A 30-foot-long glass bridge blends ancient wisdom with cutting-edge design

With more than 500 bridges crisscrossing the city of Philadelphia, they’re an integral a part of day by day life. In a metropolis outlined by its rivers, bridges make attainable the connections between individuals.

The place conventional bridges join two sides of a chasm, architect and structural engineer Masoud Akbarzadeh has taken this problem additional, developing one out of a fabric that typical knowledge says shouldn’t be used for a bridge in any respect: glass.

The result’s a wide ranging 30-foot-long construction composed totally of interlocking hole glass models. At first look, the bridge seems impossibly delicate, an ethereal span of translucent polygons that shimmer beneath gentle.

“Bridges are greater than mere buildings spanning rivers and chasms; they symbolize bodily and metaphorical connections,” says Akbarzadeh, an affiliate professor of structure on the Weitzman College of Design.

“As pathways between two factors, they embody the human endeavor to beat distances and unite disparate realms. But, past their sensible utility, bridges function potent symbols of solidarity, understanding, and collaboration.”

The Glass Bridge eliminates the necessity for conventional reinforcements like metal, as a substitute harnessing glass’s power inside a compression-dominant structural type.

“All these items alone, hole glass models, might sound fairly brittle—and they’re,” Akbarzadeh says, “however relying on the way you design to place these glass models collectively, they begin counting on one another, and the models’ meeting establishes a path for the load to be transferred effectively. Thus, the bridge positive aspects power as a complete.”

Akbarzadeh likens this notion of the items forming a larger, extra highly effective complete to human society, noting that “for a better-functioning society, we have to depend on one another. We have to belief one another, and collectively, solely with transparency, we are able to work and unite to create an advancing world that serves the individuals in it.”

He and his group fabricated the bridge over the course of three weeks in 2024. In keeping with Boyu Xiao, a 2024 Weitzman Grasp of Structure graduate who at the moment works as a analysis assistant in Akbarzadeh’s Polyhedral Buildings Laboratory, “the method was a check of each engineering ingenuity and sheer bodily endurance.”

The work is published within the journal Engineering Buildings.

The bridge, formally generally known as “Glass Bridge: The Penn Monument for Hope,” stands tall, on show on the Corning Museum of Glass, the place it would stay till Sept. 1. Main as much as its unveiling on the Museum, Greenhouse Media met with members of the group and documented the method of fabrication for an upcoming documentary.

However its journey to completion was something however easy. It took six years of planning, drafting, revising, and negotiating with distributors world wide to get the blueprints prepared. And in simply 21 intense days final November, a rotating group of architects, engineers, researchers, and fabricators converged in Corning, New York, every enjoying an important function in bringing the construction to life.

Constructing on millennia of intuitive knowledge and scientific precision

In the summertime of 2017, a 12 months into his tenure at Penn, Akbarzadeh started the preliminary conceptualization and design of what would ultimately turn into the Glass Bridge.

“Firstly, it was simply an concept about utilizing skinny sheets of glass to construct a super-efficient construction,” Akbarzadeh says. “But it surely in a short time grew into a bigger research of structural resilience.”

The bridge and its prototype, he explains, draw on millennia-old engineering and architectural rules, significantly these related to funicular design—buildings that observe the pure stream of forces appearing via them, primarily harnessing compression to realize stability and power.

The usage of these rules exists as early as 4000 BCE, when the Mesopotamians constructed arches and domes, and later with the Romans via aqueducts, bridges, and monumental buildings just like the Basilica of Maxentius that had been designed to steadiness forces via arches and vaults.

Nonetheless, whereas historical builders relied on empirical instinct, the underlying mechanics remained largely unformalized till the seventeenth century. It was Robert Hooke, an English physicist and mathematician, who articulated a foundational principle of structural design in 1675: “As hangs the versatile line, so however inverted will stand the inflexible arch.”

Hooke’s commentary, although elegantly easy, revealed a profound reality: an inverted model of a dangling chain naturally follows the right compression curve of an arch beneath uniform load.

