A large-span curved canopy designed for a car wash and petrol station complex on Dadman Street, west Tehran, won through open competition and built to solve a wind failure that had defeated the site's original fabric structure.
The Farahzadi car wash complex on Dadman Street already had an awning, a large-span fabric canopy installed by another company. It failed regularly. In any wind, even light, the structure would heave up and down, threatening safety and projecting an image of impermanence that was entirely at odds with the established Best Wash / Star Wash brand the client had built.
Syeh Sazane Mehr Gostar commissioned the designer to compete for the replacement canopy design. After winning the competition among several submitted proposals, the designer led the structure through full dimension documentation and supervised its manufacture and installation on site. From first site visit to final build, the project ran six months.
"Every design decision on this project came from one observation: the previous canopy failed because it could not resist wind. That single problem shaped everything, the truss, the cable stay, the rigid cladding, the mast."
Before this project, the car wash forecourt was sheltered by a fabric membrane canopy, a common and economical solution for commercial forecourts in Iran. The designer visited the site in multiple weather conditions before proposing any design, observing the behaviour of the structure under wind loads in real time.
The diagnosis was structural, not cosmetic. Fabric canopies of this scale fail in wind because they lack both rigid plane stiffness and sufficient anchoring tension, the membrane flexes and flaps, which amplifies load rather than shedding it. At the Dadman Street site, the height of the columns was also a compounding factor: taller columns mean a longer lever arm for any lateral wind pressure, producing greater oscillation at the canopy edge.
| Flexible membrane | No rigid plane to resist wind uplift, fabric flaps and amplifies load |
| Column height | Tall supports increase lever arm, small wind forces produce large oscillation |
| No tension system | Without cable stays, the canopy edge is free to move under lateral pressure |
| Brand perception | A moving canopy signals structural inadequacy, damaging for a premium car wash |
| Curved truss | Rigid primary structure, no membrane flex, no uplift oscillation |
| Cable stay system | Tension rods from mast top to canopy edge resist wind uplift directly |
| ACP panel cladding | Stiff, lightweight panels, add rigidity to the truss surface without dead load |
| Visual consistency | ACP colour and finish matched to the existing car wash building facade |
The designer visited the site repeatedly across different weather conditions, light wind, moderate wind, still days, observing the behaviour of the existing fabric canopy in each scenario. The failure mode, oscillation driven by wind uplift on a tall, unbraced membrane, was identified from direct observation, not from reports alone. This phase also established the key constraint: the new canopy had to clear the existing car wash portals and the height of vehicles passing beneath.
The concept went through multiple iterations in SketchUp. Two distinct structural families were explored: a tree-column system with branching curved arms supporting a polycarbonate roof, and a tensioned mast-and-cable system supporting a single continuous curved truss. The tree-column concept was visually distinctive but introduced fabrication complexity and required larger footings. The cable-stay truss was selected for its structural clarity, wind resistance, and the way it produced a clean, dramatic sweeping form consistent with the car wash's commercial identity.
The design was submitted to an open competition among multiple proposals invited by the client. The submission included 3D renders, dimensioned elevation drawings, and the structural rationale. The proposal was selected as the winning design, a competitive win for Syeh Sazane Mehr Gostar over other bidders, validating the design approach both aesthetically and technically.
Following the competition win, the designer produced the full set of dimensioned drawings, plan, section, and elevation, used for manufacture and installation. Civil engineers at Syeh Sazane Mehr Gostar consulted on structural calculation (column foundation depth of 3 m, column section of 330 mm, truss panel pitch of 750 mm). All spatial decisions, proportions, cable positions, and the overall structural concept remained the designer's authorship.
The canopy was fabricated in-house at Syeh Sazane Mehr Gostar. The main curved truss was built as a structural steelwork assembly. ACP panels in white with red stripe banding were cut and fitted as the soffit cladding, matching the existing building facade. The cable stay system, black painted steel tension rods with red ball end caps, was installed as the final structural element, transferring wind uplift directly to the base of the mast. The structure has been in use without issue since completion.
The structural concept is derived from bridge engineering, specifically the cable-stayed bridge, where a central mast under compression carries tension rods that support a horizontal deck. Applied to the canopy, the mast rises above the roof plane and the cables tie the outer canopy edge back to the mast head. This converts what would be a bending problem, wind trying to lift the canopy edge, into a pure tension problem in the cable, which steel handles with great efficiency.
The canopy surface itself is a single long curve spanning 14 metres, high at the building wall and tapering toward the far edge. This asymmetric section profile sheds rainwater outward while maintaining generous clear height for vehicles and people beneath.
