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IMd explores the structural capacity of recycled plastic with 3D-printed pavilion made of PET bottle

IIMd Raadgevende Ingenieurs has been working since 2019 on the development of an innovative 3D-printed pavilion in Rotterdam made entirely from recycled PET bottles. The structural use of this polyester plastic on this scale does not happen often, but for IMd it is not only the final product that is of relevance. The very motivation for this project lies in its long-term experiment: What is the structural capacity of the recycled material? How long will the structure hold its shape? Can this material find an architectural future? These are questions that drive the IMd team - the four directors in particular. With their curiosity and energetic approach, they are putting an end to the stigma of the conventional structural engineer in one fell swoop. And may that be the very essence of it!

Directors Rob Stark, Paul Korthagen, Remko Wiltjer and Pim Peters have been leading IMd Raadgevende Ingenieurs as of one mind for the last decade. A key objective is to facilitate innovation and progression, with a team of new school structural engineers and modelers. A desired consequence of this is an increased recognition for the structural engineer in the construction process, as the gentlemen also have a mission to demonstrate the importance of a collaborative and creative structural engineer. After all, the structural engineer can make the difference with which the building quite literally stands or falls! This mission has nothing to do with big egos, but all the more with great pride and even greater ambitions. Remko: "After all, it's a great profession! An architect creates beautiful designs, but we contribute to making sure it actually turns out.”

The structural engineer is the one making the difference, with which a building quite literally stands or falls.

Professionals on an innovation mission

Upon entering the old machine factory on Piekstraat, it is immediately clear that IMd is not just another engineering firm. Here, in Rotterdam's Feijenoord district and overlooking the River Maas, a fresh wind blows, literally and figuratively. IMd chose this building as its home base for a reason: it was part of the mission of the then new directors, Pim and Remko, to give the engineering profession new allure and to rejuvenate the company in terms of image and team. This included new premises. They were closely involved in the development and reuse of the old factory. The building brought the company the title BNA Building of the Year 2012 Delta Region as well as a lot of international exposure. In 2018, the four gentlemen directors published the book The Art of Construction. The pavilion - intended to create additional workplaces at height - is the latest in a series of "stunts" by the company in search of different perspectives and acknowledgment. With this, they are demonstrating that the plastic polyethylene terephthalate (PET) can be properly reused and offers also structural qualities.

The structure is not an end in itself, but primarily part of a research into the material and its opportunities.

The idea for this pavilion originated in 2019 and was elaborated that same year. The structure is not an end in itself, but rather part of a research into the material and its opportunities. When the structure loses its shape or strength over time, the material can simply be reused. Paul: "One purpose of the large open space of this building was to offer employees the freedom to change their working spaces. With the growth of recent years, that excess space became less and the need for more workstations arose. We thought it would be fun to give the distinctive crane track in this building a function by placing a structure on top of it. A search for the right concept and material led to PET, which is printable and recyclable. We intended to test the plastic for further properties and demonstrate that it can do more than pollute oceans." The curiosity and fun that this experiment illustrates is characteristic for the company. Pim: "You can't claim to be innovative without experimenting yourself. The pavilion is illustrative of how we think and work as a company. We are not afraid to try new things and aim to connect sustainability, design and architecture in this way."

"We intend to test the plastic for further properties and demonstrate that it can do more than pollute oceans."

First structure made of recycled PET bottles

From the very start of this ambitious plan, IMd worked closely with Ector Hoogstad on the architecture of the structure. TUDelft conducted research into material properties such as bearing capacity and acoustics. The Spanish company Nagami - known worldwide for the 3D printed chairs of Zaha Hadid Architects - is responsible for the printing process of the structure. Rob: "At the time, we couldn't find a party in the Netherlands that was able or willing to print the pavilion. Indirectly we then came across Nagami."

The structure consists of several shell parts, each weighing about 300 kilograms. The shape of the pavilion is a derivative of the material properties. Pim: "The material bears itself and has a slender shell that is partly hollow, to reduce weight." The complex, organic shape it results in is easy to print, and so the pavilion is an interplay of material properties and manufacturing technology. The pavilion will be a paragon of innovation as well as sustainability and reuse. In turn, so is the IMd building, and what's more, the building's height and crane track are put to good use: the art of construction in optima forma.

"The art of construction? Finding ways to build more effectively and more affordably."

The actual art of construction is not just the calculation of structures themselves, it turns out. The art lies actually in the step before and after. Not looking how something can be done, but how something can be done better. Or more sustainable. Or more affordable. That is the value of a good structural engineer, says Remko. "When an architect comes up with the first ideas for a building, we think about the realization, but also about alternatives in material applications and guaranteeing stability. We are constantly looking at how something can be done differently and smarter."

Not passive, but progressive

Whereas many structural engineers simply calculate what the architect draws, the IMd structural engineer is critical and proactive. The docility that seems to characterize many structural engineers does not apply to Remko. "During my career I regularly questioned certain solutions for buildings: sometimes the logic behind them was completely lacking. A building might stay standing, but it would make it much more expensive, for example. Actively contributing ideas and designs requires a different kind of structural engineer, and we have gathered that around us here, not by chance." Architects and clients like to spar and need support, Remko says. "That's what I like about this profession: you have substantial input. In America, you're a big boy as a structural engineer and, when building a 500-meter tower, the most important person of all. Yes, maybe I miss that recognition a bit here." His first project of his own, Remko remembers well. "I calculated the entire load-bearing structure and had the feeling of actually contributing, which was thrilling." Although the pure calculation and drawing is the actual craft of the structural engineer, Remko finds the collaborative thinking and design at least as important. "With our vision, we aim to inspire the construction world, a very traditional world. You don't just experiment with plastic for a client, so that's why we're first doing it for ourselves."


About IMd

IMd Raadgevende Ingenieurs (1960) is an independent engineering firm at heart, where a team of 60 women and men put their expertise at the service of developers, contractors and architects. They strive for smart, efficient but above all economic constructions that make buildings feasible. IMd ensures that the architect can realize his or her building, that consultants can perform optimally and that the contractor can build quickly and simply. IMd calculated and designed projects such as Depot Boijmans Van Beuningen, the transformation of FENIX and The Modernist (Rotterdam), Amstel Tower, Floating Gardens and Vertical (Amsterdam), Grotiusplaats (The Hague) and A Pier (Schiphol Airport), among many others.

60-Year Anniversary

In their 60th anniversary, the company combined the craft of their craft with innovation of the profession. Remko: "As a company we carry the valuable experience of 60 years with us, but in addition we are still innovating. That's what we believe is important and what sets us apart."

Text: Studio Goldfinch, Priscilla de Putter


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