“In case you have the fitting type,” Akbarzadeh explains, “you possibly can scale back the fabric and work with environment friendly and chic varieties.”

Hooke’s insights knowledgeable the work of Akbarzadeh’s main influences, James Clerk Maxwell and William John Macquorn Rankine. These Nineteenth-century engineers, he says, “formalized the mathematical foundations of graphical statics, offering strategies for visualizing and analyzing the interior forces inside buildings.”

Akbarzadeh prolonged the strategies of graphic statics from two dimensions to a few, increasing Rankine’s 1864 proposition, since his Ph.D. thesis in 2012, at Penn since 2017, and outlined it in his new e book, “Polyhedral Graphic Statics.”

Akbarzadeh and his group designed the bridge’s geometry to channel forces alongside superb compression paths. Each glass unit, joint, and angle was optimized in order that the bridge’s arch would carry the load primarily via compression fairly than bending forces—a technique as historical because the Sumerian U arches, now realized via cutting-edge computation and fabrication applied sciences.

Bridging the hole: Going from the prototype to manufacturing

Step one in realizing their idea, past sketches, calculations, and simulations, was a modest however essential almost 10-foot prototype. This mannequin was a crucial proving floor, a bodily manifestation of the group’s digital machinations.

“Each flaw, each misalignment, and each surprising failure was logged, studied, and resolved in preparation for a full-scale bridge to come back,” says Yao Lu, a core member of the design group and a 2024 Ph.D. graduate of the Weitzman College’s structure program who’s at the moment an assistant professor of structure at Thomas Jefferson College.

Lu had simply began his Ph.D. at Penn when he designed the prototype. He notes that it was constructed from the identical fundamental parts envisioned for the ultimate bridge—modular hole glass models interlocked by precision-engineered acrylic connectors —and one of many earliest hurdles was figuring out the right way to be part of the glass modules with out inducing stress factors that might result in fractures.

Lu explains that the group initially experimented with male-and-female key joints, that are interlocking geometries that might bodily forestall the modules from slipping aside, nonetheless, “the male and the feminine shapes had been actually, actually troublesome to make out of glass.”

Glass supplies are largely planar, or two-dimensional. The group’s makes an attempt to mildew the glass right into a three-dimensional construction utilizing warmth and formwork failed to provide the mandatory precision, as a substitute introducing new structural weaknesses.

Finally, Akbarzadeh says, structural double-sided tape was used to assemble the small module, and the unit was despatched 12 miles west to their collaborator Joseph Yost at Villanova College for stress testing, the place it endured as much as 41.6 kilopounds of compression.

“The check information was simply tremendous thrilling as a result of it confirmed us that this humble, low-cost materials may have lots of load-bearing capability,” says Lu.

For his or her prototype, the group settled on flat plates of glass bonded with precision-cut acrylic connectors secured utilizing structural VHB tape, an industrial adhesive recognized for its power and suppleness.

“This strategy permitted the mandatory tolerance and ease of meeting with out compromising the integrity of the glass,” Lu says.

“The group over at Villanova labored to establish an interface materials that might forestall catastrophic glass-on-glass contact between adjoining modules throughout meeting and beneath elevated load.”

Their testing finally led them to polyvinyl butyral (PVB), a laminate materials historically utilized in security glass, which acted as a buffer between the glass modules. PVB supplied simply the fitting steadiness of flexibility and rigidity, permitting the forces throughout the bridge to distribute evenly with out inflicting localized stress concentrations.

“However with these connectors, each reduce, each angle, each dimension needed to be correct inside 0.1 millimeters,” Akbarzadeh notes.

“If you’re coping with 124 separate glass models, even the tiniest misalignment can multiply throughout all the span. If we did not preserve that degree of precision, the entire construction may have collapsed beneath its personal weight.”

To realize this diploma of accuracy, the group collaborated with a number of companies from Germany and China. The logistics of assembling the bridge in Corning introduced one more layer of complexity. Every hole glass unit needed to arrive on-site unblemished and intact—a problem given the fragile nature of the supplies and the 1000’s of miles each bit traveled to the USA.

