scholarly journals Uniaxial Compressive Behavior of Concrete Columns Confined with Superelastic Shape Memory Alloy Wires

Materials ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1227 ◽  
Author(s):  
Chenkai Hong ◽  
Hui Qian ◽  
Gangbing Song
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Seismic Design ◽  
Large Deformations ◽  
Axial Loading ◽  
Concrete Columns ◽  
Confined Concrete ◽  
Loading Capacity ◽  
Compressive Behavior ◽  
Concrete Cylinders

Superelastic shape memory alloy (SMA) exhibits the ability to undergo large deformations before reverting back to its undeformed shape following the removal of the load. This unique property underlies its great potential in the seismic design and retrofitting of structure members. In this paper, superelastic SMA wires were utilized to confine concrete cylinders to enhance their axial compressive behavior. The axial carrying and deformation capacities of SMA-confined concrete cylinders are assessed by uniaxial compression testing on a total of eight SMA-confined concrete columns and one unconfined column. The influence of the amount of SMA and the prestrain level of SMA wires, as well as the reinforcing mode, on the axial carrying and deformation capacity of confined concrete columns were considered. The analysis focuses on the axial carrying capacity and deformation performance of concrete columns reinforced with superelastic SMA under different loading conditions. Based on the experimental data and analysis results, it is found that superelastic SMA wires can increase the axial loading capacity and enhance deformation performance of concrete columns. Under the same loading condition, the ultimate bearing capacity of SMA-confined concrete columns increases as the increasing of the amount of SMA wire. The results of this study verify the effectiveness of superelastic SMA in enhancing the loading capacity and deformation behavior of concrete cylinders.

Recovery and Residual Stress of Shape Memory Alloy Wires and Its Application

2009 ◽  
Author(s):  
Eunsoo Choi ◽  
Tae-hyun Nam ◽  
Man-Cheol Kim ◽  
Jong Wan Hu ◽  
Bak-Soon Cho ◽  
...  
Keyword(s):  
Residual Stress ◽  
Reinforced Concrete ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Residual Deformation ◽  
Concrete Columns ◽  
Recovery Stress ◽  
Reinforced Concrete Columns ◽  
Concrete Cylinders ◽  
Active Confinement

Two kinds of shape memory alloy wires, NiTiNb and NiTi, are manufactured and pre-elongated during the manufacturing process. After fixing the pre-elongated wires, heating on the wires induces recovery stress on them. Several tests to measure the recovery stress are conducted with varying initial strains. Stress-reduction of the recovery stress is observed after the temperature of the wires is cold down; the remaining stress is called residual stress that is also measured. Also, this study measures the stress-strain curves of the SMA wires under the state that the residual stress is working. The tension behavior of the wires under residual stress is very unique. The NiTi is martensitic state at room temperature, thus a residual deformation remains after applying a large strain. However, under residual stress, the tensile behavior of the wire does not remain residual deformation and return to the original position by unloading; this looks like viscoelastic behavior. The residual stress of the SMA wires can be used as active confinement for civil structures and the behavior under residual stress can be used as like an elastic spring with hysteretic damping. This study confines concrete cylinders and reinforced concrete columns using the pre-elongated SMA wires to introduce an active confinement on them. The SMA wire jackets on concrete cylinders increase the peak strength and the ductility so much comparing to the plain concrete cylinders. Also, the wires on reinforced concrete columns increase the ductility so much without the reduction of flexural strength.

Hysteretic Behavior of Concrete Cylinders Confined by Active Confining SMA Wire Jackets

2010 ◽  
Vol 654-656 ◽  
pp. 2099-2102
Author(s):  
Eun Soo Choi ◽  
Hack Soo Lee ◽  
Joo Nam Park ◽  
Bak Soon Cho
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Hysteretic Behavior ◽  
Confined Concrete ◽  
Concrete Cylinders ◽  
Superelastic Behavior ◽  
Active Confinement ◽  
Compressive Tests

Shape memory alloy (SMA) wire jackets are distinct from conventional jackets for concrete members since they can provide active confinement easily. The applications of SMAs in civil engineering are on the increase since SMAs show unique properties of shape memory effect and superelastic behavior. Especially, the seismic application of SMAs for confining concrete becomes a hot issues in recent. Thus, this study conducts cyclic compressive tests of concrete cylinders jacketed by shape memory alloy (SMA) wires which can provide active confinement due to shape memory effect. Monotonic compressive tests provide only the peak strength and the ultimate strain for confined concrete. However, confined concrete is exposed to the repeating of loading and unloading during an earthquake. Also, this study performs the same tests for concrete cylinders jacketed by steel jackets which provide only passive confinement and the results are compared to those of SMA wire jackets. This study provides the basic information of concrete behavior confined by active or passive external jackets.

