Level Of Energy Dissipation Research Articles

Strip Model Analysis for Steel Plate Shear Walls in Earthquake Resistant Structures

Unstiffened Steel Plate Shear Walls (SPSWs) are very effective structural systems designed to resist lateral forces. SPSW systems consist of thin web plates infilled within frames of steel horizontal and vertical boundary elements. The thin unstiffened web plates are expected to buckle in shear and to develop diagonal tension field after buckling under the action of horizontal loads. For unstiffened steel plates, buckling in shear occurs in the elastic range at low stress levels. This behaviour provides strength, stiffness and ductility and allows to have an appropriate level of energy dissipation through tension yielding of the web plates. This paper assesses the inelastic structural response and behaviour of Steel Plate Shear Wall systems using both a modified strip model approach and a new simplified strip model for only beam connected SPSWs. Both models are developed with plasticity concentrated elements and the performed analyses include the nonlinear behaviour of strips, also considering the compressive forces effects over the strip model elements. This research indicates fundamental aspects of the seismic performance of Steel Plate Shear Wall systems, such as energy dissipation capacity, panel ductility demand, seismic inter-story drift and design load demands in Vertical Boundary Elements (VBE) and Horizontal Boundary Elements (HBE) of the frame. The results obtained from the use of these models are compared with selected experimental and numerical results to enrich the research conclusions.

Methodology for studying impulse disturbance from rail joints to the railway vehicle and assessment of the efficiency of the new spring suspension

The methodology for studying the impulse disturbance of the railway track joints on the indicators of the dynamic qualities of the railway vehicle has been developed. The dependence of the impulse repetition factor on the energy dissipation level in the system and the speed of the vehicle is obtained. A comparative assessment of the dynamic qualities of a freight car with a typical scheme of spring suspension and a car with suspension based on the principle of compensation of external disturbances is performed. It has been established that the spring suspension of a freight car based on the principle of compensation of external disturbances delivers to it significantly better indicators of dynamic qualities in comparison with car equipped with a new three-piece truck with a typical scheme of springs. Vertical acceleration of the car’s body with a new scheme of vibration protection and dynamic forces in spring suspension is several times less than for a car with a typical three-piece truck structure.

Photoprotection from anthocyanins and thermal energy dissipation in senescing red and green Sambucus canadensis peduncles

Senescing photosynthetic tissues utilize a number of photoprotective mechanisms, including thermal energy dissipation involving the xanthophyll cycle, and often the screening of light energy by anthocyanins. The relative utilization of thermal energy dissipation when anthocyanins are present versus absent remains to be characterized. Using sun-acclimated Sambucus canadensis peduncles, which synthesize anthocyanins concomitant with fruit ripening, we compared pigment content (anthocyanins, carotenoids and chlorophylls) and chlorophyll fluorescence data (non-photochemical quenching [NPQ] and photochemical quantum yields of photosystem II, during and after prolonged light stress), before, during and after fruit ripening. Shade-acclimated peduncles, which remain green during senescence, were used for comparison. Additionally, we compared the xanthophyll cycle activity (i.e., constituents of the xanthophyll cycle) of sun- and shade-acclimated peduncles during fruit ripening. Before and during fruit ripening, when exposed to 1600 μmol photons m−2 s−1 white light, shade-acclimated peduncles had higher NPQ values and, during fruit ripening, greater proportions of de-epoxidized xanthophyll cycle pigments than did the sun-acclimated peduncles, although both types incurred similar levels of photoinactivation (i.e., reduction in ΦPSII). After the fruit had ripened and peduncles were at the later stages of senescence, the green peduncles were photoinactivated significantly more than were the red ones, following light stress. Collectively, our data indicate that green peduncles, at the early stages of senescence, compensate for their absence of anthocyanins by invoking higher levels of energy dissipation. However, at the later stages of senescence, the level of compensatory thermal energy dissipation in green peduncles was insufficient, and was associated with greater levels of photoinactivation, compared to red peduncles. We conclude that photoprotection by anthocyanins augments the protective functions of xanthophyll cycle pigments in S. canadensis peduncles, and is especially important for mitigating effects of light stress towards the later stages of senescence in high light environments.

