Guangdong Huizhou Port Quanwan Terminal Enclosed Coal Yard

The Quanwan terminal of Huizhou Port, on Guangdong’s coast, receives coal by sea for the power and industrial demand of the Pearl River Delta. The coal yard feeding the terminal’s storage and transshipment operation is enclosed by one of the longest continuous steel enclosures ever built for bulk-material storage: a cylindrical shell grid 1,000 metres long with a maximum clear span of 118 metres, carrying approximately 7,000 tonnes of structural steelwork.

Unusually, the enclosure’s cross-section is not a semicircle. It is a silkworm-cocoon profile — a three-center circular-arc form in which a flatter crown arc is joined to two tighter side arcs, creating a rounded, slightly flattened vault that hugs the stockpile and the reclaim machinery envelope more closely than a plain semicircle could. The three-center geometry is a small modification of arc mathematics with outsized consequences for roof area, wind response, material quantity and usable interior volume, and it is the structural signature of this project.

This case study explains the three-center shell geometry, the composite bolted-and-welded joint strategy, the bottom-chord support system, the engineering of a one-kilometre continuous structure through expansion joints, and the logistics of placing 7,000 tonnes of steel at a working port terminal.

A single-circle vault is easy to describe but rarely optimal. Its true circular arc either stands too high where the machinery is low (wasting enclosed volume, roof area and material) or sits too low where the machinery is tall (forcing the whole profile up). The three-center arc — so named because its cross-section is drawn from three circular arcs with three centres — solves both problems at once.

How the three-center profile is built

Working inward from the base on each side, the profile begins with a tight side arc rising steeply from the spring line, transitions through a shallower intermediate arc, and meets the crown in a flat central arc. The three arcs are tangent-continuous — no kinks, no stress concentrations at the geometry, a smooth vault that follows the interior envelope of a silkworm cocoon set on end. The mathematics is simple to state and quietly sophisticated in effect: the local radius controls local behaviour, and each region of the cross-section can be tuned independently.

What the three centers buy

• Volume economy: the flat crown and tight sides track the pile-and-machine envelope, enclosing the coal and the equipment without enclosing a kilometre of empty cathedral. Less enclosed volume means less roof surface, less cladding, less maintenance and less steel.
• Wind response control: a flattened crown presents a gentler profile to coastal wind than a tall semicircle of the same span, reducing suction on the roof and pressure gradients around the eaves. In a typhoon-prone region, profile is a load case before it is aesthetics.
• Structural efficiency: a shell grid’s strength comes from curvature; the three-center form keeps useful curvature where it is needed (the sides carry the bending and thrust, the crown carries membrane action) instead of spending material on curvature that buys nothing.
• Interior machinery clearance: the steep side arcs clear the reclaim machine’s boom at the rail corridor while the profile returns quickly to hugging the pile — the single most operationally relevant property of the design.

The lesson the project teaches is transferable: in long-span enclosures, the cross-section is a design variable, not a default. Choosing the profile deliberately — three arcs instead of one — is a concrete example of engineering optimisation that the casual observer sees only as an elegant silhouette.

Long structures fail quietly in exactly one way before any other: temperature. A steel shell 1,000 metres long moves by several tens of centimetres between winter and summer — and by fractions of that each day — and if the structure does not accommodate the movement, it will eventually bend, buckle, or tear its own cladding apart. The kilometre problem is a thermal-movement problem, and it shaped the design at three levels.

Expansion joints

The 1,000 m enclosure is broken into segments by transverse expansion joints, each segment short enough that internal thermal stress stays inside acceptable envelopes. Every expansion joint is a full structural and architectural detail: the shell grid terminates cleanly, movement is absorbed by sliding/gapped connections in the cladding, drainage is interrupted and re-caught, and the joint stays weather-tight. The number and spacing of joints was itself an optimisation — too few and the segments are over-long (stress), too many and the shell’s longitudinal stiffness and wind bracing are needlessly interrupted.

Support mobility

Within each segment, one longitudinal position acts as the fixed reference (typically the centre or one end of the segment), and the other supports are detailed to slide, guided along the shell axis, so that the structure breathes from the fixed point outward. The sliding bearings and guided details were verified for the frictional reactions they impose on the shell under thermal displacement — a second-order effect that grows exactly linearly with building length.

The wind-bracing consequence

A kilometre of shell is a kilometre of sail in a typhoon wind. Longitudinal stability — resisting wind along the building — requires bracing systems placed in a pattern that does not fight the expansion joints: bracing bays act within each segment between joints, and the movement at each joint is absorbed while global stability is preserved. The geometry of the three-center shell, with its stiff side arcs, contributed the longitudinal capacity that kept the bracing demand reasonable.

None of this is visible in the final photograph. It is visible in the structure’s service life — and it is the difference between an enclosure that survives a decade of coastal seasons and one that develops its first rust-streaked cladding tear within a year or two.

The service environment of this structure is unforgiving in a way inland sheds are not: typhoon-strength winds, high humidity, salt-laden coastal air and large diurnal temperature swings combine over a kilometre of roof surface. The design responded on every front.

• Wind actions: design wind loads followed the regional code provisions for the coastal exposure class, with the three-center profile’s aerodynamic benefit reflected in the pressure coefficients used for cladding and structure. Uplift-critical bolted connections were checked for tension capacity at the perimeter, where net suction is highest.
• Corrosion protection: the protective coating specification was selected for the marine-influenced atmosphere, with blast-cleaned surfaces, specified dry-film thickness and touch-up discipline at the field joints — because a kilometre of coastal steel is only as durable as its least-protected connection.
• Temperature and movement: expansion joint spacing, sliding supports and guided details were verified against the full seasonal and diurnal temperature range, as described above, so no lock-in stress accumulates in the shell.
• Seismic: the double-layer shell grid’s high redundancy gives it inherently ductile seismic behaviour; the design followed the national seismic provisions with the structure modelled as a three-dimensional coupled system.
• Serviceability: deflection criteria were set to protect the enclosure’s cladding and drainage at 118 m span with the machinery envelope undisturbed underneath.

Completion verification captured node coordinates against the model, confirmed camber after de-propping, and closed the documentation chain from mill certificate to final survey. The enclosure has since served the terminal through successive coastal seasons — the ordinary durability record that is the real performance claim of a structure designed for its environment rather than for its render.

Inside the shell: the environment the enclosure exists to create

An enclosure of this scale is more than a roof; it is the envelope within which the terminal’s air quality, fire safety and operating environment are managed. The design therefore integrated the systems that make the enclosed yard operational: monitored ventilation and dust-suppression provisions that manage the interior atmosphere during reclaiming and stacking; drainage that keeps yard runoff controlled and compliant; lighting and access provisions that keep inspection and maintenance safe across the full kilometre; and fire-safety measures appropriate to a coal storage occupancy, coordinated with the terminal’s procedures. None of these systems is glamorous, and all of them are the difference between an enclosed yard that performs and an enclosed yard that merely exists — the same discipline of thinking the operational reality of a structure before its rendering.