The Spherical Mirror Façade

An Article by Sorba

The new art depot for museum Boijmans Van Beuningen is going to be the new landmark in the city of Rotterdam. The building is designed by Winy Maas of MVRDV Architects and is meant to blend in with its surroundings. The façade is made out of double curved glass panels with a mirror coating and expected to be completed this year.

Introduction

Figure 1. Overview of the art depot with the reflection of MuseumBoijmans Van Beuningen

The design of MVRDV included the completely reflecting spherical façade. In this scheme Sorba develops the façade for main contractor BAM Bouw en Techniek. To build this façade Sorba uses double curved mirror glass panels. Through the use of glass, the mirror effect will be crystal clear. The radius of the art depot differs on ground level and at the roof. At ground level the radius is only 40 meters, and at the roof this extends to 60 meters. The façade counts 26 rows of panels with 64 panels per row. This leads to a total of 1664 3D curved panels. The glass panels are produced in China and each row has a different curvature in the glass.

The spherical and reflective façade is the greatestfeature of this new development. Sorba has been awarded with the special task to develop, engineer, produce and install this unique façade.

Figure 2. The reflection of the skyline of Rotterdam63

Similar projects compared to the Art Depot

The new art depot seems unique, but there are features that can be found in other buildings and structures throughout the world. These are not made by Sorba but give insight in the uniqueness of the Art Depot in Rotterdam. Many people compare the reflective bowl to the Cloud Gate (Anish Kapoor) artwork in Chicago, also known as The Bean. This landmark in Chicago is like the Art Depot and features a lot of double curves, but The Bean is made out of polished stainless steel and not out of glass. The polished stainless-steel panels are welded together and then polished again to create a seamless look.

A different glass structure that features double curvature is the Emporia in Malmö, Sweden. In the center of this building the architect designed a diagonal slit in the glass façade. This glass however is also the outer wall of the building and therefore they used insulated glass. This insulated glass is installed into visible frames, unlike the glass panels of the Art Depot in Rotterdam. For the Art Depot the seams need to be as invisible as possible, therefore a structure of frames like the Emporia could not be used. The few windows and doors in the art depot have a frame structure and insulated glass like the Emporia.

The challenge for the Art Depot for Boijmans Van Beuningen was to create the reflective façade with as little seams as possible. The solution was found in the double curved glass with a reflective coating. This glass will function as a cladding and not as the structure of the building. The 'glass' is applied as glass panels, just like an outer shell made out of aluminium. Therefore, Sorba had to come up with a substructure to fit the panels to the concrete base. This substructure consists of an aluminium frame that is glued to the panel. Subsequently, this panel hangs on brackets on the concrete base of the Art Depot.

Construction of the panels

The glass panels are installed onto the façade on stainless steel brackets that have been anchored into the concrete structure. The placement of these anchors has been measured from the 3D model, while taking measurements on a curved building is nearly impossible. After the installation of the brackets, the façade has been insulated. Next was the installation of the adjustable hooks, on which the glass panels are hanged. These adjustable hooks are designed in a way that the seams can be adjusted horizontally and vertically, to line them out perfectly.

Figure 3. The brackets installed onto the concrete base

Figure 4. Close up of the adjustable hooks with two panels hanging from them.

The design of the façade asks for a smooth surface ,that is why Sorba has glued an aluminium frame to the backside of the glass panels. The glue is the load bearing factor between the aluminium frame and the glass and thus has to be certified. Therefore, the gluing process is executed under specific requirements to guarantee its strength. This process is closely monitored, and quality controls are being held on regular intervals. With the aluminium frame, the glass panels are mounted to the façade. However, the city of Rotterdam required a second support system aside from the glue. Therefore, we placed tiny metal plates around the corners of the panels. These are connected to the aluminium frame and lock the panel in place.

Insulated glass

In most of the façade, the glass is used as the outer shell of the building, but at some spots, the glass makes up actual doors and windows. At these spots, Sorba placed insulated glass panels. In total there are 186 of these insulated glass panels in the façade. These have a gradient transition from reflective to translucent glass. This gradient transition is made using a dotted pattern. On the lower levels, the insulated glass has a resistance level of WK4 and on the higher levels, we used glass with a resistance level of WK3.

The doors are fitted into the façade and will function like bus doors. The doors will open to the front and subsequently slide to the side. This way, when closed, the doors will disappear in the façade. The doors are built out of heavy steel frames on which the panels are glued. After assembly, the smaller two-panel doors are about 4 meters high, 2.3 meters wide and weigh around 1000 kg. The bigger truck lock doors, three panels high, are about 5.6 meters high and 2.3 meters wide and weigh around 1500 kg. These will be installed with specialized cranes, because of the odd shape, heavyweight and fragile nature of the doors.

Figure 5. Installation of glass panels with boom lifts.

The entire project

Apart from the façade, Sorba also works on the cladding of the roof construction of the Art Depot. This roof construction is cladded with an aluminium composite material with a mirror finish. These panels are almost 7 meters long to create minimal breaks in the reflection. The façade and the entire building will be completed in 2020. The opening of the Boijmans Van Beuningen Art Depot is planned for 2021.

Figure 6. Close up of window in the façade, fitted outwith insulated glass

About Sorba

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Frequent updates on Sorba’s progress on the Art Depot can be found on our LinkedIn page and website. Scan the QR Code to go to a video about the entire process of the façade.