Feasibility of iron-based shape memory alloy strips for prestressed strengthening of concrete structures

Czaderski, Christoph; Shahverdi, Moslem; Brönnimann, Rolf; Leinenbach, Christian; Motavalli, Masoud

doi:10.1016/j.conbuildmat.2014.01.069

Cited by 145 publications

(76 citation statements)

References 21 publications

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“…Three beams prestressed by Fe-SMA strips were compared with one beam strengthened by nonactivated Fe-SMA strips. The observed higher cracking load and the smaller deflections for a given service load proved that strengthening of RC beams with prestressed Fe-SMA strips worked well [13].…”

Section: Introductionmentioning

confidence: 78%

“…In a feasibility study, the Fe-SMA strips ( Figure 1) were used to prestress concrete bars by having been centrally embedded [11]. The Fe-SMA strips were activated by resistance heating.…”

Section: Introductionmentioning

confidence: 99%

“…It is visible that they start to develop at tensile stresses of approximately 300 MPa and strains of approximately 0.25 % (inclination decreases). Tensile strains at failure of the Fe-SMA strips are approximately 10 % with a tensile stress of approximately 700 MPa [11]. Then, the applied tensile force was released to 10 N and the remaining strain was measured.…”

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confidence: 99%

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Development of Rolling Technology for an Iron-Based Shape-Memory-Alloy

Leinenbach¹,

Czaderski²,

Michels³

et al. 2016

MSF

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Abstract. Low cost Fe-Mn-Si based shape memory alloys (SMA) have drawn much attention during the last two decades as a cost-effective alternative to the expensive Ni-Ti based SMA. In particular, the alloy Fe-17Mn-5Si-10Cr-4Ni-1(V,C) (mass%), which has been developed at Empa shows very promising properties with regard to potential commercial applications in civil and mechanical engineering. This alloy has a higher reverse transformation temperature and larger thermal hysteresis in comparison to the Ni-Ti based alloys, which is adequate for producing stable recovery stresses at room temperature. Furthermore, recovery stresses of up to 300 MPa after heating to only 160 °C can be achieved without so-called 'training' treatment. Furthermore, the alloy can be easily and cost effectively produced under standard air melting and casting conditions. For availability of these heavily microstructure dependent skills for civil and mechanical engineering, e.g. as prestressing elements in concrete structures or coupling/clamping devices, a process chain for manufacturing is necessary. Therefore, a hot and cold rolling technology for strip production with thermal heat treatment processes was developed at TU Bergakademie on base of experimental simulation results. The last one helps to understand the dependencies of deformation parameters, the deformation behavior and their influence to the microstructure evolution in correlation to the recovery. This paper discusses the basic material properties, recovery stress formation behavior and finally the feasibility of the alloy as reinforcing elements in civil engineering applications by using a rolling technology for flat products. IntroductionShape memory alloy (SMA) steels based on the Fe-Mn-Si alloy system are promising candidates for a variety of advanced civil engineering applications, since they have a wide transformation hysteresis, high elastic stiffness and strength and are relatively inexpensive to produce [1]. These advantages make them promising as a cost-effective alternative to conventional NiTi-based SMAs for applications requiring high shape memory stresses, e.g. constrained recovery applications such as external confinement for reinforced concrete columns [2] or as prestressing reinforcement in prestressed concrete [3;4].The shape memory effect in Fe-Mn-Si alloys is a result of a mechanically induced phase transformation from austenite (face centered cubic phase, γ) to martensite (hexagonal close packed phase, ε) and its reversion upon heating [5]. Under pure mechanical loading, stress induced martensite forms and the resulting strain can exceed the elastic strain limit of the alloy. This strain can be recovered by the reverse transformation due to the same crystallographic path of the two transformations [6].

