Gerasimidis Research Group
Stability of Structures and Materials
Gerasimidis Group
Stability of Structures and Materials
Resilience of Building Structures
Basic Research in Structural Robustness
An extreme event during a structure’s life-time can be defined as actions/loadings that are beyond the design requirements and can potentially jeopardize the structural integrity of the building leading to its partial or complete collapse. Among the many causes of extreme events one can identify design or construction errors, abnormal man-made loads such as blast, fire, vehicle collisions, terrorist attacks, but also abnormal environmental loads such as extreme values of wind or snow loads, earthquake, etc. One of the goals of the our research proposed project is answer important questions:
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How can we design structures to avoid collapse under extreme events?
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How can we make sure that our structures will remain stable after the appearance of localized damage within their system?
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How are these goals achieved with a reasonable budget?
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Another important finding of this research work is the identication of a system collapse mode through a long-wave instability shape [13]. The results reveal for the first time in progressive collapse that even if all the structural elements of a system remain safe and have not failed, the nonlinear stability degradation of the structure can lead to a long-wave system instability mode. This finding is of extreme importance as it is not limited to progressive collapse but can be applied to any hazard such as seismic, re or blast. Furthermore, my work has challenged the notion of full component removal for progressive collapse
analysis, prescribed by [23] and [24], by identifying more critical distributed damage scenarios involving partial damage of multiple adjacent structural components [12].
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Our findings on common structural systems, such as steel framed buildings, clearly manifest that there are critical collapse modes involving loss-of-stability phenomena. Our results present, for the first time in progressive collapse, a loss-of-stability collapse mode of a building after a column removal which is unconservative when compared to the commonly accepted yielding-type collapse mechanism for the same structures. One of the major findings of this work is the development of an analytical methodology able to predict the collapse load and the collapse mode of a structure under a damage propagation scenario, using analytical expressions and therefore bypassing the need for expensive and complicated numerical analysis. This is achieved through the new concept of new Euler-type curves which characterize the 3D structural system for any damage propagation scenario.
The new Euler-type curve for progressive collapse of steel frames in contrast with the traditional Euler curve describing buckling of members under compression.
Demonstration of the long-wave instability mode for steel frames. [2D.A] and [2D.B] fail through a short-wave column mode, while [2D.C] fails through a long-wave mode.
Progressive collapse after a gravity column removal. The collapse of the building follows a sequence of column instability failures.
I have also studied the resilience of buildings with multi-hazard considerations
which include a post-event [17] showing that even when a structure can withstand an extreme event scenario, a post-event is highly critical to evaluate the remaining time of survival of the structure up to collapse. I have also examined the spatially distributed response and damage of frame members along the exterior of a building facing an external blast using a new method of analysis [14]. My work demonstrates that steel moment resisting frames offer substantial robustness against blast, while gravity columns are the weakest link of the system.
Post-event fire progressive collapse analysis method