from property files available click the Import New Properties button, or to add user defined sections click the Add New Property button, both of which will display the Frame Property Shape Type form shown in Figure Select the sections to be imported from the list e.
Click the OK button on the Frame Properties form when finished with section definitions. Auto select section lists can be assigned to frame members. When an auto select selection list is assigned to a frame member, the program can automatically select the most economical, adequate section from the auto select section list when it is designing the member.
The program has several built-in auto select section lists. However, the user can also develop a tailored list using the following steps: 1. The previous section explains how to import frame properties into the Properties list. Figure Frame Property Shape Type form 4. Type a name for the list in the Property Name edit box. Any name can be used. Scroll down the list of sections in the Choose Sections in Auto Select List area to find the beams to be included in the list.
Click once on them to highlight them. Note that the standard Windows methods for selecting items in a list can be used e. Click the Add button to add the selected beams to the Auto Select List on the right side of the form. Figure Frame Section Property Data form 7. Draw Columns Make sure that the Plan View is active. The Properties of Object box for columns shown in Figure will display docked in the lower lefthand corner of the display.
Hold the left mouse button down on the Properties of Object tab to move the box elsewhere in the display, or to dock it using the docking arrows. Figure Properties of Object Box for Columns The Properties of Object box provides various definition parameters and drawing controls.
These items differ depending on the drawing command selected. Review the parameters and controls shown in this box before drawing the column to ensure that they are what they should be. Change any entry in the box by clicking on it and making a new selection from the drop-down list or entering new information into the edit box, as appropriate.
After checking the parameters in the Properties of Object box, left click once in the Plan View at the intersection of the grid lines where you want Add Structural Objects Manually 5 - 11 User's Guide the column. An I-shaped column should appear at that point in the Plan View. Continue in this manner to place other columns. Alternatively, draw the remaining columns in one action by "windowing" around the grid intersections.
To "window," click the left mouse button above and to the left of the first grid intersection where a column is to be placed and then, while holding the left mouse button down, drag the mouse until it is below and to the right of the last grid intersection where a column is to be placed. A selection box similar to that shown in Figure should expand around the grid line intersections as the mouse is dragged across the model.
Release the left mouse button and the program will draw the column objects at the grid line intersections within the boundaries of the selection box. To leave the Draw mode, click the Select Object button,.
It is a good idea to save your models often. The Properties of Object box for beams shown in Figure will display docked in the lower left-hand corner. Figure Properties of Object Box for Beams As explained previously, the Properties of Object box provides various definition parameters. After checking the parameters in the Properties of Object box, left click once in the Plan View on a grid line where a beam is to be placed.
A beam is drawn along the selected grid line. Continue in this manner to place other beams. Alternatively, draw the remaining beams in one action by windowing around the grid intersections. Windowing is explained in the previous section.
The Properties of Object box for frames shown in Figure will display docked in the lower left-hand corner. This form is similar to that shown in Figure with the addition of an option for constraining how the frame object is to be drawn, i. After checking the parameters in the Properties of Object box, left click once in the Plan View to indicate the starting location of the beam.
Select an option from the Drawing Control Type drop-down list if some type of drawing constraint is desired, and then left click to indicate the end joint of the beam. The program will start another frame object at the location of the just drawn beam's end joint unless the right button of the mouse is clicked to stop drawing. Another aid when drawing objects is the Draw Measurement Tool shown in Figure This tool automatically displays when in the drawing mode after the starting joint of the object is drawn.
This tool displays the length and angle orientation of the frame member or edge. Similar to the other drawing operations, a Properties of Object box will display docked in the lower left-hand corner that provides the opportunity to define the parameters for the secondary beams.
To place the secondary beams, left click once in the bay bounded by grid lines where the secondary beams are to be placed. Similar to columns and the primary beams, secondary beams can be drawn by windowing over the appropriate bays. Note the Approx. Orientation parameter to set the span direction. The Properties of Object box for areas shown in Figure will appear docked in the lower left-hand corner. Figure Properties of Object Box for Shells Similar to columns and beams, this Properties of Object box provides the opportunity to check and change the parameters for the area.
Change any entry in the box by clicking on it and making a new selection from the Add Structural Objects Manually 5 - 15 User's Guide drop-down list or entering new information into the edit box, as appropriate.