The curved truss was built from structural steel with 75 cm panel bays. Each bay carries one ACP panel on the soffit face, a white panel with a red accent stripe running longitudinally, referencing the car wash brand identity painted on the building behind.
| Component | Specification |
|---|---|
| Total span | 14 m |
| Height, mast tip | 7.5 m above ground |
| Height, mid clear | 8.0 m at column connection point |
| Height, canopy low edge | 1.9 m at outer tip |
| Clear vehicle height | 4.5 m building side, 4.17 m far side |
| Column section | 330 mm diameter steel |
| Column foundation depth | 3.0 m |
| Truss panel pitch | 750 mm |
| Soffit cladding | Aluminium Composite Panel (ACP) |
Structural concept diagram, mast, cable stay, and curved truss with ACP panel soffit. Wind uplift is resolved by cable tension, not by membrane stiffness.
The early design studies explored two formally distinct structural families before the competition submission. The tree-column concept used branching curved steel arms, each rising from a single ground point and splitting to support a roofing sheet, a form that referenced organic and traditional Persian arch structures. Each branching joint, however, introduced a fabrication complexity and potential failure point, and the distributed column footprint made the structure harder to install in the existing forecourt geometry.
The cable-stay truss, a single continuous curved member supported by one central mast and stabilised by tension cables, was more direct, more buildable, and structurally superior under wind. Three variants of the cable-stay concept were drawn up for the competition submission before Concept C was selected.
"The tree-column concept was structurally interesting and visually rich, but it multiplied fabrication points and foundation requirements. The cable-stay truss solved the same problem with less material and greater wind stiffness. The simpler solution was the better one."
The finished canopy replaced the fabric structure entirely. The photographs below show the structure at installation, ACP panel fitting with the Alborz mountains visible behind, and after completion, the structure in use at the car wash forecourt, shot from the street, from below, and in soffit detail.
The soffit cladding material, referred to locally in Iran as "composite", is Aluminium Composite Panel (ACP), a sandwich construction of two thin aluminium sheet faces bonded to a rigid polyethylene core. International brand names include Alucobond, Alpolic, and Dibond, though equivalent products are manufactured domestically in Iran as well.
ACP was the correct material for this application for several reasons. It is lightweight, critical for a canopy where dead load increases the demand on the cable stay system. It is rigid in-plane, each 75 cm panel tile, once fixed to the truss, contributes to the overall surface stiffness of the canopy. It is weatherproof without painting, the coated aluminium face needs no site-applied finish and will not peel, fade, or corrode in urban Tehran conditions. And it is available in any colour, allowing the white body and red accent stripe of the soffit to match the ACM cladding on the car wash building facade exactly, producing the visual continuity between canopy and building that the client required.
| Property | Value |
|---|---|
| Construction | Two aluminium skins bonded to polyethylene core |
| Finish | PVDF or polyester powder coat, white body, red accent |
| Typical thickness | 3 to 4 mm overall, 0.5 mm aluminium skins |
| Weight | Approx. 5 to 6 kg/m², significantly lighter than steel sheet |
| Weathering | UV stable, no site painting required |
| Panel tile width | 75 cm, matching truss bay pitch |
| Installation | Dry-fixed to steel sub-frame, concealed fasteners |
| Local trade name | "Composite" in Iran, ACP / ACM internationally |
This project is unusual in a designer's portfolio because it begins with a competition win. The design was not assigned, it was selected from among competing proposals submitted by multiple firms. That selection validates the concept as the strongest submitted answer to the client's problem.
The designer's role encompassed the full project arc: site observation and problem diagnosis, structural concept development and iteration, including the rejected tree-column alternative, competition drawing preparation, dimension documentation after award, and liaison with the civil engineering team during structural calculation and fabrication. The structure standing on Dadman Street is the direct built consequence of the designer's concept.
Structural calculation, column section, foundation depth, truss load verification.
In-house steel fabrication and ACP panel installation at Syeh Sazane Mehr Gostar.
Mr. Farahzadi, Star Wash / Best Wash, Dadman Street, Tehran.
The completed canopy resolved every failure mode of its predecessor. The rigid ACP-clad curved truss does not flex or flap in wind. The cable stay system converts uplift force to pure tension in the rods, a load path that steel handles simply and reliably. The recessed soffit lighting and the red-stripe ACP banding translate the car wash's brand identity upward into the canopy, making it a piece of commercial identity as much as a piece of infrastructure.
The competition win demonstrates the strength of the design approach: diagnosing the root cause first, structural failure mode rather than aesthetic preference, proposing a concept that directly addresses that cause, and communicating it visually well enough to persuade a client who had other options.
Selected over competing proposals from other firms, design validated externally.
Rigid truss and cable stays eliminate the oscillation that failed the fabric canopy.
ACP stripe pattern reads as an extension of the car wash building, coherent commercial identity.
Structure completed and in active use at Dadman Street, west Tehran.
Concept, structure, material, and visual language all originated with the designer.