INEFFABLE: Structure and Space in Boston Architecture by Cyrus Dahmubed

INEFFABLE structure and space in boston architecture

cyrus dahmubed sulafa hariri will langevin

contents community T college

1 cables in 9 tension

2 3 4

START

5 6 7 8 9 10

1 spatial truss rigid frame 3 pinned frame 2

11 12 13 14 15 16 17 18

END

12 vault

tie-bar in 11 10 wood arch tension T back bay

masonry 4 arch

6 steel arch 5 7 thin shell planar 8 slab truss

intro We set out from Boston’s North Station with the simple goal of finding and assessing realworld examples of structural elements taught and studied in the safety of the classroom. Within moments, however, we discovered that our journey to document trusses, cables, domes, vaults, and the panoply of objects that collectively create our built environment would take us on an adventure through a city’s past and present, its struggles and triumphs, and lead us to questions of tectonic authenticity, the importance of historicity, the balance between architect and engineer, and even the very definition of “built” and “building”.

TEAM: cyrus dahmubed will langevin sulafa hariri DATE: 10|19|15 ARCH 2230: structural systems northeastern university prof. michelle laboy

Our walk explored a meandering path that used Boston’s Greenway (the product of the infamous Big Dig) as a spine, leading us through a part of the city that has been built, rebuilt, demolished, and built again for nearly four centuries. Through this, we investigated hundreds of years of architecture and came to understand that in design, all is not always as it seems. Buildings may hide, expose, celebrate, or even lie about the structures that hold them up, but the clever eye and the thoughtful mind can uncover truth in architecture, no matter how deeply beneath the skin it may lie.

cables in

tension PROJECT: leonard p. zakim bunker hill memorial bridge ARCHITECT/ENGINEER: hntb DATE: 2002 TYPE: cable-stayed bridge FEATURE: cables in tension

FBD | DETERMINATE

pins

Despite being a relatively new addition to the built environment, the Zakim Bridge has quickly become a symbol of the city. Its symbolic importance is ultimately a result of its strong and powerful visual impact, which in turn is a product of the celebration of its structural system.

The bridge’s main span stretches 745 ft. while its width of 185 ft. made it the widest cablestayed bridge in the world at the time of completion. Cables in tension carry the load of the deck up to the two towers, designed to mirror Charlestown’s Bunker Hill Monument, and the towers transfer the load to the ground. Importantly, the deck of the bridge cantilevers two lanes of traffic outside of the cable plane.

tie-bars in

tension PROJECT: back bay station ARCHITECT: kallmann, mckinnell, + wood DATE: 1987 PROGRAM: intermodal transit center FEATURE: tie-bars in tension Bostonâ&#x20AC;&#x2122;s Back Bay Station is an intermodal transit center designed by architects Kallmann, McKinnell, and Wood, best known for Boston City Hall. The elegant late-Modernist design features a central concourse of concrete and glass blocks supported by massive wooden arches. The horizontal thrust created at the base of the arches is resisted by tie-bars kept in tension.

FBD | INDETERMINATE

pins thrust resolution

In tandem, the arches and tie-bars help create an architectural and structural expression reminiscent of older, larger train stations, and serve to monumentalize the stationâ&#x20AC;&#x2122;s concourse.

planar

TRUSSES PROJECT: cafe pavilion at quincy market ARCHITECT: benjamin thompson + associates DATE: 1976 FUNCTION: cafe pavilion FEATURE: planar truss During the massive renovation and restoration of Quincy Market in the 1970’s, a series of small pavilions and glass enclosures were added to the newly created festival marketplace. Benjamin Thompson and Associates borrowed the formal composition of the market’s main buildings for the design of these small structures.