After checking the parameters in the Properties of Object box, check that the Snap to Grid Intersections and Points command is active. This will assist in accurately drawing the area object. This command is active when its associated button is depressed. By default, this command is active. Then, moving around the perimeter of the floor object, click once at other column intersections to draw the outline of the building. Press the Enter key on your keyboard to complete the floor.
If you have made a mistake while drawing this object, click the Select Object button, , to change the program from Draw mode to Select mode. To switch the fill on or off for the floor addition, click the Set Display Options button.
Click the OK button. The Properties of Object box for walls shown in Figure will appear docked in the lower left-hand corner. Figure Properties of Object Box for Walls Change any entry in the Properties of Object box by clicking on it and making a new selection from the drop-down list or entering new information into the edit box, as appropriate.
To place walls, left click once at a point to begin the wall object at that point. Then, move to the end of the wall segment and left click again. Additional wall segments may be drawn by simply moving to a new point and clicking. Press the Enter key on your keyboard to complete the wall. The New Wall Stack form shown in Figure will appear. Figure New Wall Stack form Select any of the predefined wall stacks by clicking on the representative icon. The lengths and thicknesses of the wall segments may be altered by entering changes into the edit boxes on the Layout Data tab.
The Properties of Object box for wall stacks will appear docked in the lower left-hand corner Verify that the angle and range of stories for the wall stack are correct in the Properties of Object form, and then left click once in the Plan View where the wall stack is to be placed. A wall stack is drawn at that location for the number of stories specified. Continue in this manner to place other wall stacks. The Properties of Object box for tendons shown in Figure will appear docked in the lower left-hand corner.
Figure Properties of Object Box for Tendons Change any entry in the Properties of Object box by clicking on it and making a new selection from the drop-down list or entering new information into the edit box, as appropriate. To place tendons, left click once at a point to begin the tendon object at that point. Additional tendon segments may be drawn by simply moving to a new point and clicking. Press the Enter key on your keyboard to complete the tendon.
Selecting Selecting is used to identify existing objects to which the next operation will apply. Operations that require prior selection include certain Editing, Assignment, Design, Display, and Output operations.
If multiple objects are present in the same location, one on top of the other, hold down the User's Guide Ctrl key on the keyboard and click the left mouse button on the objects.
Use the form that displays to specify which object to select. Drag a window from right to left to select all objects that are fully or partially enclosed in the window. To draw a window, first position the mouse pointer beyond the limits of the object; for example, above and to the left of the object s to be selected.
Then depress and hold down the left mouse button. While keeping the left button depressed, drag the mouse to a position below and to the right of the object s to be selected. Release the left mouse button to complete the selection. The rubber band window is a dashed rectangle that changes shape as the mouse is dragged. One corner of the rubber band window is at the point where the left mouse button was first depressed.
The diagonally opposite corner of the rubber band window is at the current mouse pointer position. When dragging the mouse from left to right, any visible object that is completely inside the rubber band window is selected when the left mouse button is released.
When dragging the mouse from right to left, any visible object that the window crosses or encloses is selected. Note about Window Selections in Plan View: When selecting by window in a plan view, the objects selected will be determined by the setting in the One Story drop-down list.
To select only the objects at the plan level displayed which include the columns in the story below , the drop-down list should be set to One Story. When set to Similar Stories or All Stories, selecting in plan view may result in objects at other levels being selected, even though only one plan level is displayed. Then position the mouse pointer outside the object s to be selected, left click to start the Selecting Chapter 6 - Select Structural Objects polygon and then left click at each of the polygon's vertices.
Hit the Enter key on the keyboard to complete the selection polygon. After using this method to make a selection, the program defaults to the window selection mode. Then position the mouse pointer outside the object s to be selected, left click to start the polygon and then left click at each of the polygon's vertices. Then position the mouse pointer to one side of the object s to be selected and click the left mouse button.
Drag the mouse across the object s to be selected and click the left mouse button followed by the Enter key on the keyboard to complete the selection. The rubber band line is a dashed line that changes length and orientation as the mouse is dragged. It extends from the point where the left mouse button is first clicked to the current mouse pointer position. Any visible object that is intersected crossed by the rubber band line is selected when the Enter key is pressed.
A Selection List form similar to the one shown in Figure pops up identifying the objects that exist at that location. Select the desired object by moving the mouse pointer over it and left clicking on it. Deselect Command Deselect objects one at a time by left clicking on the selected objects.
For example, assume that you want to select all of the objects in your model except for columns. For example, assume you have selected some frame objects by clicking on them and assigned frame section properties to them.
