from draped fabric, define the most effective structural ...designer-engineer developed his concepts...

[Deitingen Service Station, Solothurn Switzerland, 1968]

With the discussion of efficient and sustainable design more important than ever in architecture, we thought it would be relevant to brush-up on the work of Heinz Isler. Born in 1926, the Swiss artist-designer-engineer developed his concepts and methods for thin shell concrete structures in the 1950’s, came to prominence with his constructions in the 1960’s and continued developing his ideas and built-forms into the 1990’s.

[Norwich Sports Village Hotel, Norwich England, 1991, Architect: J.A. Copeland]

An anomaly of the engineering world, he directed his efforts away from the mathematics of engineering and focused on the physical model. This study into physical modeling put emphasis on form and stability. The goal to create structures of high efficiency with the lowest possible environmental impact led Isler to explore 3 types of formwork: molded earth, inflated rubber membranes, and draped fabrics.

The studies with fabric are most interesting to us because of the relationship between the fabric’s capacity for tension and the concrete’s capacity for compression. The small scale models, made

from draped fabric, define the most effective structural curvatures, however the material in this model is primarily in tension –something fabric is very good at. In order to apply this same curvature to concrete, the model is “frozen” with epoxy resins and then flipped 180 degrees, thereby putting the material into compression – a strong characteristic of concrete. This geometry can be scaled up to whatever size necessary. Such simple and elegant relationships between geometry and material properties are fascinating to us.

Adding to the overall efficiency of the built-work, Isler often used fiberboard as the construction formwork, a material known for its insulation qualities. This not only helps keep the heat in but regulates the temperature of the concrete inside and outside the shell, subsequently controlling the expansion and contraction of the concrete.

[Indoor Tennis Center, Heimberg Switzerland]

Complimenting the conceptual and structural importance of Isler’s studies in thin shell concrete structures is a poetry rarely achieved in engineering and architecture. For us architects, it’s a reminder of the important relationship between built-form and the geometries inherent in nature. All

too often, it seems us architects strive to force materials into built-forms which are contradictory to their natural properties and to physics in general. As Isler’s studies demonstrate, the solutions to built-form are often times simple and obvious; the answers are already coded into the material itself.

[Bruhl Sports Center,1982, Solothurn Switzerland, Architect: J.A. Copeland]

[Wyss Garden Center, 1961, Solothurn, Switzerland]

[La Tene Tennis Center, Neuchatel Switzerland, 1983, Architect: J.A. Copeland]

[Truffaut Villeparesis, Lle De France, France, 1977]

[Cafe-Restaurant Wiesentalstrasse, Grisons Switzerland, 1975, Architect: Th Domenig]

[Deitingen Service Station, Solothurn Switzerland, 1968]

[Ecola Nationale de Ski et d’Alpinisme (ENSA), Charmonix-Mont-Blanc, 1974, Architect: Robert Tallibert]

[Sicli Company Building, 1970, Geneva]

“The model has an answer to (nearly) everything” – Heinz Isler

[The Engineer’s Contribution to Contemporary Architecture HEINZ ISLER by John Chilton, Riba Publications]

Resources:The Engineer’s Contribution to Contemporary Architecture HEINZ ISLER by John Chilton, Riba Publications

The Art of Structural Design, A Swiss Legacy, Princeton University Art Museum, David P. Billington

Conceptual Structural Design, Bridging the gap between architects and engineers by O. Popovic Larsen & A. Tyas

All photos by Yoshito Isono, Structurae

Geodesic Shell

The structure of this shell is woven from isocurves and geodesic curves on a surface. Geodesic curves are also called plank lines, they can be build from straigth, but twisted planks. Mårten Nettelbladt studied them on his blog. Geodesic shells build in wood have been studied at the laboratory for timber construction of the EPFL.

Planks generated from lines on a surface with this script: TwistedBeams.zip

The (straight) bamboo strips of this chinese hat are following geodesic lines. Photo by drs2biz.

More Geodesic Shells

Mårten Nettelbladt kindly adviced me of the Korkeasaari Lookout Tower, an example of a geodesic structure build of wood.

The Japan Pavillion at the expo 2000 by Shigeru Ban and Frei Otto is an example of an geodesic shell build of paper tubes.