Influence of agitation intensity on flotation rate of apatite particles

Abstract The agitation intensity has a directly influence on flotation performance, lifting the particles and promoting the contact of bubbles and particles. In this paper, the energy input by the agitation on apatite flotation was investigated. The influence of pulp agitation in the flotation rate of particles with different sizes and two dosage levels was evaluated by batch testing. The flotation tests were conducted in an oscillating grid flotation cell (OGC), developed to promote a near isotropic turbulence environment. The cell is able to control the intensity of agitation and measure the energy transferred to the pulp phase. A sample of pure apatite was crushed (P80=310µm), characterized and floated with sodium oleate as collector. Four levels of energy dissipation, from 0.1 to 2 kWm-3, and two levels of collector dosage are used during the tests. The flotation kinetics by particle size were determined in function of the energy transferred. The results show a strong influence of the agitation intensity on the apatite flotation rate with both low and high dosage. For fine particles, when increasing the energy input, the flotation rate increase too, and this fact can be attributed to elevation of bubble-particle collisions. The kinetic result for the coarse particles demonstrated a reduction of the flotation rate whenever the energy input for this particle size was increased, whereby the turbulence caused by the agitation promotes the detachment of bubble-particle.

A Study of the Conditions of Energy Dissipation in Stepped Spillways with Λ-shaped step Using FLOW-3D

In the present study, energy dissipation was investigated in a specific type of stepped spillways. The purpose was to achieve the highest level of energy dissipation in downstream of the spillway. It was performed by providing a specific type of geometry for step as a great roughness. Here, steps were recognized as great roughness against flow. Their shape and number were designed in such a way that the maximum flow energy can be minimized in this stage, i.e. over steps before reaching to downstream. Accordingly, it can be stated that the highest energy dissipation rate will be obtained in the structure at downstream. Moreover, thereby, heavy costs imposed by designing and constructing stilling basin on project can be minimized. In this study, FLOW-3D was employed to analyse and obtain energy dissipation rate. The best geometry of the steps, through which the maximum energy dissipation can be achieved, was determined by reviewing related literature and inventing the proposed model in FLOW-3D. To evaluate the proposed method, analyses were performed using trial and error in mesh networks sizes as well as the mentioned methods and the results were compared to other studies. In other words, the most optimal state was obtained with Λ-shaped step at angel of 25 degree with respect to energy dissipation rate compare to smooth step.

A modal projection-based reduction method for transient dynamic responses of viscoelastic systems with multiple damping models

Large and complex engineering systems are usually assembled by subcomponents with different energy dissipation levels. Therefore, these systems often contain multiple damping models, which may lead to great difficulties in analyzing efficiently. In this paper, an efficient modal projection-based reduction method, which accounts for transient dynamic responses of structural system with multiple damping models, is proposed in the framework of a modified precise integration method. Two robust modal reduction bases, namely multi-model method (MM) and modal strain energy by first-order correction method (MSEC), are introduced to reduce the order of the original system. Based on the reduced system and a general damping model (GDM), a reduced state-space formalism for the structural system with multiple damping models is developed. Finally, the transient dynamic responses are derived using a modified precise integration method on the reduced stage. The numerical stability, accuracy and complexity are discussed. Two numerical examples are illustrated to assess the performances of the computational accuracy and efficiency. The results indicate that the proposed method is more efficient than other methods and most suitable for large-scale problems with rather good accuracy.