Use the Get Previous Selection command or the Get Previous Selection button to select the same frame objects and assign something else to them, such as member end releases. It is an all or nothing command. It cannot selectively clear a portion of a selection. Assign In creating the model, the user draws joint, frame, shell, link, and tendon objects. Note that the assign menu lists the various properties that can be assigned.
Also note that the assignment of loads is explained in Chapter 8 of this guide. As shown in Table , the types of assignments available depend on the type of object. Assignments also depend on the type of design e. View the assignments made to joint, frame, shell, link, and tendon objects by right clicking on the object. Click on the Assignments tab. In each case, select an object before executing the desired assignment command e.
As explained in Chapter 6 of this guide, using the Ctrl key and left clicking on a location in the model can simplify the process of selecting objects when multiple objects may be present at the same location or if selecting objects is new to the user and seems challenging. The availability of commands depends on the type of object selected. Modifications to the assignments can be made by accessing the input forms using the appropriate Assign menu command.
The forms typically include OK, Apply and Close buttons that can be used to accept or delete changes made to the forms. Note that the combination of the type of object, name of the command and name of the input form provides an indication of what can be achieved by using a particular command.
Thus, in making the assignment, the user should not select a joint or shell object in the model, or click the Joint or Shell commands on the Assign menu. Rather, the user should select a frame object e. Using this method, select the desired Auto Select Section list by name from the Property drop-down list in the Properties of Object Box that appears when a drawing tool is selected.
Use of the drawing tools is described in Chapter 5 of this guide along with figures showing the Properties of Object boxes for joint, frame, and shell objects. On the Model tab in the Model Explorer, click on the Properties node to expand the tree and then on the Frame Sections node to see a list of the available sections.
Click on the desired section or Auto Select List and while holding down the left-mouse button, drag the section onto a frame object - the frame object where the section will be placed will be highlighted with a colored line. Release the mouse button to assign the section. To review the sections included in any Auto Select Section Lists, whether built in or user-specified, complete the following steps: 1. The Frame Properties form will display. Assign User's Guide 2. The Frame Section Property Data form displays; the sections included in the selected auto select section list are listed in the Auto Select List area of the form, available for review.
Click the Cancel button to close the form. Structural Loads The program allows the user to define a variety of structural loads, including dead, live, earthquake and wind loads.
The user then assigns the loads to various structural objects in the model. An unlimited number of load patterns can be defined. Note that the steel frame, concrete frame, composite beam, composite column, steel joist, concrete shear wall, concrete slab, and steel connection design manuals describe design combinations in accordance with building codes.
Complete the following actions using that form: 1. Type the name of the load pattern in the Load edit box. The program does not allow use of duplicate names.
Select a load type from the Type drop-down list. Type a self-weight multiplier in the Self-Weight Multiplier edit box see the explanation about the self-weight multiplier that follows. If the load type specified is Seismic or Wind, select an option from the Auto Lateral Load drop-down list. Click the Add New Load button. Note: If you select an automatic lateral load in the Auto Lateral Load drop-down list, click the Modify Lateral Load button and review or modify the parameters for the automatic lateral load in the resulting form.
Only one code based auto lateral load may be assigned for a given load pattern. If the Type has been set to Seismic, then the Auto Lateral Load drop-down list will show an extensive list of seismic codes for determining earthquake loads.
Once a code has been selected, click the Modify Lateral Load button to display the Seismic Loading form listing parameters for site coefficients, periods, and load directions. Using a seismic Auto Lateral Load with multiple towers will likely result in an incorrect distribution of lateral loads. If the Type has been set to Wind, then the Auto Lateral Load drop-down list will show a list of available codes for wind loads. Once a code has been selected, click the Modify Lateral Load button to display the Wind Load Pattern form, where coefficients and parameters may be input and reviewed.
If the exposure is set to the Extents of Rigid Diaphragms option, the program will automatically calculate and apply the different code defined wind load permutations to the diaphragms. Select Create All Sets from the Case drop-down list. Hold the mouse cursor over the information icon to display a table listing the direction angles and ratios for the ASCE cases.
The ASCE code prescribes 12 different wind load permutations. Structural Loads User's Guide 3. Click the OK button to close the form.
Figure Wind Exposure Width Data form 1. Type ;45 after 90 in the Direction Angles edit box make sure to precede 45 with a semicolon ;. This adds an additional wind load at a direction of 45 degrees to the previously defined angles of 0 and Note that the number buttons in the lower left-hand corner of the table expand from two to three - click on these buttons to display the exposure set tables for each angle setting.
