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SIMS (Snap-Interlock Module System)

Figure 1. SIMS Prototype test (Image by Jin Young Song)

Project Background

One of the fundamental aspects in the material culture of the building industry is the fact that everything comes as panels and modules with certain sizes. How we combine them into a whole with what attitude is the core activity of the design. 

‘Stacking’ has been the simplest and oldest building methods as we see the Great Wall of China, the Hagia Sophia, the Taj Mahal, and many more ancient cases. Children’s toy blocks also present the fundamental human actions of ‘stacking’ as the ‘part to whole’ system. Using mortar (bonding material) and blocks (modules), the masonry structure conventionally uses bricks, stones, concrete blocks, and tiles. Today, masonry is still the most common type of buildings, not only as a structural system but also as a non-structural cladding system. The method of brick-stacking is simple in construction and economical compared to steel and reinforced concrete. Recently, bricklaying robots (such as Sam-100 and Hadrian X) are also used for increased efficiency. However, the nature of the masonry construction requires the control of heat, water, and skilled experts. Human masons have to help the bricklaying robots. Mineral-based masonry materials are more vulnerable to extreme weather conditions. The high compressive strength in masonry structures is unbalanced with its low tensile strength, so this asymmetric strength of the structures often requires additional reinforcement by steel.

Figure 2. USAF Aircraft Hangar by Konrad Wachsmann(1951)

(Image from 

Unlike the ‘Stacking’ of conventional masonry units, steel framing is based on the capacity of the joint system. The U.S. Air Force Aircraft Hanger proposed by Konrad Wachsmann in 1951 (Figure 2) presents the full capacity of this coordinated joint based construction. This allows excellent lateral system and cantilevered space providing open space. Wachsmann further imagined a single universal structural element that, if mass-produced, could be used in building construction for every conceivable purpose (Figure 3, 4). Even after more than 60 years, his notion of a modular, coordination based system has not been implemented and current building structures are still based on the Dom-ino system (1914) or steel-based post and beam system with conventional bolt/weld connection. Despite significant development in digital and manufacturing technologies and emerging material culture, we are simply adding new subcomponents to the primary building system which are conventional structural system. Current smart fabrication techniques with advanced digital design tools allow us to revisit Wachsmann’s holistic approach for a unit-based ‘part-to-whole’ system.

Therefore, the proposal suggests that we ‘stack’ metal-based units for an efficient construction method and the geometry of the unit enables ‘snapping and interlocking’ without the need for bonding materials. The basic module design allows the snap-interlock mechanism through the legs of the building-block and the geometric control is achieved from the center angle pieces. Advanced manufacturing tools such as additive manufacturing, CNC milling, and multi-axis waterjet cutting will provide a cost-effective method to fabricate this module design. Through successful tests, structural simulation with enhanced prototyping, we envision a scenario where one box of module pieces can be delivered to a customer, who can easily stack and assemble to build a single-story pavilion with a strength of steel construction without conventional bolting or welding. The built prototypes confirms that this ‘part-to-whole’ system can be applied to the building structure, facade, substructure, architectural partition walls, and more.

Figure 3 and 4. A study of dynamic structure by Konrad Wachsmann
(Image copied from Wachsmann, Konrad. The Turning Point of Building: Structure and Design. Reinhold Pub. Corp., 1961: 194-201 )

In 1953, Konrad Wachsmann imagined a single universal structural element which, industrially produced, could be used in building construction for every conceivable purpose. More than 60 years after his notion of the systematic modular coordination based on the industrial production, our building structure is still based on the Dom-ino system (1914) or steel based post and beam, on top of which we are adding our digital advancement and sustainable technology as functioning ornaments. Current smart fabrication techniques with advanced digital design tools allow us to revisit Wachsmann’s holistic approach for the unit-based ‘part to whole’ system.

SIMS prototype (Image by Jin Young Song)

SIMS (Snap-Interlock Module System) is a structural module prototype based on the elastic instability of steel, distributing forces through its unique stacked and interlocked mechanism. One module has 4 hooked legs in the top and bottom direction, when one module snaps into 4 legs from connecting 4 modules, the 5 modules are interlocked as one unit. Finite Element analysis shows the elastic nature of steel and confirms the structural integrity for the construction scale. The module can be cast or cut to assemble for mass production. The internal structure of the module can be controlled to increase the stiffness. The center connector can be added to allow specific angles to form a curved geometry. The snap-interlock stacking is relatively easy to do by human hands and two arch shape prototypes are built using 3d printed modules. The system can achieve limited geometric freedom. Despite further structural analysis and new interpretation necessary, this ‘part to whole’ system can be applied to the building structure, facade application as sub-structure, sheer wall, partition wall, and more.

SIMS module studies (Option 1-26)  (Image by Jin Young Song)

SIMS module studies (Option 25)  (Image by Jin Young Song)

Assembly diagram of SIMS prototype (option 26)   (Image by Jin Young Song)

Web-plate diagram of SIMS module  (Image by Jin Young Song)

SIMS prototype test  (Image by Jin Young Song)

SIMS prototype test  (Image by Jin Young Song)

Rendering of SIMS prototype

SIMS module (option 32)  (Image by Jin Young Song)

(Image by Jin Young Song)

Waterjet cutting steel (Photo by Dan Vrana)

Process of stacking using waterjet cut module (Photo by Dan Vrana)

3d printed Center joint (supported by Buffalo Manufacturing Works)

3d printing and Waterjet cutting of steel:

The project involves with innovative fabrication method to achieve geometric freedom. Keeping coordinated modular property of the SIMS modules, the geometry of the center joint can allow the organic growth of this ‘part-to-whole’ system. We acknowledge the growing potential of the additive manufacturing and as we test printed the modules with the support from Buffalo Manufacturing Works, it opens up unlimited flexibility in shaping the geometry. It provides great benefits for customizable iteration of pieces with exceptional strength, even though we have less understanding of the stress analysis comparing steel sheet legs versus 3d printed steel joints. We are learning about the time of the printing, cost, and the necessary process of post-processing. On the other hand, aiming for the market product and more ‘intimate’ use of steel, the project searches for a simpler and faster way to fabricate the 3-dimensional pieces too. The team tested 5 axis Omax waterjet cutting, carefully controlling the angled faces. This allows precise cutting and a wide range of angled cutting for 3 dimensional needs (See the movie clip below).

Waterjet cutting simulation 

Full size SIMS prototype cutting steel sheet  (Image by Jin Young Song)

Full size SIMS prototype cutting steel sheet (Image by Jin Young Song)

SIMS application for customizable vertical green wall

SIMS application for rain screen (facade application)

Finite Element analysis of SIMS prototype (Image by Jongmin Shim and Xiangdong He)

Finite Element analysis of SIMS prototype (Image by Jongmin Shim and Xiangdong He)

The SIMS prototype (Figure 1) can be packed into one typical suitcase.

SMART Convergent Conversation (3/13)
Forge Prize Phase 2 presentation (5/29)

Jin Young Song
Assistant Professor, Department of Architecture
University at Buffalo
Dan Vrana (Fabrication Manager, UB Architecture)
Jongmin Shim (Structure Analysis, UB Department of Civil, Structural and Environmental Engineering)
Xiangdong He (Structure Analysis, PhD student, UB Department of Civil, Structural and Environmental Engineering)
Michael Gac (Student researcher, UB)
Bonghwan Kim (Structure Consultant, Skidmore, Owings & Merrill LLP)

supported by: