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Selected, extended paper from the SDSS 2019 special session ECCS/TC8 – Structural Stability The cross‐sectional strength of square (SHS) and rectangular (RHS) hollow sections loaded in compression and various degrees of uniaxial or biaxial bending are governed by local instabilities in the elastic or plastic range. Common design checks for cross‐sectional strength, e.g. those found in the Eurocodes, regularly penalize these sections through a conservative omission of various mechanical effects and a categorization of cross‐sections into distinct classes with corresponding, markedly different, design rules. This leads to discontinuities and inaccuracies in the strength representation. Such conservatism is particularly detrimental to the introduction of high‐strength steel hollow sections, which often fall into the semi‐compact and slender cross‐section classes for which local buckling is more relevant. This paper discusses the results of extensive research work carried out during the RFCS research project HOLLOSSTAB. In this project, new design rules were developed for the cross‐sectional and member design checks of hollow sections with various shapes and slenderness ratios, termed the “Generalized Slenderness‐based Resistance Method – GSRM”. This paper summarizes the experimental and numerical campaign carried out within HOLLOSSTAB and describes the new GSRM design rules and their background for the case of the cross‐sectional strength of SHS and RHS.

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The paper illustrates an investigation on the effectiveness of dissipative bracing (DB) systems for seismic retrofit of buildings with sensitive non-structural components (NSCs) and technological content (TC), such as medical centers. The "Giovanni Paolo II" hospital, located in a high seismic prone area in Southern Italy, is chosen as case-study. The retrofit intervention with hysteretic braces is designed according to the Italian Building Code. The seismic response of the hospital building is investigated by means of non-linear history analyses carried out in OpenSees FE code and, in order to verify the full-operation after the earthquake, the integrity of NSCs and TC is checked. The retrofit design, thanks to the stiffening and damping effects introduced by DB system, proves suitable to protect both the structural frame and "drift-sensitive" non-structural components and content even under severe earthquakes (PGA = 0.45 g). Nevertheless, some concerns arise about the suitability of hysteretic braces for the protection of the "acceleration-sensitive" elements of the medical complex. Indeed, during weak earthquakes (PGA = 0.17 g), failures of several of these components are detected which can substantially impair the operation of the hospital in the aftermath of the seismic event.

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