PSI - Issue 64

Maximilian Fehr et al. / Procedia Structural Integrity 64 (2024) 885–892

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Maximilian FEHR, Michael BAUR, Giovacchino GENESIO / Structural Integrity Procedia 00 (2019) 000 – 000

© 2024 Maximilian FEHR, Michael BAUR, Giovacchino GENESIO . Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers Keywords: existing buildings, seismic retrofitting, external steel lattice, push-over analysis © 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of SMAR 2024 Organizers 1. University Hospital Zurich The buildings HOF, OPS, and OST are arranged in a U-shaped layout in relation to each other (Fig a). However, the three buildings are structurally separated by expansion joints located at the two ends of the HOF building. The HOF building, with a ground plan of approximately 44 m x 24 m, consists of 6 full floors with a floor height of approximately 3.4 m. The original building was constructed in 1966 in reinforced concrete. Between 1979 and 1980 an extension of 4 full stories was built. This was built as a steel- and steel-concrete composite construction. The staircase core is a continuous reinforced concrete (RC) construction through all floors. The building is in the seismic zone Z1a (0.6m/s 2 ), soil class A (rock), and building class III (equivalent to importance class IV in Eurocode 8) according to SIA 261.

Fig. 1,Building overview University Hospital Zurich (left), Cross section of the courtyard building (right)

2. Retrofitting measures One of the main objectives of the seismic retrofit of the HOF hospital building back in 2020, was to improve the highly eccentric floor plan in terms of lateral bracing elements. The strong eccentricity in the floor plan can be seen in figure 2. There are sufficient shear walls on the lower floors (RC construction, Fig b). However, from floor C (3rd floor, extension, figure 1b) the building has a very irregular layout, because only few RC walls continued upwards. To move the shear center to the center of mass, two steel braces were attached to the façade. In addition, the existing steel structure was also braced in plane with X-bracings to ensure the necessary diaphragm action of the upper floor. The second retrofit objective was to increase the lateral stiffness to reduce the displacement of the HOF building. The joints between the neighboring buildings (OST and OPS) can take up to 20 mm of horizontal displacement.