Multiframe 9 Released - Faster and even more graphical
Formation Design Systems is very pleased to announce Version 9 of Multiframe - another upgrade in our on-going program to continually improve the Multiframe suite of structural analysis and design software. The new version 9.0 release will automatically be delivered to our Multiframe Subscription members over the next few weeks. It contains a wide range of enhancements including: semi-rigid end connections, advanced member orientation, axial end releases, automatic display of maximum actions and a range of other features.
Multiframe continues to be used for a wide range of structural engineering designs all around the world. The above stadium roof is just one example recently performed by Albert Loh & Associates in Singapore.
Some of the enhancements in Version 9 of Multiframe include -
Semi-Rigid End Springs
When modelling structural members, it's always necessary to decide whether to use a rigid or pinned connection at the end of each member. Multiframe now extends that option so that you can now have an end connection which is semi-rigid i.e. somewhere between pinned and rigid in terms of its stiffness. This is useful in many situations in which it is important to take into account the fact that the connection does not transfer all of the moment, or other actions, from its member to the other members to which it is connected. Multiframe uses the terminology "End Spring" for this option to clarify that it is like inserting a zero length spring at the end of the member.
One of the issues with this type of modelling is what level of rigidity should be defined and how should it be defined? Multiframe provides three different methods with minor variations for two of the methods.
Direct Stiffness
The first and simplest method is direct specification of the stiffness of the spring. You will most commonly use this when there is test data or a known specification which defines the correct stiffness of the connection. For rotational springs, this can be directly entered in kN.m/radian, kip.ft/degree and so on.
Member Rigidity
The second option is to define the stiffness of the end spring as a proportion of the bending stiffness of the member. In the standard formulation of the stiffness matrix for a member in Multiframe, the bending stiffness is given by 4EI/L where E is the elastic or Youngs modulus, I is the moment of inertia for bending in the direction under consideration and L is the length of the member.
A proportional formulation was discussed by Lightfoot and LeMessurier (1974) in which the stiffness of the end spring is defined in terms of a Rigidity Index (r). The bending stiffness K is given by K = r*4EI/L. So r will commonly vary between 0.0 and 1.0. r could also be increased past 1.0 to model an end connection which is stiffer than the member. A value of r=0.5 will simulate a connection with 50% of the stiffness of the member, a value of r=infinity will give a fully rigid connection. Because the member may have been subdivided for modelling purposes, Multiframe gives you the option of using the length of the member, or the length of the design member of which it is a part, in the 4EI/L expression. These two options are named Member Rigidity Index and Design Member Rigidity Index respectively.
Fixity Factor
The third method of defining the stiffness of an end spring is due to work done by Romstad and Subramanian (1970) and Yu and Shanmugam (1986). In this approach the stiffness of the end spring is non-linear with respect to the stiffness of the member. The stiffness is defined in terms of a fixity factor n where the bending stiffness K = n/(1-n)*4EI/L.
In this case n varies between 0.0 and 1.0 with n=0 giving a pinned connection, n=0.5 giving a connection with the same stiffness as the member, and n=1.0 giving a fully rigid connection. The graph above illustrates the non-linear nature of this formulation.
Member end springs allow you to more accurately model the variable stiffness of connections in your structures. If you are unsure of the appropriate stiffness to use, try varying the stiffness through the range from pinned to rigid to see how much it affects your analysis results.
Finally you should note that in the case that Sc, r or n is zero, the end spring acts just like a normal pinned member release. However we recommend that you use a pinned release for this purpose, rather than a zero end spring stiffness, as Multiframe can do more error checking and perform a more efficient analysis.
Advanced Member Orientation
Getting the orientation of structural members correct can sometimes be challenging. Suppose for example you had a curved roof in which you wanted the flanges of each member to lie in the tangent plane at its location on the curve of the roof.
Multiframe now offers some advanced member orientation functions to deal with these kind of situations. Orientation can be defined for either web or flange with respect to a point in space, a particular node or a particular direction. Linking to a node is dynamic - if the node moves then the orientation adjusts to match the new node position automatically.
Enhanced 3D Drawing
While Multiframe has always been well known for its advanced interactive modelling capabilities, we are continuing to build on them as computers become faster. In this release, the following enhancements make drawing and modifying your structure even easier.
3D Drawing & Dragging
A new Drawing Settings command in the Geometry menu allows you to turn on and off some advanced Snap settings which work whenever you are drawing a member or dragging part of a structure. Now, as you draw or drag, you can optionally have your cursor snap to member mid points, quarter points or to any point on the member. You can also constrain drawing so that the cursor will dynamically align to a global axis direction in 3D. When the cursor has snapped to a joint, the movement of the cursor from the joint will automatically be constrained to the global axis direction most closely aligned to the direction in which the cursor is moved from the joint. Colour coded graphical feedback as you draw makes it easy to see which constraints are in effect.