Cyclic Behavior of Concrete Confined by Active and Passive Jackets

2010 ◽  
Author(s):  
Eunsoo Choi ◽  
Yeon-Wook Kim ◽  
Young-Soo Chung ◽  
Hong-Taek Kim ◽  
Baik-Soon Cho
Keyword(s):  
Shape Memory ◽  
Compressive Loading ◽  
Volumetric Strain ◽  
Confined Concrete ◽  
Cyclic Behavior ◽  
Temperature Hysteresis ◽  
Plastic Strains ◽  
Carbon Fiber Reinforce Polymer ◽  
Concrete Cylinders ◽  
Loading Tests

Shape memory alloy (SMA) wire jackets for concrete are distinct from the conventional jackets of steel or FRP since they provide active confinement that can be easily archived due to the shape memory effect of SMAs. This study uses NiTiNb SMA wires of 1.0 mm diameter to confine concrete cylinder with the dimension of 300 mm × 150 mm (L × D). The NiTiNb SMAs have a relative wider temperature hysteresis than NiTi SMAs and, thus, are more applicable for severe temperature-variation environment which civil structures are exposed to. Steel jackets of passive confinement are also prepared to compare the cyclic behavior of active and passive confined concrete cylinders. For this purpose, monotonic and cyclic compressive loading tests are conducted to obtain axial and circumferential strain. The both of strains are used to estimate volumetric strains of concrete cylinders. Also, plastic strains from cyclic behavior are also estimated. For the NiTiNb SMA jacketed cylinders, the monotonic axial behavior differs from the envelope of cyclic behavior; this should be studied in future. The plastic strains of the active confined concrete show a similar trend to those of the passive confinement. The trend of plastic strain of this study does not match with that of CFRP (Carbon Fiber Reinforce Polymer) jackets. For the volumetric strain, the active jackets of the NiTiNb SMA wires provide more energy dissipation than the passive jacket of steel.

Dynamic Thermo-Mechanical Properties of Shape Memory Alloy Nanowires Upon Multi-Axial Loading

2011 ◽  
Author(s):  
Rakesh P. Dhote ◽  
Roderick V. N. Melnik ◽  
Jean W. Zu
Keyword(s):  
Mechanical Properties ◽  
Phase Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Axial Stress ◽  
Phase Field Model ◽  
Axial Loading ◽  
Ginzburg Landau ◽  
Bending Load ◽  
Loading Case

In this paper, we study the behavior of shape memory alloy (SMA) nanowires subjected to multi-axial loading. We use the model developed in our earlier work to study the microstructure and mechanical properties of finite length nanowires. The phase field model with the Ginzburg-Landau free energy is used to model the phase transformation based on the chosen order parameter. The governing equations of the thermo-mechanical model are solved simultaneously for different loading cases. We observe that nanowire behaves in a stiff manner to axial load with complete conversion of the unfavorable martensite to the favorable one. The bending load aids the phase transformation by redistributing the martensitic variants based on the local axial stress sign. The nanowire behavior to multi-axial (axial and bending together) is stiffer axially than the axial loading case. The understanding of the behavior of nanowire to multi-axial loading will be useful in developing better SMA-based MEMS and NEMS devices.

Experimental study on axial compressive behavior of hybrid FRP confined concrete columns

2017 ◽  
Vol 19 (4) ◽  
pp. 395-404 ◽  
Author(s):  
Li-Juan Li ◽  
Lan Zeng ◽  
Shun-De Xu ◽  
Yong-Chang Guo
Keyword(s):  
Experimental Study ◽  
Concrete Columns ◽  
Confined Concrete ◽  
Compressive Behavior
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