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Air and space

June 1st, 2014 / By: / Feature

High-tech inflatable structure covers San Francisco city street.

The world’s largest vendor-sponsored trade show, Dreamforce 2013, brought downtown San Francisco to a standstill last November when it hosted more than 130,000 cloud computing enthusiasts from 65 countries.

The event, hosted by Salesforce.com, was staged at the Moscone Conference Center and much of the surrounding area, including Howard Street, which was closed to traffic for the duration of the four-day event.

The Dreamforce Plaza on Howard Street has traditionally been an uncovered area, but concerns about the potential for bad weather led event organizers George P Johnson to approach inflatable structure manufacturer Tectoniks Ltd., Shropshire, U.K., to provide plans for covering the huge area with a structure that would provide a visually stunning centerpiece.

The structure needed to provide shelter from bad weather while maintaining an open and airy feel. It also had to reflect the high-tech nature of the event, be totally unique, and satisfy the stringent safety requirements of the local authorities. And it had to be installed in one night.

Structure overview

To simplify transportation and handling, the Dreamforce structure was manufactured in six sections, comprised of six identical inflatable modules that are 56 ft wide by 56 ft long by 33 ft high. Five modules were joined together on site to form one long structure measuring 280 ft long by 56 ft wide that covered the length of Howard Street in front of the Moscone Center. The sixth module stood alone at the entrance to the event.

Each module is comprised of a high-pressure, inflatable, tubular framework interspersed with low-pressure inflatable hexagonal pillows. The pillows are constructed from a variety of materials to produce varying degrees of transparency and translucency throughout the structure.

The structure had to be accessible by the public from all sides. Traditionally, a structure has a “back of house” area where the inflation equipment and pipework can be located along with other ancillary equipment. With no such area available, this equipment had to be concealed within the structure.

The solution came in the design of custom cast concrete “shoes” that serve as the ballast required to secure the structure in place—even in wind speeds up to 70 mph—and provide internal compartments for the inflation equipment. The shoes also serve as benches for the public.

There are 24 shoes used to anchor the structure, each weighing 6,500 kg (14,300 lbs). Each shoe is supplied in two pieces with channels on the underside to provide an easy means to lift and place them with a forklift.

The base of each inflatable module sits in recesses on the upper sides of the shoes and is fixed in place with adjustable straps connected between tie-down hoops on the shoes and load patches on the inflatable. The load patches are rated at 1,500 kg each and there are 14 per module.

“No other type of temporary structure of this size could have been installed in the time permitted with the crew and equipment available,” says David Kelsall, Tectoniks’ technical director. “The organic shape and unique visual appeal of the finished structure would also be extremely difficult and costly to achieve with any other form of temporary structure.”

Design

The structure was designed using advanced 3D CAD modeling techniques and evaluated using a combination of finite element analysis and hand calculations. Cutting patterns were generated using proprietary software developed by Tectonik engineers and then transferred to an automated cutting machine. The patterning software converts three-dimensional surfaces into two-dimensional panels before adding seam allowances, ID labels and alignment markings.

Construction

The inflatable structure is made entirely of fabrics and flexible films and contains no rigid elements. All the fabric and film panels were cut using a Blackman and White Orion cutting machine with a 6.5 m (21.3 ft) by 3 m (9.8 ft) cutting area.

A variety of assembly methods were used for each of the elements of the structure. The panels for the high-pressure tubular framework were joined using hot air welding techniques performed using a variety of Miller Weldmaster machines. The clear PVC panels used for the pillows were also joined using this method.

The translucent pillows were designed so that each hexagonal panel could be made from a single piece to avoid any visible seams.

The pillow panels were stitched to the high-pressure framework using a high strength, heat- and UV-resistant thread. All the stitched seams were then sealed using hot air welded backing tapes.

Materials

For the high-pressure welded tubular framework, Tectoniks chose Ferrari Precontraint 602N for its high strength-to-weight characteristics, excellent weldability, dimensional stability and durability. The fabric has zero light transmission, which reduces solar gain and helps to maintain a constant air pressure within the structure.

The translucent pillow membrane is made from Ferrari Precontraint 402 Translucent. Selected for its light transmission properties and low weight, it is extremely robust and does not crease when packed.

The clear pillow membrane is 0.75 mm fire retardant clear PVC film supplied by Kayospruce. It was selected for its optical clarity, fire retardant properties and ability to resist creasing when packed.

Installation

Working to a tight delivery deadline, Tectoniks designed and manufactured the structure at its factory in Shropshire. Each completed section was test inflated and inspected before packing. One of the advantages of inflatable structures is the small packed size. The entire structure, complete with inflation equipment, was loaded into a single ISO container and delivered to the site in San Francisco on time.

Since staging the event involved the closing of Howard Street, one of the main roads through the heart of San Francisco, the installation had to be performed in a single night to minimize disruption to the city. After the road was closed by city officials (and a couple of traffic lights removed), the entire area was covered with Astroturf. The Tectoniks crew along with the client’s crew worked through the night to install the massive inflatable structure.

Staging, seating and lighting were added to complete the installation. Lighting was mounted on a series of truss arches spaced along the length of the structure. Stand-alone arches were offset from the structure to provide sufficient throw for the lighting to cover the entire surface of the canopy, producing stunning results whether viewed from inside or outside.

The venue was used for a variety of events throughout the four-day convention. Heavy rain fell on day two of the event and which continued into the night. The structure kept visitors dry and the entertainment continued without interruption.

Deflating and packing the block-long inflatable structure was completed within one day, allowing Howard Street to reopen on-schedule.

Visit Tectoniks website for more information.

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