Council on Tall Buildings and Urban Habitat
CTBUH 2015 Height Committee Meeting
October 25, 2015
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NEW YORK CITY – After providing a snapshot of the Height Committee’s duties and past actions since its last meeting in 2014, Height Committee Chairman Peter Weismantle led a discussion on a series of topics that rose to the forefront over the past year:

Mixed-Use Criteria Working

Current CTBUH building usage criteria states that a mixed-use building contains two or more functions (or uses), where each of the functions occupies a significant proportion of the tower’s total space (i.e., 15 percent or greater of either total floor area or total building height). The footnote for this criteria asserts that “care should be taken in the case of supertall towers. For example a 20-story hotel function as part of a 150-story tower does not comply with the 15 percent rule, though this would clearly constitute mixed-use.” The Height Committee discussed whether the “15 percent rule” was adequate in determining the functional mix of a building, and if there might be better ways to identify building functions on The Skyscraper Center. The committee ultimately decided that no immediate action was necessary, but will consider changing the wording of the criteria in the future to identify and catalogue mixed-use buildings more clearly.
The Height Committee at work

Defining and Using the Term “Superslim”
In the coming year, the Council plans to produce a Tall Buildings in Numbers report that addresses the “superslim” skyscraper typology, as this phenomenon has garnered a great deal of media attention recently. To this end, the question was posed to the Height Committee as to whether the Council should establish measurement criteria for this typology, which would allow these towers to be ranked according to “slimness.” A rich discussion ensued that brought many of the nuances of this building type to light. For instance, the geometric complexity of many tall buildings makes it difficult to establish consistency, like with tapering towers or those that rise from large podiums. The committee thus decided to avoid firmly defining the term, opting instead to develop a narrative/commentary that addresses the phenomenon and its various subtleties.

Research Update: Composite Sub-Categories
The current CTBUH definition for “Composite” structural systems lacks specificity in terms of structural type and material use, with now a high percentage of new buildings being lumped together in this one category on The Skyscraper Center. To address this, in 2014 the Height Committee assigned Terri Boake the task of developing subdivisions for composite structures, based on recognized, established industry terms. This year, Terri presented her findings, which were obtained with the help of several of her students at Waterloo University. Terri confirmed that there were generally four sub-categories of composite structures: concrete core with steel framing, concrete encased steel, concrete filled steel tubes, and reinforced concrete columns with steel floor beams. Terri stated that work was still ongoing in finalizing these primary composite categories and she will distribute her findings to the Height Committee for review upon completion.

Engaged in discussion
Name Company
Peter Weismantle AS+GG / Height Committee Chair
Jean-Claude Gerardy ArcelorMittal
Georges Binder Buildings & Data SA
James Parakh City of Toronto Planning Department
Steven Henry CTBUH Associate Director
Jason Gabel CTBUH Media Associate
Dario Trabucco CTBUH Research Manager
Marshall Gerometta CTBUH Skyscraper Database Editor
William Maibusch DPR Construction
Mic Patterson Enclos
Abdo Kardous Hill International
Johannes de Jong Elevating Studio
David Scott Laing O’Rourke
Ron Klemencic Magnusson Klemencic Associates
Joseph Burns Thornton Tomasetti
Robert Pratt Tishman Speyer Properties
Terri Meyer Boake University of Waterloo