C+S December 2020 Vol. 6 Issue 12 (web)

Basaksehir Pine and Sakura City Hospital By Aysegul Gogus and Atila Zekioglu

Due to its location in a high seismic region and its growing popula- tion of over 15 million, Istanbul has been taking efforts to improve its resilience. One of the key initiatives of the city’s resilience plan is providing world-class healthcare services in newly built and seismi- cally resilient large public hospitals. Başakşehir Pine and Sakura City Hospital is the first city hospital built in Istanbul as part of the“New City Hospitals” program initiated in 2007 by the Ministry of Health in Turkey. In April 2020, the hospital partially opened 1,700 beds to assist with the COVID-19 response in Istanbul. The official grand opening of the 2,682 bed-capacity hospital took place in May 2020, and the hospital has since been in full service to roughly 32,700 patients per day, with 90 operation theatres and 458 intensive care units. Use of base-isolation for the new city hospitals, which are located in high-seismic zones, has been deemed mandatory by the Ministry of Health in Turkey. Spanning an area of 10 million square feet and featuring 2,068 seismic isolators, Başakşehir Pine and Sakura City Hospital has become the largest base-isolated structure in the world. At 332 feet tall, the main hospital facility consists of three specialty tow- ers, of 14, 16, and 17 stories, three helipads, and six clinic buildings, all of which share a 5-level common podium with no seismic joints. The lower three levels of the podium accommodate underground parking to more than 8,000 cars. The hospital was built under a Public-Private-Partnership (P3, PPP) model, by Rönesans Holding, who currently operates in the roles of main contractor and investor in 28 countries around the globe, as well as Sojitz Corporation, a Japanese investment and trade corporation. Arup was responsible for the design of the base-isolation system, the foundations, and the seismic design of the super-structure. Concept design of the building started in the second quarter of 2016, and the structural design was completed within a year. In order to achieve enhanced performance objectives for seismic resil- ience, the hospital was designed to satisfy ASCE 41 “Immediate Occu- pancy” performance objective under a very rare earthquake (BSE-2N) with a drift limit of 1 percent, and “Operational” performance objec- tive under the design earthquake (BSE-1N) with drifts limited to 0.5 percent. In order to further minimize damage to nonstructural compo- nents, floor accelerations were limited to 0.2g under BSE-2N seismic hazard. The final design ensures vital functionality of the hospital not only for the patients who might need urgent treatment, but also for the resilience of the community and the city. The gravity system of the hospital consists of reinforced concrete slabs and beams supported by cast-in-place concrete columns. Given the size

of the project, a core wall-only lateral system offered the best potential of story-heights and optimization of concrete and reinforcement quan- tities. Arup conducted an extensive wall optimization study in which a total of one hundred and eighty different wall thickness configurations were evaluated to minimize construction costs and improve floor ef- ficiency. The study aimed at optimizing the concrete quantity, while providing sufficient lateral stiffness to the base-isolated building. Selection of the isolation system was of utmost importance since the procurement of isolators was a critical path item for the design and the construction process, and a primary driver influencing the overall construction cost and schedule. In order to facilitate the selection of


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