Cast Connex Sources Cast Construction Part
Cast Connex Corp. worked with its metal casting supplier to produce a construction frame connector that met several design criteria.
Carlos de Oliveira, Cast Connex Corp., Toronto, and Ryan Grant, Pacific Steel Casting Co., Berkeley, California Compiled by Steve Gonczy, Gateway Materials, Mount Prospect, Illinois
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ast Connex Corp., Toronto, had an idea for a new way to connect steel construction frames. But it had to satisfy a critical design concern to do it.
Concentrically braced frames are
widely used in steel structures because of the increased stiffness, low cost and ease of construction they offer com- pared to other lateral reinforcement systems. The diagonal bracing mem- bers of braced frames are often hollow structural sections because of their compression load efficiency and aes- thetic appearance. These braces, which come in a range of section sizes, are either welded or bolted into place in the field. Rectangular hollow section brace members are easily mill-fabricated and connected to the steel frame through tai- lored reinforced gusset-connector-brace systems. But the rectangular braces suffer from reduced ductility, notch toughness and compression strength because of residual stresses and stress concentrations in the section corners. Circular hollow section members avoid this corner effect but pose different connection challenges (Fig. 1). With the help of the metal-
casting process, researchers at the Univ. of Toronto, Toronto, Canada, were able to overcome these challenges and developed a new connector design for cir- cular hollow section members. Cast Connex licensed the pro- prietary technology and worked with its metal casting supplier in a collaborative design effort for rapid, effective design develop- ment, process optimization and quality control management. The
30 C
final steel casting connector offered a mechanical design with integrated fea- tures, reduced stress concentrations and isotropic properties, a functional design with reduced detailing and fabrication time, well-controlled welding methods, simplified assembly with straightfor- ward field bolting, and a standardized design with wide application to differ- ent 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 configurations, have low production cost, and provide simple field fabrication. The steel connector casting devel-
oped by Cast Connex consists of a solid round section transitioning into two flat plates that are bolted to a gusset plate. Bolt attachment to a single gusset plate accommodates simple fabrication, construction and site erection. It also eliminates the need for field welding and its inherent variability (Fig. 2).
The heavy end of the connector is What Is Cast Connex Corp.?
tapered to accept hollow round braces of different wall thickness for complete joint penetration welding. Cast Con- nex 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: • ultimate tensile strength: 550 MPa (80 ksi); • tensile yield strength: 345 MPa (50 ksi); • percent elongation: 22% in 50 mm; • reduction in area: 35%. The steel used for the Cast Connex connector was required to have Charpy impact strength of 27 J at -20C and had to be weldable, with the finished weld having Charpy impact strength of 27 J at -30C. The surface finish requirement for the part was 450 RMS. The quality assur- ance requirements also were extensive, covering both casting process parameters and comprehensive mechanical testing and nondestructive evaluation of the castings.
ast Connex Corp. manufactures standardized and customized cast steel structural components for building and bridge structures. The company
retains the exclusive license rights to intellectual prop- erty developed at the Univ. of Toronto for cast steel structural connectors. Cast Connex products include a range of pre-engineered cast steel connectors for use with hollow structural section members, as well as structural engineering design and design-build services for custom cast steel components.
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The Casting Design Issues Cast Connex selected Pacific
Steel Casting Co., Berkeley, Calif., to produce its steel connectors. The casting design team (Cast Con- nex design engineers and Pacific Steel casting engineers) focused on three imperatives: • design for performance • design for production/castability • design for cost
MODERN CASTING / September 2010
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