Severely Damaged Reinforced Concrete Circular Columns Repaired by Turned Steel Rebar and High-Performance Concrete Jacketing with Steel or Polymer Fibers

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.

A degrading Bouc–Wen model for the hysteresis of reinforced concrete structural elements

“…The identification of the model parameters is performed on the basis of the experimental data of a RC bridge pier. The experiment was carried out in the lab of the Fuzhou University (Xue et al, 2018). The pier considered is named R16-1B and it comes out from a repairing process of the original pier P16-1B, which was previously damaged by a cyclic test.…”

“…As Figure 5 shows, the displacement history is composed of a first part and a second part. The first part corresponds to the response of the bridge column to the Tolmezzo accelerogram (Xue et al, 2018), referred to an earthquake occurred in Italy in 1976. The second part represents the response of the bridge column to the Tolmezzo accelerogram scaled to double.…”

“…As a result, the force-displacement curve is obtained. More details on the mechanical characteristics, the repairing process and the test setup are reported in (Xue et al, 2018). simulates the dead load deriving from the superstructure (see, among the others, Colomb, Tobbi, Ferrier, & Hamelin, 2008;He, Sneed, & Belarbi, 2013;Sun, Wang, Du, & Si, 2011).…”

Progressive Collapse Analysis of SRC Frame-RC Core Tube Hybrid Structure

“…Due to the advantages of concrete-encased composite structure [1], there are extensive studies [2][3][4][5][6] focusing on its seismic performance. The research on progressive collapse has become of increasing interest in recent years, especially since the World Trade Center towers collapse following the terrorist attacks of 11 September 2001.…”

Research on the Internal Thermal Boundary Conditions of Concrete Closed Girder Cross-Sections under Historically Extreme Temperature Conditions

“…Therefore, it is particularly important to accurately predict the temperature distributions on closed girder cross-sections. Moreover, thermal influence is considered to be a key parameter not only for bridges with expansion joints but also for jointless bridges [7,13,22,[27][28][29][30][31][32][33][34][35][36][37][38][39]. Finite element simulation is one of the most commonly used and effective methods to analyze the temperature distributions on concrete bridge cross-sections.…”