Preliminary investigation of flexural strengthening of RC beams using NSM iron-based shape memory alloys bars

2015 ◽  
pp. 118-118 ◽  
Author(s):  
H.N. Rojob ◽  
R. El-Hacha
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Preliminary Investigation ◽  
Rc Beams ◽  
Flexural Strengthening ◽  
Iron Based

scholarly journals Strengthening of Reinforced Concrete Beams with Externally Mounted Sequentially Activated Iron-Based Shape Memory Alloys

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 345 ◽  
Author(s):  
Emanuel Strieder ◽  
Christoph Aigner ◽  
Gabriele Petautschnig ◽  
Sebastian Horn ◽  
Marco Marcon ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Reference Beam ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Recovery Stress ◽  
Strengthened Beam ◽  
Iron Based ◽  
Stress States

Iron based shape memory alloys (Fe-SMA) have recently been used as active flexural strengthening material for reinforced concrete (RC) beams. Fe-SMAs are characterized by a shape memory effect (SME) which allows the recovery of previously induced plastic deformations through heating. If these deformations are restrained a recovery stress is generated by the SME. This recovery stress can be used to prestress a SMA applied as a strengthening material. This paper investigates the performance and the load deformation behavior of RC beams strengthened with mechanical end anchored unbonded Fe-SMA strips activated by sequentially infrared heating. The performance of a single loop loaded and a double loop loaded SMA strengthened RC beam are compared to an un-strengthened beam and a reference beam strengthened with commercially available structural steel. In these tests the SMA strengthened beam had the highest cracking load and the highest ultimate load. It is shown that the serviceability behavior of a concrete beam can be improved by a second thermal activation. The sequential heating procedure causes different temperature and stress states during activation along the SMA strip that have not been researched previously. The possible effect of this different temperature and stress states on metal lattice phase transformation is modeled and discussed. Moreover the role of the martensitic transformation during the cooling process on leveling the inhomogeneity of phase state in the overheated section is pointed out.

Experimental behavior of iron-based shape memory alloys under cyclic loading histories

2021 ◽  
Vol 272 ◽  
pp. 121712
Author(s):  
Diego Isidoro Heredia Rosa ◽  
Alexander Hartloper ◽  
Albano de Castro e Sousa ◽  
Dimitrios G. Lignos ◽  
Masoud Motavalli ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Experimental Behavior ◽  
Iron Based

Laser Metal Deposition of Fe- and Co-Based Shape-Memory Alloys

2021 ◽  
Vol 1161 ◽  
pp. 105-112
Author(s):  
Niklas Sommer ◽  
Gabriel Mienert ◽  
Malte Vollmer ◽  
Christian Lauhoff ◽  
Philipp Krooß ◽  
...  
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Microstructural Evolution ◽  
Microstructural Analysis ◽  
Metal Deposition ◽  
Thin Wall ◽  
Laser Metal Deposition ◽  
Wall Structures ◽  
Iron Based ◽  
First Time

In the present study, Iron-based FeMnAlNi and Cobalt-based CoNiGa shape-memory alloys (SMA) were processed by laser metal deposition for the first time. The materials show susceptibility to cracking upon processing when unheated substrates are employed. Pre-heating of the substrate materials eliminated cracking completely and enabled robust deposition of thin-wall structures. Microstructural analysis using optical microscopy revealed different microstructural evolution for the two materials considered.

Iron-based superelastic alloys with near-constant critical stress temperature dependence

Science ◽  
2020 ◽  
Vol 369 (6505) ◽  
pp. 855-858 ◽  
Author(s):  
Ji Xia ◽  
Yuki Noguchi ◽  
Xiao Xu ◽  
Takumi Odaira ◽  
Yuta Kimura ◽  
...  
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Temperature Dependence ◽  
Critical Stress ◽  
Outer Space ◽  
Alloy System ◽  
Large Temperature ◽  
Superelastic Behavior ◽  
Iron Based ◽  
Metal Shape

Shape memory alloys recover their original shape after deformation, making them useful for a variety of specialized applications. Superelastic behavior begins at the critical stress, which tends to increase with increasing temperature for metal shape memory alloys. Temperature dependence is a common feature that often restricts the use of metal shape memory alloys in applications. We discovered an iron-based superelastic alloy system in which the critical stress can be optimized. Our Fe-Mn-Al-Cr-Ni alloys have a controllable temperature dependence that goes from positive to negative, depending on the chromium content. This phenomenon includes a temperature-invariant stress dependence. This behavior is highly desirable for a range of outer space–based and other applications that involve large temperature fluctuations.

Iron-based shape memory alloys for civil engineering structures: An overview

2014 ◽  
Vol 63 ◽  
pp. 281-293 ◽  
Author(s):  
A. Cladera ◽  
B. Weber ◽  
C. Leinenbach ◽  
C. Czaderski ◽  
M. Shahverdi ◽  
...  
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Civil Engineering ◽  
Engineering Structures ◽  
Iron Based ◽  
Civil Engineering Structures

scholarly journals RC Structures Strengthened by an Iron-Based Shape Memory Alloy Embedded in a Shotcrete Layer—Nonlinear Finite Element Modeling

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5504
Author(s):  
Neda Dolatabadi ◽  
Moslem Shahverdi ◽  
Mehdi Ghassemieh ◽  
Masoud Motavalli
Keyword(s):  
Finite Element ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Passive Control ◽  
Load Capacity ◽  
Finite Element Models ◽  
Rc Structures ◽  
Displacement Response ◽  
Iron Based ◽  
Load Displacement

Shape memory alloys (SMAs) have been widely used in civil engineering applications including active and passive control of structures, sensors and actuators and strengthening of reinforced concrete (RC) structures owing to unique features such as the shape memory effect and pseudo-elasticity. Iron-based shape memory alloys (Fe-SMAs) have become popular in recent years. Use of iron-based SMAs for strengthening RC structures has received attention in the recent decade due to the advantages it presents, that is, no ducts or anchor heads are required, friction losses do not occur and no space is needed for a hydraulic device to exert force. Accordingly, Fe-SMAs embedded in a shotcrete layer have been used for pre-stressing RC beams at Empa. The aim of this study is to present an approach to model and analyze the behavior of RC members strengthened and pre-stressed with Fe-SMA rebars embedded in a shotcrete layer. The lack of research on developing finite element models for studying the behavior of concrete structures strengthened by iron-based shape memory alloys is addressed. Three-dimensional finite element models were developed in the commercial finite element code ABAQUS, using the concrete damaged plasticity model to predict the studied beams’ load–displacement response. The results of the finite element analyses show a considerably good agreement with the experimental data in terms of the beams’ cracking load and ultimate load capacity. The effects of different strengthening parameters, including SMA rebar diameter, steel rebar diameter and pre-stressing force level on the beam behavior, were investigated based on the verified finite element models. The results were compared. The load-displacement response of an 18-m concrete girder strengthened and pre-stressed with iron-based SMA bars was examined by the developed finite element model as a case study.

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