Ville HaraHUT Wood Studio WorkshopKorkeasaari Lookout TowerHelsinki Zoo, Finland

Situated on a site eighteen meters above sea, with spectacular views of the sea and the city of Helsinki, the tower is a delicately transparent landmark of Korkeasaari Island.

Photo: Jussi Tiainen, HUT photography laboratory

Established in 1889 Helsinki's Korkeasaari Zoo, located on Korkeasaari Island, has animals from Finland and around the world housed in large natural enclosures.

The competition for the design of the ten-meter-high timber tower, presented to students of architecture at Helsinki University of Technology, was organized by the Korkeasaari Zoo in collaboration with Wood Focus Finland.


The load bearing structure consists of 72 long battens, with a section of 60mmx60mm, that are bent and twisted on the site from seven pre-bent types. Over 600 bolted joints hold the shell structure together.Having no weather protection the wood is treated with a linen oil-based wood balm with UV-protection.The free form of Hara’s winning entry, inspired by the natural setting, follows the existing low stone wall and skirts around a small birch grove.



When the drawing of the irregular form proved difficult Hara moulded a plastoline model. Digital images of the model then functioned as a basis for the AutoCAD drawings.Using the level drawings he constructed a 3D-computer model onto which he ”taped” the curved battens to form the grid shell.Students at the Wood Studio workshop developed the draft design further by assembling scale models and exploring structural details.


To test if the pre-bent battens, that form the basket-like grid shell, tolerated bending and twisting Hara laminated full-scale pieces of the battens. When the laminated timber resisted twisting he resorted to steaming, a traditional method in boat building.The effect of surface treatment with linen oil-based wood balm on moisture content was determined by moisture tests and the durability of the joints was proved by tension tests.


The tower was erected by an international group of eight students of architecture. With the hot, sunny summer drying up the timber, the duct pipes that were used for steaming proved useful. It took us three months to complete the job.

The Helsinki University of Technology Wood Studio workshop was started by Professor Jan Söderlund in 1994. The course was aimed to contrast the rather pragmatic building technology courses. It is characterised by innovation and artistic approach. The students are selected by an annual student competition and half of them are foreigners.The department of Architecture now has a new professorship for wood architecture with Professor Georg Grotenfelt running the Wood Studio course.More information on upcoming courses: [email protected]

Area: 82 square metersDesign phase: 2000-2002

Client:: Korkeasaari Zoo (Helsinki)Developer: PWD (Helsinki City Public Works Department)Construction Management

Architectural design:HUT Wood Studio/ Ville Hara, architect, SAFAStructural engineering: DI Hannu Hirsi, DI Lauri salokangas /Nuvo Engineering

Ville Hara (born 1974), architect, SAFAStudied in Finland at Helsinki University of technology and in France at Ecole d'Architecture Paris-Belleville, graduated 2002. Has worked in France, Croatia and Germany (Sauerbruch Hutton Architects), 1999- at SARC Architects Ltd. From 2004 own office Avanto Architects with Anu Puustinen and teacher at HUT.

Nomination for Mies van der Rohe Price 2003; Archiprix 2003: nominated for Hunter Douglas award, participants' favourite; Wuorio Price 2003; Ar+d Emerging Architecture Price 2003

Competitions: Das Neue Berlin 2nd prize 1999, HUT Department of Architecture Wood Studio competition 2nd prize 1999, 1st prize 2000, Funerary chapel competition Vantaa, Finland 1st prize 2003 (with Anu Puustinen)

Various positions of trust: architecture students' guild, HUT students union, the Finnish Association of Architects, The Museum of Finnish Architecture.

Neo Geo: geodesic construction in contemporary architecture The principles of geodesic construction were developed by the pioneering American architect and engineer R Buckminster Fuller in the middle of the last century as part of his efforts to use science and technology to address universal issues. His vision has inspired successive generations of architects and geodesic designs have played a fundamental role in defining the architectural landscape of the past few decades. Architonic takes a look at some recent projects that combine the brilliance of Bucky�s ideas with twenty-first century technology, resulting in complex yet efficient structures with a futuristic aesthetic.

• The MyZeil centre in Frankfurt by Massimilano Fuksas demonstrates the complexity of form that can be achieved with modern materials and techniques

• Geodesic construction is founded on the principle that the triangle is an inherently stable form, independent of size, and that a triangular framework held together in tension enables the creation of structures that are lightweight but profoundly strong. Applying these building methods to spherical forms encloses the maximum interior volume with the least amount of surface area, meaning significant material and cost savings can be achieved. These inherent benefits have ensured that geodesic methods remain a relevant and popular choice for architects and developers seeking to 'do more with less'.

