Abstract
A new strategy that repairs severely damaged reinforced concrete (RC) columns after an earthquake is proposed as a simpler and quicker solution with respect to the strategies currently available in the literature. The external concrete parts are removed from the column surface along the whole plastic hinge region to uncover the steel reinforcement. The transverse steel is cut away, and each longitudinal rebar is locally substituted by steel rebar segments connected by welding connections to the original undamaged rebar pieces outside the intervention zone. The new rebar segments have a reduced diameter achieved by turning to ensure plastic deformation only in the plastic hinge, protecting the original rebar and the welding connections. The connection is specifically designed to be effective and simple, and is directly realized on column reinforcement. Finally, the removed concrete is restored by a jacket built with high-performance concrete with steel or polymer fibers. The use of concrete with high volume fraction of polymer fibers to repair the column is investigated for the first time in this paper. This concrete was characterized by compression and flexural tests in the laboratory and its mechanical characteristics were compared with those of the concrete with steel fibers, which are being increasingly used in construction. The repair strategy was applied to two RC columns (1:6 scaled bridge piers), tested by asymmetric cyclic tests. The results show that the column strength, stiffness, and ductility were restored, and the energy dissipation capacity improved. The experimental evidence was investigated by fiber models in OpenSees.
Highlights
Columns were similar to the one recorded on the as-built columns (ASB) column; the repair strategy was able to restore the strength of the columns
The strategy included the removal of the concrete and the steel transverse reinforcement in the plastic hinge region to expose all the longitudinal rebar, the use of a turned rebar segment to substitute the damaged part of the longitudinal rebar, and the building of a concrete jacket using high-performance fiber reinforced concrete (HPFRC) with steel or polymer fibers to restore the concrete parts and to improve the seismic performance of the column
A HPFRC with polymer fiber was designed using a high volume fiber fraction (4%), which was investigated for structural use
Summary
In seismic regions such as Italy, the evaluation of the capacity and fragility of structural and infrastructural systems subjected to seismic events [1,2,3,4,5,6,7,8,9], and implementing proper survey programs to monitor the evolution of their capabilities [10,11] are important for preventing severe seismic damage being observed in recent seismic events [12] by means of retrofitting interventions [13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31].Appl. Repair strategies to restore or improve the seismic capacity of reinforced concrete (RC). Repairs should be performed and quickly on construction sites to assure that the strategy is appropriate in case of bridges that are strategic for the emergency response. The repair of RC components is usually performed in case of modest damage (local concrete spalling or modest deformation of the steel reinforcement) when the deformed rebar can be straightened, and the cover can be restored by simple mortar patches. An external fiber reinforced polymer (FRP) is applied to improve the shear strength and the ductility of the component [33]
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