Dr. Frame FAQ

     

Q:	Can I customize the cross section database?
A:	See the document Section Database Guide for details on creating your own cross section database.
Q:	What actions aren't supported by Undo/Redo in Dr.Frame?
A:	Envelope values do not revert after undo/redo. Visualization commands, e.g. pressing '8' to show reaction forces and '4' to show force values.
Q:	Can Joints be created explicitly by the user in Dr.Frame?
A:	No. Independently existing joints do not make sense in the Dr.Frame environment. To clarify this it is useful to differentiate between "nodes", which transparently exist along the span of members, and "joints", which define a member's ends. When the user applies a Point Load, for example, along the member's span, Dr.Frame transparently creates a node which is not visible to the user.Also, when a support is created in space a joint is automatically created to define the support's location.
Q:	What is the limit of a model's size ?
A:	The size is limited by your computer's available memory. For larger models (where the definition of large depends on your computer's speed and memory) updating may become slow enough that you may want to turn off the 'Realtime Solution' option in the Modeling menu so that model updating is only done after component manipulations.
Q:	If I connect a frame member to a truss member, what kind of connection do I get?
A:	Because the end of a truss member is free to rotate, a pin connection will be formed between the truss and frame members. However, if another frame member is connected to the same joint, a rigid (fixed) joint will exist between the two frame members and drawn as a square instead of a round pin. The truss member will still be free to rotate at this point and this pinned connection is shown by a small dot on rigid (drawn as a square) connection.
Q:	How can I tell what the constraint conditions at the end of a member are?
A:	First, truss and frame members are drawn slightly differently: trusses are thinner. The end of a truss member is a free to rotate and thus has a pinned connected. This is drawn in one of two ways: either as a circular pin or as a dot on a fixed (square) connection.The ends of frame members typically have fixed connections which are drawn as square joints.
Q:	What if I want to create a member with a pin connection at one end and fixed connection at the other?
A:	This can be done two ways: Bring up the Member Info Dialog for an existing member (by selecting the member then using the Info>Object Info... command or double clicking on the member (right clicking in Windows)) and appropriately toggling the End Conditions checkboxes. Holding the control key while clicking with the appropriate member tool near the end to change. For example, control-clicking near an end of a rigid ended member with the Pinned Member Tool will make that end become pinned.
Q:	The Main View of my newly created structure overlaps with its Aux View. How can I move the aux view relative to the main one?
A:	Select the Panner Tool (shaped like a hand). Now hold down the shift key and click-drag the aux diagram. The diagram will track the mouse movements until the mouse is released.
Q:	Sometimes the shear and moment diagrams aren't drawn even when I have them turned on. Why?
A:	When an aux diagram is on, a transparent copy of the structure will always be drawn. However, the shear and moment envelopes will only be plotted if there are no instabilities in the structure. If part or all of the structure is unstable, Dr. Frame will not be able to analyze its internal forces and support reactions. For this reason, the axial force values and coloring and support reactions will also be disabled for structures with instabilities.
Q:	How can I change the orientation of supports?
A:	Often, supports are not drawn with the desired orientation. To change this, select the support and choose Object Info (command-I) from the Info menu or double click the support to bring up the support info dialog box. Now change the orientation of the support and click OK. Note: orientation is measured in degrees and counter-clockwise from a vector pointing to the right.
Q:	How can I change the type of a support without having to delete it and then create a new one?
A:	First, select the tool for the new support. Then hold down the control key and click on the support that you want to replace. If you don't have the control key pressed, a new support will be created but the old one will not be removed.
Q:	How do I know which moments are positive and which ones are negative? They all are labeled with positive numbers.
A:	In Dr. Frame (as well as most other applications and publications), positive moments are defined as having a counter-clockwise direction. Moments are drawn as circular arrows so that it is always possible to determine the sign of the moment.
Q:	How can I modify a load without having to drag them and changing their direction?
A:	There are two ways this can be done: Select the load vector and use the up and down arrow keys. Note that only the transverse component of a member load will be affected. select the load vector and bring up the Load Info dialog from the Info menu (command-I) (or double clicking (right click on Windows)) to make the desired changes.
Q:	The hinge tool seems to always make my structures unstable. Why?
A:	Every time a hinge is added to a structure, another equation of equilibrium can be formulated. In some cases, this may make the structure determinate if the number of equilibrium equations is equal to the number of unknown forces. However, if the number of equations becomes greater than the numbers of unknowns, the structure will become under-defined and globally unstable. Hinges can also create local instabilities in structures. An example of this is adding a hinge to a truss member.
Q:	When I apply a load to a member, it's always perpendicular to the member. How can I create a non-perpendicular load?
A:	For concentrated forces you must create a joint to which to apply the load. Do this by deleting the existing member and creating a new one made up of two colinear members. Joint loads can be oriented arbitrarily. Position the joint along the member by selecting and dragging with the Select Tool. For distributed loads, holding down the control key while clicking on the member will create a vertical force.
Q:	How can I edit an ellipse that I've made with the X-ray tool? What if I want to move it without changing its shape?
A:	To edit the shape of an X-ray ellipse, simply click on the ellipse with the X-ray tool and drag the mouse. To change the anchor point of the ellipse, however, a new ellipse must be drawn. To move the ellipse with affecting its shape, click on and drag the ellipse with the X-ray tool while holding the control key down.
Q:	Can I create my labels at any point on the shear and moment diagrams?
A:	Yes. In addition to the labels created automatically using the commands in the Options>Automatic Labels menu, custom labels can be created using the Label Tool. To create a shear or moment label, click with the label tool on the aux view of the structure. Drag to position it or double click on it (right button on Windows) to bring up a dialog allowing you to precisely locate it. New labels are automatically drawn a certain distance from the structure. To modify their position relative to where they are pointing hold the control key while dragging.
Q:	What if I want to create a point that isn't exactly on the current grid?
A:	There are two ways to do this. The first way is to refine the grid so that it contains a specific point. This can be done by using the Refine/Coarsen commands in the Options>Grid menu or by bringing up the Grid dialog in the same menu. The second way is to turn off the grid snap in the Options:Grid menu or by holding the control key down, allowing you to place a support or member endpoint at any point.
Q:	Sometimes when I edit loads the mouse seems to stop working. What causes this?
A:	During editing, the effect of mouse movement does not correspond directly to the modifications being made to a load. When manipulating member loads Dr.Frame decomposes mouse movements into axial components and transverse components. Only one type of action is applied for each mouse increment so that for a slightly skewed mouse drag the effect on the load may be only to its direction or magnitude. The resulting difference between mouse location and load location can be confusing and this is the reason we don't draw the mouse cursor during dragging. One result, however, is that the mouse can reach the edge of the screen (a limiting boundary to mouse dragging) without your realizing it. In this case you should release the mouse to stop dragging and reselect the load before continuing.
Q:	I can't seem to place loads and supports on my structure. What's going on?
A:	When the displaced shape is turned on it becomes the active structure for creating and manipulating modeling components. Clicking on the faded structure will have no efffect. Only by clicking on the displaced shapae will you be abel to create new components.