Assessment of the tidal stream power potential and impacts of tidal current turbines in the Strait of Larantuka, Indonesia

In this paper, results of a tidal stream resource assessment performed for the Strait of Larantuka, Indonesia are presented. The methodology followed is comprising of the estimates of power yield and evaluation of the effects of power extraction via high-resolution, three-dimensional flow models. Power densities exceeding 10kW/m2 are observed in the main channel. Current velocities, and wake characteristics of the turbines have been resolved reasonably well with low computational cost, considering different levels of energy dissipation. Although the results are promising, investigations using in-situ measurements alongside more advanced modelling techniques are still needed, and currently underway.

Photochemical features and trace element substituted chlorophylls as early detection biomarkers of metal exposure in the model diatom Phaeodactylum tricornutum

Establishing marine species equipped with efficient biomarkers of trace element stress is a major requirement for the assessment of trace element contamination in marine ecosystems. This study investigates PS II overall activity and efficiency during light harvesting, electron transport chain (ETC) behaviour, OJIP-transient light curves, and pigment profiles, in the model marine diatom species Phaeodactylum tricornutum exposed to Cr, Co, Ni, Cu, Zn, Cd, Hg, Pb and to a mixture of all elements combined (Mix). OJIP-test parameters and trace element substituted chlorophylls were investigated as potential biomarkers of stress induced by trace elements. Hg-exposed cells showed a shift in balance towards PS I activity, promoted by increase in the electron transport from PQH2 to the reduction of PS I end electron acceptors. Other elements had more limited effects, mostly affecting energy dissipation and pigment levels to various degrees. Decoupling of PS II antennae connectivity was found in Co exposed cells. Chromium induced negative effects on PS I, but had no influence at the Oxygen Evolving Complexes (OECs) level. Copper caused a shift in the equilibrium between PS towards the PS I by reducing the PS II efficiency. Cadmium induced damage in OECs of the PS II donor side, but had no effect on the energy transduction pathway, maintaining energy processing efficiency. Lead had no significant effect on the energy transduction pathway, but produced changes at pigment level, leading to an increase in the chlorophyll and diadinoxanthin. In contrast, Ni had a beneficial role in P. tricornutum photochemistry, leading to increased number of available RC and oxidized quinone pool size, possibly because concentrations used were not able to induce severe cell damage. Copper, Cd and Zn led to substitution of Mg in chlorophyll a molecules, with the formation of less efficient CuChl a, CdChl a and ZnChl a. The biomarkers used evidenced the damaging effect of Co, Cu, Cr, Pb, Hg and all trace elements combined (Mix), pointing to Hg as the most harmful element. These physiological changes highlight P. tricornutum as a promising sentinel species for trace element contamination and the proposed photochemical features suitable as an efficient battery of biomarkers for trace element stress early detection in marine systems.

A modified precise integration method for transient dynamic analysis in structural systems with multiple damping models

Abstract Sophisticated engineering systems are usually assembled by subcomponents with significantly different levels of energy dissipation. Therefore, these damping systems often contain multiple damping models and lead to great difficulties in analyzing. This paper aims at developing a time integration method for structural systems with multiple damping models. The dynamical system is first represented by a generally damped model. Based on this, a new extended state-space method for the damped system is derived. A modified precise integration method with Gauss-Legendre quadrature is then proposed. The numerical stability and accuracy of the proposed integration method are discussed in detail. It is verified that the method is conditionally stable and has inherent algorithmic damping, period error and amplitude decay. Numerical examples are provided to assess the performance of the proposed method compared with other methods. It is demonstrated that the method is more accurate than other methods with rather good efficiency and the stable condition is easy to be satisfied in practice.