“Delivery was one among our largest nightmares,” Xiao admits. “We had to make sure that the glass wasn’t broken in transit, that customs clearances went easily, and that each half arrived on time. Even a small delay may have jeopardized our building schedule. Which is strictly what occurred.”

A leap of religion

Xiao took the lead on the mission’s day-to-day operations after Lu graduated, and have become the logistical linchpin, coordinating every little thing from half shipments to group scheduling. As he describes it, “We did not simply should construct a bridge. We had to determine the right way to construct a bridge that had by no means been constructed earlier than.”

The bridge parts arrived in Corning in early November, however the group instantly confronted a logistical setback. The delivery firm had deprioritized their freight, delaying the arrival of the glass models by two weeks. The exhibit’s opening schedule, nonetheless, was immovable. That meant the group had a matter of days—not weeks—to get every little thing in place.

“I used to be there from November twelfth to the fifteenth for the primary part, the place we put in the steel helps and wood formwork that might assist the bridge throughout building,” says Xiao. “That was simply laying the groundwork. The true push got here when the complete group arrived on November twenty first.”

From that time ahead, it was all arms on deck, Akbarzadeh says. He joined the hassle, together with Amir Motevaselian, a newly-arrived analysis assistant who had been thrown into the deep finish of the mission, and the remainder of the group from the Polyhedral Buildings Laboratory.

In contrast to a typical bridge building, the place supplies like metal and concrete permit for some margin of error, Lu says the glass bridge demanded an virtually unfathomable degree of precision. Every hole glass unit needed to match completely with its neighbors, and the tolerance for error was a mere 0.1 millimeters of accuracy, barely perceptible to the human eye.

“The museum employees had been nervous about us taking on a lot house, coming in with massive instruments,” Xiao notes. “It is a museum of glass, so every little thing round us was insanely fragile. And there we had been, sweating, lifting these huge crates, transferring heavy equipment, sawing plastics—it appeared like chaos.”

By the point the final cargo arrived in Corning, the group had rigorously choreographed each step of the meeting course of. The structural helps had already been put in to brace the arch throughout building. A brief wood formwork was designed to carry the bridge regular till the ultimate keystone glass modules could possibly be locked into place, permitting the construction to assist its personal weight.

Nonetheless, the meeting would check each the bodily stamina and emotional resilience of everybody concerned.

“We had days the place we labored from dawn till the museum closed, lifting heavy glass models by hand, triple-checking measurements, and holding our breath throughout each set up,” Xiao notes. “We needed to bodily elevate and place every unit by hand. The museum crew helped with the heavier items, however there have been moments when it felt like we had been constructing this factor with our naked arms.”

At one level, an improperly calibrated assist induced a misalignment within the arch, forcing them to painstakingly disassemble and reposition a number of sections. At one other, a miscalculation within the placement of the wood formwork meant that the bridge could not be correctly supported because it was assembled.

“The worst half was that the entire construction needed to be self-supporting by the top,” Xiao says. “It is an arch—till you place within the final keystone piece, the entire thing is unstable.”

The ultimate days of building had been significantly tense. The position of the previous couple of models was crucial; any error would compromise the structural integrity of all the span. However because the keystone unit clicked into place, there was a collective sigh of reduction among the many group.

On Nov. thirtieth, after every week of lengthy days and late nights, the bridge stood tall.

The months of calculation, fabrication, and logistical coordination converged into one thing extraordinary: a shimmering arch of glass, delicate in look however stable in construction—a bodily testomony to the concord of engineering precision, aesthetic magnificence, and human collaboration.

“This bridge exhibits that we are able to rethink supplies, that we are able to push the boundaries of engineering, and that we are able to construct in methods which might be each environment friendly and chic,” Akbarzadeh says.

Xiao, who had spent months juggling logistics, materials constraints, and sleepless nights, had a extra succinct response.

“We did it,” he says. “In opposition to all odds, we really did it.”