Assessment of robustness for composite steel-concrete frame buildings

Abstract

Robustness for buildings is a compilation of lessons learned from past experiences in the engineering world. The main purpose is always the same: to avoid the progressive collapse on buildings second to an accidental load like fire, explosion, impact or the consequence of a human error. This is why the construction norms for Europe, EN 1991 part 1-7, is focused in that matter. However, preparing a building to withstand the additional stress caused by these events, can make the final cost of the structure out of reach for the investor. This is what motivated the research at hand, so that we could design a structure, on top of the building, capable of redistributing the loads.In order to reach this objective, a parametric numeral study was done, where two buildings were designed under three different conditions. The first one was a simple structural design following the consideration on the European norms for ultimate and serviceability limit state, used as a refence point. On the second one, the buildings were design following the Eurocode 1 part 1-7 for accidental load, making the structure with enough redundancy in order to tolerate the stress applied. On the third one, the latter was applied by using a super-structure to redistribute the load. The solutions were compared based on the final weight and connection rigidity of the building. On both cases the building with the super structure was verified for the accidental combination loads. However, the smaller one, when checked for normal conditions for the ULS and SLS, was not satisfactory, having to be redesigned for the additional weight of the super structure.Making a comparison of the final solution for both buildings, we arrived at the conclusion that the super-structure that was considered, helped the structural design. Even though for the smaller building the solution was not lighter, the connection rotational stiffness was considerably lower, whereas for the second building, both conditions were satisfactory.

Robustness for buildings is a compilation of lessons learned from past experiences in the engineering world. The main purpose is always the same: to avoid the progressive collapse on buildings second to an accidental load like fire, explosion, impact or the consequence of a human error. This is why the construction norms for Europe, EN 1991 part 1-7, is focused in that matter. However, preparing a building to withstand the additional stress caused by these events, can make the final cost of the structure out of reach for the investor. This is what motivated the research at hand, so that we could design a structure, on top of the building, capable of redistributing the loads.In order to reach this objective, a parametric numeral study was done, where two buildings were designed under three different conditions. The first one was a simple structural design following the consideration on the European norms for ultimate and serviceability limit state, used as a refence point. On the second one, the buildings were design following the Eurocode 1 part 1-7 for accidental load, making the structure with enough redundancy in order to tolerate the stress applied. On the third one, the latter was applied by using a super-structure to redistribute the load. The solutions were compared based on the final weight and connection rigidity of the building. On both cases the building with the super structure was verified for the accidental combination loads. However, the smaller one, when checked for normal conditions for the ULS and SLS, was not satisfactory, having to be redesigned for the additional weight of the super structure.Making a comparison of the final solution for both buildings, we arrived at the conclusion that the super-structure that was considered, helped the structural design. Even though for the smaller building the solution was not lighter, the connection rotational stiffness was considerably lower, whereas for the second building, both conditions were satisfactory.