Parametric study of seismic performance of structures with multiple rocking joints

Abstract Research has demonstrated that base rocking lateral force resisting systems have excellent seismic performance which has resulted in their implementation in practice. However, such systems are limited in height because of force demands that are amplified by higher-mode effects. The use of multiple rocking joints, together with energy dissipation, has been proposed to mitigate higher-mode effects in rocking systems. Previous research has shown that placing a second rocking joint at the mid-height of a rocking steel braced frame, combined with the utilization of energy dissipation devices, is effective in reducing the effects of higher modes in rocking steel frames. Here, a parametric study using nonlinear response history analysis for a suite of earthquake ground motions is described that investigates the efficiency of higher-mode mitigation from multiple rocking joints and the optimal locations for second rocking joints. The parametric study is based on three prototype rocking steel frames of different heights. Other parameters studied were selected to investigate a wide-range of rocking system behaviors and include the energy dissipation level, flexural and shear stiffness of the frames, yield displacement of the energy dissipators, frame bay width, and post-tensioned bar type. Results suggest that placing a second rocking joint within the lower 22%–50% of the building height reduces the maximum story moment by approximately 10%–35% in different systems, and that energy dissipation provided at the second rocking joint is effective in controlling shear force. The interaction between changing specific parameters and the structural seismic performance is also revealed in this study. Finally, dynamic analyses of the 20- and 30-story prototype frames with 3 rocking joints reveals that a third rocking joint helps reduce the overturning moment slightly for the 20-story frames, while the reductions in overturning moment and shear force are more obvious for the 30-story frames.

Cyclic behavior of hexagonal castellated beams in steel moment-resisting frames with post-tensioned connections

In this article, behavior of ten beam specimens, including five hexagonal castellated beams and five typical wide flange beams, in the post-tensioned semi-rigid beam-to-column steel connections of moment-resisting frames has been analyzed theoretically and numerically by well-known finite element software (ABAQUS 6.11-PR3) under the earthquake simulated by cyclic loading up to 4.4% lateral drift. Hexagonal castellated beams provide lower weight and higher bending strength in comparison with typical wide flange beams in post-tensioned semi-rigid steel connections. The inelastic deformations of the bolted top and bottom angles provide reliable level of energy dissipation, and the steel strands provide self-centering capability and revert the moment-resisting frame to its initial position without residual drift after a severe earthquake. The results of finite element analysis verified against experiment have proved that the theoretical method based on the previous researches accurately predicts the behavior of hexagonal castellated beams in the post-tensioned connections. All beam specimens did not suffer from the flange buckling and web shear buckling under the standard cyclic loading up to 4% lateral drift; likewise, hexagonal castellated beams in the post-tensioned connections showed adequate strength against web-post failure and vierendeel mechanism up until 4% drift. In order to investigate the ultimate failure modes of the specimens, they have also been subjected to an added half-cycle loading up to 4.4% lateral drift beyond the standard loading. The further drifts have leaded to the web-post buckling in most specimens with hexagonal castellated beams and flange buckling in all specimens with wide flange beams. In addition, the parametric study is suggested as a further investigation to comprehensively understand the behavior of hexagonal castellated beams in the PT connections and it is required to reach more general conclusions. This research has developed a benchmark to design hexagonal castellated beams in the PT semi-rigid connections, but a step-by-step design guideline is still required to add it to design codes and specifications for steel structures.

Simplified dynamic analysis of reinforced-concrete beams under impact actions

A two-degree-of-freedom mass-spring model considering the local effect of the contact component is developed to investigate the dynamic responses of reinforced concrete beams under low-velocity impact actions. The local modified coefficient is proposed by parameter regression from drop-hammer impact test results, and then the simplified model is validated by other relevant research. As shown, the simplified model is able to capture the dynamic responses of reinforced concrete beams. In addition, the impact process is simulated and further analysed. The effects of initial impact velocity and the yield criterion of reinforced-concrete beams are investigated. The energy dissipation levels for various cases with the same initial impact energy are compared. An analysis proposal is also developed to predict the dynamic responses of reinforced concrete beams if the impact action case is uncertain.

Dual Function of Glucosamine in Gelatin/Hyaluronic Acid Cryogel to Modulate Scaffold Mechanical Properties and to Maintain Chondrogenic Phenotype for Cartilage Tissue Engineering.