Cornwall, UK: almost two million people visited the Eden Project's biomes in their first year of opening

• One of the most successful and popular modern geodesic buildings celebrates its tenth anniversary this month. The Eden Project in Cornwall, England, has become one of the top three charging attractions in the UK and is a testament to the enduring appeal of geodesic structures and an exemplar of sustainable building techniques. The eight interconnected, truncated domes that form the main part of the design by Nicholas Grimshaw Architects are closely related in form to the original geodesic domes that Buckminster Fuller envisaged as controllable environments that could house people on a small or monumental scale. The domed shape offers practical benefits that are essential to the survival of the diverse range of plants that grow inside: the large, transparent surface allows plenty of natural daylight to enter, whilst the concave interior form creates a natural airflow and reflects and concentrates the warmth, preventing radiant heat loss.

The transparent surface allows plentiful daylight to reach the plants inside the world�s largest greenhouse; photo © Grimshaw Architects

• Buckminster Fuller claimed that many of his designs were �anticipatory,� as they preempted the technology required to implement them to their maximum potential. One of the key obstacles he faced was finding a suitably robust and weatherproof material with which to skin the complex latticed framework – a problem that was subsequently solved by advanced new plastics. The Eden Project�s domes are covered in EFTE foil, a polymer that offers good corrosion resistance and excellent performance when exposed to high temperatures. The triple-layered transparent surface allows daylight to heat the interior spaces and then insulates them, maintaining the stable temperature that the plants inside need.

Shigeru Ban�s geodesic cardboard tower was sponsored by Sonoco, a global supplier of industrial and consumer packaging, and stood on London�s South Bank for the duration of the 2009 London Design Festival

• Cast-aluminium joints connected the cardboard tubes – a method that Ban has used in various previous cardboard-construction projects

• The ease with which geodesic structures can be transported and constructed is an advantage in many scenarios, saving a great deal of time, money and materials. Some of the earliest geodesic structures that Buckminster Fuller built were designed as temporary pavilions, intended to demonstrate the engineering and manufacturing capabilities of America to the world. One of the first geodesic structures seen by the general public was a dome made from cardboard tubes presented at the Milan Triennale in 1954, which came away with the highest award, the Gran Premio. For the 2009 London Design Festival, Shigeru Ban designed his own geodesic cardboard structure – a 22-metre cone made from compressed cardboard tubes that became the tallest paper tower ever made.

�� Nigel Young

• Glazed vertical strips on the northern elevation allow light to penetrate the façade� photo Nigel Young

• At last years Expo 2010 in Shanghai, China, some of the worlds leading architects employed geodesic forms in their designs. Foster + Partners 3,000-square-metre pavilion

for the United Arab Emirates was one of the largest at the fair and featured a triangulated lattice of flat stainless-steel panels joined by adjustable nodes making it easy to construct and demount quickly.

Shanghai, China: the membrane roof that covered the Expo Boulevard created by Knippers Helbig had a total surface area of 65,000 square metres – the largest of its kind in the world; photo Thomas Ott

• The diameter of the glass light funnels increases from 16 metres at the base to 80 metres at the upper edge; photo Thomas Ott

• Expo Boulevard cross section; © Knippers Helbig

• The main thoroughfare at the Expo was created by German engineers Knippers Helbig and featured six enormous 'Sun Valleys', each with a surface area of approximately 5,000 square metres. These structures funnel light and air into the basement area and are joined to a tensile membrane that provides shelter. The entire 1,000-metre-long and 100-metre-wide construction was designed with efficiency in mind whilst also needing to withstand the threat of wind, snow and earthquakes. The building is set to form the centre of a new urban district in Shanghai.

• The Admirant entrance building by Massimiliano Fuksas in Eindhoven, Netherlands, fits five floors of commercial and office spaces inside its amorphous form; photo Rob H’art

• The complexity of the surfaces and interior spaces requires detailed planning, using modelling software to create practical spaces; photo Rob H’art

• Geodesic structures do present some distinct disadvantages for conventional applications. Despite their ability to enclose a high volume using minimal material, the lack of straight sides can reduce the amount of usable space. Advanced engineering software has helped to combat this issue, enabling architects to calculate the optimum position for floors and walls and enabling the design of unusual forms that still retain acceptable levels of functionality.

