A Numerical Study on Improvement of Shape Memory Alloy Bolt Characteristics of Beam-Column Connections (original) (raw)
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Seismic Performance of Beam-Column Joint Reinforced with Different Shape Memory Alloy Alternatives
2017
For seismic design based on the structural performance, to minimize the earthquake damage and possible seismic hazard scenarios to the structure, reinforcing the beam-column joints is crucial. Shape memory alloys are specially developed materials that exhibit the unique ability to return to their original shape after experiencing large stress deformations. Incorporation of SMA in the plastic hinge regions of beams of beam-column joints could potentially increase the ductility and reduce the residual deformation. Five various types of SMAs from the literature are being purposed as potential contenders in the SMA-Steel hybrid RC beam-column joint in this study. Numerical investigations of the beam-column joints have been carried out under reversed cyclic loading. The performance of the hybrid joints is scrutinized in terms of load-storey drift, energy dissipation capacity, and storey residual drift and compared to regular steel reinforced beam-column joint response. All the SMA-Steel ...
This paper presents the development of predictive equations for the self-centering response of moment-resisting connections equipped with Shape Memory Alloy (SMA) bolts and steel angles. First, three-dimensional finite element models are developed in ANSYS. The analysis is validated using experimental results for seven beam-column connections. Using a design of experiments approach, a statistical sensitivity analysis of the cyclic response is performed to identify factors with significant effects. Next, a response surface study is presented to develop predictive equations for characterizing the cyclic response of steel beam-column connections with SMA bolts and steel angles. A confirmation study indicates acceptable accuracy of the developed equations for predicting the cyclic response of the SMAbased connections. The predictive equations can be used for developing computationally efficient models in the analysis and design of SMA-based connections and moment frames. This study also highlights the promising self-centering response of the newly developed SMA-based connections. Based on the results, deep beams should not be used to avoid possible early bolt fracture.
Steel Beam-Column Connections Using Shape Memory Alloys
Journal of Structural Engineering-asce, 2004
This study evaluates the feasibility of a new class of partially restrained connections using shape memory alloys. In the martensitic form, shape memory alloys ͑SMAs͒ have the ability to recover large residual deformations by heating the alloy above its transformation temperature. The proposed connection consists of four large diameter NiTi SMA bars connecting the beam flange to the column flange and serve as the primary moment transfer mechanism. Two full-scale connections were tested using the SAC loading protocol. The connections exhibited a high level of energy dissipation, large ductility capacity, and no strength degradation after being subjected to cycles up to 4% drift. Following the initial testing series, the tendons were heated to recover the residual beam tip displacement. After initiating the shape memory effect within the tendons, the connections were retested, displaying repeatable and stable hysteretic behavior. An additional test was performed under dynamic loading to examine the strain rate effects on the performance of the connection. The dynamic tests showed similar behavior, except for a decrease in energy dissipation capacity when compared to the quasi-static tests.
Journal of Intelligent Material Systems and Structures, 2020
Shape memory alloys have been used in developing self-centering steel moment connections. This article presents a numerical study aiming at evaluating the cyclic response sensitivity and limit states of extended endplate steel connections with shape memory alloy bolts. Three-dimensional finite element models are developed and validated against a recent experimental study. Using a statistical design-of-experiment method, the effects of 21 design factors and their interactions on the cyclic response of shape memory alloy connections are assessed. The sensitivity of six response parameters is studied. In addition, four limit states for shape memory alloy connections are discussed, including beam local buckling, bolt excessive axial strain, endplate yielding, and column flange yielding. Results show that endplate thickness, shape memory alloy bolt diameter, beam web slenderness ratio, and shape memory alloy maximum transformation strain are the most influential factors. Furthermore, end...
Cyclic Behavior of Post-Tensioned Steel Connections with Shape Memory Alloy Angles
2017
Following the 1994 Northridge earthquake, a number of code-designed steel moment frame buildings experienced unanticipated brittle fracture in beam-column connection areas. Reinforcing beam flange and using reduced beam sections were some solutions to localize damage at a pre-defined region. Although such configurations keep the damage away from critical areas, the residual drift after experiencing large deformations is inevitable. Post-tensioned steel connections are meant to overcome this problem. In such innovative connections, high strength steel strands are utilized and post-tensioned to provide a connection with a self-centering feature. Bolted top and seat angles can be added to these systems to serve as ductile components and dissipate energy. Shape memory alloys (SMAs), with excellent superelastic property and flag-shaped hysteresis, can be used to reduce localized damages in the angles. In this paper, three-dimensional finite element analyses are conducted to study the sei...
