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In this research, a detailed 3-D finite element model is developed by ABAQUS package for an existing six-story reinforced concrete framed structure in Saudi Arabia to study its response under blast loads. The building is office building designed for dead, live, wind and seismic loads. The design wind speed is 161 km/h while the mapped maximum considered earthquake spectral response acceleration at a short period and at a period of 1-second are 0.12 g and 0.034 g, respectively. Concrete damage plasticity model was used to model the concrete elements. The 'brittle cracking' concrete model was used to represent column removal in front of the explosion. The metal plasticity model was used to represent the steel. The model is exposed to blast loading with a 1.0 ton (2204.623 lb) of TNT at a distance of 5 m from the building. Another scenario was considered if the blast load is 10 m from the building to investigate the effect of the standoff distance. The structural vulnerability is assessed and compared. Alternative uncommon structural design of external columns is considered using composite cross section, which uses steel casing around concrete section. This uncommon design gave better results in terms of mitigating blast load effects on structures. [ABSTRACT FROM AUTHOR]

Ongoing terrorist attacks on many structures around the world have increased the importance of analysis of structures under blast loading. Despite the progress made in this area, there is a need to better understand the structural performance of framed concrete structures under severe loading before, inevitably, adopting any mitigation measures. Most of the structures that are damaged by bombs or impact loading are not initially designed to resist blast loads. The severe vulnerability of these structures has led to ongoing development of new provisions and guidelines of effective techniques to mitigate risks associated with explosions. In this research, detailed finite element analyses were performed using ABAQUS to assess the structural performance of reinforced concrete frames under blast loading. A model of two dimensional, 4-story reinforced concrete frame was selected for the study. The response of the structural model under the simulated blast loads is presented, along with two alternative designs as a precursor to provide mitigation guidelines in the future. Results showed that changing the design of the external columns improved the response, especially using the concrete filled steel tube section. [ABSTRACT FROM AUTHOR]