The fluid form of Fuksas� MyZeil complex connects Frankfurt's Zeil, an important shopping street, with the historic Thurn and Taxis Palace

• The building houses shops, offices, a sports centre, a cinema and various public spaces, with views of the city beyond the twisted glass façade

• MyZeil plan view; © Massimiliano and Doriana Fuksas

• Italian architect Massimiliano Fuksas has employed geodesic principles in many of his recent buildings, including the MyZeil centre in Frankfurt, Germany. The complex, twisted forms that he creates rely heavily on digital software to generate practical spaces that are also organic and dynamic in form. The MyZeil project features a geodesic skin which envelops the site and is pierced by various funnels and voids that allow light to enter the interior and help direct the flow of movement around the building.

The formal language of HOK Architects� Dalí Museum in Florida references the dynamism and contrast that are recurrent themes in Dalí�s imagery� photo © HOK/Moris Moreno

• Yann Weymouth – project architect for the recently opened Dalí Museum by HOK Architects in St Petersburg, Florida – counts Buckminster Fuller among his architectural heroes and thought it fitting to utlilise his methods in this build as Fuller was also a contemporary and friend of the surrealist master. The building features a solid concrete bunker interrupted by a glass and steel �Enigma� that allows natural daylight to enter the large atrium.

Each of the precise and unique components needed to create the Enigma arrived on site pre-coded and mapped to their specific location, ready to be fitted together like a huge jigsaw; photo © HOK/Moris Moreno

• Building Information Modelling (BIM) software was required to visualise the complex forms and evaluate their structural integrity during the development phase; © HOK

• The bulbous geometric construction is the first of its kind in the United States and was made possible by computer-generated 3D models that helped to create a structure that is organic yet remarkably robust. Yann Weymouth says: 'The flowing, free-form use of geodesic triangulation is a recent innovation enabled by modern computer analysis and digitally controlled fabrication that allows each component to be unique. No glass panel, structural node or strut is precisely the same.'

The poured concrete staircase carries visitors from the ground level entrance to the galleries on the third floor; photo © HOK/Moris Moreno

• One of the building�s most important functions is to protect the priceless collection of artworks from the potentially devastating hurricanes that plague this stretch of coastline. In this context, the choice of solid concrete seems appropriate but what about the undulating glass form? Fortunately, the inherent stability of geodesic construction and the use of 4-

centimetre thick, insulated and laminated glass panels means the Enigma can withstand the impact of winds and debris resulting from a Category Three hurricane.

Specialist geodesic dome manufacturer Pacific Domes donated this 40-foot structure to a charity in Haiti following the earthquake in 2010. It now houses a school; photo Pacific Domes, Inc

• Geodesic principles were just one part of Buckminster Fuller�s vision for a world in which advanced materials and engineering contribute to an improved standard of living for everyone. 'Through technology, man can do anything he needs to do,' he claimed, and, with increasingly sophisticated physical and digital technologies available to the current generation of architects, what is required most is a willingness to commit to using them in the creation of buildings that are as efficient and ecologically responsible as possible. In this way, perhaps we can continue progressing towards Bucky�s ultimate ambition: 'To make the world work for one hundred percent of humanity, in the shortest possible time, through spontaneous cooperation, without ecological offense or the disadvantage of anyone.'

airplane shed by uco

Véritable tour de force architectural, la toiture forme un hexagone de 90 mètres de largeur faisant ainsi écho au plan du bâtiment. Les lames de la charpente, espacées de 2,90 mètres, dessinent une trame hexagonale qui évoque le tissage d’un chapeau chinois.

CharpenteLa structure de la charpente est faite de bois lamellé-collé, hautement résistant et offrant des longueurs hors normes, superposé en deux couches dans les trois directions de l’hexagone.Ce maillage permet de franchir des portées importantes d’environ 40 mètres, et de faire de la toiture un élément autoportant, qui repose sur quelques appuis seulement.La toiture possède une géométrie non régulière, tout en courbes et contre-courbes, qui enveloppe les différents éléments du bâtiment, et notamment les trois galeries d’exposition. Cette charpente en bois est l’une des plus grandes et des plus complexes réalisées à ce jour. Des études aérauliques en soufflerie ont permis d’en contrôler les performances.Pour l’anecdote, cette structure s’inspire d’un chapeau chinois trouvé à Paris par Shigeru Ban.