FBD | DETERMINATE

pins

The fairly simple Belgian planar trusses that compose the roofing structure of the Café Pulse pavilion support a glass roof. The decision to leave the thin truss struts exposed is unsurprising given Thompson’s Modernist principles, and creates a significantly lighter interpretation of the much heavier, granite market buildings, while simultaneously providing a glimpse into their possible structural systems. 4

spatial

TRUSSES PROJECT: haymarket station busway ARCHITECT: kallmann, mckinnell + knowles DATE: 1967 PROGRAM: parking garage + transit center FEATURE: spatial truss canopy The Haymarket Station Busway canopy is a massive spatial truss suspended from the underside of the Government Center Garage. Spanning 130 ft. on its longest edge, it provides form and shelter for one of Bostonâ&#x20AC;&#x2122;s busiest bus stations.

FBD | INDETERMINATE loads on joints

pins

The fully visible structure creates an elegantly filigreed contrast to the Brutalist parking garage that surrounds and supports it. Spatial trusses (also called space frames) volumetricize planes by using inverted pyramid forms to support loads. The system relies upon and enhances the inherent rigidity of the triangular form by constructing it in three dimensions.

MASONRY

ARCHES PROJECT: hall ARCHITECT: 1740: john smilbert 1806: charles bulfinch DATE: 1740-42, 1806 PROGRAM: meeting and market hall FEATURE: brick arches One of the oldest and most famous buildings in Boston, Faneuil Hall has served as a center of the city’s commerce and culture for nearly three centuries, enduring significant changes brought on first by fire and later by the city’s need for an expanded space. As it exists today, the building is primarily the work of Charles Bulfinch, commonly cited as America’s first great architect and the man who designed many of Boston’s most famous late 18th- and early 19th-century buildings.

FBD | DETERMINATE fixed arches load

load thrust resolution

rigid reactions

load thrust resolution

rigid reactions

When Bulfinch expanded Faneuil Hall in 1806, he significantly increased its footprint, added four bays and a third floor, and moved the cupola. The resultant structural system is displayed on the building’s facade through a pattern of brick arches and pilasters. The brick arches work to transfer the stereotomic, vertical dead loads of the building 6

trussed steel

arches PROJECT: marketplace center ARCHITECT: benjamin thompson + associates DATE: 1986 PROGRAM: shopping arcade FEATURE: trussed steel arch + vault

FBD | DETERMINATE two-hinged arch/ adjustment resolution loads transfer from trussâ&#x20AC;&#x2122;s joints to arch

Building on the phenomenal success of the Quincy Market rehabilitation of 1976, Benjamin Thompson and Associates developed a new shopping and office complex at the north end of the Quincy Market complex called Marketplace Center. At the center of the building and on-axis with Quincy Market is an open-air space covered by a hipped glass roof supported by a complicated system of trussed steel arches. Two of these cross each other diagonally to create a groin vault and four others act in two dimensions at the ends of the vault and arcade. At the base of the arches, the thrust of the axial arches is restrained by rectilinear trussed beams. This space updates and makes plain the structures and forms repeatedly found in buildings within the Quincy Market complex and creates a light and filigreed pavilion-like space.

pins

wood

ARCHES PROJECT: back bay station ARCHITECT: kallmann, mckinnell, + wood DATE: 1987 PROGRAM: intermodal transit center FEATURE: glulam wood arches

FBD | INDETERMINATE

Back Bay Station’s glue-laminated (glulam) wooden arches are a massive and beautifully articulated structural system. The arches’ lateral thrust is resisted by the tie-bars previously addressed, and together these two systems are reminiscent of much older Neoclassical vaulted train stations. pins

pins

The vertical load of the roof is transferred to the arches through beams that span the full width of the station’s main concourse, which are connected to vertical members that essentially synthesize the distributed roof load into five concentrated loads evenly divided over the span of each arch.

va u l t s PROJECT: boston public library ARCHITECT: rafael guastavino for mckim, mead, + white DATE: 1889-1895 PROGRAM: public library FEATURE: guastavino tile vaulting

FBD | DETERMINATE

thrust resolution

Boston Public Library is a central and fundamental cultural center for the city and region. Designed by Charles McKim of McKim, Mead, and White, the library is now the largest public library in the country. The building features the revolutionary Guastavino tile vaulting system throughout, which are left entirely exposed in many cases. The Guastavino vaulting system used tiles to create a fireproof structural system that was stronger, cheaper, and lighter than the comparable steel technology of its day. The selection of Guastavinoâ&#x20AC;&#x2122;s system was a product of concerns over fireproofing, particularly crucial in library architecture. Guastavino had theorized, though not proven, that his tile joinery method created vaults that functioned monolithically and thereby exerted no lateral thrust, (Ochsendorf, 54) though this is now known to be untrue.