Glucosamine (GlcN) fulfills many of the requirements as an ideal component in scaffolds used in cartilage tissue engineering. The incorporation of GlcN in a gelatin/hyaluronic acid (GH) cryogel scaffold could provide biological cues in maintaining the phenotype of chondrocytes. Nonetheless, substituting gelatin with GlcN may also decrease the crosslinking density and modulate the mechanical properties of the cryogel scaffold, which may be beneficial as physical cues for chondrocytes in the scaffold. Thus, we prepared cryogel scaffolds containing 9% GlcN (GH-GlcN9) and 16% GlcN (GH-GlcN16) by carbodiimide-mediated crosslinking reactions at −16 °C. The crosslinking density and the mechanical properties of the cryogel matrix could be tuned by adjusting the content of GlcN used during cryogel preparation. In general, incorporation of GlcN did not influence scaffold pore size and ultimate compressive strain but increased porosity. The GH-GlcN16 cryogel showed the highest swelling ratio and degradation rate in hyaluronidase and collagenase solutions. On the contrary, the Young’s modulus, storage modulus, ultimate compressive stress, energy dissipation level, and rate of stress relaxation decreased by increasing the GlcN content in the cryogel. The release of GlcN from the scaffolds in the culture medium of chondrocytes could be sustained for 21 days for GH-GlcN16 in contrast to only 7 days for GH-GlcN9. In vitro cell culture experiments using rabbit articular chondrocytes revealed that GlcN incorporation affected cell proliferation, morphology, and maintenance of chondrogenic phenotype. Overall, GH-GlcN16 showed the best performance in maintaining chondrogenic phenotype with reduced cell proliferation rate but enhanced glycosaminoglycans (GAGs) and type II collagen (COL II) secretion. Quantitative real-time polymerase chain reaction also showed time-dependent up-regulation of cartilage-specific marker genes (COL II, aggrecan and Sox9) for GH-GlcN16. Implantation of chondrocytes/GH-GlcN16 constructs into full-thickness articular cartilage defects of rabbits could regenerate neocartilage with positive staining for GAGs and COL II. The GH-GlcN16 cryogel will be suitable as a scaffold for the treatment of articular cartilage defects.

Análise do comportamento hidráulico de um mecanismo de transposição de peixes do tipo escada com ranhura vertical em duas declividades

RESUMO Diferentes sistemas hidráulicos instalados em barramentos têm sido utilizados como Mecanismos de Transposição de Peixes (MTP’s) e se constituem em uma alternativa para o movimento migratório de peixes para reprodução (“piracema”). A variação da declividade do MTP influencia a extensão do mesmo e consequentemente o custo final do mecanismo. Para determinar a melhor declividade do sistema, é necessário verificar parâmetros que influenciam a migração dos peixes, como campos de velocidades, níveis de dissipação de energia e tensão cisalhante de Reynolds nos tanques além do conhecimento de variáveis biológicas das espécies aquáticas a serem transpostas. No entanto, esses parâmetros não são avaliados conjuntamente, e alguns deles são avaliados pela média do escoamento em todo o tanque. Este trabalho apresenta uma análise dos principais parâmetros hidráulicos em tanque um tanque de um mecanismo do tipo escada com ranhura vertical em duas declividades, 6% e 12%, que se encontram próximo aos limites adotados nesse tipo de projeto. Os mapas dos parâmetros hidráulicos mostram que a declividade de 6% é a mais indicada para o projeto desse tipo de MTP, pois os seus níveis de velocidades, dissipação de energia e de tensão cisalhante de Reynolds são mais compatíveis com as condições ideais para a passagem de peixes. Para a declividade de 12% ocorre limitação de área possível de passagem do peixe devido a dissipação de energia e tensão cisalhante de Reynolds locais.

