ارزیابی اصلاحات طراحی به منظور افزایش تعمیر پذیری
Abstract
1- Introduction
2- Literature review
3- Test walls
4- Test setup and loading protocol
5- Results
6- Discussion and recommendations
7- Conclusions
Acknowledgements
Appendix A. Supplementary material
Research Data
References
Abstract
As a consequence of recent earthquakes in New Zealand, many concrete buildings have been demolished due to structural damage. Observations of damage to concrete walls led to substantial research and revisions to design standards to ensure that a satisfactory ductile response was achieved. However, even when the current performance objectives of the design standards are met, reinforced concrete walls may still require extensive or costly post-earthquake repairs. The objective of this project was to evaluate simple modifications to conventional reinforced concrete walls to increase their repairability. Four modified walls were constructed and subjected to cyclic lateral in-plane loading until failure, and compared to a previously tested conventional ductile reinforced concrete benchmark wall that failed at 2.5% drift. The modifications considered included debonding of reinforcement at the wall base, substituting fiber-reinforced concrete (FRC) for conventional concrete, and substituting engineered cementitious composite (ECC) for conventional concrete in the ends of the plastic hinge region (applied in two walls). Debonding delayed vertical reinforcement buckling, but failure occurred shortly thereafter (2.5% drift) due to constricted movement of the buckled bars within the debonding sleeves. The FRC and both ECC walls had increased crack propagation up to a drift demand of 0.5%, but then the cracks localized to a single dominant crack and the walls failed at drifts lower than the benchmark wall (about 1.5%). Modifications of the tested details are recommended for future test programs that investigate the repairability of concrete walls.
Introduction
Recent earthquakes in New Zealand have resulted in significant damage to and demolition of modern reinforced concrete (RC) structures [1–۳]. RC walls have been the focus of significant research following the 2010/2011 Canterbury earthquakes, both due to the undesirable damage observed in a few modern RC wall buildings and their popularity in building construction during the rebuild. RC wall research following the Canterbury earthquakes has predominantly focused on improving the design standards for new walls to increase the reliability of achieving ductile response [4–۶]. However, the damage resulting from the conventional ductile RC walls will still require significant postearthquake repair. In reality, many structures that were only lightly damaged in the Canterbury Earthquakes were also demolished for various reasons including insurance policies, uncertainly regarding residual capacity, and the cost of repairs [7]. Nonetheless, to prepare for a better future outcome, it is pertinent to consider from a technical standpoint whether and how to repair these structures to sufficiently restore their lateral capacity. A recent study by Motter et al. [8] showed that RC walls built to satisfy the new minimum vertical reinforcement provisions in the New Zealand Concrete Structures Standard (NZS) 3101:2006-A3 [9] could be repaired to reinstate the structural capacity after being subjected to extensive structural damage, but the invasive and costly repairs required may not be practical in damaged buildings.