Case Study: Application of the Hardness Method To Estimate the Residual Capacity of Reinforcement in An Earthquake Damaged Building


Abstract eng:
apacity design and hierarchy of strength are at the base of modern seismic codes which allow an inelastic response of structures in case of severe earthquakes. Therefore, in traditional reinforced concrete (RC) structures damage develops in defined locations known as plastic hinges. As expected, during the 2010 and 2011 Christchurch earthquakes, plastic hinges formed in beams, coupling beams and at the base of columns and walls preventing collapse. However, structures were damaged permanently. Due to the lack of literature on methods to evaluate the residual capacity of damage buildings to sustain subsequent aftershocks and on reliable and cost-efficient repairing techniques to bring back the structure “at least” as it was before the earthquake, a significant number of multi-storey RC buildings were deemed irreparable and were demolished. New Zealand local authorities and industry have request to develop techniques for assessing damage to steel reinforcement bars embedded in concrete elements. Immediately following the 2010/2011 Christchurch earthquakes, low invasive techniques able to quantify the level and extent of plastic deformation and residual plastic capacity were not available. The current method (known as “in situ hardness method”) is based on measuring hardness with a Leeb hardness portable device in situ then correlating it to plastic strain based upon laboratory tensile tests. Extensive studies and practical applications have been conducted soon after the Christchurch earthquakes, but the in situ method has not yet been vetted in the open literature, and thus has not been widely accepted. In the present work, based on empirical relationships between hardness versus strain and residual strain capacity, a damage assessment procedure is presented. If damage is found in situ via Leeb hardness testing, a bar may be removed for more accurate hardness measurements in lab using the Vickers hardness methodology. The Vickers hardness profile of damaged bars is then compared with calibration curves (Vickers hardness versus strain and residual strain capacity) developed for the same steel reinforcement (grade and diameter) extracted from undamaged locations. The paper presents the findings of experimental tests conducted to estimate strain and residual strain capacity of damaged locations in individual bars in earthquake damaged buildings. The proposed methodology also accounts for the effects of strain ageing, which should not be ignored. Note also that this testing is entirely monotonic (not cyclic).

Contributors:
Conference Title:
Conference Title:
16th World Conference on Earthquake Engineering
Conference Venue:
Santiago (CL)
Conference Dates:
2017-01-09 / 2017-01-13
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Text je chráněný podle autorského zákona č. 121/2000 Sb.



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 Record created 2017-01-18, last modified 2017-01-18


Original version of the author's contribution as presented on USB, paper 2075.:
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