Influence of loading-rate on the failure mode of RC columns
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Significant challenges exist for engineers in accurately predicting the response of reinforced concrete columns to blast loads through simplified analysis techniques. Current methods of analysis rely largely on over simplified and often outdated methods that fail to fully represent the complex response of a member. A particularly important issue encountered in impulsive loading conditions, which include both blast and impact situations, is that as the rate of loading increases the propensity for a column to fail in a brittle shear manner increases. This is highly undesirable in the case of load bearing columns and can lead to devastating progressive collapses (e.g. Alfred P. Murrah building, Oklahoma). One solution to this problem is to increase the shear strength with transversely wrapped fibre reinforced polymers (FRPs), however, the lack of simplified analysis methods and fundamental understanding of the response of members makes it difficult for engineers to effectively analyse columns for retrofit. This paper presents work on a new theoretical model, based upon energy considerations, which provides a method for predicting the transition in failure mode from ductile flexure to brittle shear under a range of impulsive loading conditions. Impact tests, carried out to identify the transition from ductile to brittle shear failure modes with increased loading rate and the relationship to given reinforcing configurations, are also presented. The accuracy of the proposed model in predicting the transition in failure mode is discussed, in comparison with available impact test data, and the method is further extended to predict failure mode transition for impulsive blast loading situations. The method shows great promise in situations where counter terrorism may be a significant design consideration, allowing engineers to effectively design columns so as to ensure a ductile response, or to analyse existing structural columns for possible retrofit to prevent shear failure.
|Creators||Isaac, P., Darby, A., Ibell, T. and Evernden, M. C.|
|Departments||Faculty of Engineering & Design > Architecture & Civil Engineering|
|Research Centres||BRE Centre in Innovative Construction Materials|
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