Renaissance Tower

Location: Kozyatağı, İstanbul, Turkey

Project Type: Office

Client: RENAISANCE Construction

Architect: FX FOWLE Architects

Electrical project: Okutan Engineering

Mechanical project: Okutan Engineering

Static Project: DeSimone Consulting Engineers APCB

Plant Project: Okutan Engineering

Rönesans tower is  one of the  tallest building in Anatolian side of İstanbul. Total high is 186m. The building is in construction site now and it will be used an offıce building at May, 2014. The building has 40 floors above ground level and 4 floors below ground level. Rönesans tower building has used BRB system.The system was used firstly for tall buildings in Turkey.Because of sustainable design and creative open areas, building took LEED gold  certificate. Offices has 3.70m high- comfortable .

DESIGN

Rönesans tower, one of the tallest building on the Anatolian side of İstanbul, creates a memorable presence for the headquarters of a dynamic construction. Occuping an ‘edge city’ context at the intersection of two major highways, the tower is completely free standing and functions as an obelisk, offering 360 degrees views from its prominent corner location. Its form marks the end of long vistas and announces the entrance to the city from the east. Its crystalline, chiseled massing, which takes cues from Ottoman geometric motifs and draws inspiration from surrounding local landforms, rotates approximately 33 degrees for optimum solar control.

STRUCTURAL DESIGN CRITERIA

A performance based design procedure was utilized for the seismic  analysis and design of the structure.The structure has been constructed primarily reinforced concrete while the spire has been framed with structural steel. The Buildings unique shape posed many challenges in the analysis, design and detailing of this signature structure. The structure has been designed to safely withstand even the most severe earthquakes in this seismically sensitive region.

FOUNDATION

A Geotechnical report was prepared and provided by Kilci Muhendislik. Foundation system for the tower was recommended to be a continuous reinforced concrete mat supported by large diameter caissons (Drilled shafts or piles). The caissons or piles will be socketed into the underlying rock for both compression and tension resistance. A continuous mat is required to spread the localized forces from the tower walls and columns to the various deep foundation elements below. Additionally, the mat will resist overturning forces from the core by mobilizing the counteracting loads from the large perimeter tower columns. A support of excavation system will be required during excavation of the below grade structure. 

SLAB

Slab system is flat slab, spanning between columns with no beams or girders. Long term deflection factor of concrete due to cracking is considered for design. Slabs are also checked for punching shear under both for gravitational and lateral forces since slabs are also attracting forces from shear wall core of the structure under lateral loading, transferring it to the columns. The flat-plate slab system (30cm thick typically) was chosen because of its simplicity and Architectural flexibility.

COLUMNS and SHEAR WALLS

The tower gravity system will consist of a concrete floor system supported by the interior core shear walls, perimeter square and circular concrete columns. The shear walls are located in the central core area surrounding the stairs and elevators. The shear walls vary in thickness from 100cm at the base to 60cm at the roof. Smaller 35, 30 and 25cm thick secondary walls are also provided around some elevator and stair shafts. The columns are located along the perimeter of the tower, range in size from 125x125cm square at the base to 75cm circular at the roof. Due to the architectural shape of the tower, most of the columns become sloped at some point in the building.

SPIRE

The tower is topped with large open-air spire, which is transferred onto the tower concrete structure by means of a steel transfer, or “Hat” truss. Spire structure on top of the building is made up of steel tube elements which are designed based on the cladding pressures provided by CPP in cladding report. Weight of the cladding is also considered in design. Seismic loads are significantly lower than the wind loads since structure is very light weight. Therefore, the spire structure is designed for the wind and gravity loads only and seismic loads have been ignored.

According to wind analysis, building is experiencing higher wind loads in Y direction causing a bigger overturning moment at the base level. Building drifts are bigger in Y direction since the loading is higher and stiffness of the core in Y direction is lower. This proves us the need for an outrigger at mid height of the tower to control drifts. The effect of outriggers on the building performance can be clearly seen in Y-direction inter story drift graph.

BRB SYSTEM

“Buckling Restrained Brace” system to achieve the dual purpose of providing substantial static stiffness for wind loading, while providing substantial energy dissipation for seismic loading. BRB systems provide energy dissipation through hysteretic behavior of steel in pure axial tension and compression. Such systems are currently produced by Star Seismic and Nippon.

The bond-preventing layer decouples the casing from the core. Accordingly, the axial load of the brace is transmitted by the steel core only, while the casing - through its flexural rigidity – provides the proper lateral support against flexural buckling of the core.

4 braces was used at 18th.floor, This braces work like shock absorber and provide a precaution against to earthquake which apply forces Beams, columns and braces arranged to form a vertical truss. Resist lateral earthquake forces by truss action. BRB yield both in tension and compression - no buckling !! System combines high stiffness with high ductility.

FACADE

The unitized four-sided structural glass facade is comprised of large vision areas and full depth shadow boxes to create a monochromatic surface. The tower is highlighted by an intermittent scrim of textured metal on the south, east and west elevations that provide shading and visual interest from both the interior and exterior. The tower features double height sky gardens with a hybrid unitized curtain wall and spanning glass mullions. The podium will be comprised of a hybrid glass wall with diagonal spanning members to support the crystalline sightlines.