Grand Egyptian Museum updates pyramid aesthetic with post-tensioned folded plate roof

Grand Egyptian Museum
Grand Egyptian Museum under construction with the Pyramids in the back ground

For centuries, people have been fascinated by the culture and achievements of the ancient Egyptian civilization. Along with a legacy of art, science, spirituality and engineering, the ancient Egyptians also left in their wake a global trade in artefacts, many of which have been taken from their native Egypt over the centuries for both private collections and public display.

Now, for the first time, Egypt is set to counter that legacy of lost treasures by creating the most comprehensive collection of Egyptian antiquities in a single museum anywhere on the planet. Due to open in 2020, the Grand Egyptian Museum will be the largest archaeological museum anywhere in the world, with more than 100,000 artefacts in its collection. It will also display the full Tutankhamun collection in a single location, with many of the 3,500 pieces on view to the public for the first time.

But it’s not only the exhibits within the museum that have caused excitement around the world. Located in Giza, the museum building itself has already become a landmark ’must visit’ attraction. The project was the subject of an architectural competition, which received 1557 entries from 82 countries, with a winning design by Irish architectural practice, Heneghan Peng, selected for the project. The building’s chamfered triangle shape references the iconic pyramids, while creating a striking, contemporary structure that accommodates a huge, open-plan main hall.

The museum’s unusual silhouette has been achieved thanks to engineering from the project’s structural engineer, Arup, which relies heavily on the structural capabilities of post-tensioned concrete. The building’s design includes a roof with a total construction area of 10,000m2 of post-tensioned folded plates, along with post-tensioned edge beams and a cantilevered wall. The post-tensioning element of the project was delivered by CCL, the specialist in engineered solutions for structures, and the company’s partner in Egypt, CSS. The two companies worked together to provide the materials, equipment and expertise required on site.

Folded Plate Roof

Aesthetically, the folded plate roof continues the chamfered triangle design theme to the roof of the building. Technically, achieving this look involved considerable challenges.

The roof structure is composed of post-tensioned folded plates with different inclinations and spans varying between 18m and 30m. Arup requested that CSS supply CCL post-tensioning tendons containing 19 strands to provide the significant amount of PT forces required for lateral stability and seismic loads. Other design factors also influenced the design of the post-tensioning, including the removal of some of the lateral beams originally designed into the roof structure, which increased the amount of PT forces required.

Interior of the museum showing the folded roof

The relatively slim concrete thickness of the folded plates – just 275mm – and the varying inclinations also created buildability challenges, because it made it difficult to accommodate the live-end and dead-end PT anchors at the intersection of the angled plates. This was addressed at shop drawing stage by the CSS team, who suggested an increase in the thickness of the concrete cover at the intersection of the folded plates from the upper part of the roof. This solution provided the increased thickness needed for the PT anchors in a location where it will not be visible and was approved by both the engineering team and the client.

Beams

The structural design for the Grand Egyptian Museum building also includes six post-tensioned beams, with spans ranging from 14m to 38 m, located parallel to the folded plate roof. These beams support the structural loading of the roof and manage the deflections. Each of these beams was constructed with three tendons and installed using the CCL XM60 anchorage system.

The building also features a 22m long cantilever wall, which is 8.65 metres deep. This wall performs the role of a deep beam and was designed with six tendons, each incorporating 19 strands, using the CCL XM60 post-tensioning system. Once again, the CSS team had to address buildability challenges in the design of the wall at shop drawing stage for the PT installation, due to the narrow 45cm width of this cantilever wall/deep beam.

CCL Multistrand tendons installed on the roof of the GEM

Ahmed Zaky, CEO of CSS explains: “The live-end and dead-end PT anchors for the CCL XM60 system require a minimum concrete thickness of 50cm but the wall had been designed to provide a slim, elegant aesthetic, which could have been compromised by increasing the thickness of the concrete for structural reasons.

“To resolve the problem without altering the visual appeal of the wall/beam, we proposed increasing the width gradually over the course of around one meter of its length. This solution ensured the thickness of the concrete was sufficient to accommodate the PT anchors at the relevant points in the structure, without detracting from the slenderness of the architectural design.”

Once again, the structural engineer and the client were happy with CSS’s proposal and this was incorporated into the final scheme.

Proven Expertise

Unlike many of CCL’s projects around the world, the company was not involved in the Grand Egyptian Museum at design stage, but the involvement and expertise of CCL and CSS were critical in developing the buildability of the design and delivering the project on site.

Explains Tedy Chakhtoura, COO MENA/Africa at CCL: “During the tendering phase, the client’s primary concern was identifying a post-tensioning specialist that could complete this element of the project to the highest quality standards. Speed of project delivery and the availability of experienced personnel was also critical to ensure there was no possibility that the post-tensioning works could cause delays to the wider programme.

“CCL’s PT system and expertise has been proven around the world, including a number of showpiece projects in North Africa, and our PT anchorage system holds ETA and UK CARES certification. Consequently, we were able to offer the client the level of quality assurance they required along with local PT experts through our partner in Egypt, CSS.

CSS provided the shop drawings for all the PT works on the Grand Egyptian Museum project and technical support throughout the design development and construction process. CCL supplied all the strands and anchorages for the programme, according to the design team’s specification, and also worked with CSS on the installation of the PT on site for the folded plates, edge beams and cantilever wall, stressing the tendons using the CCL Multistressing Jack (4000 MG) and CCL Hydraulic Pump (SR5000). Finally, the CSS/CCL team was also responsible for grouting the tendons to complete the PT works.

The PT elements of the project have now been completed and the Grand Egyptian Museum is due to open its doors to the public for the first time in 2020.

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