(Above: Image by Integrated Design Associates)

Kosmas Moupagitsoglou explains the engineering excellence behind the Apple Kunming Pavilion, a feature structure built above a major new store for the world-famous brand.

The Kunming pavilion is the latest structure produced as part of our longstanding partnership with Apple. Forward thinking companies like Apple recognise the opportunities that architecture offers to both raise awareness of their brand and enhance the built environment, and we enjoy working on structures that require such innovative engineering solutions.

The partnership has seen the application of glass technology advance exponentially - from our first glass pavilion on 5th Avenue, New York (a transparent cube constructed from 106 glass panels) through Apple IFC Shanghai in 2010 (a 13m tall, 5m radius glass drum pavilion) to the Glass Lantern Apple Zorlu - which won the 2014 Supreme Award for Structural Engineering Excellence. In that case we achieved a remarkably pure structural approach using only four single glass panel walls to support a single CFRP roof, with all connections in silicone - resulting in maximum transparency.

The main challenge behind the Kunming pavilion lay in the combination of unconventional materials, combining glass, Carbon Fibre Reinforced Polymer (CFRP), and acrylic in an efficient and elegant structural system while accounting for the seismic load the structure may encounter.

CFRP and acrylic are popular materials in other industries, like yacht building and large aquariums, but less common in construction. Using glass, meanwhile, is a unique structural challenge - its purely elastic behaviour is, in many ways, predictable structurally, but accommodating the movements of the support structure that happen after the installation of the glass, the external loads, and designing for post failure robustness are far harder to account for. Understanding the characteristics of these materials through our unique experience has allowed us to create more interesting, lightweight and more complex structures.

Finite Element AnalysisAbove: Finite Element Analysis Plot under Moderate Seismic Load

In the case of the Kunming Pavilion the structure’s roof acts as a rigid diaphragm, and is the key element for transferring loads to the supporting glass columns. Lateral wind and seismic loads are resisted by both radial and circumferential columns, mainly attracted towards those aligned parallel in the direction of the lateral load. All structural columns are fixed at their base, through two pins providing a push-pull. in-plane moment restraint, acting as shear walls. The pins are held by mild steel angles which are designed to yield in the event of an exceptional earthquake, before the glass fails -  to dissipate the seismic energy and enable load distribution to other columns.

Apple Kunming facade PlanAbove: facade plan

The pavilion features 16 swing doors and 8 pivot doors, fitted between the structure’s ‘U’ columns and mechanically operated. The doors were successfully engineered to only require one titanium fitting at the top and the bottom, with the bottom fixed into a motor for opening and closing. This is the first time that SentryGuard Plus (interlayer) laminated titanium fixings have been used to support external doors subject to high wind loads – a significant challenge as each pivot door weighs 1.5 tonnes. 

The client was very happy with the result and it was well received by local people. We’re delighted to have been shortlisted alongside so many other great projects and look forward to attending on the night of The Structural Awards.
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