Optimized retrofit of steel-concrete composite buildings against progressive collapse using steel cables

This paper investigates the cost-effective use of steel cables as a means of structural retrofit for seismically designed steel-concrete composite buildings in order to withstand progressive collapse. Progressive collapse is a topic of increased scientific interest for engineering researchers, mainly due to its destructive results, as well as the fact that it is large scale structural failure caused by small scale initial damage. Extreme actions, such as a strong earthquake, or an accident can cause severe damage to load bearing elements. Even though it seems to be a problem that mainly high-rise buildings face, due to the exploitation of the materials’ capacity within the deformation range of their non-linear performance during structural design, the majority of newly designed buildings are susceptible to this type of failure.

Cables are used as a means to retrofit buildings because of their advantages over their alternatives: they are not susceptible to flexural or lateral torsional buckling, as they receive only tensile forces. Also, their installation in existing buildings and their replacement in case of failure is easy thanks to the type of connections realized. For the determination of the most cost-effective design, the “Evolution Strategies” optimization algorithm is employed, in order to enable the investigation of the overall design philosophy. An optimized design is the one which meets all applicable requirements and has the smallest cost at the same time, i.e. the design which achieves the optimum use of the materials.