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Tension revisited: MPanel

July 1st, 2008 / By: / Uncategorized

The first of Fabric Architecture’s series of reviews of tension structure software ran in these pages 10 years ago. Time for an update.

Even with computer-aided design systems, fabric structures present a challenge. The fabrics industry in general and the tensile fabrics industry in particular increasingly rely on sophisticated software for form finding, stress analysis and fabrication, which streamline the entire design and project delivery process. MPanel, one of the more useful, sophisticated and relatively new software systems, promises to deliver value for architects, engineers, designers, fabricators, educators, researchers and a host of other professionals.

UK-based firm Meliar Design, which also makes paraglider and hang glider design and testing software, produced MPanel, now in its twelfth version. In a market space dominated by highly complicated tensile fabric CAD heavyweights, MPanel occupies an interesting and increasingly expanding space.

MPanel offers one of the most easy to use and understand software interfaces in the industry. The software runs on Autodesk’s AutoCAD platform. AutoCAD, with nearly 70% market share in the AEC CAD market, offers a familiar and ubiquitous environment—which MPanel fully exploits to the user’s advantage. To my knowledge, MPanel is the only commercially available tensile fabric structure plug-in for AutoCAD.

The software presents itself as a simple toolbar. Behind the deceptively simple set of buttons lies enormous power the user can unleash. MPanel offers endless formal possibilities of tensile fabric structures through a combination of fixed-edge meshes, fixed-corner meshes, sail meshes and cone tents. As a surprise bonus, the software allows design of cable net structures. Users define meshes using sets of four consecutive “high and low” points to create preliminary mesh surfaces. After creating the meshes within a multinodal, three-dimensional, polyline frame, the software “relaxes” (actually tenses) the meshes to create truly anticlastic mesh surfaces.

Though esoteric in text, MPanel presents a simple and straightforward form-finding process, particularly for users familiar with the AutoCAD environment. After form-finding, the next step translates the three-dimensional anticlastic surfaces into flat, two-dimensional panels for stamping and eventual cutting with CNC machines or by hand. Note, however, at every step MPanel offers dozens of options and parameters to produce a desired result, including ways to define warp-weft ratio, adjustable cable tension factors and accounting for cable links and lengths.

The paneling process translates three-dimensional meshes into two-dimensional polyline patterns. Difficult or impossible to find even in more expensive software systems, MPanel offers the ability to report shear tension in relation to the number of fabric panels. For instance, a structure with aggressive curvature could exert greater shear strain on each panel unless using more and narrower panels, whereas a structure with gentle curvature could use fewer panels due to relatively less shear strain on each panel. Evidently, MPanel makers took great care in featuring detailed seam allowance, compensation for pre-stress and other practical considerations in the paneling process. The latest version (12.5) allows the users to incorporate geometric markers for integrating graphics and text on the curvilinear surfaces.

Many of the more expensive and older software systems in the market include stress analysis capabilities. Tensile fabric structures, by definition dynamic and actively pre-stressed structures, inherently require stress analysis and material characteristics in design. MPanel plans to offer advanced engineering features, such as finite element analysis, in future versions, making the software a more comprehensive system. However, architects and designers seldom conduct structural analyses of buildings. They leave that task to the engineers. And though it may not affect the typical user, MPanel lacks the triangular meshes of more expensive counterparts.

Even in the absence of a robust stress analysis capability and advanced meshing, MPanel adequately satisfies the design needs of tensile fabric structures. In fact, using MPanel, designers created inflatable structures, fuel bladders for aircraft fueling and other unorthodox applications, which speak to the software’s sophistication and versatility.

Some of my students produced amazing design results in their first few hours with the software. The ability to quickly create meshes and play with them allows the designer to evaluate multiple design alternatives in a short time. This shortened cycle of design evaluation empowers the designer with significant advantages early in the design process. The speed with which one could cycle through the entire design process using MPanel could lead to increased productivity and formal innovation. MPanel makes the design of tensile fabric structures a matter of play. Behind the cleverly simple interface, the software packs serious capabilities that could transform even a novice user into a creative designer of tensile fabric structures.

Mahesh Senagala, LEED AP, is professor of architecture and research at the University of Texas, San Antonio, and president of ACADIA, the Association for Computer Aided Design in Architecture.

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