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Section: Introductionmentioning

confidence: 78%

“…In a feasibility study, the Fe-SMA strips ( Figure 1) were used to prestress concrete bars by having been centrally embedded [11]. The Fe-SMA strips were activated by resistance heating.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Development of Rolling Technology for an Iron-Based Shape-Memory-Alloy

Leinenbach¹,

Czaderski²,

Michels³

et al. 2016

MSF

View full text Add to dashboard Cite

show abstract

“…Relatively low Young's modulus and high price of NiTi SMA compared with steel are critical problems of the SMA applications for civil structures. Recently, Fe-based SMAs have been developed with high Young's modulus and low price compared with NiTi SMA (Czaderski et al, 2014;Koster et al, 2015). In addition, Fe-based SMAs do not show stress relaxation due to decreasing temperature.…”

Section: Discussion and Applicationsmentioning

confidence: 99%

New SMA Short Fibers for Cement Composites Manufactured by Cold Drawing

Choi¹,

Kim²,

Jeon³

et al. 2016

JMSR

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This study suggests new shape memory alloy reinforcing fibers manufactured by cold drawing method. This study prepares NiTi shape memory alloy (SMA) wires with diameter of 1.0 mm. Then, the wires are elongated by cold drawing and, thus, the diameters are reduced to 0.93 or 0.965 mm, respectively. This procedure introduces prestrain into the wires. When elongated SMA wires are heated, the shape memory effect is activated; this process recovers the deformed length as well as the reduced diameter due to Poisson's effect. Cold drawn wires with diameters of 0.93 and 0.965 mm recover diameters of 0.018 and 0.024 mm, respectively, with heating. The bulging of the SMA fiber in the radial direction inside cement composites induces confining pressure around the fiber and increases bond strength. When an SMA fiber is heated at the both ends, the heated parts bulge and the fiber shape looks like a dog-bone. Such a dog-bone shaped fiber can provide a geometrical anchoring action that also increases the bond resistance of the fiber. This study conducts pullout tests of SMA fibers to understand their pullout behavior and assess bond stress. The heated fibers and dog-bone shaped fibers increase pullout force compared to those of as-received and cold-drawn fibers. When dog-bone shaped fibers are heated, they show twice the pullout force of dog-bone shaped fibers without heating because geometric anchoring action as well as additional frictional resistance due to confining pressure are activated.

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“…Many test results show that the quantity, diameter, prestrain, excitation mode, and volume of the SMA wires have a certain influence on the deformation recovery of SMA concrete beam. In addition to the built-in method, SMA wires also can be arranged outside the structure, which has the effect of controlling deformation as well [15][16][17]. However, due to the complexity of mechanical behaviors of RC structures, there is less numerical analysis than experiment of the SMA concrete structure.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Analysis for the Crack Control of SMA Smart Concrete Beam Based on a Bidirectional B-Spline QR Method

et al. 2018

Mathematical Problems in Engineering

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A bidirectional B-spline QR method (BB-sQRM) for the study on the crack control of the reinforced concrete (RC) beam embedded with shape memory alloy (SMA) wires is presented. In the proposed method, the discretization is performed with a set of spline nodes in two directions of the plane model, and structural displacement fields are constructed by the linear combination of the products of cubic B-spline interpolation functions. To derive the elastoplastic stiffness equation of the RC beam, an explicit form is utilized to express the elastoplastic constitutive law of concrete materials. The proposed model is compared with the ANSYS model in several numerical examples. The results not only show that the solutions given by the BB-sQRM are very close to those given by the finite element method (FEM) but also prove the high efficiency and low computational cost of the BB-sQRM. Meanwhile, the five parameters, such as depth-span ratio, thickness of concrete cover, reinforcement ratio, prestrain, and eccentricity of SMA wires, are investigated to learn their effects on the crack control. The results show that depth-span ratio of RC beams and prestrain and eccentricity of SMA wires have a significant influence on the control performance of beam cracks.

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Feasibility of iron-based shape memory alloy strips for prestressed strengthening of concrete structures

Cited by 145 publications

References 21 publications

Development of Rolling Technology for an Iron-Based Shape-Memory-Alloy

Development of Rolling Technology for an Iron-Based Shape-Memory-Alloy

New SMA Short Fibers for Cement Composites Manufactured by Cold Drawing

Nonlinear Analysis for the Crack Control of SMA Smart Concrete Beam Based on a Bidirectional B-Spline QR Method

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