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 seismic zones

Perhaps the most important duty of engineers is to make buildings safe. As safety is non-negotiable, however, a building’s sound design is commonly taken for granted by critics. Structures are instead often evaluated solely as “structural art,” a term Billington coined denoting a structure’s elegance in form, economy in construction and efficiency in material use [1]. Nevertheless, to gain a full sense of a building’s impressiveness, these three characteristics as well as the risks it is exposed to, and its structural soundness, should be examined and celebrated. It is thus unsurprising that the most praised works of engineering that are considered to be structural art, are located in non-seismic areas. Indeed, when we observe the list of engineers often recognized as structural artists, we see that the overwhelming majority of them, including Telford, Eiffel, Torroja, Ammann, Maillart, Isler, Menn, Dieste, Kahn, Frei Otto, Schlaig and Baker completed their signature works in areas with low or no seismicity. One might posit that creative structural design may be hampered by the safety concerns associated with building in earthquake-prone areas. However, several examples of outstanding structures in seismic zones exist, although many have been commonly overlooked in academia, likely because the relevant literature tends to skew Euro-American in focus, and many of world’s most earthquake-prone areas fall outside Europe and the United States. Investigating these structures, can reveal that seismic risk does not necessarily need to be a burden hampering creative design, but can rather act as an incentive to encourage it.

2. Thin shells: light-weight and thus earthquake-proof

One of the most celebrated structural designers of the 20th century is Félix Candela, but perhaps his most impressive accomplishment, that all of his buildings withstood two devastating earthquakes in Mexico, has hardly been examined or appreciated. Candela’s thin hyperbolic paraboloid shells are scattered across the earthquake-prone soft soils that make up Mexico City. Candela’s Church of Our Lady of the Miraculous Medal (Mexico City, 1955) is a prime example of how elegance and efficiency can be paired with excellent seismic performance. The graceful thin concrete shell structure consists of a set of tilted hyperbolic paraboloid umbrellas that are balanced against one another. The waving surface generates a lofty open space which is graceful in its simplicity, but was also economical as it could be built with reusable scaffolding made of straight-line elements. Most importantly though, by opting for an ultra-thin (less than 2 inches) doubly curved surface, Candela achieved a very stiff and lightweight structure. These characteristics are believed to have played a major role in the structure’s survival, as the induced (mass-proportional) seismic forces were low and the shells vibrated at much higher frequencies than those amplified by the soft soils on which the building stands [2]. Thus, the efficiency in material use can be directly linked to effective seismic design. Indeed, the church (as with all Candela structures) survived the disastrous 1985 and 2017 Mexico City earthquakes virtually unscathed, despite extensive damage to its surrounding buildings.

3. Earthquakes fostered a symbiosis between architects and engineers in Japan

While Japanese architects have largely been celebrated internationally, Japanese engineers have often been overlooked. Japan, however, has a remarkable track-record of achieving some of the world’s marvels of civil works in one of the globe’s most seismically active regions. For example, Japan is home to the Akashi Kaikyo Bridge (Kobe, 1998) which, in an astonishing feat of engineering, was able to accommodate an increase in span from 1990 m to 1991 m due to the relative displacements of the abutments caused by the 1995 Southern Hyogo earthquake [3]. The discrepancy in international attention paid to Japanese architects in contrast to Japanese engineers is particularly unfortunate because the hyperawareness in the country of earthquake risk has fostered a unique symbiosis between architects and engineers. This close relationship is so engrained in construction practice that the Japanese have a term, 建築 (kenchiku), which refers to a single field of structural engineering and architecture.

In Japan, it has clearly been demonstrated that aesthetic design, does not need to come at the expense of safety, as many examples can be found of elegant structures that withstood a series of destructive earthquakes. One of the foremost examples of this engineer-architect partnership is the Yoyogi National Gymnasium (Tokyo, 1964) by Kenzo Tange (architect) and Yoshikatsu Tsuboi and Mamoru Kawaguchi (engineers), which was described by the Pritzker Prize jury as “among the most beautiful buildings of the 20th century[4]. The gymnasium, a marvel of both engineering and architecture, that survived several major earthquakes, is an elegantly sculpted light-weight roof suspended from a cable hanging from two tall concrete masts. Its beauty stems in large part from the simplicity of its structural concept, which can be appreciated as a reinterpretation of a suspension bridge, covered by a tensioned metal cloth.

Another example of Japanese architect-engineer collaboration at its best, is the partnership between architect Toyo Ito and engineer Mutsurō Sasaki. Together they formed the astonishing vaults of the Tama Art University Library (Tokyo, 2007), and the undulating reinforced concrete shell of the Meiso No Mori funeral hall (Kakamigahara, 2006).

Library
Tama Art University Library (Hachioji Campus) (Image by Ishiguro Photographic Institute via Archdaily)

Recently, Sasaki worked with architect Ryue Nishizawa (SANAA) and artist Rei Naito to build the droplet-like concrete shell of the Teshima Art Museum (Teshima, 2010), which was designed with great attention to its seismic performance[5]. Just like Candela who constantly needed to innovate in order to construct his buildings efficiently, this structure’s designers required a clever solution to build the museum in an efficient manner. They developed a smart construction solution, casting the shell’s reinforced concrete directly over a soil mound, which was then excavated from under the structural surface.

4. Conclusion

Torroja wrote that “the enjoyment and conscious understanding of aesthetic pleasure will without doubt be much greater if (…) we can enjoy all the refinements and perfections of the building in question[6]. To fully grasp the refinements of buildings, we need to pay attention to how buildings guarantee the safety of their inhabitants and visitors. In earthquake-prone zones, this means that not only the aesthetics, efficiency and economy of buildings need to be considered, but also their integration with seismic design. In Mexico and Japan alone, over the past 35 years an estimated 60,000 people died during earthquakes, mostly because of building failures. In that light, the value of structures that are both beautiful and safe can hardly be overestimated. Therefore, the innovative and resilient structures examined here, and many more scattered around seismic regions throughout the world, deserve praise and renewed attention of structural designers.

Author: Tim Michiels

References

[1] Billington, David P. “The Tower and the Bridge.” NY: Basic Book Publishers, 1983.

[2] Michiels, Garlock, et al. “Seismic assessment of Candela’s concrete shells and their behavior during the 1985(…) Proc. 2016.

[3] Yasuda, Masahiko, et al. “Seismic design and behavior during the Hyogo-ken nanbu earthquake (…)” Proc. 2000.

[4] The Hyatt Foundation. “Announcement of the 1987 Pritzker Prize Laureate.” Pritzker Prize, 2017.

[5] Sasaki, M. “Structural Design of Free-Curved RC Shells.” In Shell Structures for Architecture. Routledge, 2014.

[6] Torroja Miret, Eduardo., J. J. Polivka, and Milos. Polivka. “Philosophy of Structures,” 1958.

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