Shaken but overlooked: efficiency, economy and elegance in earthquake-prone areas

Are structures outside of the Euro-American canon being overlooked when we discuss structural art? In an essay that was selected as one of three finalist submissions for the 2018 SOM Structural Engineering Travel Fellowship, Tim Michiels argues through examples from Japan and Mexico, that extraordinary structures built in earthquake-prone areas do not always receive the attention they deserve. 1. Celebrated structural art is underrepresented in … Continue reading Shaken but overlooked: efficiency, economy and elegance in earthquake-prone areas

How to form find shells that withstand earthquakes? We asked Tim Michiels who was just awarded the prestigious Hangai Prize.

Yesterday our PhD Candidate Tim Michiels was awarded the Hangai prize for his “Outstanding paper by a young talented researcher under 30”  at the annual symposium of the International Association of Shell and Spatial Structures (IASS) in Hamburg. Tim presented his research titled “Parametric study of masonry shells form found for seismic loading”  during the plenary session on Tuesday. Tim’s award marks the 3rd consecutive  … Continue reading How to form find shells that withstand earthquakes? We asked Tim Michiels who was just awarded the prestigious Hangai Prize.

The secret of egg tapping boiled down: outsmart your peers on Greek Easter

Once a year, engineers can put shell theory into practice in a less conventional way: by winning their family’s egg cracking competition (also known as egg knocking or egg tapping). On Easter Sunday, it is a tradition for Greek and Armenian families to gather and play a game of egg tapping. Similar traditions exist in many different places such as in Cajun communities in Louisiana … Continue reading The secret of egg tapping boiled down: outsmart your peers on Greek Easter

A seismic retrofit for an adobe church in the Peruvian Andes

The Peruvian countryside is dotted with earthen buildings dating back to the Spanish conquest of the Americas. The Spanish adapted traditional European building typologies to the locally available construction material: earth.Many of these earthen buildings have stood the test of time and have become of great monumental value to local communities and visitors alike. Some of them, however, have suffered extensive damage, or even fatal collapse due to one of the threats in the new world not so critically shared by Spain: earthquakes. While buildings were soon adapted and retrofitted to resist seismic action, the combination of the low-strength adobe (mud-brick) and high regional seismicity has remained a concern for many – if not all – subsequent generations.

Remains of earth-cane barrel vault roof of a church near Ica, Peru that collapsed during the 2007 Pisco earthquake. (Image Tim Michiels, copyright The Getty Conservation Institute)

Today, relatively little attention is given within the academic community to the engineering and seismic design of earthen buildings. Despite the availability of advanced structural design codes, powerful calculation tools, and extensive material research labs, experts still struggle to characterize the behavior of masonry buildings, and especially earthen structures, during earthquakes. Thus, designing sensible and non-intrusive intervention techniques to preserve often languishing adobe monuments is a major ongoing challenge.

Front facade of the church of Kuño Tambo (Image Sara Lardinois, copyright The Getty Conservation Institute)

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Our Summer Rammed Earth Experiments 2/3: Construction of swirling rammed earth wall

Before the large swirling structure in Forbes garden could be constructed, a set of tests walls were built to master the construction workflow. The tests walls will also be used to test a different set of erosion protection measures, as one of the goals of our research experiment is to assess the erosion resistance of rammed earth in New Jersey. The first test wall was built out of unstabilized earth with no erosion protection implemented for reference. The second wall was also unstabilized, but plants will be grown on top of this wall in the hope that their roots will slow down the erosion process, while their leafs protect the dirt from driving rain. The third test wall was stabilized on the outside with a 10% lime-earth mixture, which was applied only at the outer 3 cm. This technique is a traditional rammed earth construction technique originating in Spain and referred to as “calicascado” which can be freely translated as “lime shell”. The 4th and final test wall was built unstabilized earth once again again, but half of it was coated using a silicone spray, while the other half was coated with a lime wash. All of the test walls were built with a reusable plywood formwork on top of a blue stone slab..

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Scheme of the test walls
Rammed earth test walls. Both left walls are unstabilized, the wall still in the formwork was built using the calicascado technique.