A portion of the self-weight can be applied to any load pattern. The selfweight multiplier controls what portion of the self-weight is included in a load pattern. A self-weight multiplier of 1 includes the full self-weight of the structure in the load pattern.
A self-weight multiplier of 0. Normally a self-weight multiplier of 1 should only be specified in one load pattern, usually the dead load pattern. All other load patterns then have self-weight multipliers of zero.
Note that if a self-weight multiplier of 1 is included in two different load patterns, and then those two load patterns are combined in a load case or combination, the results are based on an analysis where double the self-weight of the building has been applied as a load. Highlight the existing load pattern in the Loads area of the form.
Note that the data associated with that load pattern appears in the edit boxes and drop-down lists at the top of the Loads area. Modify any of the data in the Loads area for the load case. Click the Modify Load button. If necessary, click the Modify Lateral Load button to modify the automatic lateral load parameters.
Note that when a load pattern is deleted, all of the loads assigned in the model as a part of that load pattern are also deleted. Define Shell Uniform Load Sets Shell uniform load sets define loads that consist of several different load patterns, e. Click the Add button.
Select a load pattern from the Load Pattern drop-down list only load patterns that have previously been defined may be selected. Type a load value in the Load Value edit box. The user must first select the object before a load can be assigned to the object.
Chapter 6 of this guide describes how to select structural objects. After the object has been selected, click the Assign menu command to access the applicable submenu and assignment options.
Table identifies the submenus and options. For example, a ground displacement assignment cannot be made to a frame or shell object. Thus, if a frame object e. A form will appear after clicking the Assign menu command, the submenu applicable to the type of object, and the desired assignment option.
Table identifies the forms generated when the various commands are used. Although the form names vary depending on the command used, each form has a drop-down list that allows the user to select the load pattern to be assigned. Logically, the available load patterns vary depending on the type of assignment. Analyses are classified in the broad sense as either linear or nonlinear, depending on how the model responds to the loading.
The results of linear analyses may be superposed, i. The results of nonlinear analyses normally should not be superposed. Instead, all loads acting together on the structure should be combined directly within the nonlinear load case.
The Load Cases form shown in Figure will appear. Click the Delete Case button to delete the highlighted load case. ETABS does not allow duplicate names. The default setting is linear static, but nonlinear static, nonlinear staged construction, response spectrum, time history, buckling, and hyperstatic are all available. A static case considers loads defined in a load pattern, a response spectrum performs a statistical calculation of the response caused by acceleration loads, a time history applies time-varying loads, buckling calculates the buckling modes, and hyperstatic is used in slab design.
Nonlinear static may be used for pushover analysis, while nonlinear staged construction allows portions of the structure to be added or removed. For a linear static load case type, this is typically a load pattern with a scale factor. For a load case type of response spectrum, a modal load case will be required.
This type is generally recommended unless the user is confident about the realistic behaviour of the member. For membrane and shell type elements, different membrane or bending thickness may be defined based on the actual behaviour of the slab system as shown in the following example. This option is recommended when modelling thick floor such as rafts and transfer slabs. The section property modifiers may be assigned to each section at this stage or later.
However it should be noted that property modifiers for all floor objects may be revised anytime by selecting the appropriate member floor, ramp or wall and there is no need to define them separately for each section. Define Wall Objects Walls may be defined as shell or membrane elements. Other modelling features are similar to what has been discussed for slabs except for section modifiers which will be discussed more in this chapter. When using a frame element beam to model a shear wall spandrel, keep in mind that the analysis results obtained are dependent on the fixity provided by the shell element that the beam connects to.
Different sized shell elements provide different fixities and thus, different analysis results. In general, for models where the spandrels are modelled using frame elements, better analysis results are obtained when a coarser shell element mesh is used; that is, when the shell elements that the beam connects to are larger.
If the shell element mesh is refined, consider extending the beam into the wall at least one shell element to model proper fixity. If the depth of the shell element approaches the depth of the beam, consider either extending the beam into the wall as mentioned above, or modelling the spandrel with shell elements instead of a frame element. Note that these modification factors only affect the analysis properties. They do not affect the design properties.
Member design will be based on end-face moments not centre-point. This analysis will be used in arriving at the following results; Slabs and beams section modifiers are as per ultimate limit state provisions as mentioned above. If the stress in any member exceeds the allowable tensile stress value, appropriate section modifiers corresponding to the cracked section properties shall be assigned to that member. The drift and accelerations shall be checked accordingly.
