Optimal Mimarlık completed the octagonal skylight system and the composite panel cladding of the eight-metre-high interior walls for the Kabataş–Mahmutbey Metro project undertaken by Alarko Holding. The skylight geometry, steel supporting structure, glass connections, water drainage, thermal insulation and interior surface cladding were developed as components of an integrated architectural solution.
Scope of the Kabataş–Mahmutbey Metro Skylight Project
The project included the construction of an octagonal roof skylight system designed in accordance with the architectural form of the metro structure. The transparent upper enclosure, steel supporting structure, 18 mm glass joints, concealed water drainage channels and octagonal interior wall cladding were designed along the same geometric axes.
In addition to structural safety, the design process considered exposure to exterior conditions, condensation water, thermal insulation, material interfaces and the reduction of long-term maintenance requirements.
How Was the Octagonal Skylight Designed?
The profile, glass and joint dimensions on each side of the octagonal form were coordinated to meet at the correct angles. Modular fabrication and installation details were prepared to ensure that the glass units were properly seated on the supporting structure and that the 18 mm joints maintained the architectural geometry without interruption.
Specially manufactured omega-section profiles were used at the 18 mm glass joints. These profiles supported the controlled formation of the glass edges and sealing joints while maintaining the continuity of the octagonal skylight surface.
How Was the 500 kg/m² Design Load Evaluated?
The skylight supporting structure was designed to accommodate a design load of 500 kg per square metre. The loads were transferred in a controlled sequence from the glass surfaces to the omega profiles, steel supporting members and main building structure.
The steel section dimensions, connection points and installation sequence were developed to maintain the geometric integrity and structural stability of the system under the specified design loads.
How Was the Steel Supporting Structure Designed?
NPI 140 steel sections were used in the skylight substructure. The steel supporting structure was designed with bolted connections so that no welding would be required at the construction site. This approach allowed the components to be prepared under controlled conditions, accurately assembled at the designated connection points and installed with consistent application quality.
The steel components were protected with epoxy paint over hot-dip galvanizing. As no welding was carried out at the construction site, the risk of the galvanized and epoxy protective layers being damaged by welding heat was eliminated. The bolted assembly also facilitated installation control and contributed to the creation of a durable, long-lasting supporting structure.
How Were the Glass and Joint Sealing Details Resolved?
A laminated tempered glass combination manufactured by Şişecam was used on the skylight surface. The glass components were tempered to reduce the risk of thermal breakage caused by temperature differences and thermal stress resulting from solar exposure. The laminated configuration was selected to help retain glass fragments within the interlayer in the event of breakage.
Soudal Silirub WS, an exterior-grade neutral-curing silicone, was applied to the 18 mm glass joints formed with the omega profiles. The master product code for Soudal Silirub WS is 9900424. Surface preparation and silicone joint geometry were arranged to be compatible with the glass, metal profiles and exterior weather conditions.
How Was the Concealed Water Drainage System Created?
A concealed drainage system was incorporated to prevent water that might enter the skylight and condensation forming within the channels from accumulating inside the system. The drainage channels were configured to discharge collected water safely and in a controlled manner to the exterior.
An EPDM membrane was applied to the lower reinforced-concrete surface that could potentially come into contact with drainage water. This secondary protection layer was intended to protect the concrete surface and the lower skylight details against moisture while reducing maintenance requirements and associated costs throughout the system’s service life.
How Were the Eight-Metre-High Interior Walls Clad?
The approximately eight-metre-high octagonal interior walls extending below the skylight were completed with an aluminum composite panel cladding system compatible with the architectural form of the project.
Specially bent galvanized sheets were installed beneath the composite panel edge terminations. Stone wool with a density of 50 kg/m³ was fixed over these sheets to provide perimeter thermal insulation at the panel terminations and around the skylight.
The specially bent metal sheets enabled the insulation material to be installed in a controlled manner and supported the precise completion of the composite panel edge details.
How Were the Skylight and Composite Panel Systems Integrated?
The skylight glass, NPI 140 steel supporting members, omega profiles manufactured for the 18 mm joints, concealed drainage channels, EPDM membrane, stone wool insulation layer and composite panel cladding were coordinated through common construction details.
The axes of the steel structure and the composite panel joints were evaluated together to ensure that the octagonal form continued seamlessly from the glass surface to the interior walls. This approach enabled the supporting structure, water management, perimeter thermal insulation and interior surface cladding to be combined without compromising the architectural integrity of the project.
Project Result
The Kabataş–Mahmutbey Metro skylight application combined high load-bearing capacity, exterior weather resistance, controlled water drainage, reduced thermal breakage risk, perimeter thermal insulation and architectural appearance within a single integrated system.
The octagonal skylight and composite panel cladding designed and installed by Optimal Mimarlık created an integrated overhead enclosure intended to provide a long service life, reduced maintenance requirements and performance suitable for the intensive operating conditions of the metro structure.