rigid

continuous vaults resolutions/ form-active structure/ translationsl surface

DOMES PROJECT: massachusetts state house ARCHITECT: charles bulfinch DATE: 1795-98 PROGRAM: seat of state government FEATURE: wood + copper dome The Massachusetts State House is an exploration of Bostonâ&#x20AC;&#x2122;s design history. Originally designed by Charles Bulfinch, the home of government for the Commonwealth sits atop Beacon Hill and features additions by Charles Brigham, and later the firm of Sturgis, Chapman, and Andrews.

FBD | INDETERMINATE form-active structure compression ring

tension ring support

The building is crowned by a wood-framed dome clad in copper produced by the Revere Copper Company. Significantly, the dome is built of wood and acts as a traditional dome with compression at the top and tension at the bottom. At its base, the lateral thrust of the State House dome, like all others, is buttressed by a tension ring. Through this design, Bulfinch successfully appropriated the dome from a symbol of religious architecture into one of American political strength and equity. This symbol has endured to this day, being adapted by capitol buildings around the country and world.

FRAME:

PINNED PROJECT: city hall plaza community arcade ARCHITECT: chan krieger DATE: 2001 FUNCTION: arcade + pavilion FEATURE: cantilevered pinned frame + pinned cables The filigreed structure of the Boston City Hall Plaza Community Arcade is intended to define the edge of the plaza at the urban scale, and attempts to soften the surrounding Brutalist architecture. The Arcade implements a number of pinned elements to maintain structural equilibrium. Wooden canopy shading structures are cantilevered from metal columns, and cables pinned to the columns and frames are thereby held in tension, providing additional vertical support for the canopy structures. This leaves the ground plane largely open in order to encourage events such as farmers markets and festivals, while the canopies define and form the spaces beneath them.

FBD | DETERMINATE

multi-force members cable (tensile force) cable (tensile force)

Ď&#x2030;

pins

rigid support

frame:

rigid PROJECT: new england holocaust memorial ARCHITECT: stanley saitowitz DATE: 1995 PROGRAM: memorial towers FEATURE: monolithic welded steel beams The New England Holocaust Memorial implements a beautifully simple and elegant rigid frame structural system to create an emotionally charged, multilayered reading memorializing one of the most tragic events in human history. The six towers of welded steel beams and 54 ft. columns rise as individual monoliths, legible at multiple scales as urban composition, memorial, pathway, marker, and eventually represent specific individuals murdered during the Holocaust. The rigid frames support glass panels hung as a curtain wall from the primary structure, all of which are etched with the numbers that were tattooed onto concentration camp inmates - 6 million in total. The formally simple memorial fully expresses its structural system through the a minimalist design that reveals its details as a series of scalar and experiential moments.

FBD | INDETERMINATE wind/snow/material weight loads

multi-force members

load path

rigid supports

thin shell PROJECT: boston harbor islands pavilion ARCHITECT: utile, inc. DATE: 2011 PROGRAM: visitor + info center FEATURE: thin shell canopy The Boston Harbor Islands Pavilion features two thin shell concrete slab canopies, which construction photos reveal to contain steel reinforcement bar (rebar). The elegant combination of steel and concrete creates a strong shell capable of withstanding considerable forces in both compression and tension. Because of its proportions, the canopy is further supported by thin steel beams.