To ensure that the stiffness modifiers are assigned to all the elements, it is generally recommended to assign the stiffness modifiers after completion of the model and prior to the analysis using the "Select by Object Type" option in ETABS. This not only relieves the laborious task of defining the stiffness modifiers separately for each frame section, but also provides a quick, yet reliable way to change these modifiers in no time.
Here you can specify Stiffness Modifiers for the following shell analysis section stiffness in your model. D Membrane f11 Modifier D Membrane f22 Modifier D Membrane f12 Modifier D Bending m11 Modifier D Bending m22 Modifier D bending m12 Modifier The stiffness for each of the items calculated based on the section properties specified for a shell element are multiplied by the specified modifiers to obtain the final stiffness used for the shell element in the analysis.
They do not affect any design properties. The f11, f22 and f12 modifiers are essentially equivalent to modification factors on the thickness t of the shell element. The m11, m22 and m12 modifiers are essentially equivalent to modification factors on the t 3 of the shell element. The section modifiers for Ultimate limit state analysis for Area Objects are shown in the following table based on UBC 97, clause Refer to the discussion below for further clarification.
The gross section area based on UBC 97 Clause This may be easily accounted for frame elements by just revising the section modifier for moment of inertia. However, the axial and bending stiffness for shell elements can not be de-coupled, i.
This may cause displacement incompatibility with adjacent frame column which in turn may require revising the axial stiffness for vertical frame elements, as opposed to code explicit provisions. Special care shall be taken when defining these labels to ensure realistic values. A wall pier can consist of a combination of both area objects shell elements and line objects frame elements.
If you want to get output forces reported for wall piers, or if you want to design wall piers, you must first define them. If a wall pier is made up of both line and area objects, assign the pier label to the line and area objects separately.
A wall spandrel can consist of a combination of both area objects shell elements and line objects frame elements. If you want to get output forces reported for wall spandrels, or if you want to design wall spandrels, you must first define them. If a wall spandrel is made up of both line and area objects, assign the spandrel label to the line and area objects separately. The smaller areas are three-sided or four-sided and must have beams on all sides. Select one or multiple lines.
If the selected line passes through more than one area, all of the areas will be meshed. Note that this and the Auto Mesh Area option only work in plan view. The angle will be measured in the counter clockwise direction for the x and y-axis. If the point lies in the overlapping region of two areas, both of the areas will be meshed at the given angle.
For example, specifying a meshing of 2 by 8 means that the selected area will be meshed into 2 areas along the x-axis. The size of the meshed areas will be uniform along a given direction. Only quads and triangles can be meshed using this option. One more points can be selected for this type of meshing. More than one line can be selected to mesh a desired area. Note the following about Meshing Area Objects: OThe property assignments to meshed area objects are the same as the original area object.
OLoad and mass assignments on the original area object are appropriately broken up onto the meshed area objects. If clicked again for the same selected area, they will be divided in half again, and so on. J The program does not offer any automatic meshing for walls, however, for slab elements, the automatic meshing option may be done as shown below. Area Object Auto Mesh Options..
Complex floor systems supporting many walls and columns e. Note In general triangular plate-bending element, with shearing deformations, produces excellent results. However, the triangular membrane element with drilling rotations tends to lock, and great care must be practiced in its application. Because any geometry can be modelled using quadrilateral elements, the use of the triangular element presented can always be avoided.
If the meshes on common edges of adjacent area objects do not match up, automated line constraints are generated along those edges. These Line Constraints enforce displacement compatibility between the mismatched meshes of adjacent objects and eliminate the need for mesh transition elements.
The following figures show the difference in results when applying auto-line constraint to a simple model where slab and wall meshing does not match. The auto-line constraint is the default option in ETABS and needs to be removed manually if required. F is locked or pinned. The piles for this case need to be modelled with appropriate springs. Some guidelines for this purpose is explained in the following section. The stiffness of these springs may be calculated based on the maximum allowable axial force and settlement of the pile.
On the other hand, the maximum allowable settlement for a pile is generally given by the geotechnical expert. Loading 5. The self-weight and imposed dead loads shall be defined separately as explained below: 1 5. A self-weight multiplier of 1 means that the full self-weight of the structure is included in that load case. The live load values shall be assigned in accordance with the values adopted in Design Statement and the specific code requirements.
