Multiframe News January 1996

Multiframe users will soon be offered the chance to upgrade to our most exciting version of Multiframe yet. The latest version of Multiframe 4D includes a number of modelling and analysis improvements. Chief among these are time history based dynamic analysis for seismic or general dynamic analysis, master-slave capability for linking together rigidly connected groups or members such as those found in a floor slab system, and optional shear deformation to model the behaviour of deep beams or shear wall systems.

Multiframe 4D now includes a range of load case types including seismic cases and a general dynamic case. A seismic case can be used to apply ground accelerations to the structure in the form of a series of acceleration values varying over time. A new Load Library contains a number of standard series such as El Centro, Northridge and Kobe earthquakes. Multiframe 4D makes it easy to set up your own data sets.

There are now a number of different load cases which can be added in Multiframe. These include a self weight static load case, a normal static load case, a factored combination of static load cases, a dynamic load case which can contain dynamically varying forces at one or more joints, and a seismic case which applies up to three orthogonal dynamically changing ground accelerations to any restrained joints.

The most common use for this is in applying an earthquake spectrum to a frame but it may also be used for any other ground based acceleration. Analysis is carried out by applying the specified acceleration to all of the restrained joints in the structure. Once you have defined your dynamic loads or accelerations, you can perform a Time History analysis to compute the response of the structure at each of the time steps you have specified. The resulting dynamically changing deflections, forces and stresses can be viewed as a graph at a joint, as a QuickTime movie of the structure deflecting under load over time, or exported to a text file for further processing.

Sometimes we are pleasantly surprised by the complexity and beauty of some of the structures Multiframe users are able to create. The example of the multi-span curved roof below was created by Jaime R. Gonzales Blanco for the Lucky Star factory in Aguascalientes, Mexico which manufactures Levis.

Modeling was performed using Multiframe by taking advantage of the automatic generation of curved groups of beams and using the duplicate and rotate functions to automate most of the geometry creation. The proportional subdivision option was also useful in this case by allowing intermediate spans to be easily created with a minimum of data input.

Multiframe 4D now allows you to link groups of joints together so that they move together in response to either static or dynamic loads. This has a twofold benefit, firstly it allows you to simulate rigid structural elements such as a floor slab and secondly it significantly reduces the size of the stiffness matrix resulting in much lower memory requirements and much faster analysis times.

Joints can be linked together on a degree-of-freedom basis. This means some degrees-of-freedom can be linked together and others left independent. In the case of a rigid floor slab for example, all the joints on that level could have their x, z and Øy deflections linked together to simulate the rigid translation and rotation of the slab while still allowing bending of the floor.

Some Multiframe users may not be aware of what the Section Maker module does and how it can help them in their design work. Section Maker has been developed to simplify the design and installation of custom section shapes in the Sections Library. Section Maker allows you to draw a structural shape on-screen and have its section properties automatically displayed and updated each time you make a change. Sections can be made up of circular, rectangular or polygonal shapes and can be made up from steel, concrete or any other materials. Section Maker lets you build up a section from standard structural shapes by moving, duplicating or rotating them on the screen. It even allows you to simulate a tapered section by automatically installing the shapes at a regular number of increments between two existing shapes.

Designers of concrete beams and frames will be glad to know that Section Maker will automatically take account of the modular ratio for the steel portions of a section if you create a section which is made up from steel and concrete.

Section Maker allows you to import and export geometry in DXF or Pict file format so that if you have complex shapes from another source you can import them into Section Maker for properties calculation.

If you create custom shapes using Section Maker, when you use them in a Multiframe 3D frame, the actual section shapes will be used when using the display of section orientation or rendering options.

Apple has recently announced a new piece of system software which is very significant for Multiframe users. QuickDraw3D is a new 3D graphics system for the Power Mac range. It will ship with System Software from version 7.5.3 and provides high performance, high quality 3D graphics rendering and interaction. It also provides a standard 3D file format (3DMF) which will undoubtedly become the standard method of 3D interchange among Macintosh modelling programs. Although QuickDraw3D is very fast on a standard Power Mac, it has also been designed to allow easy support for 3D graphics accelerator boards which should soon start appearing for Power Mac computers with the new PCI type expansion slots.

We will be supporting QuickDraw3D in future releases of Multiframe and taking advantage of the fast rendering and data exchange capabilities it provides. The best thing about QuickDraw3D is it's free! It will ship with all new system software from now on. Internet users can obtain more information on QuickDraw3D at: http://www.info.apple.com/qd3d/ or contact your Apple dealer for more information.

The new PowerPC chip in the Power Macintosh range has revolutionised the suitability of the Macintosh for complex technical work. It is the start of a new line of RISC based chips, it is faster than a Pentium running at the same speed, and much faster for floating point operations. It is half the size of the Pentium and costs less than half as much to produce. At the same time a real effort has been made to ensure that all software written for the Macintosh will run without modification on the PowerPC.

This commitment to protect the investment in software is a notable feature of Apple that is in marked contrast to some other manufacturers. It also means that the software suppliers have had years of continuous development without having to worry about changing their programs to match radically different operating systems as have those programmers that have had to contend with the change from DOS to Windows.

It should also be remembered that the cost of hardware is now lower than the cost of a large screen. The cost of the software is likely to be more than the cost of the actual computer. A new 66MHz PowerPC with 8MB RAM and 500MB hard disk can be purchased from $1500. It comes complete with Ethernet and Appletalk connections and a disk drive capable of reading both Macintosh and IBM format disks.

For an additional $500 you can install a card that contains a 66MHz 486 chip so that you can run Windows and DOS programs on the same machine and cut and paste between programs. Perfect compatibility, two computers easy networking and the most productive system on the market.

As a result of our continuing growth in sales world-wide, the extra space is soon filling up as we add to our development and support teams.

The newest member of our development team is Kim Walch. Kim's background includes a Bachelor's degree in engineering and a Master's degree in Computer Science.This makes him ideally suited to the increasingly complex capabilities we are adding to the Multiframe range. Kim will be bringing his technical problem solving skills to bear on some of the tougher design and analysis problems we are working on.