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Iwashita T.,Ariake National College of Technology | Packer J.A.,University of Toronto | Carlos De Oliveira J.,Cast Connex Corporation
Tubular Structures XIV - Proceedings of the 14th International Symposium on Tubular Structures, ISTS 2012 | Year: 2012

This paper describes defect tolerances for cast steel connections in braced frames and explores the possibility of brittle fracture from assumed defects in typical cast steel connectors.A parametric study, which investigates the sensitivity of brittle fracture to defect size, defect location and material mis-match effects, is described through cast steel connector models.A toughness scaling model is used for evaluating the occurrence of brittle fracture from assumed defects in the models. © 2012 Taylor & Francis Group, London.

Herion S.,Gmb Competence Center Tubes and Hollow Sections | de Oliveira J.-C.,Cast Connex Corporation | Packer J.A.,University of Toronto | Christopoulos C.,University of Toronto | Gray M.G.,University of Toronto
Proceedings of the Institution of Civil Engineers: Structures and Buildings | Year: 2010

During the past three decades, steel casting technologies and processes have developed significantly, making way for the production of high-quality castings that are capable of meeting the rigorous demands of structural applications. As a result, the use of steel castings in construction is becoming increasingly more accepted and commonplace. This article presents the state-of-theart uses of steel castings in onshore construction and summarises recent publications to give an overview of the current status of research and use of cast steel in tubular structures in North America, Europe and Asia.

Haque T.,Cast Connex Corporation | Packer J.A.,University of Toronto
Canadian Journal of Civil Engineering | Year: 2012

Elliptical hollow sections (EHS) are the newest steel shape to have emerged in the construction industry. They have been incorporated in a variety of structures around the world, including Canada, without structural design guidelines. To date, EHS are completely absent from Canadian codes and guides. A possible application of EHS is within truss-systems and, as such, a research project has been undertaken to investigate the behaviour of EHS-to-EHS welded connections. Twelve T and X connection tests have been performed to study the effect of connection angle, orientation type, and loading sense. Two methods to predict connection capacities and failure modes are investigated: an equivalent circular hollow section (CHS) approach and an equivalent rectangular hollow section (RHS) approach. The equivalent RHS approach proved to be more successful at capturing the actual failure mode of welded EHS-to-EHS connections and is therefore recommended at this time as a preliminary design method for EHS truss-type connections.

De Oliveira J.-C.,Cast Connex Corporation | Christopoulos C.,University of Toronto | Packer J.A.,University of Toronto | Tremblay R.,Ecole Polytechnique de Montreal | And 2 more authors.
Stahlbau | Year: 2011

Although concentrically braced frames are an efficient and popular choice for the lateral force resisting systems of mid- to low-rise steel frames, their bracing connections may be prone to premature failure unless complex design and fabrication procedures are undertaken. Frames utilizing Hollow Structural Section (HSS) braces, slotted to receive a concentric welded gusset plate, are particularly susceptible to connection fracture due to stress concentrations arising from the shear lag phenomenon at the net-section.To address this issue, a cast steel connector was developed at the University of Toronto that provides a bolted connection between a circular hollow section (CHS) brace and a typical corner gusset plate. Unlike standard, fabricated, slotted-tube type connections, the cast connector is designed such that shear lag in the brace member is virtually eliminated. Thus, there is no need for cumbersome reinforcing plates in the connection region. The connector was designed using solid modeling software and finite element analysis, and cast using ASTM A958 grade steel, which is very similar to most wrought grades. This paper presents the results of a series of full-scale brace tests in which four moderately slender, compact, cold-formed CHS brace assemblies were cyclically loaded to failure. Each of theWTce assemblies employed a different size of CHS and cast steel connector, with the latter in turn bolted to a typical corner gusset plate. Each of the tests followed the buckling restrained brace protocol specified in the American Institute of Steel Construction (AISC) Seismic Provisions. All of the braces survived several cycles beyond the protocol and failed in tension at the center of the brace. In each testthe cast steel connectors showed no sign of yielding, illustrating that the use of a cast steel connector is a viable means of connecting CHS brace members for seismic applications. © Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG.

Gray M.G.,Cast Connex Corporation | Christopoulos C.,University of Toronto | Packer J.A.,University of Toronto
Journal of Structural Engineering (United States) | Year: 2014

The Yielding Brace System is a highly ductile bracing system in which seismic energy is dissipated by the yielding fingers of a specially engineered cast steel connector. When the brace is severely loaded in tension and compression, the fingers yield in flexure, thus providing a full, symmetric hysteresis. Second-order geometric effects result in an increase in postyield stiffness at large displacements. The mechanics of the system are first presented, including several first principle equations used to predict a connector's response. These equations are then used to design a prototype connector. The geometry of this prototype is evaluated using nonlinear finite element analysis. Following this analysis, the results of full-scale axial component testing of the prototype are discussed. These results include tensile coupon tests from material taken directly from unyielded portions of the test specimens. The prototype design and testing program presented demonstrate that the Yielding Brace System is a ductile connector that can enhance the energy dissipation and displacement capacity of braced frames. Good agreement between predicted and experimental response showed that the mechanics of the connector were well understood and that the method used to design the prototype was effective in meeting the targeted performance. © 2013 American Society of Civil Engineers.

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