MembraneA l’instar de ce type de chapeau, l’ensemble de la structure en bois est recouvert d’une toile protectrice, membrane à base de fibre de verre et de téflon.

Cette membrane assure une étanchéité à l’eau, crée un environnement naturellement tempéré et participe à l’approche énergétique très poussée de l’ensemble du bâtiment,assurant aux

œuvres les meilleures conditions d’exposition et de conservation.

Les essais sur la toitureLa complexité de la toiture réside dans sa forme, dans ses dimensions (8 000 m2) et dans sa technique de fabrication. Des études aérauliques ont été réalisées fin 2005 pour tester les performances techniques de ce vaste chapiteau qui abritera les espaces d’exposition.La toiture spectaculaire du Centre Pompidou-Metz a fait l’objet d’études minutieuses et approfondies. A l’issue d’un appel d’offres international lancé en 2005, l’organisme nantais CSTB (Centre Scientifique et Technique du Bâtiment) a été retenu pour réaliser trois séries d’analyses : études des actions de la neige, caractéristiques et effets du vent, études du confort au vent.Spécialiste reconnu mondialement, le CSTB, dont le nom est associé à de grands projets comme le viaduc de Millau, l’Arche de la Défense ou des gratte-ciel aux Etats-Unis, est un des seuls prestataires en France dans ce domaine d’intervention. Le CSTB a travaillé sur l’exploitation des données météorologiques locales, avant la mise en fabrication de trois maquettes qu’il a équipées de

capteurs en cuivre. Les essais proprement dits ont débuté en décembre 2005.C’est dans la soufflerie Jules Verne à Nantes aménagée avec d’énormes ventilateurs et des canons à neige que le futur Centre Pompidou-Metz a été soumis à rude épreuve. Huit séries de mesures ont été effectuées pour étudier l’incidence du vent sur le bâtiment mais aussi sur son environnement, ce qui permet d’analyser sa répercussion sur les visiteurs. Une autre maquette a subi pendant plusieurs jours des chutes de neige par -15°C. Les techniciens l’ont découpée pour quantifier la neige accumulée sur les différentes

YO! here is a pretty cool construction system that have been develloped by Frei OTTO and then applied in several building like the Japanese Pavilionby Shigeru Ban with Frei Otto at Expo Hanover 2000, the Polydome of the EPFL (école polytechnique de Lausanne) or the Dowland gridshell by Edward Cullinan Architects + Structural Engineer Buro Happold.

Few words to explain how to build one in your backyard:

1- Do a planar wooden grid that can rotate on crossings...

2- Pull slowly the point(s) that you want to see up until you get the shape you wanted...

3- Block the points that you want to keep on the ground with weights or punctions...4- Cover the grid with thin plank that you nailled into the grid, do this two or three layers...5-You got your own gridshell building!

following some pictures:

Japanese Pavilion, Expo 2000 Hanover, Germany (Shigeru Ban with Frei Otto) .(D)

Polydome de l'EPFL (CH)

Downland Gridshell (UK)

Case Study: Mannheim MultihalleAs introduction to Elisava‘s Advanced Design & Digital Architecture Masters (ADDA), students where asked to work up with an interesting building and describe why they found it interesting. Oriol Carrasco developed a Case Study on the Frei Otto Mannheim Multihalle, constructed in Mannheim (Germany) in 1975, for be part of the RuralCity exhibition held in Mannheim the same year.

One of the most important facts about the Multihalle (and the reason why Oriol chose it) is the generation process of the pavilion, based on a Gridshell.

Otto developed a Gridshell form finding process that involved hundreds of scale models of Gridshells. He developed a catalog with several forms and shapes that the Gridshells can generate when hanged. Just like Gaudi, Otto worked on scale models to see the behavior of the grid he was working on. The studies he did where about form and shape but also involved architectural basic needs, as space and light.

The Gridshell is a structure which derives its strength from a double curvature surface. The most important thing about this kind of membranes is the perimeter, which has to be rigid enough to support the deadweight of the structure and most important, all the loads sitting above it. Otto worked on models with a rigid permiter from which to hang the Gridshells he fabricated. After that he hanged on the Gridshell small loads that would represent actual and real weight of the materials used to build the structure and the membrane.