These new drawing tools make it possible to draw in any direction in a 3D view. By default, drawing in a 3D view will occur in the current working plane, which is the plane most perpendicular to the current point of view. Drawing out of this plane is accomplished by snapping to other members, nodes or grid points or by using the dynamic constraints described above.
These
new drawing tools make it much easier to switch between drawing in
2D and drawing in the 3rd dimension. They can also be combined with
the new graphical versions of the duplicate, rotate, extrude, mirror
and shear tools. For example, you can sketch a frame in the current
2D working plane and then extrude beams from it using the graphical
extrude tool and by automatically aligning to the out of plane z
axis.
Custom Units
Display As models become larger and more complex, it becomes even more important to present concise, readable output. A new Units display option now lets you set up custom units and decimal places settings for each type of unit you can display in Multiframe. For example this lets you simultaneously display deflections in millimetres with 1 decimal place, lengths in metres with 3 decimal places, moments in kNm with 2 places and so on.
Dynamic Library Loading
Section Maker and Multiframe now collaborate even more smoothly in this release. When you draw a section in Section Maker, add it to the library, and then save that library to disk, when you switch to Multiframe it will automatically detect the change and ask you if you would like to reload the library so that you can use the section right away.
Time History Export
Those using Multiframe 4D's time history analysis know just how much data can be generated in a typical analysis. A 2000 node model with 3000 time steps will generate over 12 million data items per load case. You can now selectively export this data so that you can do your own post-processing in Excel and other programs. The export function allows you to just export part of the structure, selected time steps and selected degrees of freedom. As well as those selections, four different methods are provided for grouping the output data - • Time vs DOF – data is exported as a single table with each row representing a single time step and each column representing a single degree of freedom • Node vs DOF – data is exported with a separate table for each time step, each row in the table contains the data for a single joint. • Nodal Database – data is exported as a single table with each row representing the data for a particular time step for a single joint • DOF data base – data is exported as a single table with each row representing the data for a particular time step for a single DOF
Column Design Improved
Users of Steel Designer for LRFD and AS4100 design calculations will welcome the addition of some new techniques for specifying the spacing of column restraints. The new options allow the user to specify a number of column buckling segments along the member.
The segments are specified by identifying the location of restraints against column buckling. The restraints can be located at any joints along the length of the design member.
Each of the column buckling segments will be designed individually in order to determine the capacity of the member for column buckling. The definition of segments between joints along the member ensures the model is suitably discretised for a 2nd order analysis, particularly those considering p-delta effects.
Windows 98 Support Ends
As independent software developers we are somewhat dependent on Microsoft's support for Windows in determining our own level of support for the various versions of the Microsoft Windows operating system. As Microsoft has now discontinued support for Windows 98, we are following suit. This 9.0 release is the last one which will run on that platform. Future releases will require Windows 2000, XP or later.
Tips and Tricks
Multiframe automatically displays a legend in the top right hand corner of the Frame window. If you right-click inside the legend you will find options for displaying alternative legends. You can also change the size of the text in the legend.
If you double click on the label of an item in the legend, this will automatically select all of the members of that type in the window.
Multiframe Subscription Program
The Multiframe subscription program has been adopted by the majority of our users to ensure that they automatically receive any updates to Multiframe as soon as they become available. The subscription program also makes you eligible to receive an unlimited amount of technical support via email, telephone or fax.
New purchasers of Multiframe are automatically provided with a Multiframe subscription free of charge for one year after the date of purchase.
When renewal time comes around, the subscription lets you pay one annual fee for all of the programs you own and will normally give you two major upgrades as well as any minor updates during the year. Subscription fees are approximately 10% of the current retail price of each program.
Upgrades are delivered on CD and minor updates are occasionally available for download from our web site. If you haven’t already done so, please advise us of your email address so that we can notify you when updates are available for download.
Online Help, Manuals & Release Notes
Online help in Multiframe is now provided in Adobe Acrobat PDF format. We recommend you download the latest version of Acrobat Reader from the Adobe web site at www.adobe.com. The latest Reader includes improved commands for searching and navigating through the help file. This makes it much easier to find the information you are looking for.
With every new release of our software, we supply a release note which describes all of the changes in the release compared with the previous major version. This release note is available in PDF format on the CD, can be downloaded from our web site, and is provided in printed form with any update CDs. The latest versions of user manuals are also available on the CD.