FBD | INDETERMINATE distributed load/ uniformly applied load thin shell load

welded rigid connection

rigid supports

beam reaction

welded rigid connection

rigid supports

The Pavilion’s canopies also curve and fold into a canal to funnel water for conservation and to articulate this as an architectural concept. This curvature, however, appears to be a primarily formal idea without much structural purpose, which is indicated by the presence of steel horizontal support beams beneath the canopy.

slabs PROJECT: boston harbor garage ARCHITECT: i.m. pei + associates DATE: 1971 PROGRAM: parking garage FEATURE: concrete slab Located at Bostonâ&#x20AC;&#x2122;s ever-evolving boundary with the ocean, the Harbor Garage was built along with two 40-story residential towers. Now the site of a proposal for two more towers, one as tall as 600 ft., the Garage is the nexus of a debate that encompasses many of the most prescient urban issues in Boston. Because it is a parking garage, it must be designed to handle heavier-than-usual live loads of moving and parked cars. This is managed through steel-reinforced concrete slabs that transfer these loads directly to large columns through rigid connections. The use of concrete slab architecture is a logical solution in parking garages, which require large, column-free spaces. Because concrete and steel work harmoniously in compression and tension respectively, concrete slabs are the ideal building material for parking garages and other similar structures.

FBD | DETERMINATE reinforced concrete slab/ rectangular slab act as one-way spanning system Ď&#x2030;

columns connected to rigid beams

rigid supports

spatial

TRUSSES TOP: montreal biosphere ARCHITECT: r. buckminster fuller BOTTOM: haymarket station busway ARCHITECT: kallmann, mckinnell, + knowles

Considering the timescale at which architectural and structural innovation occurs, the spatial truss has had a relatively brief and disproportionately tumultuous history. Developed independently and at different times by both Alexander Bell and R. Buckminster Fuller, the spatial truss sometimes referred to as the space frame - has become a fundamental and influential structural system employed by many of the world’s most important architects. The spatial truss is the volumetricization of a plane - frequently made from glass - and as such can perhaps be thought of more as a way of giving a plane a self-supporting structure, rather than as a large scale, complicated, structural system. The rare exception to this rule can be found amongst the work of R. Buckminster Fuller, who throughout the 1950’s and ‘60’s created massive geodesic domes structures from glass

and the pyramidal spatial truss form. While two prominent examples of a spatial truss exist in Boston, neither rivals Fuller’s geodesic domes in their scope, complexity, or scale. Perhaps the most famous extant variation, is the dome Fuller designed and built for Expo ‘67 in Montreal. Originally clad in acrylic that burned away during a fire, the Biosphere and its steel spatial trusses have withstood the test of time. Because it is now unclad, it raises a unique question: without a skin, does the architectural success of the spatial truss system rely entirely on the architect’s ability to use them to form space? Without its cladding, the biosphere also highlights a structural point: in single-plane spatial trusses “roof connections should be made at panel points” (Ching, et al. 243), but because the spherical dome has no “roof ” per se, its connections to the ground are 15

spatial

TRUSSES TOP: haymarket station busway ARCHITECT: kallmann, mckinnell, + knowles BOTTOM: jfk library + museum ARCHITECT: i.m. pei

presumably managed through the same spatial trusses that make up the entire structure of the geodesic dome. Conceptually, the transformation of spatial trusses into domes allowed Fuller to explore ideas of utopianism, intensive climate management, and the simplification of all buildings through one structural system. While his domes ultimately failed to meet their potential because of a variety of shortcomings, they have grown into lasting architectural symbols of modernity and futurism. This has been partially because the apparent lightness of the structure and complimentary cladding evokes images of plasticity, and the diaphanous ephemerality of the skin suggests a ineffably thin boundary between interior and exterior, simultaneously explicitly defined and nearly imperceptible.

examples of spatial trusses are the previously discussed Haymarket Station Busway canopy of 1967 by Kallmann, McKinnell, and Knowles and the central atrium of the John F. Kennedy Presidential Library and Museum of 1977-79 by I.M. Pei. The latter is an impressive 110 ft. tall glass and steel truss space that serves as Pei’s early study into the spatial truss system. Here, both the ceiling and three of the walls are expressed as one continuous glass pavilion with the ceiling’s load transferred directly to the vertical walls. The result is a space that both structurally and experientially functions very similarly to Fuller’s Biosphere, with each truss relying on the one beneath it for support. A crucial difference, however, is that the Library’s atrium has retained its cladding, which is tinted a dark blue and therefore reads as a single object from the exterior and a fairly densely filigreed space from within.