When the form findig process was over, and Otto just had in mind what he wanted to build, the construction process begun. Take in mind that in that time computers where not as accessible as they are now, so all the calculations where done by hand.

The Gridshell was assembled on the ground and very carefully it was put it in place. Due its dimensions, this process was quite long and a lot of scaffolding was needed. The other important fact about its size was the stifness of the entire structure, Otto’s team designed it composed by hundreds of small triangular cells to give the whole structure the strenght needed. Obviously there were parts that needed and extra structural reinforcement.

The resulting building that Otto designed turn out to be an amazing construction, from the inner space to the smallest details of structure. Finally the building served as exhibition space and hosted the restaurant of the RuralCity exhibition.

If you want to know more about the Frei Otto Mannheim Multihalle, there is an IL (IL 13) that covers the entire work process, detailing technical aspects of the design and showing all construction phases.

Tang Palace by FCJZ

A woven net of bamboo creates a curved suspended ceiling inside this restaurant in Hangzhou, China by architects FCJZ.

The internal spaces of Tang Palace are defined by linear bamboo screens and the central concrete core is wrapped in back-lit bamboo sheets, creating a light-box effect.

Private rooms are located on the upper levels, suspended above and visible through the restaurant ceiling.

Photographs are by Shu He.

More restaurants on Dezeen »

The following information is from the architects:

Tang Palace, Hangzhou

The restaurant is located on the top floor of a superstore in the new town area of Hangzhou, with 9-meter high story height and a broad view to the south. Composite bamboo boards are selected as the main material, conveying the design theme of combining tradition and modernity.

In the hall, to take advantage of the story height, some of the private rooms are suspended from the roof and creating an interactive atmosphere between the upper and lower levels, thus enriching the visual enjoyments.

The original building condition has a core column and several semi-oval blocks which essentially disorganised the space. Hence, our design wants to reshape the space with a large hollowed-out ceiling which is made from interweaved thin bamboo boards; and extending from the wall to the ceiling.

The waved ceiling creates a dramatic visual expression within the hall. The hollowed-out bamboo net maintains the original story height and thereby creates an interactive relation between the levels. We also wrapped the core column with light-transmitting bamboo boards to form a light-box, which transforms the previously heavy concrete block into a light and lively focus object.

The entrance hall also follows the theme of bamboo. The wall is covered with bamboo material which follows the original outline of the wall, turning it into a wavy surface. In this way, the surface echoes the hall ceiling as well as performs a guiding function for customers.

The design of private rooms embraces different characteristics. The rooms on the first level are relatively bigger and share the features of expanded bamboo net from the wall to ceiling and ornamentally engraved wall surfaces. Meanwhile, the different folding angles and engraved patterns make each room different from one another. The rooms above on the south are smaller and feature a special waved ceiling pattern and simple bamboo wall surface, which creates interesting and spacious room features.

The key design concept of the space is that the suspended rooms are connected with suspended bridges and sideway aisles. The semi-transparent wall provides a subtle relationship between the inner and outer spaces, bestowing people with a special spatial experience.

In this design, we hope to create diversified and yet an interrelated interior spaces through the different usages of the new bamboo material, responding to the local culture while seeking intriguing spatial effects.

Project: Tang Palace, Hangzhou, ChinaLocation: 6th Floor of MixC, No. 701, Fuchun Road, Jianggan District, Hangzhou, ChinaClient: HongKong Tang Palace Food&Beverage Group Co., LTD.Area: 2460 ㎡Materials: Bamboo, Composite Panel, Rubbed Concrete

Designer: Atelier Feichang JianzhuPrincipal Designer: Chang Yung HoProject Architect: Lin YihsuanDesign Team: Yu Yue, Wu Xia, Suiming WangConstruction Period: February 2010 – July 2010General Contractor: Shenzhen C.S.C. Decoration Design Engineering CO., LTD Beijing BranchFinish material: Wall – bamboo(1f), marble(2f)/ Flooring – terrazzo(1f), carpet(2f) / Ceiling – bamboo net(1f), painting(2f)

from draped fabric, define the most effective structural ...designer-engineer developed his concepts...

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