|Title||Distributed column damage effect on progressive collapse vulnerability in steel buildings exposed to an external blast event|
|Publication Type||Journal Article|
|Year of Publication||2017|
|Authors||Sideri J., Mullen C.L, Gerasimidis S., Deodatis G.|
|Journal||Journal of Performance of Constructed Facilities|
Recent terrorist attacks on civil engineering infrastructure around the world have initiated extensive research on progressive collapse analysis of multistory buildings subjected to blast loading. The widely accepted alternate load path method is a threat-independent method that is able to assess the response of a structure in case of extreme hazard loads, without the consideration of the actual loads occurring. Such simplification offers great advantages, but at the same time fails to incorporate the role of a wider damaged area into the collapse modes of structures. To this end, the investigation of damage distribution on adjacent structural members induced by blast loads is considered critical for the evaluation of structural robustness against abnormal loads that may initiate progressive collapse. This paper presents detailed three-dimensional (3D) nonlinear finite-element dynamic analyses of steel frame buildings in order to examine the spatially distributed response and damage to frame members along the building exterior facing an external blast. A methodology to assess the progressive collapse vulnerability is also proposed, which includes four consecutive steps to simulate the loading event sequence. Three case studies of steel buildings with different structural systems serve as examples for the application of the proposed methodology. A high-rise (20-story) building is firstly subjected to a blast load scenario, while the complex 3D system results in the heavily impacted region are compared with individual single-degree-of-freedom (SDOF) column responses obtained from a simplified analytical approach consistent with current design recommendations. Parameters affecting the spatially distributed pressure and response quantities are identified, and the sensitivity of the damage results to the spatial variation of these parameters is established for the case of the 20-story building. Subsequently, two typical midrise (10-story) office steel buildings with identical floor plan layout but different lateral-load-resisting systems are examined; one including perimeter moment-resisting frames (MRFs) and one including interior reinforced concrete (RC) rigid core. It is shown that MRFs offer a substantial increase in robustness against blast events, and the role of interior gravity columns identified as the weakest links of the structural framing is discussed.