Multiframe News - July 2008

FormSys is pleased to once again announce a significant update to the Multframe suite of software. Version 11 adds an innovative new method of applying area loads to structures. Whether it be from wind, dead, live or snow loads, areas loads are common and often tedious to apply to frame structures. The new technique allows to user to sketch load panels which are supported by members in the structure. When an area load is appplied to a load panel, the resultant distributed loads along its supporting members are automatically calculated and displayed.

Multiframe now includes functions to simplify the application of pressure loads to an area which is supported by members of the structure. Multiframe provides this functionality by way of load panels.  A load panel is a triangular or quadrilateral planar area supported along 1 or more edges by members of the structure.

When the pressure load is applied to a load panel, Multiframe automatically calculates and applies the appropriate distributed loads to the supporting members. This is done using the usual tributary area method where the angles at each corner of the load panel are bisected to create load regions alongside each supporting member. Each member receives the load corresponding to the panel area which is adjacent to it.

Load panels can also be used for purely visualization purposes, ie. a user could add a panel but never apply any loads to it.  This would allow visualization of cladding, floor slabs and shear walls.

Load Panels are created in the Frame window, and then have loads applied to them in the Load window. The following functions are available for adding, editing and deleting load panels.

Adding Load Panels

There are several ways for users to add a load panel to the structure. These include rectangular panels, triangular panels, quadrilateral panels, and automatically created a group of panels in a floor or frame. These commands are available from the Geometry menu or from the Load Panel toolbar.There are many techniques and commands that are used to selecting load panels within a graphical window. 

You can edit which sides the panels is supported on, enter a label for the panel, and also edit the colour of the panel. You can also edit which members support the edges of the load panel by using the Rotate Panel Supports icon in the Load Panel toolbar.

This will change the supports o the panel so that they all move one place anti-clockwise. This is most useful when used twice to change the supporting direction of a 2-way load panel.

You can also use the same technique to change the labels and colours of a group of load panels by choosing the corresponding items form the pop up menu.

Load Panel Display

Multiframe allows you to control the display of a range of symbols associated with load panels. These options are available via the Symbols command in the Display menu or more commonly via the icons in the Load Panel Symbols toolbar.

Load Panel Loads

Multiframe allows loading on panels to be applied relative to the direction of the global coordinate system or relative to the direction of the local panel coordinate system. A global panel load is a load which is uniformly distributed along all areas of a load panel, and acts in a direction parallel to one of the reference x, y or z axes.

The axis of the load determines how the load is projected in the panel areas. With Global axes, the magnitude of a global panel load refers to its load per square meters where the area is measured perpendicular to the direction of the load.  This means a vertical distributed load applied to an inclined panel will apply a total load equivalent to the magnitude of the load times the horizontal projected area of the panel.  For loads applied in local axes, the magnitude of the distributed load refers to its load per square meters where the area is the actual area of the load measured along the panel plane.

Load panels should greatly speed up the application of common pressure loads to frames modelled in Multiframe. It also offers a preview of the kind of interface we will be offering in future to allow the modelling of plate elements in Multiframe.

User Codes in Steel Designer

Many of our Multiframe users may not be aware of the User Codes option available in the Steel Designer module. This capability allows you to select a user defined set of design check calculations rather than one of the standard steel codes. These calculations can be customised to suit your particular requirements.

The calculations in the User Code are grouped together by the type of member check to be performed, namely bending, tension, compression or combined. The default equations provided use a simple Excel/Basic style of formatting e.g. Fb<0.6*Fy,  d<L/250,  Fa<12*Pi^2*E/(23*(Kx*L/ry)^2)

The design variables available for use in these expressions are the same as those available in the calcsheet and input dialogs in Multiframe. When design checks are run, Steel Designer evaluates the equations for each member. It produces the same kind of detailed report you get with a regular design code and design efficiencies (or capacity ratios) can be displayed graphically in the Plot window and numerically in the Result window.

Steel Designer Deflection Checks

The deflection checking for the AIJ code has been changed to always use the deflection adjusted for the minimum deflection of the end nodes. This means the deflection used will be the deflection relative to the original member axis minus the smaller of the deflections at the ends of the member. i.e. the deflection is Y’’ as shown below left. X’’ is parallel to X’ and adjusted for the smaller of the two Y’ nodal deflections.

Data Import & Export

Multiframe supports a wide range of import and export formats. If basic exchange of geometry is all that is required, then DXF is usually a good choice. Typically this is used when bringing in member geometry from a CAD system. The trick is to ensure that only centreline information is included in the DXF file. Multiframe interprets each line in the file as being a member so too much information is not a good thing.
In version 11 of Multiframe, each layer in the DXF file is added to a new Group in Multiframe. For larger structures this can be very useful for selecting and isolating parts of the frame geometry based on your CAD setup.
The import and export of SDNF (Steel Detailing Neutral Format) has also been enhanced in the version 11 release. SDNF allows data to be moved to steel detailing systems like MultiSteel, X-Steel and StruCAD. The recent enhancements include improved support for custom section orientation for channel and angle sections.

Multiframe Marine

We are continuing to see a steady increase in the number of Maxsurf users who are now using Multiframe for at least some of their structural analysis requirements. The image below shows how Multiframe can be used for the analysis of a yacht rig. The Tension/Compression Only and Non-Linear options of Multiframe are particularly useful in this context.

We are currently undertaking a new round of development work in Multiframe aimed at making it even more suited to analysis of marine structures. Of course almost all of this development work will also be useful to non-marine users.

The first and most important area is in the addition of plate elements to Multiframe. Since marine structures are typically composed of stiffened plates, our goal is to make Multiframe particularly well suited to that kind of modelling and analysis. The plate element being added will in fact be a flat shell element i.e. it will have six degrees of freedom per node and so support both in-plane and out of plane actions. This will also ensure smooth compatibility with our beam elements.

We will also be harmonising the Multiframe and Workshop sections libraries and providing additional support for bulb flat sections. We would welcome your feedback on what additional capabilities could be added to Multiframe and Section Maker to make them even more suitable for marine applications. Please send your ideas to support@formsys.com.

A Brief History of Multiframe

1985
Experimental work on the Apple Lisa computer at the University of Western Australia is the precursor to Multiframe

1987
The first version of Multiframe 2D for the Macintosh. Runs in 512k RAM and is delivered on a single 400k floppy disk.

1989
Multiframe 3D appears. Features the innovative clipping and masking functionality.

1991
The first Japanese language version of Multiframe debuts including Japanese reports and design code.

1995
Multiframe 4D is added to the suite and includes modal and time history dynamic analysis. Our first web site appears on the Internet.

1997
Multiframe for Windows arrives. Runs under the new(ish) Windows 95 operating system.

1999
Multiframe is now delivered on CD, a relief for our shipping staff!

2001
Automation is added to Multiframe allowing macros in Excel  to generate structures and post-process results.

2003
The British design code and OpenGL rendering add to Multiframe abilities.

2005
Semi-rigid end springs are just one of the more advanced modelling and analysis capabilities we add.

2007
Cold formed design debuts. Modern processor performance combined with improvements to the solver allow a 5000 member structure to be analysed in 3 seconds.

Tips and Tricks

Multiframe uses the same selection convention as AutoCAD and some other CAD programs i.e. when you drag from left to right, all of the objects completely inside the selection rectangle get selected. When you drag from right to left, all of the objects inside the selection rectangle, and all of the objects which intersect the selection rectangle are selected. This is very handy for selecting beams without columns and vice versa.

Holding down the Shift key while choosing commands from the Select menu,  extends and reduces the selection in the same way as if the user had shift-clicked on them manually.