Taking swimming pool design to new heights

by Sally Bouorm | March 1, 2011 9:53 am

[1]

By Marie Lewis

The Marina Bay Sands in Singapore is not an average hotel. The 55-floor structure is the country’s first integrated resort, comprising three sloping towers connected at the 23^rd floor to create a single building. The Sands’ many amenities include 2,561 rooms and suites, a casino, nightclubs, 74,322 m² (800,000 sf) of retail and dining space and two theatres.

[2]

Sitting atop this impressive building is the Sands SkyPark, a 1.2-ha (2.9-acre) tropical park with even more features and amenities. This unique structure spans the width of all three soaring hotel towers 200 m (656 ft) above the ground and has a 56-m (183-ft) cantilever edge. It is 340 m (1,115 ft) long from the northern tip to the south end, and 40 m (131 ft) wide. It contains 7,815 tonnes of permanent steelwork; an additional 4,483 tonnes of temporary steelwork was used in the construction.

When the Las Vegas Sands Corp., and architect Moshe Safdie were awarded the bid for the Marina Bay Sands, they called upon Natare Corp., in Indianapolis, Ind., to build and install the water features slated for the SkyPark—an infinity-edge stainless steel pool, three large hydrotherapy spas, a wading pool and a reflecting pool—all 55 floors above the ground.

The basics

In keeping with the natural marine backdrop of the resort and its exotic locale as a destination for world business and leisure travellers, the resort incorporates a number of nautical elements and themes, and the SkyPark, appropriately, appears to float like a ship across the top, and the pool literally spills over an astonishing vanishing edge.

At 146 m (478 ft), the SkyPark pool is the world’s largest infinity-edge pool at that height. It comprises 181,437 kg (400,000 lbs) of stainless steel and can hold 1,438,456 L (380,000 gal) of water. It took approximately two days to fill the pools, at a rate of about 25 mm (1 in.) an hour. The design flow rate through the pool’s pump system is 21,603 litres per minute (lpm) (5,707 gallons per minute [gpm]).

The pool interior is finished with 254,000 ceramic tiles adhered directly to the stainless steel shell. All of the pool components were designed and fabricated at Natare’s Indianapolis plant, shipped in more than 30 ocean freight containers and assembled on site under Natare’s supervision.

Space limitations

Ideally, raw materials could be shipped and field-fabricated to create the structural framing system on site. In this case, crew members shared a very restricted space with multiple contractors on a construction site in the sky, so they developed a plan to prefabricate all of the components in Indianapolis and stage overseas shipments and site deliveries. These components obviously had to be shipped at very specific times throughout the course of the project.

[3]

As part of this logistical plan, each pool was successfully divided into unique segments. Then, those segments were broken down further in order to create sub-assemblies that could then be hoisted to the top of the towers via crane or service elevator, eliminating the need for extensive on-site welding and fastening tools to construct the shells. In all, 40,000 pieces were used to construct the pool enclosures; these pieces were condensed to fewer than 2,000 sub-assemblies to stage, identify and assemble on site, including:

• 2,036 slab anchor bolts;
• 496 adjustable jacks;
• 275 floor support beams (or plate girders);
• 285 floor panels;
• 10 stair sub-assemblies;
• four pre-fabricated under-terrace walls; and
• two fixed terraces, each constructed from 27 panelized sub-assemblies.

The infinity edge of the pool comprises 36 wall segments, 30 sub-assemblies and six end-wall sub-assemblies.

Movement joints and submersed connectors

Given the pool was built atop three high rise towers, engineers had to consider the fact that wind and the force of gravity would cause the towers to sway and move independently of one another. The Skypark as a whole is designed for wind pressures of up to 113 kilometres per hour (km/h) (70 miles per hour [mph]). To put this in perspective, at about 21 km/h (13 mph), it becomes uncomfortable to sit outside; at 35 km/h (22 mph), it is difficult to stand without swaying.

As such, beneath the main pools are four movement joints, designed to help the pools withstand the natural motion of the towers. Each joint has a unique range of motion; the largest movement joint can accommodate a total range of motion of 500 mm (19.6 in.).

The SkyPark pool comprises three separate shells; the middle pool shell is constructed atop the middle tower; the outer shells are constructed on bridges that connect the middle tower with the outer two. The structural bridges between each hotel tower were installed with a 76 mm (3-in.) pitch to accommodate the finished weight of the pool when filled with water.

The three pool shells are joined by uniquely-designed connectors at each of the movement joints. The connectors are submersed, allowing water to flow over them, creating one large recirculating body of water. The connectors double as shallow-water terraces for pool loungers.

Jacking system

In addition to wind, the hotel towers are subject to settlement over time that could cause the original construction plane of any one of the three pool shells to slope.

As such, engineers designed and manufactured custom jack legs to allow for future adjustment at more than 500 points beneath the pool system. This jacking system is important primarily because of the 146-m (478-ft) weir (infinity) edge. In order for the weir edge of the pool to function properly, its elevation has to be within 3 mm (0.1 in.) of its original length, which translates to less than 3.75 mm (0.125 in.) over the entire 146 m (478 ft).

A scale model of the enclosures and submersed connectors was fabricated to simulate the movement joint and test different sealing methods. Using the mock-up, engineers were able to troubleshoot and modify the sealing method to provide a superior product never before used in elevated pool construction.

A group effort

Natare had a number of integral partners who helped make the Marina Bay Sands project a success. The design team included Jaron Lubin of Moshe Safdie and Associates; Jose Silva of Aedas; Howard Fields of Howard Fields Associates International; and Marcus Ng and David Yeo of Innovez. Designers and engineers for Marina Bay Sands included Tony McKee, Justin Hotton and Mark Avery; Cory Dalton, Mark Teeter and Ramey Durbin of Ter Horse, Lamson & Fisk Structural Engineering; and Steve Hoffman of Hoffman Engineering.

 

Marie Lewis is the communications director for Natare Corporation in Indianapolis, Ind. Natare designs and builds swimming pools, spas and specialty equipment for aquatic facilities around the world. She can be reached via mkl@natare.com[4] or by visiting www.natare.com[5].

 

Source URL: https://www.poolspamarketing.com/trade/taking-swimming-pool-design-to-new-heights/

---