In Boston, the two most significant 16

spatial

TRUSSES TOP: jfk library + museum ARCHITECT: i.m. pei BOTTOM: louvre pyramid ARCHITECT: i.m. pei Pei eventually evolved the system implemented at the JFK Library into his iconic pyramids at the Louvre Museum. Completed in 1989, the pyramidal form channels a minimalist aesthetic and monumentality that allows it to both balance and pay reverence to the palatial museum building in whose courtyard it sits. Each pyramid is further articulated as one massive module of a spatial truss, and the scalar progression from urban monument to structural detail grants the project a resolution so reverential as to imply a sacred reading. The ability of the spatial truss to be adapted so freely into such a variety of forms is one of its many merits. By volumentricizing planes, the spatial truss creates the possibility for architects to craft nearly any space and form while maintaining a unique levity that would be much more difficult to achieve through other more rigid materials such as

poured concrete. An important consideration, however, is that small-member spatial trusses of the kind examined herein are not typically capable of carrying significant additional loads. They therefore present a tremendous amount of opportunity as an exterior shell and cladding system, but have limited potential as major internal structural elements unless they work in tandem with a secondary system that ensures all loads are always concentrated at pinned joints. In Building Structures Illustrated, Francis Ching takes special care to mention that â&#x20AC;&#x153;space frames should be sloped or cambered to drainâ&#x20AC;? (Ching, et al, 243) because significant rain or snow accumulation could damage both the cladding and truss. Spatial trusses present a truly harmonious marriage of structural and aesthetic intentions. Their beauty and impact a result of the use of a single module to create ineffably subliminal structures and spaces. 17

cyrus

dahmubed

PROJECT: boston harbor islands pavilion ARCHITECT: utile, inc. DATE: 2011 PROGRAM: visitor + info center FEATURE: thin shell canopy Having already been fairly familiar with much of Boston’s significant architecture, I undertook this walk with the intention of finding a new appreciation for known buildings through a deeper understanding of their structural systems. I was somewhat surprised to find, ultimately, that I became most fascinated by Utile, Inc’s Boston Harbor Islands Pavilion of 2011. Though I had previously admired the pavilion for its elegant and simple beauty, understanding the intricacy of a structural system that allows for such a thin and apparently rigid concrete slab to be so intricately and delicately folded granted me a much deeper affinity for the structure’s poetry. Upon first investigating the structure, I postured that the bend in the concrete canopy may cause it to act as a folded plane. But review of course materials revealed that folded planes must have sharp angles in order to resist lateral thrust between each fold and

successfully carry loads to the periphery of the plane. The canopy is nevertheless a compelling design both formally and structurally. Narrow steel beams support the canopy from below, and are split axially as they “bend” to the canopy’s poured form and visual weight. This creates a channel for water collected by the roof, which is then funneled from one canopy to the next through an everdeepening canal that implies a geologically scaled erosion. Finally, the water pours off the canopy in an exaggerated spout and falls into a collection vessel that has experienced erosion from the concentrated water falling on it. The ability of reinforced concrete to be molded into and maintain nearly any form is the result of a beautifully symbiotic relationship between concrete and steel, the former bearing compressive loads and the

latter tensile. At the Boston Harbor Islands Pavilion, this creates the possibility for an incredibly evocative canopy that, though a single plane, has the sensibility of evolving terrain and landscape. The experience of exploring the city and reconsidering familiar architectural friends with newly gained structurally knowledge was an incredibly gratifying way to implement the lessons learned in class and through course readings. Particularly noteworthy to me was the way in which a building’s structural system may not be what it at first appears to be. Some buildings may intentionally hide their structural processes, while others, such as the Harbor Islands Pavilion even through a celebratory expression of its thin shell canopy, may leave room (or perhaps create space) for some functional and structural ambiguity.

