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.

Case Studies of Seismic Vibration Control of Civil Structures Using Shape Memory Alloys

2011 ◽  
Vol 243-249 ◽  
pp. 5427-5434
Author(s):  
Hui Qian ◽  
Hong Nan Li ◽  
Di Cui ◽  
Huai Chen
Keyword(s):  
Reinforced Concrete ◽  
Energy Dissipation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Vibration Control ◽  
Case Studies ◽  
Precast Concrete ◽  
Reinforced Concrete Beams ◽  
Seismic Vibration ◽  
Concrete Members

Shape memory alloys (SMAs) are unique class materials that have the ability to undergo large deformations, while returning to their undeformed shape through either the applications of heat (SME) or removal of stress (SE). The unique properties lead to their wide applications in the biomedical, mechanical, aerospace, commercial industries, and recently in civil engineering. The paper presents two case studies of structural seismic vibration control using SMAs. The first one is a study of the SMA reinforced RC members. Two innovative applications in RC members, such as SMA-based Precast Concrete Frame Connection (SMA-PCFC), and SMA reinforced RC short column, were proposed. Moreover, the self-rehabilitation properties of SMAs-based Intelligent Reinforced Concrete Beams (SMA-IRCBs) were further experimentally investigated. The results show that SMAs can improve the mechanical properties of concrete members. SMA reinforced RC members have unique seismic performance compared to ordinarily steel reinforced concrete members. The second one is a study of the structural energy dissipation system using SMAs damping device. An innovative hybrid SMAs friction device (HSMAFD) which consists of pre-tensioned superelastic SMA wires and friction devices (FD) was presented. The results of cyclic tensile tests show that the HSMAFD exhibits stable large energy dissipation capacity and re-centering feature. The effectiveness of the HSMAFD in reducing horizontal response of structures subjected to strong seismic excitations was verified through shaking table tests carried out on a reduced-scale symmetric steel frame model with and without the HSMAFD.

scholarly journals Energy Absorption Evaluation of CFRP-Strengthened Two-Spans Reinforced Concrete Beams under Pure Torsion

2019 ◽  
Vol 5 (9) ◽  
pp. 2007-2018 ◽  
Author(s):  
Ammar N. Hanoon ◽  
Ali A. Abdulhameed ◽  
Haider A. Abdulhameed ◽  
Saad K. Mohaisen
Keyword(s):  
Reinforced Concrete ◽  
Energy Absorption ◽  
Concrete Beams ◽  
Absorption Capacity ◽  
Reinforced Concrete Beams ◽  
Experimental Program ◽  
Rc Beams ◽  
Pure Torsion ◽  
Energy Absorption Capacity ◽  
Strengthened Beam

For more than a decade, externally bonded carbon fiber reinforced polymer (CFRP) composites successfully utilized in retrofitting reinforced concrete structural elements. The function of CFRP reinforcement in increasing the ductility of reinforced concrete (RC) beam is essential in such members. Flexural and shear behaviors, ductility, and confinement were the main studied properties that used the CFRP as a strengthening material. However, limited attention has been paid to investigate the energy absorption of torsion strengthening of concrete members, especially two-span concrete beams. Hence, the target of this work is to investigate the effectiveness of CFRP-strengthening technique with regard to energy absorption of two-span RC beams subjected to pure torsion. The experimental program comprises the investigation of two groups; the first group comprises eight un-strengthened beam specimens, while the second group consists of eight strengthened beam specimens tested under torsional forces. The energy absorption capacity measured from the area under the curve of torque-angle of twist for tested beams. Two parameters were studied, the influence of concrete compressive strength and the angle of a twist. Experimental results indicated that all beams wrapped with CFRP sheet display superior torsional energy absorption capacity compared to the control specimens. The energy absorption may consider as a safety index for the torsional capacity of two-span RC beams under service loadings. Therefore, it is possible to avoid structural as well as material damages by understanding the concept of energy absorption that is one of the important experimental findings presented in this study.

Artificial neural network model for deflection analysis of superelastic shape memory alloy reinforced concrete beams

2010 ◽  
Vol 37 (6) ◽  
pp. 855-865 ◽  
Author(s):  
Y. I. Elbahy ◽  
M. Nehdi ◽  
M. A. Youssef
Keyword(s):  
Reinforced Concrete ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Companion Paper ◽  
Reduction Factor ◽  
Moment Of Inertia ◽  
Reinforced Concrete Beams ◽  
Rc Beams ◽  
Design Chart ◽  
Artificial Neural

The need for a new model capable of accurately predicting the deflection of shape memory alloy (SMA) reinforced concrete (RC) beams is clear from the results obtained in the companion paper. In the present paper, artificial neural networks (ANNs) are utilized to develop such a model. The objective is to create a design tool for computing a reduction factor β to be used in the calculation of the effective moment of inertia for SMA RC beams. First, a database was developed using the results obtained from the parametric study reported in the companion paper. The main factors affecting the moment of inertia have been considered. The network architecture that results in the optimum performance was selected and trained. After demonstrating the network’s ability to predict output data for unfamiliar input data, the network was used to develop a design chart that provides the reduction factor β as a function of the reinforcement ratio and the reinforcement modulus of elasticity. A design example is discussed to illustrate the advantages of using the developed design chart over existing models.

Experimental study on flexural strengthening of reinforced concrete beams with U-shaped steel under secondary load

2021 ◽  
pp. 136943322110369
Author(s):  
Qingli Lin ◽  
Yiyan Lu ◽  
Wenshui Tang ◽  
Dongshan Lei
Keyword(s):  
Reinforced Concrete ◽  
Reference Beam ◽  
Reinforced Concrete Beams ◽  
Bottom Plate ◽  
Strengthening Effect ◽  
Rc Beams ◽  
Flexural Strengthening ◽  
Flexural Performance ◽  
Initial Loading ◽  
Secondary Load

This study proposes a new method to strengthen reinforced concrete (RC) beams with U-shaped steel, which can achieve rapid construction and great improvement in the flexural performance of RC beams. To investigate the influence of secondary load defined as newly applied loads after strengthening on the strengthening effect, a total of nine specimens were tested under four-point bending, including a reference beam, a strengthened beam under initial load, and seven strengthened beams under secondary load. The initial loading degree, the thickness of the bottom plate, and the height of the steel box were the main variables considered in this study. Testing results showed that compared with the reference beam, the flexural performance of strengthened beams was significantly enhanced, indicating the good joint performance of the U-shaped steel and the RC beams. Among the three main variables, the initial loading degree was found to have a minimal effect on the flexural performance while the thickness of the bottom plate and the height of the steel box had considerable influence, with the latter having a more pronounced effect. Testing results also showed that most of the strengthened beams experienced flexural failures, which were reflected by steel web peeling and buckling, and concrete crushing. Moreover, a formula was derived for calculating the flexural capacity of strengthened beams under secondary load. The results from the derived formula were found to be in good agreement with those from experiments.

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