b'14 15MEGA DELTA FRAME JACKS VIERENDEEL TRANSFERLINK STRUCTURETRUSSESThe ability to preserve historic buildings while allowing forFor the two-tower Four Seasons Hotel & Residence, innovativeWhen faced with the challenge of designing a floating steel the construction of high-density development in urban envi- design was crucial to address multiple structural challenges.structure intended to connect two high-rise towers 15 storeys ronments is an important current issue in the industry. Due to the height of the main tower, a tube within a tubein the air, Zoran Tanasijevic (at the time with another firm) structure was used to handle lateral loads, thereby minimiz- proposed two alternatives.The Queen Richmond Centre West is an example of the abilitying walls and columns within the floor plate and facilitating of the construction industry to balance heritage and devel- flexibility oflayout. For transfer trusses in the 26-storey hotel/ The first scenario proposed using variable depth king post opment. This distinctive building in Toronto is a eleven storeycondo tower, conventional Warren trusses were nixed in favortrusses,located below the Level 15 suspended structure, to office building floating above existing four and five storeyof floor-to-floor height Vierendeel trusses to accommodatecreate an unusual spine effect.The trusses would be vertically masonry and timber heritage buildings.floor circulation and mechanical distribution.supported on the tower structure and laterally separated from one of the towers with a sliding bearing assembly.To support the building above, we created a unique Mega Delta Frame structure utilizing a central node of steel cast- An alternate design proposed linking the towers with a ing. The Mega Delta Frame can be visualized as two spacethree-storey high hanging structure, suspended at the roof frame pyramids stacked on each other with the upper onelevel by a steel truss system.inverted such that the points of the two pyramids join at a central node. The configuration of the structure enables the Mega Delta Frame to contribute to the lateral stiffness of the building under wind and seismic loading in addition to supporting the gravity loads of the columns above. The end result of the Mega Delta Frame is a visually pleasing architecturally dynamic structure which has become the signature of the building.Queen Richmond Centre West has received numerous awards,Award, a 2015 Award of Excellence in Engineering from the including: the 2015 Canadian Consulting Engineering SchreyerCISC Ontario Steel Design Awards, a 2015 R+D Award for Award rewarding a project that best demonstrates excel- Architectural and Engineering Solutions and Innovations lence and innovation, the 2017 Toronto Urban Design Awardsfrom the Journal of the American Institute of Architects, and Award of Excellence for Private Buildings - Tall, the 2017 OAAthe 2015 Canadian Urban Institute Brownie Award for Best Design Excellence Award, the 2013 Innovation Award by theOverall Building.Toronto Construction Association, a 2016 CISC National Design STEPHENSON ENGINEERINGCREATIVE SOLUTIONS 02'