35 Lower Long
Realising the architectural intent for 35 Lower Long, Cape Town
Cape Town’s Foreshore has evolved from a disused industrial marine area into a residential, commercial, retail and hospitality destination with signature towers, bold architectural forms, and striking façades.
Asserting itself in the city’s skyline as the most iconic commercial building in the precinct, is the R500-million 35 Lower Long skyscraper developed by Abland. The 25-storey office and retail tower has a total floor area in excess of 27 500 m².
Due to the company’s recognised knowledge and expertise in designing tall structures, Zutari was appointed as the civil and structural engineer for the project. The overriding requirement was to develop an engineering design solution that maximised the cost-benefits for the client, while completing the building with quality finishes in a short time-frame.
The project featured a range of interesting challenges, one of which was the historic reinforced coal bunker underlying the site, which the project team had to consider during excavation, lateral support and foundation works. Zutari overcame this constraint by designing a system of strap and bridge beams, together with some advanced shoring techniques, ensuring that the building was founded within the project budget.
Responding to a unique architectural form
Striking architectural features of the glazed façade structure are the two main corners, which are cut away and slope towards the roof line, breaking the solidity of the building. To establish the most appropriate structural design and construction methodology, Zutari worked in collaboration with dhk Architects, the client (Abland) and the contractor (Stabilid Cape) to achieve the external architectural intent for the building. This was particularly important as the sculpted form of the building mass, and the defragmentation and the articulation of the corners now provide the unparalleled views of the magnificent surroundings.
The overriding requirement was to develop an engineering design solution that maximised the cost-benefits for the client, while completing the building with quality finishes in a short time-frame.
Sophisticated use of a small footprint
Providing unrivalled all-round views across the city of Cape Town, the harbour and Table Mountain, the building’s individuality and beauty is a beacon of transformation for the city’s Foreshore.
The small footprint of the site and the sculpted shape of the 24-storey building presented Zutari with significant engineering challenges; whereas a central lift shaft is typically the structural backbone of a tall tower, 35 Lower Long had a discontinuous lift shaft due to an additional lift lobby on the 10th floor. The challenge was to create lateral stiffness and structural integrity to withstand seismic activity, vibration and wind drift.
Zutari used response-spectrum analysis in designing the tall building to withstand seismic activity. This is a linear-dynamic statistical analysis method that measures the contribution from each natural mode of vibration to assess the likely maximum seismic response of a structure.
Working closely with the architect and client, Zutari also developed a K-brace system over the height of the building to prop at the core on Level 18, accommodating the lateral loads of wind and vibration pressure. The innovative feature puts the geometry of the beautiful, slanted glazed façade corners of the building to functional use as the K-brace.
35 Lower Long was designed to attract large corporate tenants with its premium-grade office rating and sustainability initiatives. In addition to providing unrivalled all-round views across the city of Cape Town, the harbour and Table Mountain, the building’s individuality and beauty is a beacon of transformation for the city’s Foreshore.
*The Aurecon Africa business has been officially renamed Zutari as at 21 July 2020. Zutari acquired Aurecon Middle East on 20 November 2020.