Quasi-static cyclic testing of emulative cast-in-place connections for Accelerated Bridge Construction in seismic regions

This paper presents findings from the first phase of testing at the University of Canterbury on seismic performance of emulative connections for Accelerated Bridge Construction (ABC) in regions of moderate to high seismicity. Emulative connections between precast concrete elements aim to target similar seismic behaviour as traditional ductile monolithic construction. The emulative solution in this research is called “High Damage Connection” (HDC). HDCs intend to achieve similar levels of seismic performance and ductility in a precast column as that can be expected of a monolithic one. HDC relies on formation of plastic hinges in the precast column during a design level earthquake to emulate monolithic ductile behaviour. Two types of HDCs, the grouted duct connection and member socket connection, were investigated in this research. Four half-scale precast segmental columns were constructed. Two columns featured grouted duct connections as the primary connection type. The other two columns used member socket connections. For a better understanding of the connection response under severe lateral loading, both uniaxial and biaxial testing of the columns was carried out. In this paper, an introduction to each connection type followed by design procedure, detailing considerations and construction methodology are explained in detail. Testing results and observations of seismic performance for each connection are thoroughly presented. The research concludes that High Damage Connections have good potential for ABC in regions of moderate to high seismicity. The connections that were tested achieved good levels of energy dissipation and ductility with similar performance to conventional monolithic connections.

Experimental study on in-plane cyclic response of partially grouted reinforced concrete masonry shear walls

This article describes the experimental results of ten partially grouted reinforced concrete masonry shear walls (PG-RCMSW) that were subjected to reverse lateral in-plane cyclic loads. The variables analysed in this study were: aspect ratio, shear reinforcement ratio and level of axial pre-compression. The influence of each of these variables on different structural parameters such as degradation of stiffness, shear strength, displacement ductility, dissipation of energy, hysteretic damping and level of drift, was evaluated. In addition, the precision of certain analytical expressions reported in the literature to predict the maximum shear strength of walls was examined and contrasted with the experimental results obtained.The results showed that the evolution of the damage was propagated in a similar way in all the walls tested until reaching the level of maximum strength. From this point, the evolution and extension of the damage depended on the characteristics and loading conditions particular to each wall. Also, a strong interdependence of the variables studied was identified, which became evident in the evaluation of shear strength, dissipation of energy, hysteretic damping, and level of drift. Using a bilinear idealization, displacement ductility values between 2.85 and 7.94 were found to reflect the presence of a moderate level of ductility in the walls tested. The equivalent viscous damping ratio associated with a non-linear response was found to range from 5% to 11%, indicating a moderate level of energy dissipation before the peak load was reached. Finally, the comparison between the predictions of the analytical expressions from the literature and the experimental results showed that those expressions that incorporated some interdependence in their design variables did not possess an appropriate degree of confidence to be applied in assessing the shear strength of PG-RCMSW, while expressions proposed by some international codes seem to be more reliable and conservative.

Innovative multi-level control with concentric pipes along brace to reduce seismic response of steel frames

The Painful experiences of past earthquakes and their related financial and physical damages have shown poor seismic performance of some structures; thus using new tools and equipment are inevitable. Application of two-level control systems is one of the cases that recently attracted the attention of researchers. The main idea of these systems is to combine two separate control devices with different strength and stiffness resulting in dual seismic behaviors due to their different energy dissipation levels. In this study, at first a multi-level pipe in pipe passive control system is presented and its cyclic behavior is evaluated with nonlinear static and dynamic analyses using finite element method by ABAQUS software. Then, hysteresis curves are studied representing a highly ductile behavior for the proposed damper. In addition, obtained hysteresis curves show that the multi-level system as expected can reliably dissipate energy in different energy levels leading to ductility ratios about 15 to 37 and equivalent viscous damping ratios about 36 to 50%. Finally for the 5, 10 and 15-story steel frames with the proposed dampers, maximum displacements decreased up to 79%, 63% and 27%, respectively, compared to bare frames.

