Structural Studio

Tokyu Kabukicho Tower, Shinjuku, Tokyo, Japan
Architect: Yuko Nagayama & Associates + KUME SEKKEI
Structural Engineer: KUME SEKKEI

Tokyu Kabukicho Tower is a 225 m, 48-storey (B5–48F–PH) mixed-use high-rise completed in 2023 on the former Shinjuku TOKYU MILANO site. The program stacks entertainment and hospitality rather than offices: live venue and night uses in the basements, retail and food at the lower levels, theatre and cinema in the mid-zone, and hotels above. Total floor area is about 87,400 m², with a deep basement package supporting the tower and the large-span venues.

The structural concept is a deliberately “mixed-by-use” stack with clear switching points. The lower theatre/cinema zone forms large, column-reduced volumes using an exterior braced system (with dampers) rather than dense interior frames. Above, the hotel tower is a high-stiffness moment-frame system using CFT columns to control drift in a slender shaft. The key transfer is a mega-truss zone (about 6 m deep) that re-routes vertical and lateral actions between the low-rise long-span volume and the taller hotel frame; floor diaphragms and collectors lock the truss and slabs together so in-plane forces can move reliably across the step in geometry. Seismic and wind response is reduced with a hybrid damping strategy: oil dampers are applied where brace demand is high in the large-volume zone, while the upper hotel uses combined devices tuned to both frequent wind comfort and rare large earthquakes. Roof-level active mass dampers target wind-induced acceleration to protect habitability at the highest occupied floors. The basements extend to roughly 52 m below grade, with the foundation strategy described as direct bearing via a mat slab supporting the stacked systems.

Operationally, the structure is sized around performance differences between venue and hotel: long-span spaces prioritize clear volume and vibration control, while the upper tower prioritizes drift and acceleration limits for comfort. The mega-truss + diaphragm strategy keeps the transfer legible and maintainable, avoiding scattered transfer beams across multiple floors. For students, it is a compact case study of “program-driven structure”: braced-and-damped large spans below, CFT moment framing above, and a single engineered switching layer that makes the whole stack behave as one building under earthquake and wind.

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Jubilee Place, Fortitude Valley, Brisbane, Australia
Architect: Blight Rayner
Structural Engineer: Robert Bird Group

Jubilee Place is a 14-storey commercial tower completed in 2022 beside the heritage-listed Jubilee Hotel. The 18,000 m² building sits on a tight urban corner above a major transport node, using a distinctive external diagrid to lift office floors clear of the site constraints. A through-site public laneway and podium terraces link the restored hotel, new retail fronts and the tower lobby, forming a combined commercial and civic precinct for Fortitude Valley’s renewal.

The structural concept centres on a full-height steel diagrid placed outside the façade to maximise usable floor area and remove the need for deep internal transfer structures. Large X-shaped perimeter members carry vertical and lateral loads to a limited number of foundation points, allowing the tower to “bridge” over easements and tunnels. Floor plates are lightweight composite steel decks spanning between diagrid nodes, keeping floor depths shallow and services zones efficient. At the ground level, a transfer column system and braced steel cores stabilise the building during er****on and in service. Digital modelling and coordinated node prefabrication reduced on-site welding, enabling rapid assembly of the complex geometry within the constrained site.

Operationally, the exposed diagrid improves daylight access by reducing the number of internal supports and permitting more transparent façades. Deeply shaded façades, operable elements and efficient floorplates reduce heat load and lighting demand. The integration of the historic Jubilee Hotel—retained, strengthened and reopened—anchors the project in its heritage setting, while the publicly accessible laneway and terraces provide additional circulation and activation for the precinct. The project demonstrates how an external diagrid can resolve site constraints, increase net lettable area, and create a recognisable structural identity in a dense urban context.

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Frank Gehry reshaped our skylines and showed the world that buildings can be bold, emotional and alive. He may be gone, but his shimmering halls and twisted towers will carry his spirit on forever

Dechatiwong Bridge, Nakhon Sawan, Thailand
Designer / Owner: Department of Highways (Thailand)
Structural Type: Reinforced-concrete road arch bridge

Dechatiwong Bridge opened in 1950 as a key highway crossing of the Chao Phraya River on Phaholyothin Road, just before entering central Nakhon Sawan. Construction began in 1942 during the Greater East Asia War, was interrupted, then completed after the war as part of a national policy to shift long-distance travel from river to road. The bridge’s name comes from Major M.L. Kri Dechatiwong, then Director-General of the Department of Highways. Today it forms part of a group of three parallel bridges (1–3), with the original structure preserved as a historic gateway and viewpoint over the confluence of the Ping and Nan Rivers into the Chao Phraya.

The original bridge is a reinforced-concrete arch structure about 404 m long, composed of four arch spans each slightly over 60 m. The roadway is approximately 6.5 m wide with sidewalks on both sides, reflecting early post-war highway dimensions. The deck is carried on spandrel columns over the concrete arches, which deliver thrust to river piers and abutments on the banks. The design was adapted from the earlier Pridi Thamrong Bridge in Ayutthaya, modified to reduce material usage while maintaining the required span and clearance. Later twin bridges (Dechatiwong 2 and 3) use parallel reinforced-concrete systems to carry increased traffic volumes, allowing the historic first bridge to operate with lower structural demand and mainly local loads.

Operationally, Dechatiwong Bridge shifted north–south movement from boats to highway traffic and became a symbolic “gateway to the North.” Its position above the “two-colour river” makes it a natural lookout, now supported by viewing points and lighting installations that highlight the arches and river junction. The bridge’s continued use, alongside newer structures, illustrates how early ferro-concrete infrastructure can be conserved within an expanded corridor instead of being demolished, and how a relatively modest four-span highway bridge can become both a heritage object and a contemporary urban landmark for Nakhon Sawan.

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