It is important to ensure that the self-weight multiplier is set to zero 0 for all load cases except self-weight. It should also be noted that Load Combinations do not include live load reduction unless required specifically.
Therefore, this shall be considered when using other supplementary design software e. This definition will help to differentiate between the live loads that are NOT permitted by the code to be reduced.
Therefore these loads shall be defined as a MECH load to ensure that they are not reduced for member design. The latter is used to apply the wind loads determined from the Wind Tunnel Test. Then ETABS will automatically calculate the wind loads acting on each story level and use it in the static analysis processor. A sample form of ASCE wind parameters is shown below followed by a brief description on key items.
Gust Factor Windward Coefl. Eccentricity: Determine the eccentricity values for the structure as per Clause 6. Otherwise, use Equation in Clause 6. The exposure type is generally taken as Exposure C for Dubai, but should be verified with the wind specialist accordingly.
An approved design spreadsheet may be used to reliably calculate all the parameters of ASCE wind load data. ETABS will automatically calculate the wind loads acting on each story level and use it in the static analysis processor. A sample form of BS wind parameters is shown below followed by a brief description on each item. Ca Dyn Augment Factor. Cp Size Effect Factor: The size effect factor shall be determined from Clause 2.
Dynamic Augmentation Factor: The dynamic augmentation factor shall be determined from Clause 1. Note 1- An approved design spreadsheet may be used to reliably calculate all the parameters of BS wind load data. For this purpose, wind loads may be determined as per note-1 and then applied to the building as a User Defined Load in Auto Lateral Load drop-down menu.
Refer to Section 7. These loads are generally calculated by recognized wind tunnel testing laboratories based on the dynamic properties of the structure as modelled during the preliminary or concept design stages. Wind loads are reported as separate load cases that should be combined through the set of load combinations as reflected in the wind tunnel report. It is important to note that these loads shall be applied to the analytical model at the same reference points that were initially defined for the wind tunnel consultant.
Moreover since the Wind consultants generally carry out their calculations at the center of the diaphragm of each floor, it is recommended that these points are taken in locations where are as close to the center of mass of diaphragm as possible. A separate wind load case shall be defined representing the load case as per wind tunnel report. The load values may directly be copied from a spreadsheet.
Various load combinations shall also be defined accordingly. The following figures show an example of defining user defined wind load cases. StOI J Oiaph,a! J,d Y. J,d "'1 TOP 01 J' 51TH 01 However, the results of response spectrum analysis may be scaled to the Equivalent Static Force Method as per Clause Therefore, the Equivalent Static Force Method shall be initially used.
Ratio All Diaph. User Defined Ca Override Diaph. Five percent is the default and is entered as 0. The program ignores eccentricities where diaphragms are not present. Note that since the Equivalent Static analysis is often used for scaling the Response , Spectrum parameters, the eccentricities need only be calculated for both directions with only one direction of eccentricity Le.
This value shall be taken as 0. However, in some cases, a lower level may be chosen. For example if a penthouse is included in the model, it may be best to calculate the automatic lateral load based on the roof level, excluding the penthouse roof level, as the top story, and then add in additional user-defined load to the load case to account for the penthouse.
However, if, for example, a o building has several below-grade levels, and the seismic loads are assumed to be transferred to the ground at ground level, it may be best to specify the bottom story to be above the base of the building. Note: No seismic loads are calculated for the bottom story. They are calculated for the first story above the bottom story and for all stories up to and including the top story. Refer to Section Note: For structures where more than one system is used throughout all or part of the J structure, the provisions of UBC 97 for Dual systems shall be met.
Alternatively, one system may be assumed to take all the lateral loads and the other is taken as a building frame system. For such cases, the lateral forces need to be scaled up to ensure that all the lateral loads are carried by respective system. The Soil profile type shall be taken from the site soil investigation report.
J The following topics describe key parameters for the response spectrum case data: Spect,,, Cick. Ratio [All Oiaph. Override Diaph. I Override Essentially ETASS assumes the response spectrum functions are unitless normalized and that the scale factor converts them into the appropriate units i. In that case you would input a scale factor equal to the product of the scale factor to convert the spectrum to the appropriate units and the scale factor to scale the response spectrum base shear to the appropriate level.
It is recommended that a uniform approach is adopted to provide a consistent method of incorporating scale factors. Then based on the results of first-run, the appropriate scale factor between the equivalent static method and the response spectrum method may be calculated and used in an appropriate Load Combination.
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