Seismic retrofit for RC columns by NiTi and NiTiNb SMA wires

Chung

et al. 2010

Smart Mater. Struct.

The purpose of this study is to assess the confining effectiveness of shape memory alloy (SMA) wire jackets for concrete. The performance of SMA wire jackets was compared to that of steel jackets. A prestrained martensitic SMA wire was wrapped around a concrete cylinder and then heated by a heating jacket. In the process, a confining stress around the cylinder was developed in the SMA wire due to the shape memory effect; this jacketing method can increase the strength and ductility of the cylinder under an axial compressive load. In this study, NiTi and NiTiNb SMA wires of 1.0 mm in diameter were used for the confinement. Recovery tests were conducted on the wires to assess their recovery and residual stress.The confinement by SMA wire jackets increased the strength slightly and greatly increased the ductility compared to the strength and ductility of plain concrete cylinders. The NiTiNb SMA wire jacket showed better performance than that of the NiTi SMA wire jacket. The confining effectiveness of the SMA wire jackets of this study was estimated to be similar to that of the steel jackets. This study showed the potential of the SMA wire jacketing method to retrofit reinforced concrete columns and protect them from seismic risks.

Section: Introductionmentioning

confidence: 99%

The confining effectiveness of NiTiNb and NiTi SMA wire jackets for concrete

Chung

et al. 2010

Smart Mater. Struct.

Journal of Intelligent Material Systems and Structures

“…NiTiNb wire can be used as a reliable source of active stress to reinforce, remediate, and retrofit structures. Several studies have demonstrated the use of NiTiNb spirals to strengthen concrete columns (Andrawes et al, 2010; Chen and Andrawes, 2014, 2017; Choi et al, 2009, 2010b, 2010d, 2011, 2013; Shin and Andrawes, 2010). It was found that (Chen and Andrawes, 2017) the strength of concrete confined with SMA spirals was approximately 51% higher than that of unconfined concrete.…”

Section: Introductionmentioning

confidence: 99%

Enhancement of recovery stress by annealing and prestraining of NiTiNb wires

Yang

Liu

Zhong

et al. 2023

NiTiNb shape memory alloy has attracted much attention for its use in prestressing and remedying structural steel and concrete members due to its unique shape memory effect. However, the recovery stress values reported in the literature vary significantly, as the interplay between recovery stress and treatment parameters is not fully understood. In this study, we carefully investigated the effects of annealing and prestraining on the martensitic transformation behavior and mechanical properties of NiTiNb alloy and clarified their correlations to the recovery stress. Our results showed that the yield strength and superelasticity decreased while the ductility and retained stress-induced martensite increased with increasing annealing temperature. We found that high recovery stress can be achieved by annealing the sample above the recrystallization temperature while keeping the annealing temperature as low as possible to maintain high strength. Prestraining the sample to beyond the stress plateau but before yielding was found to be most effective for enhancing the recovery stress. By using these criteria, we were able to obtain large recovery stresses of greater than 550 MPa from 20°C to 200°C through a simple one-step annealing at 700°C and a 10% prestrain using commercial superelastic NiTiNb wire products.

Advances in Structural Engineering

“…However, bonding failure along the interface between FRP sheet and concrete was a defect limiting its further application (Lu et al, 2015;Quiertant and Clement, 2011;Rahai and Akbarpour, 2014;Zhang et al, 2000Zhang et al, , 2015. The seismic performance of the columns which were retrofitted at plastic hinge region by the prestressed memory alloy wire was studied (Choi et al, 2009). The study results indicated that the RC column with circular section could be confined actively by the prestressed memory alloy wire and the ductility of the column could also be enhanced.…”

Section: Introductionmentioning

confidence: 99%

Experimental study on seismic performance of reinforced concrete column retrofitted by asymmetric increased single lateral section

Liu

Chen

et al. 2016

In this article, a new retrofit method that the frame column is strengthened by asymmetric increased single lateral concrete section is proposed. The new added section could be ordinary reinforced concrete, bonded prestressed concrete, or unbonded prestressed concrete. The new added section could be connected with the column through anchor rebars, or prefabricated first, then be connected to the column through high strength bolts. The low cyclic reversed load experiment has been launched on understanding the seismic performance of one unretrofit specimen and six retrofitted specimens. The experiment has considered four main factors that is loading direction, material adopted on the new added section, different orders of unification of the retrofit column, and the process of prestress applying. Based on the experiment study, the characteristics including the failure mode, hysteresis loops behavior, bearing capacity, ductility, stiffness degradation, and energy dissipation ability are demonstrated. The bearing capacity calculation method of the retrofit column under compression–bending action is established. The calculation results and the experiment results show good agreement. Some suggestions for seismic design of the retrofit column are proposed. The experimental results show that the retrofitted column has good seismic performance and good retrofit effects. The research results could be references to the practical engineering design works.