sulafa

hariri

PROJECT: leonard p. zakim bunker hill memorial bridge ARCHITECT/ENGINEER: hntb DATE: 2002 TYPE: cable-stayed bridge FEATURE: cables in tension The Leonard P. Zakim Bunker Hill Memorial Bridge really stood out amongst all the projects we investigated as the best integration of architectural intent and structural system. In my opinion, it represents a correspondence between structural form and architectural spatial intent, but it even goes beyond this. It is even more than correspondence; it is the celebration of structure through all means. The thin concrete span is made possible by using the tensile force of the cables to transfer the loads to the large, thick towers, then to the ground. By expressing the resolved method of the large, thin span, which in this case features the use of cables, the structural system became a fundamental design element - an iconic one. It is very clear that in this example, usage and structure were considered together as an integrated entity. The harmony and correspondence

between structure and spatial composition is what makes architectural forms visually appealing to me. This approach is present in the Zakim Bridge. In addition, by illuminating the structural elements with differently colored lights every day, the bridge is strikingly appealing and constantly changing and revived. This simple yet powerful gesture reinforces the idea of celebrating the structure even further. From a technical point of view, this project was extremely helpful to provide hands-on experience. Seeing the different types of structural systems in reality gave me a better understanding about each one of them. They used to be just conceptual representations in a course textbook, but now these representations have a significantly elevated meaning to me. In particular, my understands of joints has been increased. Until completing this project, I had not

pictured the different shapes of the variety of joints that can be categorized as either pins or rollers. This experience has left me well prepared me to embrace the next part of the semester. I learned tremendously from my team members. Walking around Boston for architecture hunting was very useful and fun, and I even learned some architectural history from them.

will

langevin

PROJECT: back bay station ARCHITECT: kallmann, mckinnell, + wood DATE: 1987 PROGRAM: intermodal transit center FEATURE: glulam wood arches After completing a walking tour examining Boston architecture, the wooden arches that span across the Back Bay Station stood out as one of the most compelling integrations of structural systems found in the city. Designed by Kallmann, McKinnell & Wood (KMW Architects), the decision to use wood, an organic material, as the focal, structural members of the roof juxtaposes the highly modern, glass and steel John Hancock Tower in the background. I also was able to appreciate the size and span of the wooden arches, a feat made possible through the use of glulam members. The sheer size of the arches allows the wood to stand out as the dominant structural material, yet it manages to effectively integrate with steel connectors and tie-rods, a glass facade, and concrete walls. Perhaps most impressive about the structural system was the feeling of material lightness I experienced when walking through the space. Back Bay Stationâ&#x20AC;&#x2122;s concrete walls

feel extremely heavy and dense, and yet the roof seems incredibly light. That feeling of lightness encouraged me to investigate the structural systems to better appreciate how the members worked together. From a technical standpoint, I was excited to see the use of steel tie rods pin connected to the bottom of the wooden arches in order to counter lateral thrust. The tie rods helped me conceptualize how tension can be used to create a more stable system and, while functional, they became aesthetically beautiful elements of the design. This exercise was extremely beneficial to my understanding of structural systems, as it forced me to scrutinize every structure I walked by. As the walking tour progressed, I became more confident in my ability to recognize the various structural elements being used in a system and was able to make assumptions about their applications and why they were being utilized. I also welcome any

opportunity to explore Boston architecture, especially with people who are unfamiliar with the area, as I believe there is so much to see and learn in my backyard. I grew up in the Boston suburbs and took for granted all of the creativity in structural engineering and design, so the project ultimately helped me develop a new appreciation for the city. I can now better understand its architectural history and growth, empowering me to make wellinformed design decisions moving forward. I do not have much criticism for this project, as it accomplished everything I am sure it was designed to.

works

cited

1: Ching, Francis D.K., Barry S. Onouye, Douglas Zuberbuhler. Building Systems Illustrated: Patterns, Systems, and Design. Princeton Architectural Press, 2013 2: Ochsendorf, John, Guastavino Vaulting: The Art of Structural Tile. John Wiley & Sons. 2011 3: www.hntb.com http://www.hntb.com/ expertise/bridges/zakim. Accessed: Oct. 21, 2015 All photos from the authorsâ&#x20AC;&#x2122; collections.