After the successful completion of the test walls, we moved on to the much larger spiraling wall inside Forbes garden. As explained in the previous blog post, the spiral consists of a lower bench area and a taller wall, separated by an opening. At its lowest point the bench is 40 centimeters high, and at its highest point it is 3 meters tall. Both rest on a blue stone foundation. Again, different erosion-protection measures were implemented. The bottom 15 cm of the entire wall was made out of a 25% lime- earth mixture, and placed on a water impermeable membrane to avoid capillary rise. The outside of the bench and most of the rest of the spiraling wall was stabilized using the calicascado technique after its promising results on the test walls. A great advantage of this technique is that it allows for a minimum volume of soil that needs to be stabilized with lime and thus requires less material transport. To compare the durability of the technique once again a section was left unprotected. Additionally, one section of the wall was entirely lime-stabilized using 6% lime as an extra test.

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Design-and-build bamboo shells

Bamboo is a building material that lends itself excellently to the construction of sustainable gridshells. Two of the Form Finding Lab’s graduating senior students, Lu Lu and Russell Archer (’16), worked under the guidance of PhD candidate Tim Michiels and Professor Adriaenssens on the analysis of a set of hyperbolic paraboloid (hypar) gridshell roofs in Cali, Colombia. The Form Finding Lab’s team collaborated closely with … Continue reading Design-and-build bamboo shells

Happy (rammed) earth day!

(image credit: Pat Dumas, flickr)

In celebration of earth day, we want to show you the explorations of earth construction at the Form Finding Lab, in particular our focus on rammed earth. Rammed earth buildings are constructed by pouring soil into a form work, similar to the one used to make concrete elements. This soil is then compacted in successive layers, either by hand or using tampers to create highly compacted dirt walls like those in the Tuscon Mountain house.

Rick Joy House
Rammed earth walls at the Tucson Mountain House designed by Architect Rick Joy (photo credit: designmilk – flickr)

For his senior thesis, Aaron Katz (’16) studied rammed earth buildings and the earthquake loading capacity of rammed earth walls.  His research project evaluated the application of limit state analysis developed for masonry to assess the overturning of rammed earth walls during earthquakes.

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Destructive form-finding using robotics

Can you improve the resistance of a shell structure by smashing, and subsequently repairing it? To do so you would require a very controlled environment, and thus Form-Finding Lab researchers resorted to Princeton’s School of Architecture robot.

Interactive digital fabrication environment to explore gypsum shell reinforcement from T Michiels on Vimeo.

In the context of the course ARC 596 “Embodied Computation”, a project was developed to explore novel forms for gypsum shell by repeatedly breaking and repairing these types of shells using digitally controlled tools.

The School of Architecture’s ABB 7600 robot is used to repetitively break, scan and repair gypsum shells. The broken shells are repaired by selectively gluing weak areas in order to create a bond that is stronger than the initial unreinforced gypsum. The investigated hypothesis is that after every iteration the newly repaired shell has the potential of a greater load bearing capacity than its predecessor. The reinforcement pattern is directly determined by the shell’s crack pattern and does not arise from an analytical approach typical to common reinforcement strategies. Indeed, the process is not dependent on a preconceived design, but much rather evolves from the intrinsic material properties and the initial form and imperfections of the shell. The process can still be steered by the designer in real-time through a set of interactive overlays in a custom control software.

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Form exploration of shells in seismic areas

News broadcasts showing images of collapsed buildings, ravaged roads and torn-apart cities regularly remind us about the destructive power of earthquakes. While decades of research have greatly improved the understanding of these cataclysmic events, building professionals and researchers continuously try to adapt and employ the most sophisticated numerical methods to improve the behavior of buildings during a seismic event in order to safeguard their occupants.

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Las Manantiales Restaurant in Mexico City, a concrete shell designed by Félix Candela that behaved excellently during the 1985 Mexico City earthquake. (Image courtesy Félix and Dorothy Candela Archive, Princeton University)

Researchers at the Form-Finding Lab of Princeton University ( are exploring the design of elegant and expressive structures that can safely be employed in seismic areas. They focus on shell structures, which are very thin, curved and typically large span structures made out of wide range of materials going from steel and glass, to concrete and even bricks or mud.

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