Influence of fluid motion on growth and vertical distribution of cyanobacterium Microcystis aeruginosa

Cyanobacterium Microcystis aeruginosa (M. aeruginosa) is one of the dominant algae in lakes surrounded by urban and agriculture-dominated landscapes. Microcystis blooms pose ecological, economical, and human health risk, and there is a need to identify the forcing factors that influence Microcystis growth and blooms. We hypothesize that fluid motion has an influence on the growth and the vertical variability of M. aeruginosa, and its influence can be quantified by measuring the corresponding rate of energy dissipation levels of fluid motion. We conducted laboratory experiment measuring the population growth and vertical distribution of M. aeruginosa in a dual tower bioreactor with one tower used as experimental control. Fluid velocities were measured using a two-dimensional particle image velocimetry allowing the estimate of turbulence statistics that were related to measured M. aeruginosa growth rates and vertical cell concentration profiles. The effects of turbulence on M. aeruginosa physiology was evident by a 22 % increase in growth rate at depth-averaged energy dissipation rate ( $$\left\langle \varepsilon \right\rangle$$ ) of 8.5 × 10−5 m2 s−3, suppressed growth rate at $$\left\langle \varepsilon \right\rangle$$ > 2.8 × 10−4 m2 s−3, and no impact for $$\left\langle \varepsilon \right\rangle$$ < 4 × 10−6 m2 s−3. A similar trend was observed by analyzing the depth-dependent M. aeruginosa concentration versus the corresponding time-averaged local turbulent kinetic energy dissipation rate. A maximum cell biomass was discovered at e ~ 8.0 × 10−5 m2 s−3. Findings from this study can facilitate a greater understanding of physiology and spatial distribution of M. aeruginosa in aquatic ecosystems. The results will be instrumental in developing mechanistic models of the spatial and temporal distribution of M. aeruginosa that can improve management of aquatic ecosystems.

State-space based time integration method for structural systems involving multiple nonviscous damping models

Engineering structures are often assembled by subsections with various levels of energy dissipation, which lead to great difficulties in analyzing. In this paper, a direct time integration method is proposed to solve the dynamic responses of structural systems involving multiple nonviscous damping models. Based on a general non-viscously damped model, an extended state-space scheme for the damped system is derived. Then, an implicit time integration method using linear approximations is developed built on the extended state-space formalism. The stability and efficiency of the method are discussed by theoretical and numerical analyses. The method is illustrated by two examples.

STATE OF ART REVIEW OF SHAPE MEMORY ALLOY USED IN CIVIL STRUCTURES AS SEISMIC CONTROL DEVICE

Shape memory alloys (SMAs) are a kind of smart materials that remember their original shapes and can be utilized as an actuators that shape, stiffness, position, natural frequency and other mechanical characteristics in response to temperature or electromagnetic fields. SMAs exhibit two different phases i.e. martensite and austensite. Temperature and internal stresses (that play a role in super elasticity) determines the phases that SMA exhibits. The aim of this paper is to discuss about SMAs and its application in civil engineering structures like cable stayed bridges, elevated highway bridges, simply supported bridges and buildings as seismic control device. SMA is used as aactive, semi-active andpassive damper in civil structures. Passive damper has energy dissipation capacity and recentering ability. The recentering property areachieved by SMAs in austenite phase while dissipation ability of austenite is not so muchtherefore detwinning behaviour of SMA in martensite phase is considered increasing the damper's dissipating ability. NiTi SMAs showhigh level of superelastic hysteresis and energy dissipation and it solidify after transformation to stress-inducedMartensite, at roughly 6 to 8% strain. This property aremainly used for utilizing SMAs for hinge restrainer purposes for bridges. By using SMA's actuation property, Intelligent reinforced Concrete (IRC) was developed. IRC utilises strandedmartensite SMA wires for post tensioning and by monitoring electric resistance change of shape memory alloy wires, the strain allocation within concrete are obtained. If there is occurrence of cracks either by earthquakes or explosions, then by heating SMA wire strands results in its contraction and the cracks get reduced. It is observed from the study that SMA is effectively used as a seismic control device for civil structures.