Enhancing the progressive collapse resistance of seismically designed steel-concrete composite buildings

The present work is concerned with designing steel-concrete composite buildings under requirements on: (a) safety of structural members based on provisions of Eurocodes 3 and 4, (b) structural system resistance against seismic actions without the development of extensive lateral deflection and inter-storey drifts and (c) progressive collapse resistance, which ensures that local failure in structural elements due to accidental actions does not trigger disproportionate collapse of the structure. The first two are conventional design requirements typically taken into account, while the third is an additional design requirement, therefore an increase to the total structural cost is inevitable. Thus, an engineer is required to put significant effort in the limitation of the extra cost induced, ensuring at the same time that the desirable structural performance is achieved.
Automatic optimization algorithms are valuable tools for this purpose. However, the same goal might be pursued using manual strategies and exploiting one’s experience. Four manual beam upgrade strategies are proposed, in order to improve the progressive collapse resistance of steel-concrete composite buildings already designed against earthquake. The effectiveness of the aforementioned strategies is assessed in comparison with the design defined using an optimization algorithm.