Characteristics of a bolted joint with a shape memory alloy stud
Materials Characterisation V, 2011
Creep is an important factor that contributes to the load loss and tightness failure of bolted joints. Retightening of the joint can be expensive, time consuming and therefore is an undesirable solution. Currently most efforts are focussed on reducing load losses directly by tightening to yield, improving material creep properties or making joints less rigid. An alternative solution of current interest is the use of bolts in shape memory alloy (SMAs). However, very few experimental studies are available that demonstrate its feasibility. The objective of this study is to exploit the benefit of the shape memory and superelasticity behaviors of a SMA stud to recover the load losses due to creep and thermal exposure of a gasket in a bolted joint assembly. This paper explores several avenues to investigate and model the thermo-mechanical properties of a bolted joint with a Nickel-Titanium SMA stud. A stiffness-based analytical model which incorporates the Likhachev model of SMA is used as a representation of an experimental bolted joint assembly. Using this model the rigidity of the experimental setup is optimized to make the best use of the SMA properties of the stud. This theoretical model is validated by a Finite Element (FE) Model using a custom FE material model which also implements the SMA material model. Finally an experimental test bench with an optimized stiffness derived from analytical simulations is used, with and without gaskets to demonstrate the ability of the SMA stud to recover load losses.
Shape memory alloys (SMAs) have the ability to undergo large deformations with minimum residual strain and also the extraordinary ability to undergo reversible hysteretic shape change known as the shape memory effect. The shape memory effect of these alloys can be utilised to develop a convenient way of actively confining concrete sections to improve their shear strength, flexural ductility and ultimate strain capacity. Most of the previous work on active confinement of concrete using SMA has been carried out on circular sections. In this study retrofitting strategies for active confinement of non-circular sections have been proposed. The proposed schemes presented in this paper are conceived with an aim to seismically retrofit a beam-column joint in non-seismically detailed reinforced concrete buildings. The complex material behaviour of SMAs depends on number of parameters. Depending upon the alloying elements, SMAs exhibit different behaviour in different conditions and are highly sensitive to variation in temperature, phase in which it is used, loading pattern, strain rate and pre-strain conditions. Therefore, a detailed discussion on the behaviour of SMAs under different thermo-mechanical conditions is presented in this paper.
SECED 2015 Conference: Earthquake Risk and Engineering towards a Resilient World, 2015
Shape memory alloys (SMAs) have the ability to undergo large deformations with minimum residual strain and also the extraordinary ability to undergo reversible hysteretic shape change known as the shape memory effect. The shape memory effect of these alloys can be utilised to develop a convenient way of actively confine concrete sections to improve their shear strength, flexural ductility and ultimate strain. Most of the previous work on active confinement of concrete using SMA has been carried out on circular sections. In this study retrofitting strategies for active confinement of non-circular sections have been proposed. The proposed schemes presented in this paper are conceived with an aim to seismically retrofit beam-column joints in non-seismically designed reinforced concrete buildings. SMAs are complex materials and their material behaviour depends on number of parameters. Depending upon the alloying elements, SMAs exhibit different behaviour in different conditions and are highly sensitive to variation in temperature, phase in which it is used, loading pattern, strain rate and pre-strain conditions. Therefore, a detailed discussion on the behaviour of SMAs under different thermo-mechanical conditions is presented first.
Shape Memory Alloy Features for Seismic Retrofitting of External RC Beam- Column Joint
Shape memory alloys (SMAs) have the ability to undergo large deformations with minimum residual strain and also the extraordinary ability to undergo reversible hysteretic shape change known as the shape memory effect. The shape memory effect of these alloys can be utilised to develop a convenient way of actively confining concrete sections to improve their shear strength, flexural ductility and ultimate strain capacity. Most of the previous work on active confinement of concrete using SMA has been carried out on circular sections. In this study retrofitting strategies for active confinement of non-circular sections have been proposed. The proposed schemes presented in this paper are conceived with an aim to seismically retrofit a beam-column joint in non-seismically designed reinforced concrete buildings. The complex material behaviour of SMAs depends on number of parameters. Depending upon the alloying elements, SMAs exhibit different behaviour in different conditions and are highly sensitive to variation in temperature, phase in which it is used, loading pattern, strain rate and pre-strain conditions. Therefore, a detailed discussion on the behaviour of SMAs under different thermo-mechanical conditions is presented first in this paper.
Recently two experimental investigations were carried out on beam-column elements under seismic loading, one in the University of Western Ontario and the other in the University of Nevada, Reno, where superelastic Shape Memory Alloy (SMA) rebars were used as reinforcement at their plastic hinge regions. Such SMA reinforced beam-column elements experienced reduced residual deformation at the end of seismic loading. This study aims in developing finite element (FE) models in order to simulate the seismic behaviour of SMAreinforced concrete (RC) beam-column elements. The predicted behaviour of the two specimens from FE analysis, their load-storey drift relationship, and energy dissipation ability are compared with the experimental results. The results showed that the model could predict the behaviour of both SMA-RC beam-column elements with reasonable accuracy.