Cast Connex Sources Cast
Cast Connex Corp. worked with a metal casting supplier to produce a construction frame connector that met several design criteria.
Carlos de Oliveira, Cast Connex Corp., Toronto, and Ryan Grant, Pacifi c Steel Casting Co., Berkeley, California Compiled by Steve Gonczy, Gateway Materials, Mount Prospect, Illinois
concern to do it. Concentrically braced frames are
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widely used in steel structures because of the increased stiffness, low cost and ease of construction they offer compared to other lateral reinforce- ment systems. The diagonal bracing members of braced frames are often hollow structural sections because of their compression load effi ciency and aesthetic appearance. These braces, which come in a range of section sizes, are either welded or bolted into place in the fi eld. Rectangular hol- low section brace members are easily mill-fabricated and connected to the steel frame through tailored reinforced gusset-connector-brace systems. But the rectangular braces suffer from reduced ductility, notch toughness and compression strength because of residual stresses and stress concentra- tions in the section corners. Circular hollow section members avoid this corner effect but pose different con- nection challenges (Fig. 1). With the help of the metalcasting
process, researchers at the Univ. of Toronto, Toronto, Canada, were able to overcome these challenges and developed a new connector design for circular hollow section members. Cast Connex licensed the proprietary technology and worked with its metal casting supplier in a collaborative de- sign effort for rapid, effective design development, process optimization and quality control management. The fi nal steel casting connector offered a mechanical design with integrated features, reduced stress concentra- tions and isotropic properties, a functional design with re- duced detailing and fabrica- tion time, well-controlled welding methods, sim-
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ast Connex Corp., Toronto, had an idea for a new way to connect steel construc- tion frames. But it had to satisfy a critical design
plifi ed assembly with straightforward fi eld bolting, and a standardized design with wide application to different load requirements, eliminating the need for one-off connector designs.
Meeting Stringent Requirements
A structural connector in building construction has to meet stringent building code requirements, be easy to design for a range of structural forces and confi gurations, have low production cost, and provide simple fi eld fabrication. The steel connector casting devel-
oped by Cast Connex consists of a solid round section transitioning into two fl at plates that are bolted to a gusset plate. Bolt attachment to a single gusset plate accommodates simple fabrica- tion, construction and site erection. It also eliminates the need for fi eld welding and its inherent variabil- ity (Fig. 2). The heavy end of the con-
nector is tapered to accept hollow round braces of different wall thickness for complete joint penetration weld- ing. Cast Connex developed the steel connector in four sizes
to connect to different outer diameter braces (4, 5.5625, 6.625 and 8.625 in. [10.16, 14.13, 16.83 and 21.91 cm]). The four connectors range in size from 14 x 7 to 27 x 14 in. (35.6 x 17.8 to 68.6 x 35.6 cm) with weights between 41 and 320 lbs. (18.6 and 145.1 kg). A structural connector in building construction must meet the following mechanical strength requirements:
METAL CASTING DESIGN AND PURCHASING
JANUARY/FEBRUARY 2010
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